SPEECHSC D. Burnett
Internet-Draft Voxeo
Intended status: Standards Track S. Shanmugham
Expires: September 15, 2011 Cisco Systems, Inc.
March 14, 2011
Media Resource Control Protocol Version 2 (MRCPv2)
draft-ietf-speechsc-mrcpv2-24
Abstract
The MRCPv2 protocol allows client hosts to control media service
resources such as speech synthesizers, recognizers, verifiers and
identifiers residing in servers on the network. MRCPv2 is not a
"stand-alone" protocol - it relies on other protocols, such as
Session Initiation Protocol (SIP) to rendezvous MRCPv2 clients and
servers and manage sessions between them, and the Session Description
Protocol (SDP) to describe, discover and exchange capabilities. It
also depends on SIP and SDP to establish the media sessions and
associated parameters between the media source or sink and the media
server. Once this is done, the MRCPv2 protocol exchange operates
over the control session established above, allowing the client to
control the media processing resources on the speech resource server.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 9
2. Document Conventions . . . . . . . . . . . . . . . . . . . . 10
2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . 10
2.2. State-Machine Diagrams . . . . . . . . . . . . . . . . . 11
2.3. URI Schemes . . . . . . . . . . . . . . . . . . . . . . 11
3. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1. MRCPv2 Media Resource Types . . . . . . . . . . . . . . 13
3.2. Server and Resource Addressing . . . . . . . . . . . . . 14
4. MRCPv2 Protocol Basics . . . . . . . . . . . . . . . . . . . 14
4.1. Connecting to the Server . . . . . . . . . . . . . . . . 15
4.2. Managing Resource Control Channels . . . . . . . . . . . 15
4.3. SIP session example . . . . . . . . . . . . . . . . . . 17
4.4. Media Streams and RTP Ports . . . . . . . . . . . . . . 22
4.5. MRCPv2 Message Transport . . . . . . . . . . . . . . . . 24
4.6. MRCPv2 Session Termination . . . . . . . . . . . . . . . 24
5. MRCPv2 Specification . . . . . . . . . . . . . . . . . . . . 24
5.1. Common Protocol Elements . . . . . . . . . . . . . . . . 25
5.2. Request . . . . . . . . . . . . . . . . . . . . . . . . 27
5.3. Response . . . . . . . . . . . . . . . . . . . . . . . . 28
5.4. Status Codes . . . . . . . . . . . . . . . . . . . . . . 29
5.5. Events . . . . . . . . . . . . . . . . . . . . . . . . . 31
6. MRCPv2 Generic Methods, Headers, and Result Structure . . . . 32
6.1. Generic Methods . . . . . . . . . . . . . . . . . . . . 32
6.1.1. SET-PARAMS . . . . . . . . . . . . . . . . . . . . . 32
6.1.2. GET-PARAMS . . . . . . . . . . . . . . . . . . . . . 33
6.2. Generic Message Headers . . . . . . . . . . . . . . . . 34
6.2.1. Channel-Identifier . . . . . . . . . . . . . . . . . 35
6.2.2. Accept . . . . . . . . . . . . . . . . . . . . . . . 36
6.2.3. Active-Request-Id-List . . . . . . . . . . . . . . . 36
6.2.4. Proxy-Sync-Id . . . . . . . . . . . . . . . . . . . 37
6.2.5. Accept-Charset . . . . . . . . . . . . . . . . . . . 37
6.2.6. Content-Type . . . . . . . . . . . . . . . . . . . . 37
6.2.7. Content-ID . . . . . . . . . . . . . . . . . . . . . 37
6.2.8. Content-Base . . . . . . . . . . . . . . . . . . . . 38
6.2.9. Content-Encoding . . . . . . . . . . . . . . . . . . 38
6.2.10. Content-Location . . . . . . . . . . . . . . . . . . 38
6.2.11. Content-Length . . . . . . . . . . . . . . . . . . . 39
6.2.12. Fetch Timeout . . . . . . . . . . . . . . . . . . . 39
6.2.13. Cache-Control . . . . . . . . . . . . . . . . . . . 40
6.2.14. Logging-Tag . . . . . . . . . . . . . . . . . . . . 41
6.2.15. Set-Cookie and Set-Cookie2 . . . . . . . . . . . . . 41
6.2.16. Vendor Specific Parameters . . . . . . . . . . . . . 43
6.3. Generic Result Structure . . . . . . . . . . . . . . . . 44
6.3.1. Natural Language Semantics Markup Language . . . . . 45
7. Resource Discovery . . . . . . . . . . . . . . . . . . . . . 45
8. Speech Synthesizer Resource . . . . . . . . . . . . . . . . . 47
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8.1. Synthesizer State Machine . . . . . . . . . . . . . . . 47
8.2. Synthesizer Methods . . . . . . . . . . . . . . . . . . 48
8.3. Synthesizer Events . . . . . . . . . . . . . . . . . . . 48
8.4. Synthesizer Header Fields . . . . . . . . . . . . . . . 49
8.4.1. Jump-Size . . . . . . . . . . . . . . . . . . . . . 49
8.4.2. Kill-On-Barge-In . . . . . . . . . . . . . . . . . . 50
8.4.3. Speaker Profile . . . . . . . . . . . . . . . . . . 50
8.4.4. Completion Cause . . . . . . . . . . . . . . . . . . 51
8.4.5. Completion Reason . . . . . . . . . . . . . . . . . 51
8.4.6. Voice-Parameter . . . . . . . . . . . . . . . . . . 52
8.4.7. Prosody-Parameters . . . . . . . . . . . . . . . . . 52
8.4.8. Speech Marker . . . . . . . . . . . . . . . . . . . 53
8.4.9. Speech Language . . . . . . . . . . . . . . . . . . 54
8.4.10. Fetch Hint . . . . . . . . . . . . . . . . . . . . . 54
8.4.11. Audio Fetch Hint . . . . . . . . . . . . . . . . . . 54
8.4.12. Failed URI . . . . . . . . . . . . . . . . . . . . . 55
8.4.13. Failed URI Cause . . . . . . . . . . . . . . . . . . 55
8.4.14. Speak Restart . . . . . . . . . . . . . . . . . . . 55
8.4.15. Speak Length . . . . . . . . . . . . . . . . . . . . 55
8.4.16. Load-Lexicon . . . . . . . . . . . . . . . . . . . . 56
8.4.17. Lexicon-Search-Order . . . . . . . . . . . . . . . . 56
8.5. Synthesizer Message Body . . . . . . . . . . . . . . . . 57
8.5.1. Synthesizer Speech Data . . . . . . . . . . . . . . 57
8.5.2. Lexicon Data . . . . . . . . . . . . . . . . . . . . 59
8.6. SPEAK Method . . . . . . . . . . . . . . . . . . . . . . 60
8.7. STOP . . . . . . . . . . . . . . . . . . . . . . . . . . 62
8.8. BARGE-IN-OCCURED . . . . . . . . . . . . . . . . . . . . 63
8.9. PAUSE . . . . . . . . . . . . . . . . . . . . . . . . . 65
8.10. RESUME . . . . . . . . . . . . . . . . . . . . . . . . . 66
8.11. CONTROL . . . . . . . . . . . . . . . . . . . . . . . . 68
8.12. SPEAK-COMPLETE . . . . . . . . . . . . . . . . . . . . . 70
8.13. SPEECH-MARKER . . . . . . . . . . . . . . . . . . . . . 71
8.14. DEFINE-LEXICON . . . . . . . . . . . . . . . . . . . . . 73
9. Speech Recognizer Resource . . . . . . . . . . . . . . . . . 73
9.1. Recognizer State Machine . . . . . . . . . . . . . . . . 75
9.2. Recognizer Methods . . . . . . . . . . . . . . . . . . . 75
9.3. Recognizer Events . . . . . . . . . . . . . . . . . . . 76
9.4. Recognizer Header Fields . . . . . . . . . . . . . . . . 76
9.4.1. Confidence Threshold . . . . . . . . . . . . . . . . 78
9.4.2. Sensitivity Level . . . . . . . . . . . . . . . . . 78
9.4.3. Speed Vs Accuracy . . . . . . . . . . . . . . . . . 79
9.4.4. N Best List Length . . . . . . . . . . . . . . . . . 79
9.4.5. Input Type . . . . . . . . . . . . . . . . . . . . . 79
9.4.6. No Input Timeout . . . . . . . . . . . . . . . . . . 80
9.4.7. Recognition Timeout . . . . . . . . . . . . . . . . 80
9.4.8. Waveform URI . . . . . . . . . . . . . . . . . . . . 80
9.4.9. Media Type . . . . . . . . . . . . . . . . . . . . . 81
9.4.10. Input-Waveform-URI . . . . . . . . . . . . . . . . . 81
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9.4.11. Completion Cause . . . . . . . . . . . . . . . . . . 81
9.4.12. Completion Reason . . . . . . . . . . . . . . . . . 83
9.4.13. Recognizer Context Block . . . . . . . . . . . . . . 83
9.4.14. Start Input Timers . . . . . . . . . . . . . . . . . 84
9.4.15. Speech Complete Timeout . . . . . . . . . . . . . . 84
9.4.16. Speech Incomplete Timeout . . . . . . . . . . . . . 85
9.4.17. DTMF Interdigit Timeout . . . . . . . . . . . . . . 85
9.4.18. DTMF Term Timeout . . . . . . . . . . . . . . . . . 86
9.4.19. DTMF-Term-Char . . . . . . . . . . . . . . . . . . . 86
9.4.20. Failed URI . . . . . . . . . . . . . . . . . . . . . 86
9.4.21. Failed URI Cause . . . . . . . . . . . . . . . . . . 86
9.4.22. Save Waveform . . . . . . . . . . . . . . . . . . . 87
9.4.23. New Audio Channel . . . . . . . . . . . . . . . . . 87
9.4.24. Speech-Language . . . . . . . . . . . . . . . . . . 87
9.4.25. Ver-Buffer-Utterance . . . . . . . . . . . . . . . . 88
9.4.26. Recognition-Mode . . . . . . . . . . . . . . . . . . 88
9.4.27. Cancel-If-Queue . . . . . . . . . . . . . . . . . . 88
9.4.28. Hotword-Max-Duration . . . . . . . . . . . . . . . . 89
9.4.29. Hotword-Min-Duration . . . . . . . . . . . . . . . . 89
9.4.30. Interpret-Text . . . . . . . . . . . . . . . . . . . 89
9.4.31. DTMF-Buffer-Time . . . . . . . . . . . . . . . . . . 89
9.4.32. Clear-DTMF-Buffer . . . . . . . . . . . . . . . . . 90
9.4.33. Early-No-Match . . . . . . . . . . . . . . . . . . . 90
9.4.34. Num-Min-Consistent-Pronunciations . . . . . . . . . 90
9.4.35. Consistency-Threshold . . . . . . . . . . . . . . . 91
9.4.36. Clash-Threshold . . . . . . . . . . . . . . . . . . 91
9.4.37. Personal-Grammar-URI . . . . . . . . . . . . . . . . 91
9.4.38. Enroll-Utterance . . . . . . . . . . . . . . . . . . 92
9.4.39. Phrase-Id . . . . . . . . . . . . . . . . . . . . . 92
9.4.40. Phrase-NL . . . . . . . . . . . . . . . . . . . . . 92
9.4.41. Weight . . . . . . . . . . . . . . . . . . . . . . . 92
9.4.42. Save-Best-Waveform . . . . . . . . . . . . . . . . . 93
9.4.43. New-Phrase-Id . . . . . . . . . . . . . . . . . . . 93
9.4.44. Confusable-Phrases-URI . . . . . . . . . . . . . . . 93
9.4.45. Abort-Phrase-Enrollment . . . . . . . . . . . . . . 93
9.5. Recognizer Message Body . . . . . . . . . . . . . . . . 94
9.5.1. Recognizer Grammar Data . . . . . . . . . . . . . . 94
9.5.2. Recognizer Result Data . . . . . . . . . . . . . . . 98
9.5.3. Enrollment Result Data . . . . . . . . . . . . . . . 99
9.5.4. Recognizer Context Block . . . . . . . . . . . . . . 99
9.6. Recognizer Results . . . . . . . . . . . . . . . . . . . 99
9.6.1. Markup Functions . . . . . . . . . . . . . . . . . . 100
9.6.2. Overview of Recognizer Result Elements and their
Relationships . . . . . . . . . . . . . . . . . . . 101
9.6.3. Elements and Attributes . . . . . . . . . . . . . . 101
9.7. Enrollment Results . . . . . . . . . . . . . . . . . . . 106
9.7.1. NUM-CLASHES Element . . . . . . . . . . . . . . . . 106
9.7.2. NUM-GOOD-REPETITIONS Element . . . . . . . . . . . . 107
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9.7.3. NUM-REPETITIONS-STILL-NEEDED Element . . . . . . . . 107
9.7.4. CONSISTENCY-STATUS Element . . . . . . . . . . . . . 107
9.7.5. CLASH-PHRASE-IDS Element . . . . . . . . . . . . . . 107
9.7.6. TRANSCRIPTIONS Element . . . . . . . . . . . . . . . 107
9.7.7. CONFUSABLE-PHRASES Element . . . . . . . . . . . . . 107
9.8. DEFINE-GRAMMAR . . . . . . . . . . . . . . . . . . . . . 107
9.9. RECOGNIZE . . . . . . . . . . . . . . . . . . . . . . . 111
9.10. STOP . . . . . . . . . . . . . . . . . . . . . . . . . . 117
9.11. GET-RESULT . . . . . . . . . . . . . . . . . . . . . . . 118
9.12. START-OF-INPUT . . . . . . . . . . . . . . . . . . . . . 119
9.13. START-INPUT-TIMERS . . . . . . . . . . . . . . . . . . . 120
9.14. RECOGNITION-COMPLETE . . . . . . . . . . . . . . . . . . 120
9.15. START-PHRASE-ENROLLMENT . . . . . . . . . . . . . . . . 122
9.16. ENROLLMENT-ROLLBACK . . . . . . . . . . . . . . . . . . 123
9.17. END-PHRASE-ENROLLMENT . . . . . . . . . . . . . . . . . 124
9.18. MODIFY-PHRASE . . . . . . . . . . . . . . . . . . . . . 124
9.19. DELETE-PHRASE . . . . . . . . . . . . . . . . . . . . . 125
9.20. INTERPRET . . . . . . . . . . . . . . . . . . . . . . . 125
9.21. INTERPRETATION-COMPLETE . . . . . . . . . . . . . . . . 126
9.22. DTMF Detection . . . . . . . . . . . . . . . . . . . . . 128
10. Recorder Resource . . . . . . . . . . . . . . . . . . . . . . 128
10.1. Recorder State Machine . . . . . . . . . . . . . . . . . 129
10.2. Recorder Methods . . . . . . . . . . . . . . . . . . . . 129
10.3. Recorder Events . . . . . . . . . . . . . . . . . . . . 129
10.4. Recorder Header Fields . . . . . . . . . . . . . . . . . 129
10.4.1. Sensitivity Level . . . . . . . . . . . . . . . . . 130
10.4.2. No Input Timeout . . . . . . . . . . . . . . . . . . 130
10.4.3. Completion Cause . . . . . . . . . . . . . . . . . . 130
10.4.4. Completion Reason . . . . . . . . . . . . . . . . . 131
10.4.5. Failed URI . . . . . . . . . . . . . . . . . . . . . 131
10.4.6. Failed URI Cause . . . . . . . . . . . . . . . . . . 131
10.4.7. Record URI . . . . . . . . . . . . . . . . . . . . . 132
10.4.8. Media Type . . . . . . . . . . . . . . . . . . . . . 132
10.4.9. Max Time . . . . . . . . . . . . . . . . . . . . . . 132
10.4.10. Trim-Length . . . . . . . . . . . . . . . . . . . . 133
10.4.11. Final Silence . . . . . . . . . . . . . . . . . . . 133
10.4.12. Capture On Speech . . . . . . . . . . . . . . . . . 133
10.4.13. Ver-Buffer-Utterance . . . . . . . . . . . . . . . . 134
10.4.14. Start Input Timers . . . . . . . . . . . . . . . . . 134
10.4.15. New Audio Channel . . . . . . . . . . . . . . . . . 134
10.5. Recorder Message Body . . . . . . . . . . . . . . . . . 134
10.6. RECORD . . . . . . . . . . . . . . . . . . . . . . . . . 134
10.7. STOP . . . . . . . . . . . . . . . . . . . . . . . . . . 136
10.8. RECORD-COMPLETE . . . . . . . . . . . . . . . . . . . . 136
10.9. START-INPUT-TIMERS . . . . . . . . . . . . . . . . . . . 137
10.10. START-OF-INPUT . . . . . . . . . . . . . . . . . . . . . 137
11. Speaker Verification and Identification . . . . . . . . . . . 138
11.1. Speaker Verification State Machine . . . . . . . . . . . 139
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11.2. Speaker Verification Methods . . . . . . . . . . . . . . 141
11.3. Verification Events . . . . . . . . . . . . . . . . . . 142
11.4. Verification Header Fields . . . . . . . . . . . . . . . 142
11.4.1. Repository-URI . . . . . . . . . . . . . . . . . . . 143
11.4.2. Voiceprint-Identifier . . . . . . . . . . . . . . . 143
11.4.3. Verification-Mode . . . . . . . . . . . . . . . . . 144
11.4.4. Adapt-Model . . . . . . . . . . . . . . . . . . . . 145
11.4.5. Abort-Model . . . . . . . . . . . . . . . . . . . . 145
11.4.6. Min-Verification-Score . . . . . . . . . . . . . . . 145
11.4.7. Num-Min-Verification-Phrases . . . . . . . . . . . . 145
11.4.8. Num-Max-Verification-Phrases . . . . . . . . . . . . 146
11.4.9. No-Input-Timeout . . . . . . . . . . . . . . . . . . 146
11.4.10. Save-Waveform . . . . . . . . . . . . . . . . . . . 146
11.4.11. Media Type . . . . . . . . . . . . . . . . . . . . . 147
11.4.12. Waveform-URI . . . . . . . . . . . . . . . . . . . . 147
11.4.13. Voiceprint-Exists . . . . . . . . . . . . . . . . . 147
11.4.14. Ver-Buffer-Utterance . . . . . . . . . . . . . . . . 148
11.4.15. Input-Waveform-Uri . . . . . . . . . . . . . . . . . 148
11.4.16. Completion-Cause . . . . . . . . . . . . . . . . . . 148
11.4.17. Completion Reason . . . . . . . . . . . . . . . . . 150
11.4.18. Speech Complete Timeout . . . . . . . . . . . . . . 150
11.4.19. New Audio Channel . . . . . . . . . . . . . . . . . 150
11.4.20. Abort-Verification . . . . . . . . . . . . . . . . . 150
11.4.21. Start Input Timers . . . . . . . . . . . . . . . . . 151
11.5. Verification Message Body . . . . . . . . . . . . . . . 151
11.5.1. Verification Result Data . . . . . . . . . . . . . . 151
11.5.2. Verification Result Elements . . . . . . . . . . . . 151
11.6. START-SESSION . . . . . . . . . . . . . . . . . . . . . 155
11.7. END-SESSION . . . . . . . . . . . . . . . . . . . . . . 156
11.8. QUERY-VOICEPRINT . . . . . . . . . . . . . . . . . . . . 157
11.9. DELETE-VOICEPRINT . . . . . . . . . . . . . . . . . . . 158
11.10. VERIFY . . . . . . . . . . . . . . . . . . . . . . . . . 159
11.11. VERIFY-FROM-BUFFER . . . . . . . . . . . . . . . . . . . 159
11.12. VERIFY-ROLLBACK . . . . . . . . . . . . . . . . . . . . 162
11.13. STOP . . . . . . . . . . . . . . . . . . . . . . . . . . 162
11.14. START-INPUT-TIMERS . . . . . . . . . . . . . . . . . . . 163
11.15. VERIFICATION-COMPLETE . . . . . . . . . . . . . . . . . 164
11.16. START-OF-INPUT . . . . . . . . . . . . . . . . . . . . . 164
11.17. CLEAR-BUFFER . . . . . . . . . . . . . . . . . . . . . . 165
11.18. GET-INTERMEDIATE-RESULT . . . . . . . . . . . . . . . . 165
12. Security Considerations . . . . . . . . . . . . . . . . . . . 166
12.1. Rendezvous and Session Establishment . . . . . . . . . . 167
12.2. Control channel protection . . . . . . . . . . . . . . . 167
12.3. Media session protection . . . . . . . . . . . . . . . . 167
12.4. Indirect Content Access . . . . . . . . . . . . . . . . 168
12.5. Protection of stored media . . . . . . . . . . . . . . . 169
12.6. DTMF and recognition buffers . . . . . . . . . . . . . . 169
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 169
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13.1. New registries . . . . . . . . . . . . . . . . . . . . . 169
13.1.1. MRCPv2 resource types . . . . . . . . . . . . . . . 169
13.1.2. MRCPv2 methods and events . . . . . . . . . . . . . 170
13.1.3. MRCPv2 header fields . . . . . . . . . . . . . . . . 172
13.1.4. MRCPv2 status codes . . . . . . . . . . . . . . . . 174
13.1.5. Grammar Reference List Parameters . . . . . . . . . 174
13.1.6. MRCPv2 vendor-specific parameters . . . . . . . . . 175
13.2. NLSML-related registrations . . . . . . . . . . . . . . 175
13.2.1. application/nlsml+xml Media Type registration . . . 175
13.3. NLSML XML Schema registration . . . . . . . . . . . . . 176
13.4. MRCPv2 XML Namespace registration . . . . . . . . . . . 176
13.5. text Media Type Registrations . . . . . . . . . . . . . 176
13.5.1. text/grammar-ref-list . . . . . . . . . . . . . . . 177
13.6. session URL scheme registration . . . . . . . . . . . . 177
13.7. SDP parameter registrations . . . . . . . . . . . . . . 178
13.7.1. sub-registry "proto" . . . . . . . . . . . . . . . . 178
13.7.2. sub-registry "att-field (session-level)" . . . . . . 179
13.7.3. sub-registry "att-field (media-level)" . . . . . . . 179
14. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 180
14.1. Message Flow . . . . . . . . . . . . . . . . . . . . . . 180
14.2. Recognition Result Examples . . . . . . . . . . . . . . 189
14.2.1. Simple ASR Ambiguity . . . . . . . . . . . . . . . . 189
14.2.2. Mixed Initiative . . . . . . . . . . . . . . . . . . 190
14.2.3. DTMF Input . . . . . . . . . . . . . . . . . . . . . 191
14.2.4. Interpreting Meta-Dialog and Meta-Task Utterances . 191
14.2.5. Anaphora and Deixis . . . . . . . . . . . . . . . . 192
14.2.6. Distinguishing Individual Items from Sets with
One Member . . . . . . . . . . . . . . . . . . . . . 193
14.2.7. Extensibility . . . . . . . . . . . . . . . . . . . 194
15. ABNF Normative Definition . . . . . . . . . . . . . . . . . . 194
16. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . . 209
16.1. NLSML Schema Definition . . . . . . . . . . . . . . . . 209
16.2. Enrollment Results Schema Definition . . . . . . . . . . 210
16.3. Verification Results Schema Definition . . . . . . . . . 212
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 215
17.1. Normative References . . . . . . . . . . . . . . . . . . 215
17.2. Informative References . . . . . . . . . . . . . . . . . 218
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 219
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 220
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 220
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1. Introduction
The MRCPv2 protocol is designed to allow a client device to control
media processing resources on the network. Some of these media
processing resources include speech recognition engines, speech
synthesis engines, speaker verification and speaker identification
engines. MRCPv2 enables the implementation of distributed
Interactive Voice Response platforms using VoiceXML
[W3C.REC-voicexml20-20040316] browsers or other client applications
while maintaining separate back-end speech processing capabilities on
specialized speech processing servers. MRCPv2 is based on the
earlier Media Resource Control Protocol (MRCP) [RFC4463] developed
jointly by Cisco Systems, Inc., Nuance Communications, and
Speechworks Inc.
The protocol requirements of SPEECHSC [RFC4313] include that the
solution be capable of reaching a media processing server and setting
up communication channels to the media resources, and sending and
receiving control messages and media streams to/from the server. The
Session Initiation Protocol (SIP) [RFC3261] meets these requirements.
The proprietary version of MRCP ran over RTSP [RFC2326]. At the time
work on MRCPv2 was begun, the consensus was that this use of RTSP
would break the RTSP protocol or cause backward-compatibility
problems, something forbidden by Section 3.2 of the above mentioned
requirements document. This is the reason why MRCPv2 does not run
over RTSP.
MRCPv2 leverages these capabilities by building upon SIP and the
Session Description Protocol (SDP) [RFC4566]. MRCPv2 uses SIP to
setup and tear down media and control sessions with the server. In
addition, the client can use a SIP re-INVITE method (an INVITE dialog
sent within an existing SIP Session) to change the characteristics of
these media and control session while maintaining the SIP dialog
between the client and server. SDP is used to describe the
parameters of the media sessions associated with that dialog. It is
mandatory to support SIP as the session establishment protocol to
ensure interoperability. Other protocols can be used for session
establishment by prior agreement. This document only describes the
use of SIP and SDP.
MRCPv2 uses SIP and SDP to create the speech client/server dialog and
set up the media channels to the server. It also uses SIP and SDP to
establish MRCPv2 control sessions between the client and the server
for each media processing resource required for that dialog. The
MRCPv2 protocol exchange between the client and the media resource is
carried on that control session. MRCPv2 protocol exchanges do not
change the state of the SIP dialog, the media sessions, or other
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parameters of the dialog initiated via SIP. It controls and affects
the state of the media processing resource associated with the MRCPv2
session(s).
MRCPv2 defines the messages to control the different media processing
resources and the state machines required to guide their operation.
It also describes how these messages are carried over a transport
layer protocol such as TCP or TLS (Note: SCTP is a viable transport
for MRCPv2 as well, but the mapping onto SCTP is not described in
this specification).
2. Document Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119].
Since many of the definitions and syntax are identical to HTTP/1.1
(RFC2616 [RFC2616]), this specification refers to the section where
they are defined rather than copying it. For brevity, [HX.Y] is to
be taken to refer to Section X.Y of RFC2616.
All the mechanisms specified in this document are described in both
prose and an augmented Backus-Naur form (ABNF [RFC5234]).
The complete message format in ABNF form is provided in Section 15
and is the normative format definition. Note that productions may be
duplicated within the main body of the document for reading
convenience. If a production in the body of the text conflicts with
one in the normative definition, the latter rules.
2.1. Definitions
Media Resource
An entity on the speech processing server that can be
controlled through the MRCPv2 protocol.
MRCP Server
Aggregate of one or more "Media Resource" entities on
a Server, exposed through the MRCPv2 protocol
("Server" for short).
MRCP Client
An entity controlling one or more Media Resources
through the MRCPv2 protocol ("Client" for short).
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DTMF
Dual Tone Multi-Frequency; a method of transmitting
key presses in-band, either as actual tones (Q.23
[Q.23]) or as named tone events (RFC4733 [RFC4733]).
Endpointing
The process of automatically detecting the beginning
and end of speech in an audio stream. This is
critical both for speech recognition and for automated
recording as one would find in voice mail systems.
Hotword Mode
A mode of speech recognition where a stream of
utterances is evaluated for match against a small set
of command words. This is generally employed to
either trigger some action, or to control the
subsequent grammar to be used for further recognition
2.2. State-Machine Diagrams
The state-machine diagrams in this document do not show every
possible method call. Rather, they reflect the state of the resource
based on the methods that have moved to IN-PROGRESS or COMPLETE
states (see Section 5.3). Note that since PENDING requests
essentially have not affected the resource yet and are in queue to be
processed, they are not reflected in the state-machine diagrams.
2.3. URI Schemes
This document defines many protocol headers that contain URIs or
lists of URIs for referencing media. The entire document, including
the Security Considerations section (Section 12), assumes that HTTP/
HTTPS will be used as the URI addressing scheme unless otherwise
stated. However, implementations MAY support other schemes (such as
"file") provided they have addressed any security considerations
described in this document and any others particular to the specific
scheme. For example, implementations where the client and server
both reside on the same physical hardware and the file system is
secured by traditional user-level file access controls could be
reasonable candidates for supporting the "file" scheme.
3. Architecture
A system using MRCPv2 consists of a client that requires the
generation and/or consumption of media streams and a media resource
server that has the resources or "engines" to process these streams
as input or generate these streams as output. The client uses SIP
and SDP to establish an MRCPv2 control channel with the server to use
its media processing resources. MRCPv2 servers are addressed using
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SIP URIs.
The session initiation protocol (SIP) uses SDP with the offer/answer
model described in RFC3264 [RFC3264] to set up the MRCPv2 control
channels and describe their characteristics. A separate MRCPv2
session is needed to control each of the media processing resources
associated with the SIP dialog between the client and server. Within
a SIP dialog, the individual resource control channels for the
different resources are added or removed through SDP offer/answer
carried in a SIP re-INVITE transaction.
The server, through the SDP exchange, provides the client with an
unambiguous channel identifier and a TCP port number. The client MAY
then open a new TCP connection with the server on this port number.
Multiple MRCPv2 channels can share a TCP connection between the
client and the server. All MRCPv2 messages exchanged between the
client and the server carry the specified channel identifier that the
server MUST ensure is unambiguous among all MRCPv2 control channels
that are active on that server. The client uses this channel
identifier to indicate the media processing resource associated with
that channel. For information on message framing, see Section 5.
The session initiation protocol (SIP) also establishes the media
sessions between the client (or other source/sink of media) and the
MRCPv2 server using SDP m-lines. One or more media processing
resources may share a media session under a SIP session, or each
media processing resource may have its own media session.
The following diagram shows the general architecture of a system that
uses MRCPv2. To simplify the diagram only a few resources are shown.
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MRCPv2 client MRCPv2 Media Resource Server
|--------------------| |------------------------------------|
||------------------|| ||----------------------------------||
|| Application Layer|| ||Synthesis|Recognition|Verification||
||------------------|| || Engine | Engine | Engine ||
||Media Resource API|| || || | || | || ||
||------------------|| ||Synthesis|Recognizer | Verifier ||
|| SIP | MRCPv2 || ||Resource | Resource | Resource ||
||Stack | || || Media Resource Management ||
|| | || ||----------------------------------||
||------------------|| || SIP | MRCPv2 ||
|| TCP/IP Stack ||---MRCPv2---|| Stack | ||
|| || ||----------------------------------||
||------------------||----SIP-----|| TCP/IP Stack ||
|--------------------| || ||
| ||----------------------------------||
SIP |------------------------------------|
| /
|-------------------| RTP
| | /
| Media Source/Sink |------------/
| |
|-------------------|
Figure 1: Architectural Diagram
3.1. MRCPv2 Media Resource Types
An MRCPv2 server may offer one or more of the following media
processing resources to its clients.
Basic Synthesizer
A speech synthesizer resource with very limited
capabilities, that can generate its media stream
exclusively from concatenated audio clips. The speech
data is described using a limited subset of SSML
[W3C.REC-speech-synthesis-20040907] elements. A basic
synthesizer MUST support the SSML tags <speak>,
<audio>, <say-as> and <mark>.
Speech Synthesizer
A full capability speech synthesis resource capable of
rendering speech from text. Such a synthesizer MUST
have full SSML [W3C.REC-speech-synthesis-20040907]
support.
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Recorder
A resource capable of recording audio and providing a
URI pointer to the recording. A recorder MUST provide
some endpointing capabilities for suppressing silence
at the beginning and end of a recording, and MAY also
suppress silence in the middle of a recording. If
such suppression is done, the recorder MUST maintain
timing metadata to indicate the actual time stamps of
the recorded media.
DTMF Recognizer
A recognition resource capable of extracting and
interpreting DTMF digits in a media stream and
matching them against a supplied digit grammar It
could also do a semantic interpretation based on
semantic tags in the grammar.
Speech Recognizer
A full speech recognition resource that is capable of
receiving a media stream containing audio and
interpreting it to recognition results. It also has a
natural language semantic interpreter to post-process
the recognized data according to the semantic data in
the grammar and provide semantic results along with
the recognized input. The recognizer may also support
enrolled grammars, where the client can enroll and
create new personal grammars for use in future
recognition operations.
Speaker Verifier
A resource capable of verifying the authenticity of a
claimed identity by matching a media stream containing
spoken input to a pre-existing voiceprint. This may
also involve matching the caller's voice against more
than one voiceprint, also called multi-verification or
speaker identification.
3.2. Server and Resource Addressing
The MRCPv2 server is a generic SIP server, and is thus addressed by a
SIP URI.
For example:
sip:mrcpv2@example.net
4. MRCPv2 Protocol Basics
MRCPv2 requires a connection-oriented transport layer protocol such
as TCP or SCTP to guarantee reliable sequencing and delivery of
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MRCPv2 control messages between the client and the server. In order
to meet the requirements for security enumerated in SpeechSC
Requirements [RFC4313], clients and servers MUST implement TLS as
well. One or more connections between the client and the server can
be shared among different MRCPv2 channels to the server. The
individual messages carry the channel identifier to differentiate
messages on different channels. MRCPv2 protocol encoding is text
based with mechanisms to carry embedded binary data. This allows
arbitrary data like recognition grammars, recognition results,
synthesizer speech markup etc. to be carried in MRCPv2 messages. For
information on message framing, see Section 5.
4.1. Connecting to the Server
MRCPv2 employs a session establishment and management protocol such
as SIP in conjunction with SDP. The client reaches an MRCPv2 server
using conventional INVITE and other SIP requests for establishing,
maintaining, and terminating SIP dialogs. The SDP offer/answer
exchange model over SIP is used to establish a resource control
channel for each resource. The SDP offer/answer exchange is also
used to establish media sessions between the server and the source or
sink of audio.
4.2. Managing Resource Control Channels
The client needs a separate MRCPv2 resource control channel to
control each media processing resource under the SIP dialog. A
unique channel identifier string identifies these resource control
channels. The channel identifier is an unambiguous, opaque string
followed by an "@", then by a string token specifying the type of
resource. The server generates the channel identifier and MUST make
sure it does not clash with the identifier of any other MRCP channel
currently allocated by that server. MRCPv2 defines the following
IANA-registered types of media processing resources. Additional
resource types, their associated methods/events and state machines
may be added as described below in Section 13.
+---------------+----------------------+--------------+
| Resource Type | Resource Description | Described in |
+---------------+----------------------+--------------+
| speechrecog | Speech Recognizer | Section 9 |
| dtmfrecog | DTMF Recognizer | Section 9 |
| speechsynth | Speech Synthesizer | Section 8 |
| basicsynth | Basic Synthesizer | Section 8 |
| speakverify | Speaker Verification | Section 11 |
| recorder | Speech Recorder | Section 10 |
+---------------+----------------------+--------------+
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Resource Types
The SIP INVITE or re-INVITE transaction and the SDP offer/answer
exchange it carries contain m-lines describing the resource control
channel to be allocated. There MUST be one SDP m-line for each
MRCPv2 resource to be used in the session. This m-line MUST have a
media type field of "application" and a transport type field of
either "TCP/MRCPv2" or "TCP/TLS/MRCPv2". (The usage of SCTP with
MRCPv2 may be addressed in a future specification). The port number
field of the m-line MUST contain the "discard" port of the transport
protocol (port 9 for TCP) in the SDP offer from the client and MUST
contain the TCP listen port on the server in the SDP answer. The
client may then either set up a TCP or TLS connection to that server
port or share an already established connection to that port. Since
MRCPv2 allows multiple sessions to share the same TCP connection,
multiple m-lines in a single SDP document may share the same port
field value; MRCPv2 servers MUST NOT assume any relationship between
resources using the same port other than the sharing of the
communication channel.
MRCPv2 resources do not use the port or format field of the m-line to
distinguish themselves from other resources using the same channel.
The client MUST specify the resource type identifier in the resource
attribute associated with the control m-line of the SDP offer. The
server MUST respond with the full Channel-Identifier (which includes
the resource type identifier and an unambiguous string) in the
"channel" attribute associated with the control m-line of the SDP
answer. To remain backwards compatible with conventional SDP usage,
the format field of the m-line MUST have the arbitrarily-selected
value of "1".
When the client wants to add a media processing resource to the
session, it issues a SIP re-INVITE transaction. The SDP offer/answer
exchange carried by this SIP transaction contains one or more
additional control m-lines for the new resources to be allocated to
the session. The server, on seeing the new m-line, allocates the
resources (if they are available) and responds with a corresponding
control m-line in the SDP answer carried in the SIP response. If the
new resources are not available, the re-INVITE receives an error
message, and existing media processing going on before the re-INVITE
will continue as it was before.
The a=setup attribute, as described in RFC4145 [RFC4145], MUST be
"active" for the offer from the client and MUST be "passive" for the
answer from the MRCPv2 server. The a=connection attribute MUST have
a value of "new" on the very first control m-line offer from the
client to an MRCPv2 server. Subsequent control m-line offers from
the client to the MRCP server MAY contain "new" or "existing",
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depending on whether the client wants to set up a new connection or
share an existing connection, respectively. If the client specifies
a value of "new", the server MUST respond with a value of "new". If
the client specifies a value of "existing", the server MAY respond
with a value of "existing" if it prefers to share an existing
connection or can answer with a value of "new", in which case the
client MUST initiate a new transport connection.
When the client wants to de-allocate the resource from this session,
it issues a SIP re-INVITE transaction with the server. The SDP MUST
offer the control m-line with port 0. The server MUST then answer
the control m-line with a response of port 0. This de-allocates the
associated MRCPv2 identifier and resource. The server MUST NOT close
the TCP, SCTP or TLS connection if it is currently being shared among
multiple MRCP channels. When all MRCP channels that may be sharing
the connection are released and/or the associated SIP dialog is
terminated, the client or server terminates the connection.
All servers MUST support TLS. Servers MAY support TCP without TLS in
physically secure environments. It is up to the client, through the
SDP offer, to choose which transport it wants to use for an MRCPv2
session. Aside from the exceptions given above, when using TCP the
m-lines MUST conform to RFC4145 [RFC4145], which describes the usage
of SDP for connection-oriented transport. When using TLS the SDP
m-line for the control stream MUST conform to comedia over TLS
[RFC4572], which specifies the usage of SDP for establishing a secure
connection-oriented transport over TLS.
4.3. SIP session example
This first example shows the power of using SIP to route to the
appropriate resource. In the example, note the use of a request to a
domain's speech server service in the INVITE to
mresources@example.com. The SIP routing machinery in the domain
locates the actual server, mresources@server.example.com, which gets
returned in the 200 OK. Note that "cmid" is defined in Section 4.4.
This example exchange adds a resource control channel for a
synthesizer. Since a synthesizer also generates an audio stream,
this interaction also creates a receive-only RTP media session for
the server to send audio to. The SIP dialog with the media source/
sink is independent of MRCP and is not shown.
C->S: INVITE sip:mresources@example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf1
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>
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From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:314161 INVITE
Contact:<sip:sarvi@client.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=sarvi 2890844526 2890844526 IN IP4 192.0.2.4
s=-
c=IN IP4 192.0.2.12
m=application 9 TCP/MRCPv2 1
a=setup:active
a=connection:new
a=resource:speechsynth
a=cmid:1
m=audio 49170 RTP/AVP 0
a=rtpmap:0 pcmu/8000
a=recvonly
a=mid:1
S->C: SIP/2.0 200 OK
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf1;received=192.0.32.10
To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:314161 INVITE
Contact:<sip:mresources@server.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=- 2890842808 2890842808 IN IP4 192.0.2.4
s=-
c=IN IP4 192.0.2.11
m=application 32416 TCP/MRCPv2 1
a=setup:passive
a=connection:new
a=channel:32AECB234338@speechsynth
a=cmid:1
m=audio 48260 RTP/AVP 0
a=rtpmap:0 pcmu/8000
a=sendonly
a=mid:1
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C->S: ACK sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf2
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
From:Sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:314161 ACK
Content-Length:0
Example: Add Synthesizer Control Channel
This example exchange continues from the previous figure and
allocates an additional resource control channel for a recognizer.
Since a recognizer would need to receive an audio stream for
recognition, this interaction also updates the audio stream to
sendrecv, making it a 2-way RTP media session.
C->S: INVITE sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf3
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:314162 INVITE
Contact:<sip:sarvi@client.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=sarvi 2890844526 2890844527 IN IP4 192.0.2.4
s=-
c=IN IP4 192.0.2.12
m=application 9 TCP/MRCPv2 1
a=setup:active
a=connection:existing
a=resource:speechsynth
a=cmid:1
m=audio 49170 RTP/AVP 0 96
a=rtpmap:0 pcmu/8000
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-15
a=sendrecv
a=mid:1
m=application 9 TCP/MRCPv2 1
a=setup:active
a=connection:existing
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a=resource:speechrecog
a=cmid:1
S->C: SIP/2.0 200 OK
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf3;received=192.0.32.10
To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:314162 INVITE
Contact:<sip:mresources@server.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=- 2890842808 2890842809 IN IP4 192.0.2.4
s=-
c=IN IP4 192.0.2.11
m=application 32416 TCP/MRCPv2 1
a=setup:passive
a=connection:existing
a=channel:32AECB234338@speechsynth
a=cmid:1
m=audio 48260 RTP/AVP 0 96
a=rtpmap:0 pcmu/8000
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-15
a=sendrecv
a=mid:1
m=application 32416 TCP/MRCPv2 1
a=setup:passive
a=connection:existing
a=channel:32AECB234338@speechrecog
a=cmid:1
C->S: ACK sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf4
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
From:Sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:314162 ACK
Content-Length:0
Add Recognizer example
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This example exchange continues from the previous figure and de-
allocates recognizer channel. Since a recognizer no longer needs to
receive an audio stream, this interaction also updates the RTP media
session to recvonly.
C->S: INVITE sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf5
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:314163 INVITE
Contact:<sip:sarvi@client.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=sarvi 2890844526 2890844528 IN IP4 192.0.2.4
s=-
c=IN IP4 192.0.2.12
m=application 9 TCP/MRCPv2 1
a=resource:speechsynth
a=cmid:1
m=audio 49170 RTP/AVP 0
a=rtpmap:0 pcmu/8000
a=recvonly
a=mid:1
m=application 0 TCP/MRCPv2 1
a=resource:speechrecog
a=cmid:1
S->C: SIP/2.0 200 OK
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf5;received=192.0.32.10
To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:314163 INVITE
Contact:<sip:mresources@server.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=- 2890842808 2890842810 IN IP4 192.0.2.4
s=-
c=IN IP4 192.0.2.11
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m=application 32416 TCP/MRCPv2 1
a=channel:32AECB234338@speechsynth
a=cmid:1
m=audio 48260 RTP/AVP 0
a=rtpmap:0 pcmu/8000
a=sendonly
a=mid:1
m=application 0 TCP/MRCPv2 1
a=channel:32AECB234338@speechrecog
a=cmid:1
C->S: ACK sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf6
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
From:Sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:314163 ACK
Content-Length:0
Deallocate Recognizer example
4.4. Media Streams and RTP Ports
Since MRCPv2 resources either generate or consume media streams, the
client or the server needs to associate media sessions with their
corresponding resource or resources. More than one resource could be
associated with a single media session or each resource could be
assigned a separate media session. Also note that more than one
media session can be associated with a single resource if need be,
but this scenario is not useful for the current set of resources.
For example, a synthesizer and a recognizer could be associated to
the same media session (m=audio line), if it is opened in "sendrecv"
mode. Alternatively, the recognizer could have its own "sendonly"
audio session and the synthesizer could have its own "recvonly" audio
session.
The association between control channels and their corresponding
media sessions is established using a new "resource channel media
identifier" media-level attribute ("cmid"). Valid values of this
attribute are the values of the "mid" attribute defined in RFC3388
[RFC3388]. If there is more than 1 audio m-line, then each audio
m-line MUST have a "mid" attribute. Each control m-line MAY have one
or more "cmid" attributes that match the resource control channel to
the "mid" attributes of the audio m-lines it is associated with.
Note that if a control m-line does not have a "cmid" attribute it
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will not be associated with any media. The operations on such a
resource will hence be limited. For example, if it was a recognizer
resource, the RECOGNIZE method requires an associated media to
process while the INTERPRET method does not. The formatting of the
"cmid" attribute is described by the following ABNF:
cmid-attribute = "a=cmid:" identification-tag
identification-tag = token
To allow this flexible mapping of media sessions to MRCPv2 control
channels, a single audio m-line can be associated with multiple
resources or each resource can have its own audio m-line. For
example, if the client wants to allocate a recognizer and a
synthesizer and associate them with a single 2-way audio stream, the
SDP offer would contain two control m-lines and a single audio m-line
with an attribute of "sendrecv". Each of the control m-lines would
have a "cmid" attribute whose value matches the "mid" of the audio
m-line. If, on the other hand, the client wants to allocate a
recognizer and a synthesizer each with its own separate audio stream,
the SDP offer would carry two control m-lines (one for the recognizer
and another for the synthesizer) and two audio m-lines (one with the
attribute "sendonly" and another with attribute "recvonly"). The
"cmid" attribute of the recognizer control m-line would match the
"mid" value of the "sendonly" audio m-line and the "cmid" attribute
of the synthesizer control m-line would match the "mid" attribute of
the "recvonly" m-line.
When a server receives media (e.g. audio) on a media session that is
associated with more than one media processing resource, it is the
responsibility of the server to receive and fork the media to the
resources that need to consume it. If multiple resources in an
MRCPv2 session are generating audio (or other media) to be sent on a
single associated media session, it is the responsibility of the
server to either multiplex the multiple streams onto the single RTP
session or contain an embedded RTP mixer (see RFC3550 [RFC3550]) to
combine the multiple streams into one. In the former case, the media
stream will contain RTP packets generated by different sources, and
hence the packets will have different Synchronization Source
identifiers (SSRCs). In the latter case, the RTP packets will
contain multiple (CSRCs) corresponding to the original streams before
being combined by the mixer. An MRCPv2 implementation MUST either
multiplex or mix unless it cannot correctly do either, in which case
the server MUST disallow the client from associating multiple such
resources to a single audio stream by rejecting the SDP offer with a
SIP 488 "Not Acceptable" error. Note that there is a large installed
base that will return a SIP 501 "Not Implemented" error in this case.
To facilitate interoperability with this installed base, new
implementations should consider adding configuration to treat a 501
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in this context as a 488 when it is received from an element known to
be a legacy implementation.
4.5. MRCPv2 Message Transport
The MRCPv2 messages defined in this document are transported over a
TCP, TLS or SCTP (in the future) connection between the client and
the server. The method for setting up this transport connection and
the resource control channel is discussed in Section 4.1 and
Section 4.2. Multiple resource control channels between a client and
a server that belong to different SIP dialogs can share one or more
TLS, TCP or SCTP connections between them; the server and client MUST
support this mode of operation. The individual MRCPv2 messages carry
the MRCPv2 channel identifier in their Channel-Identifier header
field, which MUST be used to differentiate MRCPv2 messages from
different resource channels (see Section 6.2.1 for details). All
MRCPv2 servers MUST support TLS. Servers MAY support TCP without TLS
in physically secure environments. It is up to the client to choose
which mode of transport it wants to use for an MRCPv2 session.
Most examples from here on show only the MRCPv2 messages and do not
show the SIP messages that may have been used to establish the MRCPv2
control channel.
4.6. MRCPv2 Session Termination
If an MRCP client notices that the underlying connection has been
closed for one of its MRCP channels, and it has not previously
initiated a reINVITE to close that channel, it MUST send a BYE to
close down the SIP dialog and all other MRCP channels. If an MRCP
server notices that the underlying connection has been closed for one
of its MRCP channels, and it has not previously received and accepted
a reINVITE closing that channel, then it MUST send a BYE to close
down the SIP dialog and all other MRCP channels.
5. MRCPv2 Specification
MRCPv2 messages are textual using the ISO 10646 character set in the
UTF-8 encoding (RFC3629 [RFC3629]) to allow many different languages
to be represented. However, to assist in compact representations,
MRCPv2 also allows message bodies to be represented in other
character sets such as ISO 8859-1. This may be useful for languages
such as Chinese where the default character set for most documents is
not UTF-8. The MRCPv2 protocol headers (the first line of an MRCP
message) and header field names use only the US-ASCII subset of
UTF-8. Internationalization only applies to certain fields like
grammar, results, speech markup etc, and not to MRCPv2 as a whole.
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Lines are terminated by CRLF. Also, some parameters in the message
may contain binary data or a record spanning multiple lines. Such
fields have a length value associated with the parameter, which
indicates the number of octets immediately following the parameter.
5.1. Common Protocol Elements
The MRCPv2 message set consists of requests from the client to the
server, responses from the server to the client and asynchronous
events from the server to the client. All these messages consist of
a start-line, one or more header fields, an empty line (i.e. a line
with nothing preceding the CRLF) indicating the end of the header
fields, and an optional message body.
generic-message = start-line
message-header
CRLF
[ message-body ]
message-body = *OCTET
start-line = request-line / response-line / event-line
message-header = 1*(generic-header / resource-header / generic-field)
resource-header = synthesizer-header
/ recognizer-header
/ recorder-header
/ verifier-header
The message-body contains resource-specific and message-specific
data. The actual Media Types used to carry the data are specified
later in the sections defining the individual messages. Generic
header fields are described in Section 6.2.
If a message contains a message body, the message MUST contain
content-headers indicating the Media Type and encoding of the data in
the message body.
Request, response and event messages (described in following
sections) include the version of MRCP that the message conforms to.
Version compatibility rules follow [H3.1] regarding version ordering,
compliance requirements, and upgrading of version numbers. The
version information is indicated by "MRCP" (as opposed to "HTTP" in
[H3.1]) or "MRCP/2.0" (as opposed to "HTTP/1.1" in [H3.1]). To be
compliant with this specification, clients and servers sending MRCPv2
messages MUST indicate an mrcp-version of "MRCP/2.0".
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mrcp-version = "MRCP" "/" 1*2DIGIT "." 1*2DIGIT
The message-length field specifies the length of the message in
octets, including the start-line, and MUST be the 2nd token from the
beginning of the message. This is to make the framing and parsing of
the message simpler to do. This field specifies the length of the
message including data that may be encoded into the body of the
message. Note that this value MAY be printed as a fixed-length
integer that is zero-padded in front in order to eliminate or reduce
inefficiency in cases where the message-length value would change as
a result of the length of the message-length token itself. This
value, as with all lengths in MRCP, is to be interpreted as a base-10
number. In particular, leading zeros do not indicate that the value
is to be interpreted as a base-8 number.
message-length = 1*19DIGIT
The following sample MRCP exchange demonstrates proper message-length
values. The values for message-length have been removed from all
other examples in the specification and replaced by '...' to reduce
confusion in the case of minor message-length computation errors in
those examples.
C->S: MRCP/2.0 877 INTERPRET 543266
Channel-Identifier:32AECB23433801@speechrecog
Interpret-Text:may I speak to Andre Roy
Content-Type:application/srgs+xml
Content-ID:<request1@form-level.store>
Content-Length:661
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0" root="request">
<!-- single language attachment to tokens -->
<rule id="yes">
<one-of>
<item xml:lang="fr-CA">oui</item>
<item xml:lang="en-US">yes</item>
</one-of>
</rule>
<!-- single language attachment to a rule expansion -->
<rule id="request">
may I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
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</one-of>
</rule>
</grammar>
S->C: MRCP/2.0 82 543266 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
S->C: MRCP/2.0 634 INTERPRETATION-COMPLETE 543267 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
Content-Type:application/nlsml+xml
Content-Length:441
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="session:request1@form-level.store">
<interpretation>
<instance name="Person">
<ex:Person>
<ex:Name> Andre Roy </ex:Name>
</ex:Person>
</instance>
<input> may I speak to Andre Roy </input>
</interpretation>
</result>
All MRCPv2 messages, responses and events MUST carry the Channel-
Identifier header field so the server or client can differentiate
messages from different control channels that may share the same
transport connection.
In the resource-specific header field descriptions in sections 8-11,
a header field is disallowed on a method (request, response, or
event) for that resource unless specifically listed as being allowed.
Also, the phrasing "This header field MAY occur on method X"
indicates that the header field is allowed on that method but is not
required to be used in every instance of that method.
5.2. Request
An MRCPv2 request consists of a Request line followed by the message
header section and an optional message body containing data specific
to the request message.
The Request message from a client to the server includes within the
first line the method to be applied, a method tag for that request
and the version of the protocol in use.
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request-line = mrcp-version SP message-length SP method-name
SP request-id CRLF
The mrcp-version field is the MRCP protocol version that is being
used by the client.
The message-length field specifies the length of the message,
including the start-line.
Details about the mrcp-version and message-length fields are given in
Section 5.1.
The method-name field identifies the specific request that the client
is making to the server. Each resource supports a subset of the
MRCPv2 methods. The subset for each resource is defined in the
section of the specification for the corresponding resource.
method-name = generic-method
/ synthesizer-method
/ recognizer-method
/ recorder-method
/ verifier-method
The request-id field is a unique identifier representable as an
unsigned 32 bit integer created by the client and sent to the server.
Consecutive requests within an MRCP session MUST utilize
monotonically increasing request-id's. The request-id space is
linear, (i.e. not mod(32)) so the space does not wrap and validity
can be checked with a simple unsigned comparison operation. The
client may choose any initial value for its first request, but a
small integer is RECOMMENDED to avoid exhausting the space in long
sessions. If the server receives duplicate or out-of-order requests
the server MUST reject the request with a response code of 410.
Since request-id's are scoped to the MRCP session, they are unique
across all TCP connections and all resource channels in the session.
The server resource MUST use the client-assigned identifier in its
response to the request. If the request does not complete
synchronously, future asynchronous events associated with this
request MUST carry the client-assigned request-id.
request-id = 1*10DIGIT
5.3. Response
After receiving and interpreting the request message for a method,
the server resource responds with an MRCPv2 response message. The
response consists of a response line followed by the message header
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section and an optional message body containing data specific to the
method.
response-line = mrcp-version SP message-length SP request-id
SP status-code SP request-state CRLF
The mrcp-version field MUST contain the version of the request if
supported; otherwise, it must contain the highest version of the
MRCPv2 protocol supported by the server.
The message-length field specifies the length of the message,
including the start-line.
Details about the mrcp-version and message-length fields are given in
Section 5.1.
The request-id used in the response MUST match the one sent in the
corresponding request message.
The status-code field is a 3-digit code representing the success or
failure or other status of the request.
status-code = 3DIGIT
The request-state field indicates if the action initiated by the
Request is PENDING, IN-PROGRESS or COMPLETE. The COMPLETE status
means that the Request was processed to completion and that there
will be no more events or other messages from that resource to the
client with that request-id. The PENDING status means that the
request has been placed on a queue and will be processed in first-in-
first-out order. The IN-PROGRESS status means that the request is
being processed and is not yet complete. A PENDING or IN-PROGRESS
status indicates that further Event messages may be delivered with
that request-id.
request-state = "COMPLETE"
/ "IN-PROGRESS"
/ "PENDING"
5.4. Status Codes
The status codes are classified under the Success (2XX) codes, Client
Failure (4XX) codes, and Server Failure (5XX).
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Success Codes
+------------+--------------------------------------------------+
| Code | Meaning |
+------------+--------------------------------------------------+
| 200 | Success |
| 201 | Success with some optional header fields ignored |
+------------+--------------------------------------------------+
Success 2xx
Client Failure 4xx Codes
+------------+------------------------------------------------------+
| Code | Meaning |
+------------+------------------------------------------------------+
| 401 | Method not allowed |
| 402 | Method not valid in this state |
| 403 | Unsupported header field |
| 404 | Illegal value for header field. This is the error |
| | for a syntax violation. |
| 405 | Resource not allocated for this session or does not |
| | exist |
| 406 | Mandatory Header Field Missing |
| 407 | Method or Operation Failed (e.g., Grammar |
| | compilation failed in the recognizer. Detailed |
| | cause codes MAY BE available through a resource |
| | specific header.) |
| 408 | Unrecognized or unsupported message entity |
| 409 | Unsupported Header Field Value. This is a value |
| | that is syntactically legal but exceeds the |
| | implementation's capabilities or expectations. |
| 410 | Non-Monotonic or Out of order sequence number in |
| | request. |
| 411-420 | Reserved for future assignment |
+------------+------------------------------------------------------+
Client Failure 4xx
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Server Failure 5xx Codes
+------------+--------------------------------+
| Code | Meaning |
+------------+--------------------------------+
| 501 | Server Internal Error |
| 502 | Protocol Version not supported |
| 503 | Reserved for future assignment |
| 504 | Message too large |
+------------+--------------------------------+
Server Failure 4xx
5.5. Events
The server resource may need to communicate a change in state or the
occurrence of a certain event to the client. These messages are used
when a request does not complete immediately and the response returns
a status of PENDING or IN-PROGRESS. The intermediate results and
events of the request are indicated to the client through the event
message from the server. The event message consists of an event
header line followed by the message header section and an optional
message body containing data specific to the event message. The
header line has the request-id of the corresponding request and
status value. The request-state value is COMPLETE if the request is
done and this was the last event, else it is IN-PROGRESS.
event-line = mrcp-version SP message-length SP event-name
SP request-id SP request-state CRLF
The mrcp-version used here is identical to the one used in the
Request/Response Line and indicates the version of the MRCPv2
protocol running on the server.
The message-length field specifies the length of the message,
including the start-line.
Details about the mrcp-version and message-length fields are given in
Section 5.1.
The event-name identifies the nature of the event generated by the
media resource. The set of valid event names depends on the resource
generating it. See the corresponding resource-specific section of
the document.
event-name = synthesizer-event
/ recognizer-event
/ recorder-event
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/ verifier-event
The request-id used in the event MUST match the one sent in the
request that caused this event.
The request-state indicates whether the Request/Command causing this
event is complete or still in progress, and is the same as the one
mentioned in Section 5.3. The final event for a request has a
COMPLETE status indicating the completion of the request.
6. MRCPv2 Generic Methods, Headers, and Result Structure
MRCPv2 supports a set of methods and header fields that are common to
all resources. These are discussed here; resource-specific methods
and header fields are discussed in the corresponding resource-
specific section of the document.
6.1. Generic Methods
MRCPv2 supports two generic methods for reading and writing the state
associated with a resource.
generic-method = "SET-PARAMS"
/ "GET-PARAMS"
These are described in the following sub-sections.
6.1.1. SET-PARAMS
The "SET-PARAMS" method, from the client to the server, tells the
MRCPv2 resource to define parameters for the session, such as voice
characteristics and prosody on synthesizers, recognition timers on
recognizers, etc. If the server accepts and sets all parameters it
MUST return a Response-Status of 200. If it chooses to ignore some
optional header fields that can be safely ignored without affecting
operation of the server it MUST return 201.
If one or more of the header fields being sent is incorrect, error
403, 404, or 409 MUST be returned as follows:
o If one or more of the header fields being set has an illegal
value, the server MUST reject the request with a 404 Illegal Value
for Header Field.
o If one or more of the header fields being set is unsupported for
the resource, the server MUST reject the request with a 403
Unsupported Header Field, except as described in the next
paragraph.
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o If one or more of the header fields being set has an unsupported
value, the server MUST reject the request with a 409 Unsupported
Header Field Value, except as described in the next paragraph.
If both error 404 and another error have occurred, only error 404
MUST be returned. If both errors 403 and 409 have occurred, but not
error 404, only error 403 MUST be returned.
If error 403, 404, or 409 is returned, the response MUST include the
bad or unsupported header fields and their values exactly as they
were sent from the client. Session parameters modified using
"SET-PARAMS" do not override parameters explicitly specified on
individual requests or requests that are in-PROGRESS.
C->S: MRCP/2.0 ... SET-PARAMS 543256
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:female
Voice-variant:3
S->C: MRCP/2.0 ... 543256 200 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
6.1.2. GET-PARAMS
The "GET-PARAMS" method, from the client to the server, asks the
MRCPv2 resource for its current session parameters, such as voice
characteristics and prosody on synthesizers, recognition-timer on
recognizers, etc. For every header field the client sends in the
request without a value, the server MUST include the corresponding
header fields and their values in the response. If no parameter
header fields are specified by the client then the server MUST return
all the settable parameters and their values in the corresponding
header section of the response, including vendor-specific parameters.
Such wild-card parameter requests can be very processing-intensive,
since the number of settable parameters can be large depending on the
implementation. Hence, it is RECOMMENDED that the client not use the
wildcard "GET-PARAMS" operation very often. Note that "GET-PARAMS"
returns header field values that apply to the whole session and not
values that have a request level scope. For example, Input-Waveform-
URI is a request-level header field and thus would not be returned by
GET-PARAMS.
If all of the header fields requested are supported, the server MUST
return a Response-Status of 200. If some of the header fields being
retrieved are unsupported for the resource, the server MUST reject
the request with a 403 Unsupported Header Field. Such a response
MUST include the unsupported header fields exactly as they were sent
from the client, without values.
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C->S: MRCP/2.0 ... GET-PARAMS 543256
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:
Voice-variant:
Vendor-Specific-Parameters:com.example.param1;
com.example.param2
S->C: MRCP/2.0 ... 543256 200 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:female
Voice-variant:3
Vendor-Specific-Parameters:com.example.param1="Company Name";
com.example.param2="124324234@example.com"
6.2. Generic Message Headers
All MRCPv2 header fields, which include both the generic-headers
defined in the following sub-sections and the resource-specific
header fields defined later, follow the same generic format as that
given in Section 3.1 of RFC5322 [RFC5322]. Each header field
consists of a name followed by a colon (":") and the value. Header
field names are case-insensitive. The value MAY be preceded by any
amount of LWS, though a single SP is preferred. Header fields may
extend over multiple lines by preceding each extra line with at least
one SP or HT.
generic-field = field-name ":" [ field-value ]
field-name = token
field-value = *LWS field-content *( CRLF 1*LWS field-content)
field-content = <the OCTETs making up the field-value
and consisting of either *TEXT or combinations
of token, separators, and quoted-string>
The field-content does not include any leading or trailing LWS (i.e.
linear white space occurring before the first non-whitespace
character of the field-value or after the last non-whitespace
character of the field-value). Such leading or trailing LWS MAY be
removed without changing the semantics of the field value. Any LWS
that occurs between field-content MAY be replaced with a single SP
before interpreting the field value or forwarding the message
downstream.
MRCPv2 servers and clients MUST NOT depend on header field order. It
is "good practice" to send general-header fields first, followed by
request-header or response-header fields, and ending with the entity-
header fields. However, MRCPv2 servers and clients MUST be prepared
to process the header fields in any order. The only exception to
this rule is when there are multiple header fields with the same name
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in a message.
Multiple header fields with the same name MAY be present in a message
if and only if the entire value for that header field is defined as a
comma-separated list [i.e., #(values)].
Since vendor-specific parameters may be order-dependent, it MUST be
possible to combine multiple header fields of the same name into one
"name:value" pair without changing the semantics of the message, by
appending each subsequent value to the first, each separated by a
comma. The order in which header fields with the same name are
received is therefore significant to the interpretation of the
combined header field value, and thus an intermediary MUST NOT change
the order of these values when a message is forwarded.
generic-header = channel-identifier
/ accept
/ active-request-id-list
/ proxy-sync-id
/ accept-charset
/ content-type
/ content-id
/ content-base
/ content-encoding
/ content-location
/ content-length
/ fetch-timeout
/ cache-control
/ logging-tag
/ set-cookie
/ set-cookie2
/ vendor-specific
6.2.1. Channel-Identifier
All MRCPv2 requests, responses and events MUST contain the Channel-
Identifier header field. The value is allocated by the server when a
control channel is added to the session and communicated to the
client by the "a=channel" attribute in the SDP answer from the
server. The header field value consists of 2 parts separated by the
'@' symbol. The first part is an unambiguous string identifying the
MRCPv2 session. The second part is a string token which specifies
one of the media processing resource types listed in Section 3.1.
The unambiguous string (first part) MUST BE unique among the resource
instances managed by the server and is common to all resource
channels with that server established through a single SIP dialog.
channel-identifier = "Channel-Identifier" ":" channel-id CRLF
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channel-id = 1*alphanum "@" 1*alphanum
6.2.2. Accept
The Accept header field follows the syntax defined in [H14.1]. The
semantics are also identical, with the exception that if no Accept
header field is present, the server MUST assume a default value that
is specific to the resource type that is being controlled. This
default value can be changed for a resource on a session by sending
this header field in a SET-PARAMS method. The current default value
of this header field for a resource in a session can be found through
a GET-PARAMS method. This header field MAY occur on any request.
6.2.3. Active-Request-Id-List
In a request, this header field indicates the list of request-ids to
which the request applies. This is useful when there are multiple
requests that are PENDING or IN-PROGRESS and the client wants this
request to apply to one or more of these specifically.
In a response, this header field returns the list of request-ids that
the method modified or affected. There could be one or more requests
in a request-state of PENDING or IN-PROGRESS. When a method
affecting one or more PENDING or IN-PROGRESS requests is sent from
the client to the server, the response MUST contain the list of
request-ids that were affected or modified by this command in its
header section.
The active-request-id-list is only used in requests and responses,
not in events.
For example, if a "STOP" request with no active-request-id-list is
sent to a synthesizer resource which has one or more "SPEAK" requests
in the PENDING or IN-PROGRESS state, all "SPEAK" requests MUST be
cancelled, including the one IN-PROGRESS. The response to the "STOP"
request contains in the active-request-id-list the request-ids of all
the "SPEAK" requests that were terminated. After sending the STOP
response, the server MUST NOT send any SPEAK-COMPLETE or RECOGNITION-
COMPLETE events for the terminated requests.
active-request-id-list = "Active-Request-Id-List" ":"
request-id *("," request-id) CRLF
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6.2.4. Proxy-Sync-Id
When any server resource generates a barge-in-able event, it also
generates a unique tag. The tag is sent as this header field's value
in an event to the client. The client then acts as a intermediary
among the server resources and sends a BARGE-IN-OCCURRED method to
the synthesizer server resource with the Proxy-Sync-Id it received
from the server resource. When the recognizer and synthesizer
resources are part of the same session, they may choose to work
together to achieve quicker interaction and response. Here the
proxy-sync-id helps the resource receiving the event, intermediated
by the client, to decide if this event has been processed through a
direct interaction of the resources. This header field MAY occur
only on events and the BARGE-IN-OCCURRED method. The name of this
header field contains the word 'proxy' only for historical reasons
and does not imply that a proxy server is involved.
proxy-sync-id = "Proxy-Sync-Id" ":" 1*VCHAR CRLF
6.2.5. Accept-Charset
See [H14.2]. This specifies the acceptable character sets for
entities returned in the response or events associated with this
request. This is useful in specifying the character set to use in
the NLSML results of a "RECOGNITION-COMPLETE" event. This header
field is only used on requests.
6.2.6. Content-Type
See [H14.17]. MRCPv2 supports a restricted set of registered Media
Types for content, including speech markup, grammar, and recognition
results. The content types applicable to each MRCPv2 resource-type
are specified in the corresponding section of the document. The
multi-part content type "multi-part/mixed" is supported to
communicate multiple of the above mentioned contents, in which case
the body parts MUST NOT contain any MRCPv2 specific header fields.
This header field MAY occur on all messages.
6.2.7. Content-ID
This header field contains an ID or name for the content by which it
can be referenced. This header field operates according to the
specification in RFC2392 [RFC2392] and is required for content
disambiguation in multi-part messages. In MRCPv2 whenever the
associated content is stored, by either the client or the server, it
MUST be retrievable using this ID. Such content can be referenced
later in a session by addressing it with the "session:" URI scheme
described in Section 13.6. This header field MAY occur on all
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messages.
6.2.8. Content-Base
The content-base entity-header may be used to specify the base URI
for resolving relative URLs within the entity.
content-base = "Content-Base" ":" absoluteURI CRLF
Note, however, that the base URI of the contents within the entity-
body may be redefined within that entity-body. An example of this
would be multi-part media, which in turn can have multiple entities
within it. This header field MAY occur on all messages.
6.2.9. Content-Encoding
The content-encoding entity-header is used as a modifier to the
media-type. When present, its value indicates what additional
content encoding has been applied to the entity-body, and thus what
decoding mechanisms must be applied in order to obtain the media-type
referenced by the content-type header field. Content-encoding is
primarily used to allow a document to be compressed without losing
the identity of its underlying media type. Note that the SDP session
can be used to determine accepted encodings (see Section 7). This
header field MAY occur on all messages.
content-encoding = "Content-Encoding" ":"
*WSP content-coding
*(*WSP "," *WSP content-coding *WSP )
CRLF
Content-coding is defined in [H3.5]. An example of its use is
Content-Encoding:gzip
If multiple encodings have been applied to an entity, the content
encodings MUST be listed in the order in which they were applied.
6.2.10. Content-Location
The content-location entity-header MAY be used to supply the resource
location for the entity enclosed in the message when that entity is
accessible from a location separate from the requested resource's
URI. Refer to [H14.14].
content-location = "Content-Location" ":"
( absoluteURI / relativeURI ) CRLF
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The content-location value is a statement of the location of the
resource corresponding to this particular entity at the time of the
request. This header field is provided for optimization purposes
only. The receiver of this header field MAY assume that the entity
being sent is identical to what would have been retrieved or might
already have been retrieved from the content-location URI.
For example, if the client provided a grammar markup inline, and it
had previously retrieved it from a certain URI, that URI can be
provided as part of the entity, using the content-location header
field. This allows a resource like the recognizer to look into its
cache to see if this grammar was previously retrieved, compiled and
cached. In this case, it might optimize by using the previously
compiled grammar object.
If the content-location is a relative URI, the relative URI is
interpreted relative to the content-base URI. This header field MAY
occur on all messages.
6.2.11. Content-Length
This header field contains the length of the content of the message
body (i.e. after the double CRLF following the last header field).
Unlike HTTP, it MUST be included in all messages that carry content
beyond the header section. If it is missing, a default value of zero
is assumed. Otherwise, it is interpreted according to [H14.13].
When a message having no use for a message body contains one, i.e.
the Content-Length is non-zero, the receiver MUST ignore the content
of the message body. This header field MAY occur on all messages.
content-length = "Content-Length" ":" 1*19DIGIT CRLF
6.2.12. Fetch Timeout
When the recognizer or synthesizer needs to fetch documents or other
resources this header field controls the corresponding URI access
properties. This defines the timeout for content that the server may
need to fetch over the network. The value is interpreted to be in
milliseconds and ranges from 0 to an implementation-specific maximum
value. The default value for this header field is implementation-
specific. This header field MAY occur in "DEFINE-GRAMMAR",
"RECOGNIZE", "SPEAK", "SET-PARAMS" or "GET-PARAMS".
fetch-timeout = "Fetch-Timeout" ":" 1*19DIGIT CRLF
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6.2.13. Cache-Control
If the server implements content caching, it MUST adhere to the cache
correctness rules of HTTP 1.1 [RFC2616] when accessing and caching
stored content. In particular, the "expires" and "cache-control"
header fields of the cached URI or document MUST be honored and take
precedence over the Cache-Control defaults set by this header field.
The cache-control directives are used to define the default caching
algorithms on the server for the session or request. The scope of
the directive is based on the method it is sent on. If the
directives are sent on a "SET-PARAMS" method, it applies for all
requests for external documents the server makes during that session,
unless overridden by a cache-control header field on an individual
request. If the directives are sent on any other requests they apply
only to external document requests the server makes for that request.
An empty cache-control header field on the "GET-PARAMS" method is a
request for the server to return the current cache-control directives
setting on the server. This header field MAY occur only on requests.
cache-control = "Cache-Control" ":"
[*WSP cache-directive
*( *WSP "," *WSP cache-directive *WSP )]
CRLF
cache-directive = "max-age" "=" delta-seconds
/ "max-stale" [ "=" delta-seconds ]
/ "min-fresh" "=" delta-seconds
delta-seconds = 1*19DIGIT
Here delta-seconds is a decimal time value specifying the number of
seconds since the instant the message response or data was received
by the server.
The cache-directives allow the client to ask the server to override
the default cache expiration mechanisms.
max-age Indicates that the client can tolerate the server
using content whose age is no greater than the
specified time in seconds. Unless a max-stale
directive is also included, the client is not willing
to accept a response based on stale data.
min-fresh Indicates that the client is willing to accept a
server response with cached data whose expiration is
no less than its current age plus the specified time
in seconds. If the server's cache time to live
exceeds the client-supplied min-fresh value, the
server MUST NOT utilize cached content.
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max-stale Indicates that the client is willing to allow a server
to utilize cached data that has exceeded its
expiration time. If max-stale is assigned a value,
then the client is willing to allow the server to use
cached data that has exceeded its expiration time by
no more than the specified number of seconds. If no
value is assigned to max-stale, then the client is
willing to allow the server to use stale data of any
age.
The server cache MAY be requested to use stale response/data without
validation, but only if this does not conflict with any "MUST"-level
requirements concerning cache validation (e.g., a "must-revalidate"
cache-control directive in the HTTP 1.1 specification pertaining to
the corresponding URI).
If both the MRCPv2 cache-control directive and the cached entry on
the server include "max-age" directives, then the lesser of the two
values is used for determining the freshness of the cached entry for
that request.
6.2.14. Logging-Tag
This header field MAY be sent as part of a "SET-PARAMS"/"GET-PARAMS"
method to set or retrieve the logging tag for logs generated by the
server. Once set, the value persists until a new value is set or the
session ends. The MRCPv2 server MAY provide a mechanism to subset
its output logs so that system administrators can examine or extract
only the log file portion during which the logging tag was set to a
certain value.
It is RECOMMENDED that clients have some identifying information in
the logging tag, so that one can determine which client request
generated a given log message at the server.
logging-tag = "Logging-Tag" ":" 1*UTFCHAR CRLF
6.2.15. Set-Cookie and Set-Cookie2
Since the associated HTTP client on an MRCPv2 server fetches
documents for processing on behalf of the MRCPv2 client, the cookie
store in the HTTP client of the MRCPv2 server is treated as an
extension of the cookie store in the HTTP client of the MRCPv2
client. This requires that the MRCPv2 client and server be able to
synchronize their common cookie store as needed. To enable the
MRCPv2 client to push its stored cookies to the MRCPv2 server and get
new cookies from the MRCPv2 server stored back to the MRCPv2 client,
the set-cookie and set-cookie2 entity-header fields MAY be included
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in MRCPv2 requests to update the cookie store on a server and be
returned in final MRCPv2 responses or events to subsequently update
the client's own cookie store. The stored cookies on the server
persist for the duration of the MRCPv2 session and MUST be destroyed
at the end of the session. To ensure support for the type of cookie
header field dictated by the HTTP origin server, MRCPv2 clients and
servers MUST support both the set-cookie and set-cookie2 entity
header fields.
set-cookie = "Set-Cookie:" cookies CRLF
cookies = cookie *("," *LWS cookie)
cookie = attribute "=" value *(";" cookie-av)
cookie-av = "Comment" "=" value
/ "Domain" "=" value
/ "Max-Age" "=" value
/ "Path" "=" value
/ "Secure"
/ "Version" "=" 1*19DIGIT
/ "Age" "=" delta-seconds
set-cookie2 = "Set-Cookie2:" cookies2 CRLF
cookies2 = cookie2 *("," *LWS cookie2)
cookie2 = attribute "=" value *(";" cookie-av2)
cookie-av2 = "Comment" "=" value
/ "CommentURL" "=" DQUOTE uri DQUOTE
/ "Discard"
/ "Domain" "=" value
/ "Max-Age" "=" value
/ "Path" "=" value
/ "Port" [ "=" DQUOTE portlist DQUOTE ]
/ "Secure"
/ "Version" "=" 1*19DIGIT
/ "Age" "=" delta-seconds
portlist = portnum *("," *LWS portnum)
portnum = 1*19DIGIT
The set-cookie and set-cookie2 header fields are specified in RFC2109
[RFC2109] and RFC2965 [RFC2965], respectively. The "Age" attribute
is introduced in this specification to indicate the age of the cookie
and is optional. An MRCPv2 client or server MUST calculate the age
of the cookie according to the age calculation rules in the HTTP/1.1
specification [RFC2616] and append the "Age" attribute accordingly.
The MRCPv2 client or server MUST supply defaults for the Domain and
Path attributes if omitted by the HTTP origin server as specified in
RFC2109 (set-cookie) and RFC2965 (set-cookie2). Note that there is
no leading dot present in the Domain attribute value in this case.
Although an explicitly specified Domain value received via the HTTP
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protocol may be modified to include a leading dot, an MRCPv2 client
or server MUST NOT modify the Domain value when received via the
MRCPv2 protocol.
An MRCPv2 client or server MAY combine multiple cookie header fields
of the same type into a single "field-name:field-value" pair as
described in Section 6.2.
The set-cookie and set-cookie2 header fields MAY be specified in any
request that subsequently results in the server performing an HTTP
access. When a server receives new cookie information from an HTTP
origin server, and assuming the cookie store is modified according
RFC2109 or RFC2965, the server MUST return the new cookie information
in the MRCPv2 COMPLETE response or event as appropriate to allow the
client to update its own cookie store.
The "SET-PARAMS" request MAY specify the set-cookie and set-cookie2
header fields to update the cookie store on a server. The GET-PARAMS
request MAY be used to return the entire cookie store of "Set-Cookie"
or "Set-Cookie2" type cookies to the client.
6.2.16. Vendor Specific Parameters
This set of header fields allows for the client to set or retrieve
Vendor Specific parameters.
vendor-specific = "Vendor-Specific-Parameters" ":"
[vendor-specific-av-pair
*(";" vendor-specific-av-pair)] CRLF
vendor-specific-av-pair = vendor-av-pair-name "="
value
vendor-av-pair-name = 1*UTFCHAR
header fields of this form MAY be sent in any method (request) and
are used to manage implementation-specific parameters on the server
side. The vendor-av-pair-name follows the reverse Internet Domain
Name convention (see Section 13.1.6 for syntax and registration
information). The value of the vendor attribute is specified after
the "=" symbol and MAY be quoted. For example:
com.example.companyA.paramxyz=256
com.example.companyA.paramabc=High
com.example.companyB.paramxyz=Low
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When used in GET-PARAMS to get the current value of these parameters
from the server, this header field value may contain a semicolon-
separated list of implementation-specific attribute names.
6.3. Generic Result Structure
Result data from the server for the Recognizer and Verifier resources
is carried as a typed media entity in the MRCPv2 message body of
various events. The Natural Language Semantics Markup Language
(NLSML), an XML markup based on an early draft from the W3C, is the
default standard for returning results back to the client. Hence,
all servers implementing these resource types MUST support the Media
Type application/nlsml+xml. The Extensible MultiModal Annotation
[W3C.REC-emma-20090210] format can be used to return results as well.
This can be done by negotiating the format at session establishment
time with SDP (a=resultformat:application/emma+xml) or with SIP
(Allow/Accept). With SIP, for example, if a client wants results in
EMMA, an MRCPv2 server can route the request to another server that
supports EMMA by inspecting the SIP header fields, rather than having
to introspect into the SDP.
MRCPv2 uses this representation to convey content among the clients
and servers that generate and make use of the markup. MRCPv2 uses
NSLML specifically to convey recognition, enrollment, and
verification results between the corresponding resource on the MRCPv2
server and the MRCPv2 client. Details of this result format are
fully described in Section 6.3.1.
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="http://theYesNoGrammar">
<interpretation>
<instance>
<ex:response>yes</ex:response>
</instance>
<input>ok</input>
</interpretation>
</result>
Result Example
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6.3.1. Natural Language Semantics Markup Language
The Natural Language Semantics Markup Language (NLSML) is an XML data
structure with elements and attributes designed to carry result
information from recognizer (including enrollment) and verifier
resources. The normative definition of NLSML is the RelaxNG schema
in Section 16.1. Note that the elements and attributes of this
format are defined in the MRCPv2 namespace. In the result structure,
they must either be prefixed by a namespace prefix declared within
the result or must be children of an element identified as belonging
to the respective namespace. For details on how to use XML
Namespaces, see [W3C.REC-xml-names11-20040204]. Section 2 of
[W3C.REC-xml-names11-20040204] provides details on how to declare
namespaces and namespace prefixes.
The root element of NLSML is <result>. Optional child elements are
<interpretation>, <enrollment-result>, and <verification-result>, at
least one of which must be present. A single <result> may contain
all of the optional child elements. Details of the <result> and
<interpretation> elements and their subelements and attributes can be
found in Section 9.6. Details of the <enrollment-result> element and
its subelements can be found in Section 9.7. Details of the
<verification-result> element and its subelements can be found in
Section 11.5.2.
7. Resource Discovery
Server resources may be discovered and their capabilities learned by
clients through standard SIP machinery. The client can issue a SIP
OPTIONS transaction to a server, which has the effect of requesting
the capabilities of the server. The server MUST respond to such a
request with an SDP-encoded description of its capabilities according
to RFC3264 [RFC3264]. The MRCPv2 capabilities are described by a
single m-line containing the media type "application" and transport
type "TCP/TLS/MRCPv2" or "TCP/MRCPv2". There MUST be one "resource"
attribute for each media resource that the server supports with the
resource type identifier as its value.
The SDP description MUST also contain m-lines describing the audio
capabilities and the coders the server supports.
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In this example, the client uses the SIP OPTIONS method to query the
capabilities of the MRCPv2 server.
C->S:
OPTIONS sip:mrcp@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf7
Max-Forwards:6
To:<sip:mrcp@example.com>
From:Sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:63104 OPTIONS
Contact:<sip:sarvi@client.example.com>
Accept:application/sdp
Content-Length:0
S->C:
SIP/2.0 200 OK
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bf7;received=192.0.32.10
To:<sip:mrcp@example.com>;tag=62784
From:Sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:63104 OPTIONS
Contact:<sip:mrcp@server.example.com>
Allow:INVITE, ACK, CANCEL, OPTIONS, BYE
Accept:application/sdp
Accept-Encoding:gzip
Accept-Language:en
Supported:foo
Content-Type:application/sdp
Content-Length:...
v=0
o=sarvi 2890844536 2890842811 IN IP4 192.0.2.4
s=-
i=MRCPv2 server capabilities
c=IN IP4 192.0.2.12/127
m=application 0 TCP/TLS/MRCPv2 1
a=resource:speechsynth
a=resource:speechrecog
a=resource:speakverify
m=audio 0 RTP/AVP 0 3
a=rtpmap:0 PCMU/8000
a=rtpmap:3 GSM/8000
Using SIP OPTIONS for MRCPv2 Server Capability Discovery
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8. Speech Synthesizer Resource
This resource processes text markup provided by the client and
generates a stream of synthesized speech in real-time. Depending
upon the server implementation and capability of this resource, the
client can also dictate parameters of the synthesized speech such as
voice characteristics, speaker speed, etc.
The synthesizer resource is controlled by MRCPv2 requests from the
client. Similarly, the resource can respond to these requests or
generate asynchronous events to the client to indicate conditions of
interest to the client during the generation of the synthesized
speech stream.
This section applies for the following resource types:
speechsynth
basicsynth
The capabilities of these resources are defined in Section 3.1.
8.1. Synthesizer State Machine
The synthesizer maintains a state machine to process MRCPv2 requests
from the client. The state transitions shown below describe the
states of the synthesizer and reflect the state of the request at the
head of the synthesizer resource queue. A "SPEAK" request in the
PENDING state can be deleted or stopped by a "STOP" request without
affecting the state of the resource.
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Idle Speaking Paused
State State State
| | |
|----------SPEAK-------->| |--------|
|<------STOP-------------| CONTROL |
|<----SPEAK-COMPLETE-----| |------->|
|<----BARGE-IN-OCCURRED--| |
| |---------| |
| CONTROL |-----------PAUSE--------->|
| |-------->|<----------RESUME---------|
| | |----------|
|----------| | PAUSE |
| BARGE-IN-OCCURRED | |--------->|
|<---------| |----------| |
| | SPEECH-MARKER |
| |<---------| |
|----------| |----------| |
| STOP | RESUME |
| | |<---------| |
|<---------| | |
|<---------------------STOP-------------------------|
|----------| | |
| DEFINE-LEXICON | |
| | | |
|<---------| | |
|<---------------BARGE-IN-OCCURRED------------------|
Synthesizer State Machine
8.2. Synthesizer Methods
The synthesizer supports the following methods.
synthesizer-method = "SPEAK"
/ "STOP"
/ "PAUSE"
/ "RESUME"
/ "BARGE-IN-OCCURRED"
/ "CONTROL"
/ "DEFINE-LEXICON"
8.3. Synthesizer Events
The synthesizer may generate the following events.
synthesizer-event = "SPEECH-MARKER"
/ "SPEAK-COMPLETE"
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8.4. Synthesizer Header Fields
A synthesizer method may contain header fields containing request
options and information to augment the Request, Response or Event it
is associated with.
synthesizer-header = jump-size
/ kill-on-barge-in
/ speaker-profile
/ completion-cause
/ completion-reason
/ voice-parameter
/ prosody-parameter
/ speech-marker
/ speech-language
/ fetch-hint
/ audio-fetch-hint
/ failed-uri
/ failed-uri-cause
/ speak-restart
/ speak-length
/ load-lexicon
/ lexicon-search-order
8.4.1. Jump-Size
This header field MAY be specified in a CONTROL method and controls
the amount to jump forward or backward in an active "SPEAK" request.
A + or - indicates a relative value to what is being currently
played. This header field MAY also be specified in a "SPEAK" request
as a desired offset into the synthesized speech. In this case, the
synthesizer MUST begin speaking from this amount of time into the
speech markup. Note that an offset that extends beyond the end of
the produced speech will result in audio of length zero. The
different speech length units supported are dependent on the
synthesizer implementation. If the synthesizer resource does not
support a unit or the operation, the resource MUST respond with a
status code of 409 "Unsupported Header Field Value".
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jump-size = "Jump-Size" ":" speech-length-value CRLF
speech-length-value = numeric-speech-length
/ text-speech-length
text-speech-length = 1*UTFCHAR SP "Tag"
numeric-speech-length = ("+" / "-") positive-speech-length
positive-speech-length = 1*19DIGIT SP numeric-speech-unit
numeric-speech-unit = "Second"
/ "Word"
/ "Sentence"
/ "Paragraph"
8.4.2. Kill-On-Barge-In
This header field MAY be sent as part of the "SPEAK" method to enable
kill-on-barge-in support. If enabled, the "SPEAK" method is
interrupted by DTMF input detected by a signal detector resource or
by the start of speech sensed or recognized by the speech recognizer
resource.
kill-on-barge-in = "Kill-On-Barge-In" ":" BOOLEAN CRLF
The client MUST send a BARGE-IN-OCCURRED method to the synthesizer
resource when it receives a barge-in-able event from any source.
This source could be a synthesizer resource or signal detector
resource and MAY be either local or distributed. If this header
field is not specified in a "SPEAK" request or explicitly set by a
"SET-PARAMS", the default value for this header field is "true".
If the recognizer or signal detector resource is on the same server
as the synthesizer and both are part of the same session, the server
MAY work with both to provide internal notification to the
synthesizer so that audio may be stopped without having to wait for
the client's BARGE-IN-OCCURRED event.
8.4.3. Speaker Profile
This header field MAY be part of the "SET-PARAMS"/"GET-PARAMS" or
"SPEAK" request from the client to the server and specifies a URI
which references the profile of the speaker. Speaker profiles are
collections of voice parameters like gender, accent etc.
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speaker-profile = "Speaker-Profile" ":" uri CRLF
8.4.4. Completion Cause
This header field MUST be specified in a "SPEAK-COMPLETE" event
coming from the synthesizer resource to the client. This indicates
the reason the "SPEAK" request completed.
completion-cause = "Completion-Cause" ":" 3DIGIT SP
1*VCHAR CRLF
+------------+-----------------------+------------------------------+
| Cause-Code | Cause-Name | Description |
+------------+-----------------------+------------------------------+
| 000 | normal | SPEAK completed normally. |
| 001 | barge-in | SPEAK request was terminated |
| | | because of barge-in. |
| 002 | parse-failure | SPEAK request terminated |
| | | because of a failure to |
| | | parse the speech markup |
| | | text. |
| 003 | uri-failure | SPEAK request terminated |
| | | because access to one of the |
| | | URIs failed. |
| 004 | error | SPEAK request terminated |
| | | prematurely due to |
| | | synthesizer error. |
| 005 | language-unsupported | Language not supported. |
| 006 | lexicon-load-failure | Lexicon loading failed. |
| 007 | cancelled | A prior SPEAK request failed |
| | | while this one was still in |
| | | the queue. |
+------------+-----------------------+------------------------------+
Synthesizer Resource Compleion Cause Codes
8.4.5. Completion Reason
This header field MAY be specified in a "SPEAK-COMPLETE" event coming
from the synthesizer resource to the client. This contains the
reason text behind the "SPEAK" request completion. This header field
communicates text describing the reason for the failure, such as an
error in parsing the speech markup text.
completion-reason = "Completion-Reason" ":"
quoted-string CRLF
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The completion reason text is provided for client use in logs and for
debugging and instrumentation purposes. Clients MUST NOT interpret
the completion reason text.
8.4.6. Voice-Parameter
This set of header fields defines the voice of the speaker.
voice-parameter = voice-gender
/ voice-age
/ voice-variant
/ voice-name
voice-gender = "Voice-Gender:" voice-gender-value CRLF
voice-gender-value = "male"
/ "female"
/ "neutral"
voice-age = "Voice-Age:" 1*3DIGIT CRLF
voice-variant = "Voice-Variant:" 1*19DIGIT CRLF
voice-name = "Voice-Name:"
1*UTFCHAR *(1*WSP 1*UTFCHAR) CRLF
The Voice- parameters are derived from the similarly-named attributes
of the voice element specified in W3C's Speech Synthesis Markup
Language Specification [W3C.REC-speech-synthesis-20040907]. Legal
values for these parameters are as defined in that specification.
These header fields MAY be sent in "SET-PARAMS"/"GET-PARAMS" request
to define/get default values for the entire session or MAY be sent in
the "SPEAK" request to define default values for that speak request.
Note that SSML content can itself set these values internal to the
SSML document, of course.
Voice parameter header fields MAY also be sent in a CONTROL method to
affect a "SPEAK" request in progress and change its behavior on the
fly. If the synthesizer resource does not support this operation, it
MUST reject the request with a status of 403 "Unsupported Header
Field".
8.4.7. Prosody-Parameters
This set of header fields defines the prosody of the speech.
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prosody-parameter = "Prosody-" prosody-param-name ":"
prosody-param-value CRLF
prosody-param-name = 1*VCHAR
prosody-param-value = 1*VCHAR
prosody-param-name is any one of the attribute names under the
prosody element specified in W3C's Speech Synthesis Markup Language
Specification [W3C.REC-speech-synthesis-20040907]. The prosody-
param-value is any one of the value choices of the corresponding
prosody element attribute specified in the above section.
These header fields MAY be sent in "SET-PARAMS"/"GET-PARAMS" request
to define/get default values for the entire session or MAY be sent in
the "SPEAK" request to define default values for that speak request.
Furthermore, these attributes can be part of the speech text marked
up in SSML.
The prosody parameter header fields in the "SET-PARAMS" or "SPEAK"
request only apply if the speech data is of type text/plain and does
not use a speech markup format.
These prosody parameter header fields MAY also be sent in a CONTROL
method to affect a "SPEAK" request in progress and change its
behavior on the fly. If the synthesizer resource does not support
this operation, it MUST respond back to the client with a status of
403 "Unsupported Header Field".
8.4.8. Speech Marker
This header field contains timestamp information in a "timestamp"
field. This is an NTP timestamp, a 64 bit number in decimal form.
It MUST be synced with the RTP timestamp of the media stream through
RTCP.
Markers are bookmarks that are defined within the markup. Most
speech markup formats provide mechanisms to embed marker fields
within speech texts. The synthesizer generates SPEECH-MARKER events
when it reaches these marker fields. This header field MUST be part
of the SPEECH-MARKER event and contain the marker tag value after the
timestamp, separated by a semicolon. In these events the timestamp
marks the time the text corresponding to the marker was emitted as
speech by the synthesizer.
This header field MUST also be returned in responses to STOP,
CONTROL, and BARGE-IN-OCCURRED methods, in the "SPEAK-COMPLETE"
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event, and in an IN-PROGRESS SPEAK response. In these messages, if
any markers have been encountered for the current SPEAK, the marker
tag value MUST be the last embedded marker encountered. If no
markers have yet been encountered for the current SPEAK, only the
timestamp is REQUIRED. Note than in these events the purpose of this
header field is to provide timestamp information associated with
important events within the lifecycle of a request (start of SPEAK
processing, end of SPEAK processing, receipt of CONTROL/STOP/
BARGE-IN-OCCURRED).
timestamp = "timestamp" "=" time-stamp-value
time-stamp-value = 1*20DIGIT
speech-marker = "Speech-Marker" ":"
timestamp
[";" 1*(UTFCHAR / %x20)] CRLF
8.4.9. Speech Language
This header field specifies the default language of the speech data
if the language is not specified in the markup. The value of this
header field MUST follow RFC4646 [RFC4646] for its values. The
header field MAY occur in "SPEAK", "SET-PARAMS" or "GET-PARAMS"
requests.
speech-language = "Speech-Language" ":" 1*VCHAR CRLF
8.4.10. Fetch Hint
When the synthesizer needs to fetch documents or other resources like
speech markup or audio files, this header field controls the
corresponding URI access properties. This provides client policy on
when the synthesizer should retrieve content from the server. A
value of "prefetch" indicates the content MAY be downloaded when the
request is received, whereas "safe" indicates that content MUST NOT
be downloaded until actually referenced. The default value is
"prefetch". This header field MAY occur in "SPEAK", "SET-PARAMS" or
"GET-PARAMS" requests.
fetch-hint = "Fetch-Hint" ":" ("prefetch" / "safe") CRLF
8.4.11. Audio Fetch Hint
When the synthesizer needs to fetch documents or other resources like
speech audio files, this header field controls the corresponding URI
access properties. This provides client policy whether or not the
synthesizer may attempt to optimize speech by pre-fetching audio.
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The value is either "safe" to say that audio is only fetched when it
is referenced, never before; "prefetch" to permit, but not require
the implementation to pre-fetch the audio; or "stream" to allow it to
stream the audio fetches. The default value is "prefetch". This
header field MAY occur in "SPEAK", "SET-PARAMS" or "GET-PARAMS".
requests.
audio-fetch-hint = "Audio-Fetch-Hint" ":"
("prefetch" / "safe" / "stream") CRLF
8.4.12. Failed URI
When a synthesizer method needs a synthesizer to fetch or access a
URI and the access fails, the server SHOULD provide the failed URI in
this header field in the method response, unless there are multiple
URI failures, in which case one of the failed URIs MUST be provided
in this header field in the method response.
failed-uri = "Failed-URI" ":" absoluteURI CRLF
8.4.13. Failed URI Cause
When a synthesizer method needs a synthesizer to fetch or access a
URI and the access fails the server MUST provide the URI-specific or
protocol-specific response code for the URI in the Failed-URI header
field in the method response through this header field. The value
encoding is UTF-8 to accommodate any access protocol, some of which
might have a response string instead of a numeric response code.
failed-uri-cause = "Failed-URI-Cause" ":" 1*UTFCHAR CRLF
8.4.14. Speak Restart
When a CONTROL request to jump backward is issued to a currently
speaking synthesizer resource, and the target jump point is before
the start of the current "SPEAK" request, the current "SPEAK" request
MUST restart from the beginning of its speech data and the response
to the CONTROL request MUST contain this header field with a value of
"true" indicating a restart.
speak-restart = "Speak-Restart" ":" BOOLEAN CRLF
8.4.15. Speak Length
This header field MAY be specified in a CONTROL method to control the
length of speech to speak, relative to the current speaking point in
the currently active "SPEAK" request. If numeric, the value MUST be
a positive integer. If a header field with a Tag unit is specified,
then the speech output continues until the tag is reached or the
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"SPEAK" request complete, whichever comes first. This header field
MAY be specified in a "SPEAK" request to indicate the length to speak
from the speech data and is relative to the point in speech that the
"SPEAK" request starts. The different speech length units supported
are synthesizer implementation dependent. If a server does not
support the specified unit, the resource MUST respond with a status
code of 409 "Unsupported Header Field Value".
speak-length = "Speak-Length" ":" positive-length-value
CRLF
positive-length-value = positive-speech-length
/ text-speech-length
text-speech-length = 1*UTFCHAR SP "Tag"
positive-speech-length = 1*19DIGIT SP numeric-speech-unit
numeric-speech-unit = "Second"
/ "Word"
/ "Sentence"
/ "Paragraph"
8.4.16. Load-Lexicon
This header field is used to indicate whether a lexicon has to be
loaded or unloaded. The default value for this header field is
"true". This header field MAY be specified in a DEFINE-LEXICON
method.
load-lexicon = "Load-Lexicon" ":" BOOLEAN CRLF
8.4.17. Lexicon-Search-Order
This header field is used to specify a list of active Lexicon URIs
and the search order among the active lexicons. Lexicons specified
within the SSML document take precedence over the lexicons specified
in this header field. This header field MAY be specified in the
SPEAK, SET-PARAMS, and GET-PARAMS methods.
lexicon-search-order = "Lexicon-Search-Order" ":"
"<" absoluteURI ">" *(" " "<" absoluteURI ">") CRLF
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8.5. Synthesizer Message Body
A synthesizer message may contain additional information associated
with the Request, Response or Event in its message body.
8.5.1. Synthesizer Speech Data
Marked-up text for the synthesizer to speak is specified as a typed
media entity in the message body. The speech data to be spoken by
the synthesizer can be specified inline by embedding the data in the
message body or by reference by providing a URI for accessing the
data. In either case the data and the format used to markup the
speech needs to be of a content type supported by the server.
All MRCPv2 servers containing synthesizer resources MUST support both
plain text speech data and W3C's Speech Synthesis Markup Language
[W3C.REC-speech-synthesis-20040907] and hence MUST support the Media
Types text/plain and application/ssml+xml. Other formats MAY be
supported.
If the speech data is to be fetched by URI reference, the Media Type
text/uri-list RFC2483 [RFC2483] is used to indicate one or more URIs
that, when dereferenced, will contain the content to be spoken. If a
list of speech URIs is specified, speech data provided by each URI
MUST be spoken in the order in which the URIs are specified in the
content.
A mix of URI and inline speech data may be indicated through the
multipart/mixed Media Type. Embedded within the multipart there MAY
be content for the text/uri-list, application/ssml+xml and/or text/
plain media types. The character set and encoding used in the speech
data is specified according to standard Media Type definitions. The
multi-part content MAY also contain actual audio data. Clients may
have recorded audio clips stored in memory or on a local device and
wish to play it as part of the "SPEAK" request. The audio portions
MAY be sent by the client as part of the multi-part content block.
This audio is referenced in the speech markup data that is another
part in the multi-part content block according to the multipart/mixed
Media Type specification.
Content-Type:text/uri-list
Content-Length:...
http://www.example.com/ASR-Introduction.ssml
http://www.example.com/ASR-Document-Part1.ssml
http://www.example.com/ASR-Document-Part2.ssml
http://www.example.com/ASR-Conclusion.ssml
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URI List Example
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams
and arrived at <break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<s>The subject is <prosody
rate="-20%">ski trip</prosody></s>
</p>
</speak>
SSML Example
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Content-Type:multipart/mixed; boundary="break"
--break
Content-Type:text/uri-list
Content-Length:...
http://www.example.com/ASR-Introduction.ssml
http://www.example.com/ASR-Document-Part1.ssml
http://www.example.com/ASR-Document-Part2.ssml
http://www.example.com/ASR-Conclusion.ssml
--break
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams
and arrived at <break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<s>The subject is <prosody
rate="-20%">ski trip</prosody></s>
</p>
</speak>
--break--
Multipart Example
8.5.2. Lexicon Data
Synthesizer lexicon data from the client to the server can be
provided inline or by reference. Either way they are carried as
typed media in the message body of the MRCPv2 request message (see
Section 8.14).
When a lexicon is specified in-line in the message, the client MUST
provide a Content-ID for that lexicon as part of the content header
fields. The server MUST store the lexicon associated with that
Content-ID for the duration of the session. A stored lexicon can be
overwritten by defining a new lexicon with the same Content-ID.
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Lexicons that have been associated with a Content-ID can be
referenced through the "session:" URI scheme (see Section 13.6).
If lexicon data is specified by external URI reference, the Media
Type text/uri-list RFC2483 [RFC2483] is used to list the one or more
URIs that may be dereferenced to obtain the lexicon data. All MRCPv2
servers MUST support the HTTP and HTTPS uri access mechanisms, and
MAY support other mechanisms.
If the data in the message body consists of a mix of URI and inline
lexicon data the multipart/mixed Media Type is used. The character
set and encoding used in the lexicon data may be specified according
to standard Media Type definitions.
8.6. SPEAK Method
The "SPEAK" Request provides the synthesizer resource with the speech
text and initiates speech synthesis and streaming. The "SPEAK"
method can carry voice and prosody header fields that alter the
behavior of the voice being synthesized, as well as a typed media
message body containing the actual marked-up text to be spoken.
The SPEAK method implementation MUST do a fetch of all external URIs
that are part of that operation. If caching is implemented, this URI
fetching MUST conform to the cache control hints and parameter header
fields associated with the method in deciding whether it is to be
fetched from cache or from the external server. If these hints/
parameters are not specified in the method, the values set for the
session using SET-PARAMS/GET-PARAMS apply. If it was not set for the
session their default values apply.
When applying voice parameters there are 3 levels of precedence. The
highest precedence are those specified within the speech markup text,
followed by those specified in the header fields of the "SPEAK"
request and hence apply for that "SPEAK" request only, followed by
the session default values which can be set using the "SET-PARAMS"
request and apply for subsequent methods invoked during the session.
If the resource was idle at the time the "SPEAK" request arrived at
the server and the "SPEAK" method is being actively processed, the
resource responds immediately with a success status code and a
request-state of IN-PROGRESS.
If the resource is in the speaking or paused state when the "SPEAK"
method arrives at the server, i.e. it is in the middle of processing
a previous "SPEAK" request, the status returns success with a
request-state of PENDING. The server places the "SPEAK" request in
the synthesizer resource request queue. The request queue operates
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strictly FIFO: requests are processed serially in order of receipt.
If the current SPEAK fails, all SPEAK methods in the pending queue
are cancelled and each generates a SPEAK-COMPLETE event with a
Completion-Cause of "cancelled".
For the synthesizer resource, "SPEAK" is the only method that can
return a request-state of IN-PROGRESS or PENDING. When the text has
been synthesized and played into the media stream, the resource
issues a "SPEAK-COMPLETE" event with the request-id of the "SPEAK"
request and a request-state of COMPLETE.
C->S: MRCP/2.0 ... SPEAK 543257
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:neutral
Voice-Age:25
Prosody-volume:medium
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams and arrived at
<break/>
<say-as interpret-as="vxml:time">0345p</say-as>.
</s>
<s>The subject is
<prosody rate="-20%">ski trip</prosody>
</s>
</p>
</speak>
S->C: MRCP/2.0 ... 543257 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@speechsynth
Speech-Marker:timestamp=857206027059
S->C: MRCP/2.0 ... SPEAK-COMPLETE 543257 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Completion-Cause:000 normal
Speech-Marker:timestamp=857206027059
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SPEAK Example
8.7. STOP
The "STOP" method from the client to the server tells the synthesizer
resource to stop speaking if it is speaking something.
The "STOP" request can be sent with an active-request-id-list header
field to stop the zero or more specific "SPEAK" requests that may be
in queue and return a response code of 200 (Success). If no active-
request-id-list header field is sent in the "STOP" request the server
terminates all outstanding "SPEAK" requests.
If a "STOP" request successfully terminated one or more PENDING or
IN-PROGRESS "SPEAK" requests, then the response MUST contain an
active-request-id-list header field enumerating the "SPEAK" request-
ids that were terminated. Otherwise there is no active-request-id-
list header field in the response. No "SPEAK-COMPLETE" events are
sent for such terminated requests.
If a "SPEAK" request that was IN-PROGRESS and speaking was stopped,
the next pending "SPEAK" request, if any, becomes IN-PROGRESS at the
resource and enters the speaking state.
If a "SPEAK" request that was IN-PROGRESS and paused was stopped, the
next pending "SPEAK" request, if any, becomes IN-PROGRESS and enters
the paused state.
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C->S: MRCP/2.0 ... SPEAK 543258
Channel-Identifier:32AECB23433802@speechsynth
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams and arrived at
<break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<s>The subject is
<prosody rate="-20%">ski trip</prosody></s>
</p>
</speak>
S->C: MRCP/2.0 ... 543258 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@speechsynth
Speech-Marker:timestamp=857206027059
C->S: MRCP/2.0 ... STOP 543259
Channel-Identifier:32AECB23433802@speechsynth
S->C: MRCP/2.0 ... 543259 200 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Active-Request-Id-List:543258
Speech-Marker:timestamp=857206039059
STOP Example
8.8. BARGE-IN-OCCURED
The BARGE-IN-OCCURRED method, when used with the synthesizer
resource, provides a client which has detected a barge-in-able event
a means to communicate the occurrence of the event to the synthesizer
resource.
This method is useful in two scenarios,
1. The client has detected DTMF digits in the input media or some
other barge-in-able event and wants to communicate that to the
synthesizer resource.
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2. The recognizer resource and the synthesizer resource are in
different servers. In this case the client acts as an
intermediary for the two servers. It receives an event from the
recognition resource and sends a BARGE-IN-OCCURRED request to the
synthesizer. In such cases, the BARGE-IN-OCCURRED method would
also have a proxy-sync-id header field received from the resource
generating the original event.
If a "SPEAK" request is active with kill-on-barge-in enabled (see
Section 8.4.2), and the BARGE-IN-OCCURRED event is received, the
synthesizer MUST immediately stop streaming out audio. It MUST also
terminate any speech requests queued behind the current active one,
irrespective of whether they have barge-in enabled or not. If a
barge-in-able "SPEAK" request was playing and it was terminated, the
response MUST contain the an active-request-list header field listing
the request-ids of all "SPEAK" requests that were terminated. The
server generates no "SPEAK-COMPLETE" events for these requests.
If there were no "SPEAK" requests terminated by the synthesizer
resource as a result of the BARGE-IN-OCCURRED method, the server
responds to the BARGE-IN-OCCURRED with a 200 success which MUST NOT
contain an active-request-id-list header field.
If the synthesizer and recognizer resources are part of the same
MRCPv2 session, they can be optimized for a quicker kill-on-barge-in
response if the recognizer and synthesizer interact directly. In
these cases, the client MUST still react to a START-OF-INPUT event
from the recognizer by invoking the BARGE-IN-OCCURRED method to the
synthesizer. The client MUST invoke the BARGE-IN-OCCURRED if it has
any outstanding requests to the synthesizer resource in either the
PENDING or IN-PROGRESS state.
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C->S: MRCP/2.0 ... SPEAK 543258
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:neutral
Voice-Age:25
Prosody-volume:medium
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams and arrived at
<break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<s>The subject is
<prosody rate="-20%">ski trip</prosody></s>
</p>
</speak>
S->C: MRCP/2.0 ... 543258 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@speechsynth
Speech-Marker:timestamp=857206027059
C->S: MRCP/2.0 ... BARGE-IN-OCCURRED 543259
Channel-Identifier:32AECB23433802@speechsynth
Proxy-Sync-Id:987654321
S->C:MRCP/2.0 ... 543259 200 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Active-Request-Id-List:543258
Speech-Marker:timestamp=857206039059
BARGE-IN-OCCURED Example
8.9. PAUSE
The PAUSE method from the client to the server tells the synthesizer
resource to pause speech output if it is speaking something. If a
PAUSE method is issued on a session when a "SPEAK" is not active the
server MUST respond with a status of 402 "Method not valid in this
state". If a PAUSE method is issued on a session when a "SPEAK" is
active and paused the server MUST respond with a status of 200
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"Success". If a "SPEAK" request was active the server MUST return an
active-request-id-list header field with the request-id of the
"SPEAK" request that was paused.
C->S: MRCP/2.0 ... SPEAK 543258
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:neutral
Voice-Age:25
Prosody-volume:medium
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams and arrived at
<break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<s>The subject is
<prosody rate="-20%">ski trip</prosody></s>
</p>
</speak>
S->C: MRCP/2.0 ... 543258 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@speechsynth
Speech-Marker:timestamp=857206027059
C->S: MRCP/2.0 ... PAUSE 543259
Channel-Identifier:32AECB23433802@speechsynth
S->C: MRCP/2.0 ... 543259 200 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Active-Request-Id-List:543258
PAUSE Example
8.10. RESUME
The RESUME method from the client to the server tells a paused
synthesizer resource to resume speaking. If a RESUME request is
issued on a session with no active "SPEAK" request, the server MUST
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respond with a status of 402 "Method not valid in this state". If a
RESUME request is issued on a session with an active "SPEAK" request
that is speaking (i.e., not paused) the server MUST respond with a
status of 200 "Success". If a "SPEAK" request was paused the server
MUST return an active-request-id-list header field with the
request-id of the "SPEAK" request that was resumed.
C->S: MRCP/2.0 ... SPEAK 543258
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:neutral
Voice-age:25
Prosody-volume:medium
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams and arrived at
<break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<s>The subject is
<prosody rate="-20%">ski trip</prosody></s>
</p>
</speak>
S->C: MRCP/2.0 ... 543258 200 IN-PROGRESS@speechsynth
Channel-Identifier:32AECB23433802
Speech-Marker:timestamp=857206027059
C->S: MRCP/2.0 ... PAUSE 543259
Channel-Identifier:32AECB23433802@speechsynth
S->C: MRCP/2.0 ... 543259 200 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Active-Request-Id-List:543258
C->S: MRCP/2.0 ... RESUME 543260
Channel-Identifier:32AECB23433802@speechsynth
S->C: MRCP/2.0 ... 543260 200 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
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Active-Request-Id-List:543258
RESUME Example
8.11. CONTROL
The CONTROL method from the client to the server tells a synthesizer
that is speaking to modify what it is speaking on the fly. This
method is used to request the synthesizer to jump forward or backward
in what it is speaking, change speaker rate, speaker parameters, etc.
It affects only the currently IN-PROGRESS "SPEAK" request. Depending
on the implementation and capability of the synthesizer resource it
may or may not support the various modifications indicated by header
fields in the CONTROL request.
When a client invokes a CONTROL method to jump forward and the
operation goes beyond the end of the active "SPEAK" method's text,
the CONTROL request still succeeds. The active "SPEAK" request
completes and returns a "SPEAK-COMPLETE" event following the response
to the CONTROL method. If there are more "SPEAK" requests in the
queue, the synthesizer resource starts at the beginning of the next
"SPEAK" request in the queue.
When a client invokes a CONTROL method to jump backward and the
operation jumps to the beginning or beyond the beginning of the
speech data of the active "SPEAK" method, the CONTROL request still
succeeds. The response to the CONTROL request contains the speak-
restart header field, and the active "SPEAK" request restarts from
the beginning of its speech data.
These two behaviors can be used to rewind or fast-forward across
multiple speech requests, if the client wants to break up a speech
markup text to multiple "SPEAK" requests.
If a "SPEAK" request was active when the CONTROL method was received
the server MUST return an active-request-id-list header field with
the Request-id of the "SPEAK" request that was active.
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C->S: MRCP/2.0 ... SPEAK 543258
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:neutral
Voice-age:25
Prosody-volume:medium
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams
and arrived at <break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<s>The subject is <prosody
rate="-20%">ski trip</prosody></s>
</p>
</speak>
S->C: MRCP/2.0 ... 543258 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@speechsynth
Speech-Marker:timestamp=857205016059
C->S: MRCP/2.0 ... CONTROL 543259
Channel-Identifier:32AECB23433802@speechsynth
Prosody-rate:fast
S->C: MRCP/2.0 ... 543259 200 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Active-Request-Id-List:543258
Speech-Marker:timestamp=857206027059
C->S: MRCP/2.0 ... CONTROL 543260
Channel-Identifier:32AECB23433802@speechsynth
Jump-Size:-15 Words
S->C: MRCP/2.0 ... 543260 200 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Active-Request-Id-List:543258
Speech-Marker:timestamp=857206039059
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CONTROL Example
8.12. SPEAK-COMPLETE
This is an Event message from the synthesizer resource to the client
indicating that the corresponding "SPEAK" request was completed. The
request-id header field matches the request-id of the "SPEAK" request
that initiated the speech that just completed. The request-state
field is set to COMPLETE by the server, indicating that this is the
last event with the corresponding request-id. The completion-cause
header field specifies the cause code pertaining to the status and
reason of request completion such as the "SPEAK" completed normally
or because of an error, kill-on-barge-in etc.
C->S: MRCP/2.0 ... SPEAK 543260
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:neutral
Voice-age:25
Prosody-volume:medium
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams
and arrived at <break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<s>The subject is
<prosody rate="-20%">ski trip</prosody></s>
</p>
</speak>
S->C: MRCP/2.0 ... 543260 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@speechsynth
Speech-Marker:timestamp=857206027059
S->C: MRCP/2.0 ... SPEAK-COMPLETE 543260 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Completion-Cause:000 normal
Speech-Marker:timestamp=857206039059
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SPEAK-COMPLETE Example
8.13. SPEECH-MARKER
This is an event generated by the synthesizer resource to the client
when the synthesizer encounters a marker tag in the speech markup it
is currently processing. The request-id field in the header field
matches the corresponding "SPEAK" request. The request-state field
indicates IN-PROGRESS as the speech is still not complete. The value
of the speech marker tag hit, describing where the synthesizer is in
the speech markup, is returned in the speech-marker header field,
along with an NTP timestamp indicating the instant in the output
speech stream that the marker was encountered. The SPEECH-MARKER
event MUST also be generated with a null marker value and output NTP
timestamp when a SPEAK request in Pending-State (i.e. in the queue)
changes state to IN-PROGRESS and starts speaking. The NTP timestamp
MUST be synchronized with the RTP timestamp used to generate the
speech stream through standard RTCP machinery.
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C->S: MRCP/2.0 ... SPEAK 543261
Channel-Identifier:32AECB23433802@speechsynth
Voice-gender:neutral
Voice-age:25
Prosody-volume:medium
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams
and arrived at <break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<mark name="here"/>
<s>The subject is
<prosody rate="-20%">ski trip</prosody>
</s>
<mark name="ANSWER"/>
</p>
</speak>
S->C: MRCP/2.0 ... 543261 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@speechsynth
Speech-Marker:timestamp=857205015059
S->C: MRCP/2.0 ... SPEECH-MARKER 543261 IN-PROGRESS
Channel-Identifier:32AECB23433802@speechsynth
Speech-Marker:timestamp=857206027059;here
S->C: MRCP/2.0 ... SPEECH-MARKER 543261 IN-PROGRESS
Channel-Identifier:32AECB23433802@speechsynth
Speech-Marker:timestamp=857206039059;ANSWER
S->C: MRCP/2.0 ... SPEAK-COMPLETE 543261 COMPLETE
Channel-Identifier:32AECB23433802@speechsynth
Completion-Cause:000 normal
Speech-Marker:timestamp=857207689259;ANSWER
SPEECH-MARKER Example
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8.14. DEFINE-LEXICON
The DEFINE-LEXICON method, from the client to the server, provides a
lexicon and tells the server to load or unload the lexicon (see
Section 8.4.16). The media type of the lexicon is provided in the
Content-Type header (see Section 8.5.2). One such media type is PLS
[W3C.REC-pronunciation-lexicon-20081014].
If the server resource is in the speaking or paused state, the server
MUST respond 402 (Method not valid in this state) failure status.
If the resource is in the idle state and is able to successfully
load/unload the lexicon the status MUST return a success code and the
request-state MUST be COMPLETE.
If the synthesizer could not define the lexicon for some reason, for
example because the download failed or the lexicon was in an
unsupported form, the server MUST respond with a failure status code
of 407, and a Completion-Cause header field describing the failure
reason.
9. Speech Recognizer Resource
The speech recognizer resource receives an incoming voice stream and
provides the client with an interpretation of what was spoken in
textual form.
The recognizer resource is controlled by MRCPv2 requests from the
client. The recognizer resource can both respond to these requests
and generate asynchronous events to the client to indicate conditions
of interest during the processing of the method.
This section applies to the following resource types.
1. speechrecog
2. dtmfrecog
The difference between the above two resources is in their level of
support for recognition grammars. The "dtmfrecog" resource type is
capable of recognizing only DTMF digits and hence accepts only DTMF
grammars. It only generates barge-in for DTMF inputs and ignores
speech. The "speechrecog" resource type can recognize regular speech
as well as DTMF digits and hence MUST support grammars describing
either speech or DTMF. This resource generates barge-in events for
speech and/or DTMF. By analyzing the grammars that are activated by
the RECOGNIZE method, it determines if a barge-in should occur for
speech and/or DTMF. When the recognizer decides it needs to generate
barge-in it also generates a START-OF-INPUT event to the client. The
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recognition resource may support recognition in the normal or hotword
modes or both (although note that a single speechrecog resource does
not perform normal and hotword mode recognition simultaneously). For
implementations where a single recognition resource does not support
both modes, or simultaneous normal and hotword recognition is
desired, the two modes can be invoked through separate resources
allocated to the same SIP dialog (with different MRCP session
identifiers) and share the RTP audio feed.
The capabilities of the recognition resource are enumerated below:
Normal Mode Recognition Normal mode recognition tries to match all
of the speech or DTMF against the grammar and returns a no-match
status if the input fails to match or the method times out.
Hotword Mode Recognition Hotword mode is where the recognizer looks
for a match against specific speech grammar or DTMF sequence and
ignores speech or DTMF that does not match. The recognition
completes only for a successful match of grammar or if the client
cancels the request or if there is a a non-input or recognition
timeout.
Voice Enrolled Grammars A recognition resource may optionally
support Voice Enrolled Grammars. With this functionality,
enrollment is performed using a person's voice. For example, a
list of contacts can be created and maintained by recording the
person's names using the caller's voice. This technique is
sometimes also called speaker-dependent recognition.
Interpretation A recognition resource may be employed strictly for
its natural language interpretation capabilities by supplying it
with a text string as input instead of speech. In this mode the
resource takes text as input and produces an "interpretation" of
the input according to the supplied grammar.
Voice Enrollment has the concept of an enrollment session. A session
to add a new phrase to a personal grammar involves the initial
enrollment followed by a repeat of enough utterances before
committing the new phrase to the personal grammar. Each time an
utterance is recorded, it is compared for similarity with the other
samples and a clash test is performed against other entries in the
personal grammar to ensure there are no similar and confusable
entries.
Enrollment is done using a recognizer resource. Controlling which
utterances are to be considered for enrollment of a new phrase is
done by setting a header field (see Section 9.4.39) in the Recognize
request.
Interpretation is accomplished through the INTERPRET method
(Section 9.20) and the interpret-text header field (Section 9.4.30).
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9.1. Recognizer State Machine
The recognizer resource maintains a state machine to process MRCPv2
requests from the client.
Idle Recognizing Recognized
State State State
| | |
|---------RECOGNIZE---->|---RECOGNITION-COMPLETE-->|
|<------STOP------------|<-----RECOGNIZE-----------|
| | |
| |--------| |-----------|
| START-OF-INPUT | GET-RESULT |
| |------->| |---------->|
|------------| | |
| DEFINE-GRAMMAR |----------| |
|<-----------| | START-INPUT-TIMERS |
| |<---------| |
|------| | |
| INTERPRET | |
|<-----| |------| |
| | RECOGNIZE |
|-------| |<-----| |
| STOP |
|<------| |
|<-------------------STOP--------------------------|
|<-------------------DEFINE-GRAMMAR----------------|
Recognizer State Machine
If a recognition resource supports voice enrolled grammars, starting
an enrollment session does not change the state of the recognizer
resource. Once an enrollment session is started, then utterances are
enrolled by calling the RECOGNIZE method repeatedly. The state of
the speech recognizer resource goes from IDLE to RECOGNIZING state
each time RECOGNIZE is called.
9.2. Recognizer Methods
The recognizer supports the following methods.
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recognizer-method = recog-only-method
/ enrollment-method
recog-only-method = "DEFINE-GRAMMAR"
/ "RECOGNIZE"
/ "INTERPRET"
/ "GET-RESULT"
/ "START-INPUT-TIMERS"
/ "STOP"
It is OPTIONAL for a recognizer resource to support voice enrolled
grammars. If the recognizer resource does support voice enrolled
grammars it MUST support the following methods.
enrollment-method = "START-PHRASE-ENROLLMENT"
/ "ENROLLMENT-ROLLBACK"
/ "END-PHRASE-ENROLLMENT"
/ "MODIFY-PHRASE"
/ "DELETE-PHRASE"
9.3. Recognizer Events
The recognizer may generate the following events.
recognizer-event = "START-OF-INPUT"
/ "RECOGNITION-COMPLETE"
/ "INTERPRETATION-COMPLETE"
9.4. Recognizer Header Fields
A recognizer message may contain header fields containing request
options and information to augment the Method, Response or Event
message it is associated with.
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recognizer-header = recog-only-header
/ enrollment-header
recog-only-header = confidence-threshold
/ sensitivity-level
/ speed-vs-accuracy
/ n-best-list-length
/ no-input-timeout
/ input-type
/ recognition-timeout
/ waveform-uri
/ input-waveform-uri
/ completion-cause
/ completion-reason
/ recognizer-context-block
/ start-input-timers
/ speech-complete-timeout
/ speech-incomplete-timeout
/ dtmf-interdigit-timeout
/ dtmf-term-timeout
/ dtmf-term-char
/ failed-uri
/ failed-uri-cause
/ save-waveform
/ media-type
/ new-audio-channel
/ speech-language
/ ver-buffer-utterance
/ recognition-mode
/ cancel-if-queue
/ hotword-max-duration
/ hotword-min-duration
/ interpret-text
/ dtmf-buffer-time
/ clear-dtmf-buffer
/ early-no-match
If a recognition resource supports voice enrolled grammars, the
following header fields are also used.
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enrollment-header = num-min-consistent-pronunciations
/ consistency-threshold
/ clash-threshold
/ personal-grammar-uri
/ enroll-utterance
/ phrase-id
/ phrase-nl
/ weight
/ save-best-waveform
/ new-phrase-id
/ confusable-phrases-uri
/ abort-phrase-enrollment
For enrollment-specific header fields that can appear as part of
"SET-PARAMS" or "GET-PARAMS" methods, the following general rule
applies: the START-PHRASE-ENROLLMENT method must be invoked before
these header fields may be set through the "SET-PARAMS" method or
retrieved through the "GET-PARAMS" method.
Note that the Waveform-URI header field of the Recognizer resource
can also appear in the response to the END-PHRASE-ENROLLMENT method.
9.4.1. Confidence Threshold
When a recognition resource recognizes or matches a spoken phrase
with some portion of the grammar, it associates a confidence level
with that match. The confidence-threshold header field tells the
recognizer resource what confidence level the client considers a
successful match. This is a float value between 0.0-1.0 indicating
the recognizer's confidence in the recognition. If the recognizer
determines that there is no candidate match with a confidence that is
greater than the confidence threshold, then it MUST return no-match
as the recognition result. This header field MAY occur in RECOGNIZE,
"SET-PARAMS" or "GET-PARAMS". The default value for this header
field is implementation specific, as is the interpretation of any
specific value for this header field. Although values for servers
from different vendors are not comparable, it is expected that
clients will tune this value over time for a given server.
confidence-threshold = "Confidence-Threshold" ":" FLOAT CRLF
9.4.2. Sensitivity Level
To filter out background noise and not mistake it for speech, the
recognizer may support a variable level of sound sensitivity. The
sensitivity-level header field is a float value between 0.0 and 1.0
and allows the client to set the sensitivity level for the
recognizer. This header field MAY occur in RECOGNIZE, "SET-PARAMS"
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or "GET-PARAMS". A higher value for this header field means higher
sensitivity. The default value for this header field is
implementation specific, as is the interpretation of any specific
value for this header field. Although values for servers from
different vendors are not comparable, it is expected that clients
will tune this value over time for a given server.
sensitivity-level = "Sensitivity-Level" ":" FLOAT CRLF
9.4.3. Speed Vs Accuracy
Depending on the implementation and capability of the recognizer
resource it may be tunable towards Performance or Accuracy. Higher
accuracy may mean more processing and higher CPU utilization, meaning
fewer active sessions per server and vice versa. The value is a
float between 0.0 and 1.0. A value of 0.0 means fastest recognition.
A value of 1.0 means best accuracy. This header field MAY occur in
RECOGNIZE, "SET-PARAMS" or "GET-PARAMS". The default value for this
header field is implementation specific. Although values for servers
from different vendors are not comparable, it is expected that
clients will tune this value over time for a given server.
speed-vs-accuracy = "Speed-Vs-Accuracy" ":" FLOAT CRLF
9.4.4. N Best List Length
When the recognizer matches an incoming stream with the grammar, it
may come up with more than one alternative match because of
confidence levels in certain words or conversation paths. If this
header field is not specified, by default, the recognition resource
returns only the best match above the confidence threshold. The
client, by setting this header field, can ask the recognition
resource to send it more than 1 alternative. All alternatives must
still be above the confidence-threshold. A value greater than one
does not guarantee that the recognizer will provide the requested
number of alternatives. This header field MAY occur in RECOGNIZE,
"SET-PARAMS" or "GET-PARAMS". The minimum value for this header
field is 1. The default value for this header field is 1.
n-best-list-length = "N-Best-List-Length" ":" 1*19DIGIT CRLF
9.4.5. Input Type
When the recognizer detects barge-in-able input and generates a
START-OF-INPUT event, that event MUST carry this header field to
specify whether the input that caused the barge-in was DTMF or
speech.
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input-type = "Input-Type" ":" inputs CRLF
inputs = "speech" / "dtmf"
9.4.6. No Input Timeout
When recognition is started and there is no speech detected for a
certain period of time, the recognizer can send a RECOGNITION-
COMPLETE event to the client with a Completion-Cause of "no-input-
timeout" and terminate the recognition operation. The client can use
the no-input-timeout header field to set this timeout. The value is
in milliseconds and may range from 0 to an implementation specific
maximum value. This header field MAY occur in RECOGNIZE,
"SET-PARAMS" or "GET-PARAMS". The default value is implementation
specific.
no-input-timeout = "No-Input-Timeout" ":" 1*19DIGIT CRLF
9.4.7. Recognition Timeout
When recognition is started and there is no match for a certain
period of time, the recognizer can send a RECOGNITION-COMPLETE event
to the client and terminate the recognition operation. The
Recognition-Timeout header field allows the client to set this
timeout value. The value is in milliseconds. The value for this
header field ranges from 0 to an implementation specific maximum
value. The default value is 10 seconds. This header field MAY occur
in RECOGNIZE, SET-PARAMS or GET-PARAMS.
recognition-timeout = "Recognition-Timeout" ":" 1*19DIGIT CRLF
9.4.8. Waveform URI
If the Save-Waveform header field is set to true, the recognizer MUST
record the incoming audio stream of the recognition into a stored
form and provide a URI for the client to access it. This header
field MUST be present in the RECOGNITION-COMPLETE event if the Save-
Waveform header field was set to true. The value of the header field
MUST be empty if there was some error condition preventing the server
from recording. Otherwise, the URI generated by the server MUST be
unambiguous across the server and all its recognition sessions. The
content associated with the URI MUST be available to the client until
the MRCPv2 session terminates.
Similarly, if the Save-Best-Waveform header field is set to true, the
recognizer MUST save the audio stream for the best repetition of the
phrase that was used during the enrollment session. The recognizer
MUST then record the recognized audio and make it available to the
client by returning a URI in the Waveform-URI header field in the
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response to the END-PHRASE-ENROLLMENT method. The value of the
header field MUST be empty if there was some error condition
preventing the server from recording. Otherwise, the URI generated
by the server MUST be unambiguous across the server and all its
recognition sessions. The content associated with the URI MUST be
available to the client until the MRCPv2 session terminates. See the
discussion on the sensitivity of saved waveforms in Section 12.
The server MUST also return the size in octets and the duration in
milliseconds of the recorded audio wave-form as parameters associated
with the header field.
waveform-uri = "Waveform-URI" ":" ["<" uri ">"
";" "size" "=" 1*19DIGIT
";" "duration" "=" 1*19DIGIT] CRLF
9.4.9. Media Type
This header field MAY be specified in the SET-PARAMS, GET-PARAMS or
the RECOGNIZE methods and tells the server resource the Media Type in
which to store captured audio or video such as the one captured and
returned by the Waveform-URI header field.
media-type = "Media-Type" ":" media-type-value
CRLF
9.4.10. Input-Waveform-URI
This optional header field specifies a URI pointing to audio content
to be processed by the RECOGNIZE operation. This enables the client
to request recognition from a specified buffer or audio file.
input-waveform-uri = "Input-Waveform-URI" ":" uri CRLF
9.4.11. Completion Cause
This header field MUST be part of a RECOGNITION-COMPLETE, event
coming from the recognizer resource to the client. It indicates the
reason behind the RECOGNIZE method completion. This header field
MUST be sent in the DEFINE-GRAMMAR and RECOGNIZE responses, if they
return with a failure status and a COMPLETE state.
completion-cause = "Completion-Cause" ":" 3DIGIT SP
1*VCHAR CRLF
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+---------+--------------------------+------------------------------+
| Cause-C | Cause-Name | Description |
| ode | | |
+---------+--------------------------+------------------------------+
| 000 | success | RECOGNIZE completed with a |
| | | match or DEFINE-GRAMMAR |
| | | succeeded in downloading and |
| | | compiling the grammar |
| 001 | no-match | RECOGNIZE completed, but no |
| | | match was found |
| 002 | no-input-timeout | RECOGNIZE completed without |
| | | a match due to a |
| | | no-input-timeout |
| 003 | hotword-maxtime | RECOGNIZE in hotword mode |
| | | completed without a match |
| | | due to a recognition-timeout |
| 004 | grammar-load-failure | RECOGNIZE failed due grammar |
| | | load failure. |
| 005 | grammar-compilation-fail | RECOGNIZE failed due to |
| | ure | grammar compilation failure. |
| 006 | recognizer-error | RECOGNIZE request terminated |
| | | prematurely due to a |
| | | recognizer error. |
| 007 | speech-too-early | RECOGNIZE request terminated |
| | | because speech was too |
| | | early. This happens when |
| | | the audio stream is already |
| | | "in-speech" when the |
| | | RECOGNIZE request was |
| | | received. |
| 008 | success-maxtime | RECOGNIZE request terminated |
| | | because speech was too long |
| | | but whatever was spoken till |
| | | that point was a full match. |
| 009 | uri-failure | Failure accessing a URI. |
| 010 | language-unsupported | Language not supported. |
| 011 | cancelled | A new RECOGNIZE cancelled |
| | | this one, or a prior |
| | | RECOGNIZE failed while this |
| | | one was still in the queue. |
| 012 | semantics-failure | Recognition succeeded but |
| | | semantic interpretation of |
| | | the recognized input failed. |
| | | The RECOGNITION-COMPLETE |
| | | event MUST contain the |
| | | Recognition result with only |
| | | input text and no |
| | | interpretation. |
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| 013 | partial-match | Speech Incomplete timeout |
| | | expired before there was a |
| | | full match. But whatever |
| | | that was spoken till that |
| | | point was a partial match to |
| | | one or more grammars. |
| 014 | partial-match-maxtime | The Recognition-Timer |
| | | expired before full match |
| | | was achieved. But whatever |
| | | was spoken till that point |
| | | was a partial match to one |
| | | or more grammars. |
| 015 | no-match-maxtime | The Recognition-Timer |
| | | expired. Whatever was |
| | | spoken till that point |
| | | either did not match any of |
| | | the grammars. This cause |
| | | could also be returned if |
| | | the recognizer does not |
| | | support detecting partial |
| | | grammar matches. |
| 016 | grammar-definition-failu | any DEFINE-GRAMMAR error |
| | re | other than |
| | | grammar-load-failure and |
| | | grammar-compilation-failure. |
+---------+--------------------------+------------------------------+
9.4.12. Completion Reason
This header field MAY be specified in a RECOGNITION-COMPLETE event
coming from the recognizer resource to the client. This contains the
reason text behind the RECOGNIZE request completion. The server uses
this header field to communicate text describing the reason for the
failure, such as the specific error encountered in parsing a grammar
markup.
The completion reason text is provided for client use in logs and for
debugging and instrumentation purposes. Clients MUST NOT interpret
the completion reason text.
completion-reason = "Completion-Reason" ":"
quoted-string CRLF
9.4.13. Recognizer Context Block
This header field MAY be sent as part of the "SET-PARAMS" or
"GET-PARAMS" request. If the "GET-PARAMS" method contains this
header field with no value, then it is a request to the recognizer to
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return the recognizer context block. The response to such a message
MAY contain a recognizer context block as a typed media message body.
If the server returns a recognizer context block, the response MUST
contain this header field and its value MUST match the Content-ID of
the corresponding media block.
If the "SET-PARAMS" method contains this header field, it MUST also
contain a message body containing the recognizer context data, and a
Content-ID matching this header field value. This Content-ID MUST
match the Content-ID that came with the context data during the
"GET-PARAMS" operation.
An implementation choosing to use this mechanism to hand off
recognizer context data between servers MUST distinguish its
implementation-specific block of data by using an IANA-registered
content type in the IANA Media Type vendor tree.
recognizer-context-block = "Recognizer-Context-Block" ":"
[1*VCHAR] CRLF
9.4.14. Start Input Timers
This header field MAY be sent as part of the RECOGNIZE request. A
value of false tells the recognizer to start recognition, but not to
start the no-input timer yet. The recognizer MUST NOT start the
timers until the client sends a START-INPUT-TIMERS request to the
recognizer. This is useful in the scenario when the recognizer and
synthesizer engines are not part of the same session. In such
configurations, when a kill-on-barge-in prompt is being played (see
Section 8.4.2), the client wants the RECOGNIZE request to be
simultaneously active so that it can detect and implement kill-on-
barge-in. However, the recognizer ought not start the no-input
timers until the prompt is finished. The default value is "true".
start-input-timers = "Start-Input-Timers" ":" BOOLEAN CRLF
9.4.15. Speech Complete Timeout
This header field specifies the length of silence required following
user speech before the speech recognizer finalizes a result (either
accepting it or generating a nomatch event). The speech-complete-
timeout value applies when the recognizer currently has a complete
match against an active grammar, and specifies how long the
recognizer MUST wait for more input before declaring a match. By
contrast, the incomplete timeout is used when the speech is an
incomplete match to an active grammar. The value is in milliseconds.
speech-complete-timeout = "Speech-Complete-Timeout" ":" 1*19DIGIT CRLF
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A long speech-complete-timeout value delays the result to the client
and therefore makes the application's response to a user slow. A
short speech-complete-timeout may lead to an utterance being broken
up inappropriately. Reasonable speech complete timeout values are
typically in the range of 0.3 seconds to 1.0 seconds. The value for
this header field ranges from 0 to an implementation specific maximum
value. The default value for this header field is implementation
specific. This header field MAY occur in RECOGNIZE, "SET-PARAMS" or
"GET-PARAMS".
9.4.16. Speech Incomplete Timeout
This header field specifies the required length of silence following
user speech after which a recognizer finalizes a result. The
incomplete timeout applies when the speech prior to the silence is an
incomplete match of all active grammars. In this case, once the
timeout is triggered, the partial result is rejected (with a
Completion-Cause of "partial-match"). The value is in milliseconds.
The value for this header field ranges from 0 to an implementation
specific maximum value. The default value for this header field is
implementation specific.
speech-incomplete-timeout = "Speech-Incomplete-Timeout" ":" 1*19DIGIT
CRLF
The speech-incomplete-timeout also applies when the speech prior to
the silence is a complete match of an active grammar, but where it is
possible to speak further and still match the grammar. By contrast,
the complete timeout is used when the speech is a complete match to
an active grammar and no further spoken words can continue to
represent a match.
A long speech-incomplete-timeout value delays the result to the
client and therefore makes the application's response to a user slow.
A short speech-incomplete-timeout may lead to an utterance being
broken up inappropriately.
The speech-incomplete-timeout is usually longer than the speech-
complete-timeout to allow users to pause mid-utterance (for example,
to breathe). This header field MAY occur in RECOGNIZE, "SET-PARAMS"
or "GET-PARAMS".
9.4.17. DTMF Interdigit Timeout
This header field specifies the inter-digit timeout value to use when
recognizing DTMF input. The value is in milliseconds. The value for
this header field ranges from 0 to an implementation specific maximum
value. The default value is 5 seconds. This header field MAY occur
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in RECOGNIZE, "SET-PARAMS" or "GET-PARAMS".
dtmf-interdigit-timeout = "DTMF-Interdigit-Timeout" ":" 1*19DIGIT CRLF
9.4.18. DTMF Term Timeout
This header field specifies the terminating timeout to use when
recognizing DTMF input. The DTMF-Term-Timeout applies only when no
additional input is allowed by the grammar; otherwise, the DTMF-
Interdigit-Timeout applies. The value is in milliseconds. The value
for this header field ranges from 0 to an implementation specific
maximum value. The default value is 10 seconds. This header field
MAY occur in RECOGNIZE, "SET-PARAMS" or "GET-PARAMS".
dtmf-term-timeout = "DTMF-Term-Timeout" ":" 1*19DIGIT CRLF
9.4.19. DTMF-Term-Char
This header field specifies the terminating DTMF character for DTMF
input recognition. The default value is NULL which is indicated by
an empty header field value. This header field MAY occur in
RECOGNIZE, "SET-PARAMS" or "GET-PARAMS".
dtmf-term-char = "DTMF-Term-Char" ":" VCHAR CRLF
9.4.20. Failed URI
When a recognizer needs to fetch or access a URI and the access fails
the server SHOULD provide the failed URI in this header field in the
method response, unless there are multiple URI failures, in which
case one of the failed URIs MUST be provided in this header field in
the method response.
failed-uri = "Failed-URI" ":" absoluteURI CRLF
9.4.21. Failed URI Cause
When a recognizer method needs a recognizer to fetch or access a URI
and the access fails the server MUST provide the URI specific or
protocol specific response code for the URI in the Failed-URI header
field through this header field in the method response. The value
encoding is UTF-8 to accommodate any access protocol, some of which
might have a response string instead of a numeric response code.
failed-uri-cause = "Failed-URI-Cause" ":" 1*UTFCHAR CRLF
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9.4.22. Save Waveform
This header field allows the client to request the recognizer
resource to save the audio input to the recognizer. The recognizer
resource MUST then attempt to record the recognized audio, without
endpointing, and make it available to the client in the form of a URI
returned in the Waveform-URI header field in the RECOGNITION-COMPLETE
event. If there was an error in recording the stream or the audio
content is otherwise not available, the recognizer MUST return an
empty Waveform-URI header field. The default value for this field is
"false". This header field MAY occur in RECOGNIZE, "SET-PARAMS" or
"GET-PARAMS". See the discussion on the sensitivity of saved
waveforms in Section 12.
save-waveform = "Save-Waveform" ":" BOOLEAN CRLF
9.4.23. New Audio Channel
This header field MAY be specified in a RECOGNIZE request and allows
the client to tell the server that, from this point on, further input
audio comes from a different audio source, channel or speaker. If
the recognition resource had collected any input statistics or
adaptation state, the recognition resource MUST do what is
appropriate for the specific recognition technology, which includes
but is not limited to discarding any collected input statistics or
adaptation state before starting the RECOGNIZE request. Note that if
there are multiple resources that are sharing a media stream and are
collecting or using this data, and the client issues this header
field to one of the resources, the reset operation applies to all
resources that use the shared media stream. This helps in a number
of use cases, including where the client wishes to reuse an open
recognition session with an existing media session for multiple
telephone calls.
new-audio-channel = "New-Audio-Channel" ":" BOOLEAN
CRLF
9.4.24. Speech-Language
This header field specifies the language of recognition grammar data
within a session or request, if it is not specified within the data.
The value of this header field MUST follow RFC4646 [RFC4646] for its
values. This MAY occur in DEFINE-GRAMMAR, RECOGNIZE, "SET-PARAMS" or
"GET-PARAMS" request.
speech-language = "Speech-Language" ":" 1*VCHAR CRLF
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9.4.25. Ver-Buffer-Utterance
This header field lets the client request the server to buffer the
utterance associated with this recognition request into a buffer
available to a co-resident verifier resource. The buffer is shared
across resources within a session and is allocated when a verifier
resource is added to this session. The client MUST NOT send this
header field unless a verifier resource is instantiated for the
session. The buffer is released when the verifier resource is
released from the session.
9.4.26. Recognition-Mode
This header field specifies what mode the RECOGNIZE method will
operate in. The value choices are "normal" or "hotword". If the
value is "normal", the RECOGNIZE starts matching speech and DTMF to
the grammars specified in the RECOGNIZE request. If any portion of
the speech does not match the grammar, the RECOGNIZE command
completes with a no-match status. Timers may be active to detect
speech in the audio (see Section 9.4.14), so the RECOGNIZE method may
complete because of a timeout waiting for speech. If the value of
this header field is "hotword", the RECOGNIZE method operates in
hotword mode, where it only looks for the particular keywords or DTMF
sequences specified in the grammar and ignores silence or other
speech in the audio stream. The default value for this header field
is "normal". This header field MAY occur on the RECOGNIZE method.
recognition-mode = "Recognition-Mode" ":" 1*ALPHA CRLF
9.4.27. Cancel-If-Queue
This header field specifies what will happen if the client attempts
to invoke another RECOGNIZE method when this RECOGNIZE request is
already in progress for the resource. The value for this header
field is Boolean. A value of "true" means the server MUST terminate
this RECOGNIZE request, with a Completion-Cause of "cancelled", if
the client issues another RECOGNIZE request for the same resource. A
value of "false" for this header field indicates to the server that
this RECOGNIZE request will continue to completion and if the client
issues more RECOGNIZE requests to the same resource, they are queued.
When the currently active RECOGNIZE request is stopped or completes
with a successful match, the first RECOGNIZE method in the queue
becomes active. If the current RECOGNIZE fails, all RECOGNIZE
methods in the pending queue are cancelled and each generates a
RECOGNITION-COMPLETE event with a Completion-Cause of "cancelled".
This header field MUST be present in every RECOGNIZE request. There
is no default value.
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cancel-if-queue = "Cancel-If-Queue" ":" BOOLEAN CRLF
9.4.28. Hotword-Max-Duration
This header field MAY be sent in a hotword mode RECOGNIZE request.
It specifies the maximum length of an utterance (in seconds) that
will be considered for Hotword recognition. This header field, along
with Hotword-Min-Duration, can be used to tune performance by
preventing the recognizer from evaluating utterances that are too
short or too long to be one of the hotwords in the grammar(s). The
value is in milliseconds. The default is implementation dependent.
If present in a RECOGNIZE request specifying a mode other than
"hotword", the header field is ignored.
hotword-max-duration = "Hotword-Max-Duration" ":" 1*19DIGIT
CRLF
9.4.29. Hotword-Min-Duration
This header field MAY be sent in a hotword mode RECOGNIZE request.
It specifies the minimum length of an utterance (in seconds) that
will be considered for Hotword recognition. This header field, along
with Hotword-Max-Duration, can be used to tune performance by
preventing the recognizer from evaluating utterances that are too
short or too long to be one of the hotwords in the grammar(s). The
value is in milliseconds. The default value is implementation
dependent. If present in a RECOGNIZE request specifying a mode other
than "hotword", the header field is ignored.
hotword-min-duration = "Hotword-Min-Duration" ":" 1*19DIGIT CRLF
9.4.30. Interpret-Text
The value of this header field is used to provide a pointer to the
text for which a natural language interpretation is desired. The
value is either a URI or text. If the value is a URI, it MUST be a
Content-ID that refers to an entity of type text/plain in the body of
the message. Otherwise, the server MUST treat the value as the text
to be interpreted. This header field MUST be used when invoking the
INTERPRET method.
interpret-text = "Interpret-Text" ":" 1*VCHAR CRLF
9.4.31. DTMF-Buffer-Time
This header field MAY be specified in a GET-PARAMS or SET-PARAMS
method and is used to specify the size in time, in milliseconds, of
the typeahead buffer for the recognizer. This is the buffer that
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collects DTMF digits as they are pressed even when there is no
RECOGNIZE command active. When a subsequent RECOGNIZE method is
received it MAY look to this buffer to match the RECOGNIZE request.
If the digits in the buffer is not sufficient then it can continue to
listen to more digits to match the grammar. The default size of this
DTMF buffer is platform specific.
dtmf-buffer-time = "DTMF-Buffer-Time" ":" 1*19DIGIT CRLF
9.4.32. Clear-DTMF-Buffer
This header field MAY be specified in a RECOGNIZE method and is used
to tell the recognizer to clear the DTMF type-ahead buffer before
starting the recognize. The default value of this header field is
FALSE, which does not clear the typeahead buffer before starting the
RECOGNIZE method. If this header field is specified to be TRUE, then
the recognize will clear the DTMF buffer before starting recognition.
This means digits pressed by the caller before the RECOGNIZE command
was issued are discarded.
clear-dtmf-buffer = "Clear-DTMF-Buffer" ":" BOOLEAN CRLF
9.4.33. Early-No-Match
This header field MAY be specified in a RECOGNIZE method and is used
to tell the recognizer that it MUST NOT wait for the end of speech
before processing the collected speech to match active grammars. A
value of TRUE indicates the recognizer MUST do early matching. The
default value for this header field if not specified is FALSE. If
the recognizer does not support the processing of the collected audio
before the end of speech this header field can be safely ignored.
early-no-match = "Early-No-Match" ":" BOOLEAN CRLF
9.4.34. Num-Min-Consistent-Pronunciations
This header field MAY be specified in a START-PHRASE-ENROLLMENT,
"SET-PARAMS", or "GET-PARAMS" method and is used to specify the
minimum number of consistent pronunciations that must be obtained to
voice enroll a new phrase. The minimum value is 1. The default
value is implementation specific and MAY be greater than 1.
num-min-consistent-pronunciations =
"Num-Min-Consistent-Pronunciations" ":" 1*19DIGIT CRLF
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9.4.35. Consistency-Threshold
This header field MAY be sent as part of the START-PHRASE-ENROLLMENT,
"SET-PARAMS", or "GET-PARAMS" method. Used during voice-enrollment,
this header field specifies how similar to a previously enrolled
pronunciation of the same phrase an utterance needs to be in order to
be considered "consistent." The higher the threshold, the closer the
match between an utterance and previous pronunciations must be for
the pronunciation to be considered consistent. The range for this
threshold is a float value between is 0.0 to 1.0. The default value
for this header field is implementation specific.
consistency-threshold = "Consistency-Threshold" ":" FLOAT CRLF
9.4.36. Clash-Threshold
This header field MAY be sent as part of the START-PHRASE-ENROLLMENT,
SET-PARAMS, or "GET-PARAMS" method. Used during voice-enrollment,
this header field specifies how similar the pronunciations of two
different phrases can be before they are considered to be clashing.
For example, pronunciations of phrases such as "John Smith" and "Jon
Smits" may be so similar that they are difficult to distinguish
correctly. A smaller threshold reduces the number of clashes
detected. The range for this threshold is float value between 0.0
and 1.0. The default value for this header field is implementation
specific. Clash testing can be turned off completely by setting the
Clash-Threshold header field value to 0.
clash-threshold = "Clash-Threshold" ":" FLOAT CRLF
9.4.37. Personal-Grammar-URI
This header field specifies the speaker-trained grammar to be used or
referenced during enrollment operations. Phrases are added to this
grammar during enrollment. For example, a contact list for user
"Jeff" could be stored at the Personal-Grammar-URI
"http://myserver.example.com/myenrollmentdb/jeff-list". The
generated grammar syntax MAY be implementation specific. There is no
default value for this header field. This header field MAY be sent
as part of the START-PHRASE-ENROLLMENT, SET-PARAMS, or "GET-PARAMS"
method.
personal-grammar-uri = "Personal-Grammar-URI" ":" uri CRLF
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9.4.38. Enroll-Utterance
This header field MAY be specified in the RECOGNIZE method. If this
header field is set to "true" and an Enrollment is active, the
RECOGNIZE command MUST add the collected utterance to the personal
grammar that is being enrolled. The way in which this occurs is
engine-specific and may be an area of future standardization. The
default value for this header field is "false".
enroll-utterance = "Enroll-Utterance" ":" BOOLEAN CRLF
9.4.39. Phrase-Id
This header field in a request identifies a phrase in an existing
personal grammar for which enrollment is desired. It is also
returned to the client in the RECOGNIZE complete event. This header
field MAY occur in START-PHRASE-ENROLLMENT, MODIFY-PHRASE or DELETE-
PHRASE requests. There is no default value for this header field.
phrase-id = "Phrase-ID" ":" 1*VCHAR CRLF
9.4.40. Phrase-NL
This string specifies the interpreted text to be returned when the
phrase is recognized. This header field MAY occur in START-PHRASE-
ENROLLMENT and MODIFY-PHRASE requests. There is no default value for
this header field.
phrase-nl = "Phrase-NL" ":" 1*UTFCHAR CRLF
9.4.41. Weight
The value of this header field represents the occurrence likelihood
of a phrase in an enrolled grammar. When using grammar enrollment,
the system is essentially constructing a grammar segment consisting
of a list of possible match phrases. This can be thought of to be
similar to the dynamic construction of a <one-of> tag in the W3C
grammar specification. Each enrolled-phrase becomes an item in the
list that can be matched against spoken input similar to the <item>
within a <one-of> list. This header field allows you to assign a
weight to the phrase (i.e., <item> entry) in the <one-of> list that
is enrolled. Grammar weights are normalized to a sum of one at
grammar compilation time, so a weight value of 1 for each phrase in
an enrolled grammar list indicates all items in that list have the
same weight. This header field MAY occur in START-PHRASE-ENROLLMENT
and MODIFY-PHRASE requests. The default value for this header field
is implementation specific.
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weight = "Weight" ":" weight-value CRLF
weight-value = FLOAT
9.4.42. Save-Best-Waveform
This header field allows the client to request the recognizer
resource to save the audio stream for the best repetition of the
phrase that was used during the enrollment session. The recognizer
MUST attempt to record the recognized audio and make it available to
the client in the form of a URI returned in the Waveform-URI header
field in the response to the END-PHRASE-ENROLLMENT method. If there
was an error in recording the stream or the audio data is otherwise
not available, the recognizer MUST return an empty Waveform-URI
header field. This header field MAY occur in the START-PHRASE-
ENROLLMENT, SET-PARAMS, and GET-PARAMS methods.
save-best-waveform = "Save-Best-Waveform" ":" BOOLEAN CRLF
9.4.43. New-Phrase-Id
This header field replaces the id used to identify the phrase in a
personal grammar. The recognizer returns the new id when using an
enrollment grammar. This header field MAY occur in MODIFY-PHRASE
requests.
new-phrase-id = "New-Phrase-ID" ":" 1*VCHAR CRLF
9.4.44. Confusable-Phrases-URI
This header field specifies a grammar that defines invalid phrases
for enrollment. For example, typical applications do not allow an
enrolled phrase that is also a command word. This header field MAY
occur in RECOGNIZE requests that are part of an enrollment session.
confusable-phrases-uri = "Confusable-Phrases-URI" ":" uri CRLF
9.4.45. Abort-Phrase-Enrollment
This header field can optionally be specified in the END-PHRASE-
ENROLLMENT method to abort the phrase enrollment, rather than
committing the phrase to the personal grammar.
abort-phrase-enrollment = "Abort-Phrase-Enrollment" ":"
BOOLEAN CRLF
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9.5. Recognizer Message Body
A recognizer message may carry additional data associated with the
request, response or event. The client may provide the grammar to be
recognized in DEFINE-GRAMMAR or RECOGNIZE requests. When one or more
grammars are specified using the DEFINE-GRAMMAR method, the server
MUST attempt to fetch, compile and optimize the grammar before
returning a response to the DEFINE-GRAMMAR method. A RECOGNIZE
request MUST completely specify the grammars to be active during the
recognition operation, except when the RECOGNIZE method is being used
to enroll a grammar. During grammar enrollment, such grammars are
optional. The server resource may send the recognition results in
the RECOGNITION-COMPLETE event or the GET-RESULT response. Grammars
and recognition results are carried in the message body of the
corresponding MRCPv2 messages.
9.5.1. Recognizer Grammar Data
Recognizer grammar data from the client to the server can be provided
inline or by reference. Either way, grammar data is carried as typed
media entities in the message body of the RECOGNIZE or DEFINE-GRAMMAR
request. All MRCPv2 servers MUST accept grammars in the XML form
(Media Type application/srgs+xml) of the W3C's XML-based Speech
Grammar Markup Format (SRGS) [W3C.REC-speech-grammar-20040316] and
MAY accept grammars in other formats. Examples include but are not
limited to:
o the ABNF form (Media Type application/srgs) of SRGS
o Sun's Java Speech Grammar Format [refs.javaSpeechGrammarFormat]
Additionally, MRCPv2 servers MAY support the Semantic Interpretation
for Speech Recognition (SISR)
[W3C.REC-semantic-interpretation-20070405] specification.
When a grammar is specified inline in the request, the client MUST
provide a Content-ID for that grammar as part of the content header
fields. If there is no space on the server to store the inline
grammar, the request MUST return with a Completion-Cause code of 016
grammar-definition-failure. Otherwise, the server MUST associate the
inline grammar block with that Content-ID and MUST store it on the
server for the duration of the session. However, if the Content-ID
is redefined later in the session through a subsequent DEFINE-
GRAMMAR, the inline grammar previously associated with the Content-ID
MUST be freed. If the Content-ID is redefined through a subsequent
DEFINE-GRAMMAR with an empty message body (i.e. no grammar
definition), then in addition to freeing any grammar previously
associated with the Content-ID the server MUST clear all bindings and
associations to the Content-ID. Unless and until subsequently
redefined, this URI MUST be interpreted by the server as one that has
never been set.
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Grammars that have been associated with a Content-ID can be
referenced through the "session:" URI scheme (see Section 13.6). For
example:
session:help@root-level.store
Grammar data MAY be specified using external URI references. To do
so, the client uses a body of Media Type text/uri-list RFC2483
[RFC2483] to list the one or more URIs that point to the grammar
data. The client can use a body of Media Type text/grammar-ref-list
if it wants to assign weights to the list of grammar URI. All MRCPv2
servers MUST support grammar access using the HTTP and HTTPS uri
schemes.
If the grammar data the client wishes to be used on a request
consists of a mix of URI and inline grammar data the client uses the
multipart/mixed Media Type to enclose the text/uri-list, application/
srgs or application/srgs+xml content entities. The character set and
encoding used in the grammar data are specified using to standard
Media Type definitions.
When more than one grammar URI or inline grammar block is specified
in a message body of the RECOGNIZE request, the server interprets
this as a list of grammar alternatives to match against.
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Content-Type:application/srgs+xml
Content-ID:<request1@form-level.store>
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0" root="request">
<!-- single language attachment to tokens -->
<rule id="yes">
<one-of>
<item xml:lang="fr-CA">oui</item>
<item xml:lang="en-US">yes</item>
</one-of>
</rule>
<!-- single language attachment to a rule expansion -->
<rule id="request">
may I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
</one-of>
</rule>
<!-- multiple language attachment to a token -->
<rule id="people1">
<token lexicon="en-US,fr-CA"> Robert </token>
</rule>
<!-- the equivalent single-language attachment expansion -->
<rule id="people2">
<one-of>
<item xml:lang="en-US">Robert</item>
<item xml:lang="fr-CA">Robert</item>
</one-of>
</rule>
</grammar>
SRGS Grammar Example
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Content-Type:text/uri-list
Content-Length:...
session:help@root-level.store
http://www.example.com/Directory-Name-List.grxml
http://www.example.com/Department-List.grxml
http://www.example.com/TAC-Contact-List.grxml
session:menu1@menu-level.store
Grammar Reference Example
Content-Type:multipart/mixed; boundary="break"
--break
Content-Type:text/uri-list
Content-Length:...
http://www.example.com/Directory-Name-List.grxml
http://www.example.com/Department-List.grxml
http://www.example.com/TAC-Contact-List.grxml
--break
Content-Type:application/srgs+xml
Content-ID:<request1@form-level.store>
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0">
<!-- single language attachment to tokens -->
<rule id="yes">
<one-of>
<item xml:lang="fr-CA">oui</item>
<item xml:lang="en-US">yes</item>
</one-of>
</rule>
<!-- single language attachment to a rule expansion -->
<rule id="request">
may I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
</one-of>
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</rule>
<!-- multiple language attachment to a token -->
<rule id="people1">
<token lexicon="en-US,fr-CA"> Robert </token>
</rule>
<!-- the equivalent single-language attachment expansion -->
<rule id="people2">
<one-of>
<item xml:lang="en-US">Robert</item>
<item xml:lang="fr-CA">Robert</item>
</one-of>
</rule>
</grammar>
--break--
Mixed Grammar Reference Example
9.5.2. Recognizer Result Data
Recognition results are returned to the client in the message body of
the RECOGNITION-COMPLETE event or the GET-RESULT response message as
described in Section 6.3). Element and attribute descriptions for
the recognition portion of the NLSML format are provided in
Section 9.6 with a normative definition of the schema in
Section 16.1.
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="http://www.example.com/theYesNoGrammar">
<interpretation>
<instance>
<ex:response>yes</ex:response>
</instance>
<input>ok</input>
</interpretation>
</result>
Result Example
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9.5.3. Enrollment Result Data
Enrollment results are returned to the client in the message body of
the RECOGNITION-COMPLETE event as described in Section 6.3). Element
and attribute descriptions for the enrollment portion of the NLSML
format are provided in Section 9.7 with a normative definition of the
schema in Section 16.2.
9.5.4. Recognizer Context Block
When a client changes servers while operating on the behalf of the
same incoming communication session, this header field allows the
client to collect a block of opaque data from one server and provide
it to another server. This capability is desirable if the client
needs different language support or because the server issued a
redirect. Here the first recognizer resource may have collected
acoustic and other data during its execution of recognition methods.
After a server switch, communicating this data may allow the
recognition resource on the new server to provide better recognition.
This block of data is implementation-specific and MUST be carried as
Media Type application/octets in the body of the message.
This block of data is communicated in the "SET-PARAMS" and
"GET-PARAMS" method/response messages. In the "GET-PARAMS" method,
if an empty recognizer-context-block header field is present, then
the recognizer SHOULD return its vendor-specific context block, if
any, in the message body as an entity of Media Type application/
octets with a specific Content-ID. The Content-ID value MUST also be
specified in the recognizer-context-block header field in the
"GET-PARAMS" response. The "SET-PARAMS" request wishing to provide
this vendor-specific data MUST send it in the message body as a typed
entity with the same Content-ID that it received from the
"GET-PARAMS". The Content-ID MUST also be sent in the recognizer-
context-block header field of the "SET-PARAMS" message.
Each speech recognition implementation choosing to use this mechanism
to hand off recognizer context data among servers MUST distinguish
its implementation-specific block of data from other implementations
by choosing a Content-ID that is recognizable among the participating
servers and unlikely to collide with values chosen by another
implementation.
9.6. Recognizer Results
The recognizer portion of NLSML (see Section 6.3.1) represents
information automatically extracted from a user's utterances by a
semantic interpretation component, where "utterance" is to be taken
in the general sense of a meaningful user input in any modality
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supported by the MRCPv2 implementation.
9.6.1. Markup Functions
MRCPv2 recognition resources employ the Natural Language Semantics
Markup Language to interpret natural language speech input and to
format the interpretation for consumption by an MRCPv2 client.
The elements of the markup fall into the following general functional
categories: Interpretation, Side Information, and Multi-Modal
Integration.
9.6.1.1. Interpretation
Elements and attributes represent the semantics of a user's
utterance, including the <result>, <interpretation>, and <instance>
elements. The <result> element contains the full result of
processing one utterance. It may contain multiple <interpretation>
elements if the interpretation of the utterance results in multiple
alternative meanings due to uncertainty in speech recognition or
natural language understanding. There are at least two reasons for
providing multiple interpretations:
1. the client application might have additional information, for
example, information from a database, that would allow it to
select a preferred interpretation from among the possible
interpretations returned from the semantic interpreter.
2. a client-based dialog manager (e.g. VXML) that was unable to
select between several competing interpretations could use this
information to go back to the user and find out what was
intended. For example, it could issue a "SPEAK" request to a
synthesizer resource to emit "Did you say 'Boston' or 'Austin'?"
9.6.1.2. Side Information
These are elements and attributes representing additional information
about the interpretation, over and above the interpretation itself.
Side information includes:
1. Whether an interpretation was achieved (the <nomatch> element)
and the system's confidence in an interpretation (the
"confidence" attribute of <interpretation>).
2. Alternative interpretations (<interpretation>)
3. Input formats and ASR information: the <input> element,
representing the input to the semantic interpreter.
9.6.1.3. Multi-Modal Integration
When more than one modality is available for input, the
interpretation of the inputs need to be coordinated. The "mode"
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attribute of <input> supports this by indicating whether the
utterance was input by speech, dtmf, pointing, etc. The
"timestamp_start" and "timestamp_end" attributes of <interpretation>
also provide for temporal coordination by indicating when inputs
occurred.
9.6.2. Overview of Recognizer Result Elements and their Relationships
The recognizer elements in NLSML fall into two categories:
1. description of the input that was processed.
2. description of the meaning which was extracted from the input.
Next to each element are its attributes. In addition, some elements
can contain multiple instances of other elements. For example, a
<result> can contain multiple <interpretations>, each of which is
taken to be an alternative. Similarly, <input> can contain multiple
child <input> elements which are taken to be cumulative. To
illustrate the basic usage of these elements, as a simple example,
consider the utterance "ok" (interpreted as "yes"). The example
illustrates how that utterance and its interpretation would be
represented in the NL Semantics markup.
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="http://www.example.com/theYesNoGrammar">
<interpretation>
<instance>
<ex:response>yes</ex:response>
</instance>
<input>ok</input>
</interpretation>
</result>
This example includes only the minimum required information. There
is an overall <result> element which includes one interpretation and
an input element. The interpretation contains the application-
specific element "<response>" which is the semantically interpreted
result.
9.6.3. Elements and Attributes
9.6.3.1. RESULT Root Element
The root element of the markup is <result>. The <result> element
includes one or more <interpretation> elements. Multiple
interpretations can result from ambiguities in the input or in the
semantic interpretation. If the "grammar" attribute does not apply
to all of the interpretations in the result it can be overridden for
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individual interpretations at the <interpretation> level.
Attributes:
1. grammar: The grammar or recognition rule matched by this result.
The format of the grammar attribute will match the rule reference
semantics defined in the grammar specification. Specifically,
the rule reference is in the external XML form for grammar rule
references. The markup interpreter needs to know the grammar
rule that is matched by the utterance because multiple rules may
be simultaneously active. The value is the grammar URI used by
the markup interpreter to specify the grammar. The grammar can
be overridden by a grammar attribute in the <interpretation>
element if the input was ambiguous as to which grammar it
matched. If all interpretation elements within the result
element contain carry their own grammar attributes, the attribute
can be dropped from the result element.
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
grammar="http://www.example.com/grammar">
<interpretation>
....
</interpretation>
</result>
9.6.3.2. INTERPRETATION Element
An <interpretation> element contains a single semantic
interpretation.
Attributes:
1. confidence: A float value from 0.0-1.0 indicating the semantic
analyzer's confidence in this interpretation. A value of 1.0
indicates maximum confidence. The values are implementation-
dependent, but are intended to align with the value
interpretation for the confidence MRCPv2 header field defined in
Section 9.4.1. This attribute is optional.
2. grammar: The grammar or recognition rule matched by this
interpretation (if needed to override the grammar specification
at the <interpretation> level.) This attribute is only needed
under <interpretation> if it is necessary to override a grammar
that was defined at the <result> level.) Note that the grammar
attribute for the interpretation element is OPTIONAL if and only
if the grammar attribute is specified in the result element.
Interpretations MUST be sorted best-first by some measure of
"goodness". The goodness measure is "confidence" if present,
otherwise, it is some implementation-specific indication of quality.
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The grammar is expected to be specified most frequently at the
<result> level. However, it can be overridden at the
<interpretation> level because it is possible that different
interpretations may match different grammar rules.
The <interpretation> element includes an optional <input> element
which contains the input being analyzed, and an <instance> element
containing the interpretation of the utterance.
<interpretation confidence="0.75"
grammar="http://www.example.com/grammar">
...
</interpretation>
9.6.3.3. INSTANCE Element
The <instance> element contains the interpretation of the utterance.
When the Semantic Interpretation for Speech Recognition format is
used, the <instance> element contains the XML serialization of the
result using the approach defined in that specification. When there
is semantic markup in the grammar that does not create semantic
objects, but instead only does a semantic translation of a portion of
the input, such as translating "coke" to "coca-cola", the instance
contains the whole input but with the translation applied. The NLSML
looks like the markup in Figure 2 below. If there are no semantic
objects created, nor any semantic translation the instance value is
the same as the input value.
Attributes:
1. confidence: Each element of the instance may have a confidence
attribute, defined in the NL semantics namespace. The confidence
attribute contains an float value in the range from 0.0-1.0
reflecting the system's confidence in the analysis of that slot.
A value of 1.0 indicates maximum confidence. The values are
implementation-dependent, but are intended to align with the
value interpretation for the confidence MRCPv2 header field
defined in Section 9.4.1. This attribute is optional.
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<instance>
<nameAddress>
<street confidence="0.75">123 Maple Street</street>
<city>Mill Valley</city>
<state>CA</state>
<zip>90952</zip>
</nameAddress>
</instance>
<input>
My address is 123 Maple Street,
Mill Valley, California, 90952
</input>
<instance>
I would like to buy a coca-cola
</instance>
<input>
I would like to buy a coke
</input>
Figure 2: NSLML Example
9.6.3.4. INPUT Element
The <input> element is the text representation of a user's input. It
includes an optional "confidence" attribute which indicates the
recognizer's confidence in the recognition result (as opposed to the
confidence in the interpretation, which is indicated by the
"confidence" attribute of <interpretation>). Optional "timestamp-
start" and "timestamp-end" attributes indicate the start and end
times of a spoken utterance, in ISO 8601 format.
Attributes:
1. timestamp-start: The time at which the input began. (optional)
2. timestamp-end: The time at which the input ended. (optional)
3. mode: The modality of the input, for example, speech, dtmf, etc.
(optional)
4. confidence: the confidence of the recognizer in the correctness
of the input in the range 0.0 to 1.0 (optional)
Note that it may not make sense for temporally overlapping inputs to
have the same mode; however, this constraint is not expected to be
enforced by implementations.
When there is no time zone designator, ISO 8601 time representations
default to local time.
There are three possible formats for the <input> element.
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1. The <input> element can contain simple text:
<input>onions</input>
A future possibility is for <input> to contain not only text but
additional markup that represents prosodic information that was
contained in the original utterance and extracted by the speech
recognizer. This depends on the availability of ASR's that are
capable of producing prosodic information. MRCPv2 clients MUST
be prepared to receive such markup and MAY make use of it.
2. An <input> tag can also contain additional <input> tags. Having
additional input elements allows the representation to support
future multi-modal inputs as well as finer-grained speech
information, such as timestamps for individual words and word-
level confidences.
<input>
<input mode="speech" confidence="0.5"
timestamp-start="2000-04-03T0:00:00"
timestamp-end="2000-04-03T0:00:00.2">fried</input>
<input mode="speech" confidence="1.0"
timestamp-start="2000-04-03T0:00:00.25"
timestamp-end="2000-04-03T0:00:00.6">onions</input>
</input>
3. Finally, the <input> element can contain <nomatch> and <noinput>
elements, which describe situations in which the speech
recognizer received input that it was unable to process, or did
not receive any input at all, respectively.
9.6.3.5. NOMATCH Element
The <nomatch> element under <input> is used to indicate that the
semantic interpreter was unable to successfully match any input with
confidence above the threshold. It can optionally contain the text
of the best of the (rejected) matches.
<interpretation>
<instance/>
<input confidence="0.1">
<nomatch/>
</input>
</interpretation>
<interpretation>
<instance/>
<input mode="speech" confidence="0.1">
<nomatch>I want to go to New York</nomatch>
</input>
</interpretation>
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9.6.3.6. NOINPUT Element
<noinput> indicates that there was no input - a timeout occurred in
the speech recognizer due to silence.
<interpretation>
<instance/>
<input>
<noinput/>
</input>
</interpretation>
If there are multiple levels of inputs, the most natural place for
<nomatch> and <noinput> elements to appear is under the highest level
of <input> for <noinput>, and under the appropriate level of
<interpretation> for <nomatch>. So <noinput> means "no input at all"
and <nomatch> means "no match in speech modality" or "no match in
dtmf modality". For example, to represent garbled speech combined
with dtmf "1 2 3 4", the markup would be:
<input>
<input mode="speech"><nomatch/></input>
<input mode="dtmf">1 2 3 4</input>
</input>
Note: while <noinput> could be represented as an attribute of input,
<nomatch> cannot, since it could potentially include PCDATA content
with the best match. For parallelism, <noinput> is also an element.
9.7. Enrollment Results
All enrollment elements are contained within a single <enrollment-
result> element under <result>. The elements are described below and
have the schema defined in Section 16.2. The following elements are
defined:
1. num-clashes
2. num-good-repetitions
3. num-repetitions-still-needed
4. consistency-status
5. clash-phrase-ids
6. transcriptions
7. confusable-phrases
9.7.1. NUM-CLASHES Element
The <num-clashes> element contains the number of clashes that this
pronunciation has with other pronunciations in an active enrollment
session. The associated Clash-Threshold header field determines the
sensitivity of the clash measurement. Note that clash testing can be
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turned off completely by setting the Clash-Threshold header field
value to 0.
9.7.2. NUM-GOOD-REPETITIONS Element
The <num-good-repetitions> element contains the number of consistent
pronunciations obtained so far in an active enrollment session.
9.7.3. NUM-REPETITIONS-STILL-NEEDED Element
The <num-repetitions-still-needed> element contains the number of
consistent pronunciations that must still be obtained before the new
phrase can be added to the enrollment grammar. The number of
consistent pronunciations required is specified by the client in the
request header field Num-Min-Consistent-Pronunciations. The returned
value must be 0 before the client can successfully commit a phrase to
the grammar by ending the enrollment session.
9.7.4. CONSISTENCY-STATUS Element
The <consistency-status> element is used to indicate how consistent
the repetitions are when learning a new phrase. It can have the
values of consistent, inconsistent, and undecided.
9.7.5. CLASH-PHRASE-IDS Element
The <clash-phrase-ids> element contains the phrase ids of clashing
pronunciation(s), if any. This element is absent if there are no
clashes.
9.7.6. TRANSCRIPTIONS Element
The <transcriptions> element contains the transcriptions returned in
the last repetition of the phrase being enrolled.
9.7.7. CONFUSABLE-PHRASES Element
The <confusable-phrases> element contains a list of phrases from a
command grammar that are confusable with the phrase being added to
the personal grammar. This element may be absent if there are no
confusable phrases.
9.8. DEFINE-GRAMMAR
The DEFINE-GRAMMAR method, from the client to the server, provides
one or more grammars and requests the server to access, fetch, and
compile the grammars as needed. The DEFINE-GRAMMAR method
implementation MUST do a fetch of all external URIs that are part of
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that operation. If caching is implemented, this URI fetching MUST
conform to the cache control hints and parameter header fields
associated with the method in deciding whether it should be fetched
from cache or from the external server. If these hints/parameters
are not specified in the method, the values set for the session using
SET-PARAMS/GET-PARAMS apply. If it was not set for the session their
default values apply.
If the server resource is in the recognition state, the DEFINE-
GRAMMAR request MUST respond with a failure status.
If the resource is in the idle state and is able to successfully
process the supplied grammars, the server MUST return a success code
status and the request-state MUST be COMPLETE.
If the recognizer resource could not define the grammar for some
reason, for example if the download failed, the grammar failed to
compile, or the grammar was in an unsupported form, the MRCPv2
response for the DEFINE-GRAMMAR method MUST contain a failure status
code of 407, and contain a completion-cause header field describing
the failure reason.
C->S:MRCP/2.0 ... DEFINE-GRAMMAR 543257
Channel-Identifier:32AECB23433801@speechrecog
Content-Type:application/srgs+xml
Content-ID:<request1@form-level.store>
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0">
<!-- single language attachment to tokens -->
<rule id="yes">
<one-of>
<item xml:lang="fr-CA">oui</item>
<item xml:lang="en-US">yes</item>
</one-of>
</rule>
<!-- single language attachment to a rule expansion -->
<rule id="request">
may I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
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</one-of>
</rule>
</grammar>
S->C:MRCP/2.0 ... 543257 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
C->S:MRCP/2.0 ... DEFINE-GRAMMAR 543258
Channel-Identifier:32AECB23433801@speechrecog
Content-Type:application/srgs+xml
Content-ID:<helpgrammar@root-level.store>
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0">
<rule id="request">
I need help
</rule>
S->C:MRCP/2.0 ... 543258 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
C->S:MRCP/2.0 ... DEFINE-GRAMMAR 543259
Channel-Identifier:32AECB23433801@speechrecog
Content-Type:application/srgs+xml
Content-ID:<request2@field-level.store>
Content-Length:...
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN"
"http://www.w3.org/TR/speech-grammar/grammar.dtd">
<grammar xmlns="http://www.w3.org/2001/06/grammar" xml:lang="en"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/06/grammar
http://www.w3.org/TR/speech-grammar/grammar.xsd"
version="1.0" mode="voice" root="basicCmd">
<meta name="author" content="Stephanie Williams"/>
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<rule id="basicCmd" scope="public">
<example> please move the window </example>
<example> open a file </example>
<ruleref
uri="http://grammar.example.com/politeness.grxml#startPolite"/>
<ruleref uri="#command"/>
<ruleref
uri="http://grammar.example.com/politeness.grxml#endPolite"/>
</rule>
<rule id="command">
<ruleref uri="#action"/> <ruleref uri="#object"/>
</rule>
<rule id="action">
<one-of>
<item weight="10"> open <tag>open</tag> </item>
<item weight="2"> close <tag>close</tag> </item>
<item weight="1"> delete <tag>delete</tag> </item>
<item weight="1"> move <tag>move</tag> </item>
</one-of>
</rule>
<rule id="object">
<item repeat="0-1">
<one-of>
<item> the </item>
<item> a </item>
</one-of>
</item>
<one-of>
<item> window </item>
<item> file </item>
<item> menu </item>
</one-of>
</rule>
</grammar>
S->C:MRCP/2.0 ... 543259 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
C->S:MRCP/2.0 ... RECOGNIZE 543260
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Channel-Identifier:32AECB23433801@speechrecog
N-Best-List-Length:2
Content-Type:text/uri-list
Content-Length:...
session:request1@form-level.store
session:request2@field-level.store
session:helpgramar@root-level.store
S->C:MRCP/2.0 ... 543260 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
S->C:MRCP/2.0 ... START-OF-INPUT 543260 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
S->C:MRCP/2.0 ... RECOGNITION-COMPLETE 543260 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
Waveform-URI:<http://web.media.com/session123/audio.wav>;
size=124535;duration=2340
Content-Type:application/x-nlsml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="session:request1@form-level.store">
<interpretation>
<instance name="Person">
<ex:Person>
<ex:Name> Andre Roy </ex:Name>
</ex:Person>
</instance>
<input> may I speak to Andre Roy </input>
</interpretation>
</result>
Define Grammar Example
9.9. RECOGNIZE
The RECOGNIZE method from the client to the server requests the
recognizer to start recognition and provides it with one or more
grammar references for grammars to match against the input media.
The RECOGNIZE method can carry header fields to control the
sensitivity, confidence level and the level of detail in results
provided by the recognizer. These header field values override the
current values set by a previous "SET-PARAMS" method.
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The RECOGNIZE method can request the recognizer resource to operate
in normal or hotword mode as specified by the Recognition-Mode header
field. The default value is "normal". If the resource could not
start a recognition, the server MUST respond with a failure status
code of 407 and a completion-cause header field in the response
describing the cause of failure.
The RECOGNIZE request uses the message body to specify the grammars
applicable to the request. The active grammar(s) for the request can
be specified in one of 3 ways. If the client needs to explicitly
control grammar weights for the recognition operation, it must employ
method 3 below. The order of these grammars specifies the precedence
of the grammars which is used when more than one grammar in the list
matches the speech; in this case, the grammar with the higher
precedence is returned as a match. This precedence capability is
useful in applications like VoiceXML browsers to order grammars
specified at the dialog, document and root level of a VoiceXML
application.
1. The grammar may be placed directly in the message body as typed
content. If more than one grammar is included in the body, the
order of inclusion controls the corresponding precedence for the
grammars during recognition, with earlier grammars in the body
having a higher precedence than later ones.
2. The body may contain a list of grammar URIs specified in content
of Media Type text/uri-list RFC2483 [RFC2483]. The order of the
URIs determines the corresponding precedence for the grammars
during recognition, with highest-precedence first and decreasing
for each URI thereafter.
3. The body may contain a list of grammar URIs specified in content
of Media Type text/grammar-ref-list. This type defines a list of
grammar URIs and allows each grammar URI to be assigned a weight
in the list. This weight has the same meaning as the W3C grammar
weights.
In addition to performing recognition on the input, the recognizer
may also enroll the collected utterance in a personal grammar if the
Enroll-Utterance header field is set to true and an Enrollment is
active (via an earlier execution of the START-PHRASE-ENROLLMENT
method). If so, and if the RECOGNIZE request contains a Content-ID
header field, then the resulting grammar (which includes the personal
grammar as a sub-grammar) can be referenced through the "session:"
URI scheme (see Section 13.6).
If the resource was able to successfully start the recognition, the
server MUST return a success code and a request-state of IN-PROGRESS.
This means that the recognizer is active and that the client MUST be
prepared to receive further events with this request-id.
If the resource was able to queue the request the server MUST return
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a success code and request-state of PENDING. This means that the
recognizer is currently active with another request and that this
request has been queued for processing.
If the resource could not start a recognition, the server MUST
respond with a failure status code of 407 and a completion-cause
header field in the response describing the cause of failure.
For the recognizer resource, RECOGNIZE and INTERPRET are the only
requests that returns a request-state of IN-PROGRESS, meaning that
recognition is in progress. When the recognition completes by
matching one of the grammar alternatives or by a time-out without a
match or for some other reason, the recognizer resource MUST send the
client a RECOGNITION-COMPLETE event (or INTERPRETATION-COMPLETE, if
INTERPRET was the request) with the result of the recognition and a
request-state of COMPLETE.
Large grammars can take a long time for the server to compile. For
grammars which are used repeatedly, the client can improve server
performance by issuing a DEFINE-GRAMMAR request with the grammar
ahead of time. In such a case the client can issue the RECOGNIZE
request and reference the grammar through the "session:" URI scheme
(see Section 13.6). This also applies in general if the client wants
to repeat recognition with a previous inline grammar.
The RECOGNIZE method implementation MUST do a fetch of all external
URIs that are part of that operation. If caching is implemented,
this URI fetching MUST conform to the cache control hints and
parameter header fields associated with the method in deciding
whether it should be fetched from cache or from the external server.
If these hints/parameters are not specified in the method, the values
set for the session using SET-PARAMS/GET-PARAMS apply. If it was not
set for the session their default values apply.
Note that since the audio and the messages are carried over separate
communication paths there may be a race condition between the start
of the flow of audio and the receipt of the RECOGNIZE method. For
example, if an audio flow is started by the client at the same time
as the RECOGNIZE method is sent, either the audio or the RECOGNIZE
can arrive at the recognizer first. As another example, the client
may choose to continuously send audio to the Server and signal the
Server to recognize using the RECOGNIZE method. Mechanisms to
resolve this condition are outside the scope of this specification.
The recognizer can expect the media to start flowing when it receives
the recognize request, but MUST NOT buffer anything it receives
beforehand in order to preserve the semantics that application
authors expect with respect to the input timers.
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When a RECOGNIZE method has been received the recognition is
initiated on the stream. The No-Input-Timer MUST BE started at this
time if the Start-Input-Timers header field is specified as "true".
If this header field is set to "false", the No-Input-Timer MUST be
started when it receives the START-INPUT-TIMERS method from the
client. The Recognition-Timer MUST be started when the recognition
resource detects speech or a DTMF digit in the media stream.
Non-Hotword mode recognition:
When the recognition resource detects speech or a DTMF digit in the
media stream it MUST send the START-OF-INPUT event. When enough
speech has been collected for the server to process, the recognizer
can try to match the collected speech with the active grammars. If
the speech collected at this point fully matches with any of the
active grammars, the Speech-Complete-Timer is started. If it matches
partially with one or more of the active grammars, with more speech
needed before a full match is achieved, then the Speech-Incomplete-
Timer is started.
1. When the No-Input-Timer expires, the recognizer must complete
with a Completion-Cause code of "no-input-timeout".
2. The recognizer MUST support detecting a no-match condition upon
detecting end of speech. The recognizer MAY support detecting a no-
match condition before waiting for end-of-speech. If this is
supported, this capability is enabled by setting the "Early-No-Match"
header field to "true". Upon detecting a no-match condition the
RECOGNIZE MUST return with "no-match".
3. When the Speech-Incomplete-Timer expires the recognizer SHOULD
complete with a Completion-Cause code of "partial-match", unless the
recognizer cannot differentiate a partial-match in which case it MUST
return a Completion-Cause code of "no-match". The recognizer MAY
return results for the partially matched grammar.
4. When the Speech-Complete-Timer expires the recognizer MUST
complete with a Completion-Cause code of "success".
5. When the Recognition-Timer expires one of the following MUST
happen:
5.1 If there was a partial-match the recognizer SHOULD complete with
a Completion-Cause code of "partial-match-maxtime", unless the
recognizer cannot differentiate a partial-match in which case it MUST
complete with a Completion-Cause code of "no-match-maxtime". The
recognizer MAY return results for the partially matched grammar.
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5.2 If there was a full-match the recognizer MUST complete with a
Completion-Cause code of "success-maxtime".
5.3 If there was a no match the recognizer MUST complete with a
Completion-Cause code of "no-match-maxtime".
For the Hotword mode recognition:
Note that for Hotword mode recognition the START-OF-INPUT event is
not generated when speech or a DTMF digit is detected.
1. When the No-Input-Timer expires, the recognizer must complete
with a Completion-Cause code of "no-input-timeout".
2. When there is match at anytime, the RECOGNIZE completes with a
Completion-Cause code of "success".
3. When the Recognition-Timer expires and there is not a match, the
RECOGNIZE MUST complete with a Completion-Cause code of "hotword-
maxtime".
4. When the Recognition-Timer expires and there is a match, the
RECOGNIZE MUST complete with a Completion-Cause code of "success-
maxtime".
5. When the Recognition-Timer is running but the detected speech/
DTMF has not resulted in a match, the Recognition-Timer MUST be
stopped and reset. It MUST then be restarted when speech/DTMF is
again detected.
C->S:MRCP/2.0 ... RECOGNIZE 543257
Channel-Identifier:32AECB23433801@speechrecog
Confidence-Threshold:0.9
Content-Type:application/srgs+xml
Content-ID:<request1@form-level.store>
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0" root="request">
<!-- single language attachment to tokens -->
<rule id="yes">
<one-of>
<item xml:lang="fr-CA">oui</item>
<item xml:lang="en-US">yes</item>
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</one-of>
</rule>
<!-- single language attachment to a rule expansion -->
<rule id="request">
may I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
</one-of>
</rule>
</grammar>
S->C: MRCP/2.0 ... 543257 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
S->C:MRCP/2.0 ... START-OF-INPUT 543257 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
S->C:MRCP/2.0 ... RECOGNITION-COMPLETE 543257 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
Waveform-URI:<http://web.media.com/session123/audio.wav>;
size=424252;duration=2543
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="session:request1@form-level.store">
<interpretation>
<instance name="Person">
<ex:Person>
<ex:Name> Andre Roy </ex:Name>
</ex:Person>
</instance>
<input> may I speak to Andre Roy </input>
</interpretation>
</result>
RECOGNIZE Example
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C->S: MRCP/2.0 ... RECOGNIZE 543257
Channel-Identifier:32AECB23433801@speechrecog
Confidence-Threshold:0.9
Fetch-Timeout:20
Content-Type:application/srgs+xml
Content-Length:...
<?xml version="1.0"? Version="1.0" mode="voice"
root="Basic md">
<rule id="rule_list" scope="public">
<one-of>
<item weight=10>
<ruleref uri=
"http://grammar.example.com/world-cities.grxml#canada"/>
</item>
<item weight=1.5>
<ruleref uri=
"http://grammar.example.com/world-cities.grxml#america"/>
</item>
<item weight=0.5>
<ruleref uri=
"http://grammar.example.com/world-cities.grxml#india"/>
</item>
</one-of>
</rule>
Second RECOGNIZE Example
9.10. STOP
The "STOP" method from the client to the server tells the resource to
stop recognition if a request is active. If a RECOGNIZE request is
active and the "STOP" request successfully terminated it, then the
response header section contains an active-request-id-list header
field containing the request-id of the RECOGNIZE request that was
terminated. In this case, no RECOGNITION-COMPLETE event is sent for
the terminated request. If there was no recognition active, then the
response MUST NOT contain an active-request-id-list header field.
Either way the response MUST contain a status of 200 (Success).
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C->S: MRCP/2.0 ... RECOGNIZE 543257
Channel-Identifier:32AECB23433801@speechrecog
Confidence-Threshold:0.9
Content-Type:application/srgs+xml
Content-ID:<request1@form-level.store>
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0" root="request">
<!-- single language attachment to tokens -->
<rule id="yes">
<one-of>
<item xml:lang="fr-CA">oui</item>
<item xml:lang="en-US">yes</item>
</one-of>
</rule>
<!-- single language attachment to a rule expansion -->
<rule id="request">
may I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
</one-of>
</rule>
</grammar>
S->C: MRCP/2.0 ... 543257 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
C->S: MRCP/2.0 ... STOP 543258 200
Channel-Identifier:32AECB23433801@speechrecog
S->C: MRCP/2.0 ... 543258 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Active-Request-Id-List:543257
9.11. GET-RESULT
The GET-RESULT method from the client to the server may be issued
when the recognizer resource is in the recognized state. This
request allows the client to retrieve results for a completed
recognition. This is useful if the client decides it wants more
alternatives or more information. When the server receives this
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request it re-computes and returns the results according to the
recognition constraints provided in the GET-RESULT request.
The GET-RESULT request can specify constraints such as a different
confidence-threshold, or n-best-list-length. This capability is
optional for MRCPv2 servers and the automatic speech recognition
engine in the server MAY return a status of unsupported feature.
C->S: MRCP/2.0 ... GET-RESULT 543257
Channel-Identifier:32AECB23433801@speechrecog
Confidence-Threshold:0.9
S->C: MRCP/2.0 ... 543257 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="session:request1@form-level.store">
<interpretation>
<instance name="Person">
<ex:Person>
<ex:Name> Andre Roy </ex:Name>
</ex:Person>
</instance>
<input> may I speak to Andre Roy </input>
</interpretation>
</result>
9.12. START-OF-INPUT
This is an event from the server to the client indicating that the
recognition resource has detected speech or a DTMF digit in the media
stream. This event is useful in implementing kill-on-barge-in
scenarios when a synthesizer resource is in a different session from
the recognizer resource and hence is not aware of an incoming audio
source (see Section 8.4.2). In these cases, it is up to the client
to act as a intermediary and respond to this event by issuing a
BARGE-IN-OCCURRED event to the synthesizer resource. The recognizer
resource also MUST send a Proxy-Sync-Id header field with a unique
value for this event.
This event MUST be generated by the server irrespective of whether
the synthesizer and recognizer are on the same server or not.
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9.13. START-INPUT-TIMERS
This request is sent from the client to the recognition resource when
it knows that a kill-on-barge-in prompt has finished playing (see
Section 8.4.2). This is useful in the scenario when the recognition
and synthesizer engines are not in the same session. When a kill-on-
barge-in prompt is being played, the client may want a RECOGNIZE
request to be simultaneously active so that it can detect and
implement kill on barge-in. But at the same time the client doesn't
want the recognizer to start the no-input timers until the prompt is
finished. The Start-Input-Timers header field in the RECOGNIZE
request allows the client to say whether the timers should be started
immediately or not. If not, the recognizer resource MUST NOT start
the timers until the client sends a START-INPUT-TIMERS method to the
recognizer.
9.14. RECOGNITION-COMPLETE
This is an Event from the recognizer resource to the client
indicating that the recognition completed. The recognition result is
sent in the body of the MRCPv2 message. The request-state field MUST
be COMPLETE indicating that this is the last event with that
request-id, and that the request with that request-id is now
complete. The server MUST maintain the recognizer context containing
the results and the audio waveform input of that recognition until
the next RECOGNIZE request is issued for that resource or the session
terminates. A URI to the audio waveform MAY be returned to the
client in a Waveform-URI header field in the RECOGNITION-COMPLETE
event. The client can use this URI to retrieve or playback the
audio.
Note if an enrollment session was active, the RECOGNITION-COMPLETE
event can contain either recognition or enrollment results depending
on what was spoken. The following example shows a complete exchange
with a recognition result.
C->S: MRCP/2.0 ... RECOGNIZE 543257
Channel-Identifier:32AECB23433801@speechrecog
Confidence-Threshold:0.9
Content-Type:application/srgs+xml
Content-ID:<request1@form-level.store>
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0" root="request">
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<!-- single language attachment to tokens -->
<rule id="yes">
<one-of>
<item xml:lang="fr-CA">oui</item>
<item xml:lang="en-US">yes</item>
</one-of>
</rule>
<!-- single language attachment to a rule expansion -->
<rule id="request">
may I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
</one-of>
</rule>
</grammar>
S->C: MRCP/2.0 ... 543257 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
S->C: MRCP/2.0 ... START-OF-INPUT 543257 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
S->C: MRCP/2.0 ... RECOGNITION-COMPLETE 543257 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
Waveform-URI:<http://web.media.com/session123/audio.wav>;
size=342456;duration=25435
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="session:request1@form-level.store">
<interpretation>
<instance name="Person">
<ex:Person>
<ex:Name> Andre Roy </ex:Name>
</ex:Person>
</instance>
<input> may I speak to Andre Roy </input>
</interpretation>
</result>
If the result were instead an enrollment result, the final message
from the server above could have instead been:
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S->C: MRCP/2.0 ... RECOGNITION-COMPLETE 543257 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version= "1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
grammar="Personal-Grammar-URI">
<enrollment-result>
<num-clashes> 2 </num-clashes>
<num-good-repetitions> 1 </num-good-repetitions>
<num-repetitions-still-needed>
1
</num-repetitions-still-needed>
<consistency-status> consistent </consistency-status>
<clash-phrase-ids>
<item> Jeff </item> <item> Andre </item>
</clash-phrase-ids>
<transcriptions>
<item> m ay b r ow k er </item>
<item> m ax r aa k ah </item>
</transcriptions>
<confusable-phrases>
<item>
<phrase> call </phrase>
<confusion-level> 10 </confusion-level>
</item>
</confusable-phrases>
</enrollment-result>
</result>
9.15. START-PHRASE-ENROLLMENT
The START-PHRASE-ENROLLMENT method from the client to the server
starts a new phrase enrollment session during which the client may
call RECOGNIZE multiple times to enroll a new utterance in a grammar.
An enrollment session consists of a set of calls to RECOGNIZE in
which the caller speaks a phrase several times so the system can
"learn" it. The phrase is then added to a personal grammar (speaker-
trained grammar), so that the system can recognize it later.
Only one phrase enrollment session may be active at a time for a
resource. The Personal-Grammar-URI identifies the grammar that is
used during enrollment to store the personal list of phrases. Once
RECOGNIZE is called, the result is returned in a RECOGNITION-COMPLETE
event and may contain either an enrollment result OR a recognition
result for a regular recognition.
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Calling END-PHRASE-ENROLLMENT ends the ongoing phrase enrollment
session, which is typically done after a sequence of successful calls
to RECOGNIZE. This method can be called to commit the new phrase to
the personal grammar or to abort the phrase enrollment session.
The grammar to contain the new enrolled phrase, specified by
Personal-Grammar-URI, is created if it does not exist. Also, the
personal grammar may ONLY contain phrases added via a phrase
enrollment session.
The Phrase-ID passed to this method is used to identify this phrase
in the grammar and will be returned as the speech input when doing a
RECOGNIZE on the grammar. The Phrase-NL similarly is returned in a
RECOGNITION-COMPLETE event in the same manner as other NL in a
grammar. The tag-format of this NL is implementation specific.
If the client has specified Save-Best-Waveform as true, then the
response after ending the phrase enrollment session MUST contain the
location/URI of a recording of the best repetition of the learned
phrase.
C->S: MRCP/2.0 ... START-PHRASE-ENROLLMENT 543258
Channel-Identifier:32AECB23433801@speechrecog
Num-Min-Consistent-Pronunciations:2
Consistency-Threshold:30
Clash-Threshold:12
Personal-Grammar-URI:<personal grammar uri>
Phrase-Id:<phrase id>
Phrase-NL:<NL phrase>
Weight:1
Save-Best-Waveform:true
S->C: MRCP/2.0 ... 543258 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
9.16. ENROLLMENT-ROLLBACK
The ENROLLMENT-ROLLBACK method discards the last live utterance from
the RECOGNIZE operation. The client can invoke this method when the
caller provides undesirable input such as non-speech noises, side-
speech, commands, utterance from the RECOGNIZE grammar, etc. Note
that this method does not provide a stack of rollback states.
Executing ENROLLMENT-ROLLBACK twice in succession without an
intervening recognition operation has no effect the second time.
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C->S: MRCP/2.0 ... ENROLLMENT-ROLLBACK 543261
Channel-Identifier:32AECB23433801@speechrecog
S->C: MRCP/2.0 ... 543261 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
9.17. END-PHRASE-ENROLLMENT
The END-PHRASE-ENROLLMENT method may be called ONLY during an active
phrase enrollment session. It MUST NOT be called during an ongoing
RECOGNIZE operation. To commit the new phrase in the grammar, the
client MAY call this method once successive calls to RECOGNIZE have
succeeded and Num-Repetitions-Still-Needed has been returned as 0 in
the RECOGNITION-COMPLETE event. Alternatively, the client can abort
the phrase enrollment session by calling this method with the Abort-
Phrase-Enrollment header field.
If the client has specified Save-Best-Waveform as true in the START-
PHRASE-ENROLLMENT request, then the response MUST contain the
location/URI of a recording of the best repetition of the learned
phrase.
C->S: MRCP/2.0 ... END-PHRASE-ENROLLMENT 543262
Channel-Identifier:32AECB23433801@speechrecog
S->C: MRCP/2.0 ... 543262 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Waveform-URI:<http://mediaserver.com/recordings/file1324.wav>;
size=242453;duration=25432
9.18. MODIFY-PHRASE
The MODIFY-PHRASE method sent from the client to the server is used
to change the phrase ID, NL phrase and/or weight for a given phrase
in a personal grammar.
If no fields are supplied then calling this method has no effect.
C->S: MRCP/2.0 ... MODIFY-PHRASE 543265
Channel-Identifier:32AECB23433801@speechrecog
Personal-Grammar-URI:<personal grammar uri>
Phrase-Id:<phrase id>
New-Phrase-Id:<new phrase id>
Phrase-NL:<NL phrase>
Weight:1
S->C: MRCP/2.0 ... 543265 200 COMPLETE
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Channel-Identifier:32AECB23433801@speechrecog
9.19. DELETE-PHRASE
The DELETE-PHRASE method sent from the client to the server is used
to delete a phase in a personal grammar added through voice
enrollment or text enrollment. If the specified phrase does not
exist, this method has no effect.
C->S: MRCP/2.0 ... DELETE-PHRASE 543266
Channel-Identifier:32AECB23433801@speechrecog
Personal-Grammar-URI:<personal grammar uri>
Phrase-Id:<phrase id>
S->C: MRCP/2.0 ... 543266 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
9.20. INTERPRET
The INTERPRET method from the client to the server takes as input an
interpret-text header field containing the text for which the
semantic interpretation is desired, and returns, via the
INTERPRETATION-COMPLETE event, an interpretation result which is very
similar to the one returned from a RECOGNIZE method invocation. Only
portions of the result relevant to acoustic matching are excluded
from the result. The interpret-text header field MUST be included in
the INTERPRET request.
Recognizer grammar data is treated in the same way as it is when
issuing a RECOGNIZE method call.
If a RECOGNIZE, RECORD or another INTERPRET operation is already in
progress for the resource, the server MUST reject the request with a
response having a status code of 402, "Method not valid in this
state", and a COMPLETE request state.
C->S: MRCP/2.0 ... INTERPRET 543266
Channel-Identifier:32AECB23433801@speechrecog
Interpret-Text:may I speak to Andre Roy
Content-Type:application/srgs+xml
Content-ID:<request1@form-level.store>
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0" root="request">
<!-- single language attachment to tokens -->
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<rule id="yes">
<one-of>
<item xml:lang="fr-CA">oui</item>
<item xml:lang="en-US">yes</item>
</one-of>
</rule>
<!-- single language attachment to a rule expansion -->
<rule id="request">
may I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
</one-of>
</rule>
</grammar>
S->C: MRCP/2.0 ... 543266 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
S->C: MRCP/2.0 ... INTERPRETATION-COMPLETE 543267 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="session:request1@form-level.store">
<interpretation>
<instance name="Person">
<ex:Person>
<ex:Name> Andre Roy </ex:Name>
</ex:Person>
</instance>
<input> may I speak to Andre Roy </input>
</interpretation>
</result>
9.21. INTERPRETATION-COMPLETE
This event from the recognition resource to the client indicates that
the INTERPRET operation is complete. The interpretation result is
sent in the body of the MRCP message. The request state MUST be set
to COMPLETE.
The completion-cause header field MUST be included in this event and
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MUST be set to an appropriate value from the list of cause codes.
C->S: MRCP/2.0 ... INTERPRET 543266
Channel-Identifier:32AECB23433801@speechrecog
Interpret-Text:may I speak to Andre Roy
Content-Type:application/srgs+xml
Content-ID:<request1@form-level.store>
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0" root="request">
<!-- single language attachment to tokens -->
<rule id="yes">
<one-of>
<item xml:lang="fr-CA">oui</item>
<item xml:lang="en-US">yes</item>
</one-of>
</rule>
<!-- single language attachment to a rule expansion -->
<rule id="request">
may I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
</one-of>
</rule>
</grammar>
S->C: MRCP/2.0 ... 543266 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
S->C: MRCP/2.0 ... INTERPRETATION-COMPLETE 543267 200 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="session:request1@form-level.store">
<interpretation>
<instance name="Person">
<ex:Person>
<ex:Name> Andre Roy </ex:Name>
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</ex:Person>
</instance>
<input> may I speak to Andre Roy </input>
</interpretation>
</result>
9.22. DTMF Detection
Digits received as DTMF tones are delivered to the recognition
resource in the MRCPv2 server in the RTP stream according to RFC4733
[RFC4733]. The automatic speech recognizer (ASR) MUST support
RFC4733 to recognize digits and it MAY support recognizing DTMF tones
[Q.23] in the audio.
10. Recorder Resource
This resource captures received audio and video and stores it as
content pointed to by a URI. The main usages of recorders are
1. to capture speech audio that may be submitted for recognition at
a later time, and
2. recording voice or video mails.
Both these applications require functionality above and beyond those
specified by protocols such as RTSP. This includes Audio endpointing
(i.e. detecting speech or silence). The support for video is
optional and is mainly capturing video mails that may require the
speech or audio processing mentioned above.
A recorder MUST provide some endpointing capabilities for suppressing
silence at the beginning and end of a recording, and MAY also
suppress silence in the middle of a recording. If such suppression
is done, the recorder MUST maintain timing metadata to indicate the
actual time stamps of the recorded media.
See the discussion on the sensitivity of saved waveforms in
Section 12.
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10.1. Recorder State Machine
Idle Recording
State State
| |
|---------RECORD------->|
| |
|<------STOP------------|
| |
|<--RECORD-COMPLETE-----|
| |
| |--------|
| START-OF-INPUT |
| |------->|
| |
| |--------|
| START-INPUT-TIMERS |
| |------->|
| |
Recorder State Machine
10.2. Recorder Methods
The recorder resource supports the following methods.
recorder-method = "RECORD"
/ "STOP"
/ "START-INPUT-TIMERS"
10.3. Recorder Events
The recorder resource may generate the following events.
recorder-event = "START-OF-INPUT"
/ "RECORD-COMPLETE"
10.4. Recorder Header Fields
Method invocations for the recorder resource may contain resource-
specific header fields containing request options and information to
augment the Method, Response or Event message it is associated with.
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recorder-header = sensitivity-level
/ no-input-timeout
/ completion-cause
/ completion-reason
/ failed-uri
/ failed-uri-cause
/ record-uri
/ media-type
/ max-time
/ trim-length
/ final-silence
/ capture-on-speech
/ ver-buffer-utterance
/ start-input-timers
/ new-audio-channel
10.4.1. Sensitivity Level
To filter out background noise and not mistake it for speech, the
recorder may support a variable level of sound sensitivity. The
sensitivity-level header field is a float value between 0.0 and 1.0
and allows the client to set the sensitivity level for the recorder.
This header field MAY occur in RECORD, "SET-PARAMS" or "GET-PARAMS".
A higher value for this header field means higher sensitivity. The
default value for this header field is implementation specific.
sensitivity-level = "Sensitivity-Level" ":" FLOAT CRLF
10.4.2. No Input Timeout
When recording is started and there is no speech detected for a
certain period of time, the recorder can send a RECORD-COMPLETE event
to the client and terminate the record operation. The no-input-
timeout header field can set this timeout value. The value is in
milliseconds. This header field MAY occur in RECORD, "SET-PARAMS" or
"GET-PARAMS". The value for this header field ranges from 0 to an
implementation specific maximum value. The default value for this
header field is implementation specific.
no-input-timeout = "No-Input-Timeout" ":" 1*19DIGIT CRLF
10.4.3. Completion Cause
This header field MUST be part of a RECORD-COMPLETE event from the
recorder resource to the client. This indicates the reason behind
the RECORD method completion. This header field MUST be sent in the
RECORD responses if they return with a failure status and a COMPLETE
state.
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completion-cause = "Completion-Cause" ":" 3DIGIT SP
1*VCHAR CRLF
+------------+-----------------------+------------------------------+
| Cause-Code | Cause-Name | Description |
+------------+-----------------------+------------------------------+
| 000 | success-silence | RECORD completed with a |
| | | silence at the end |
| 001 | success-maxtime | RECORD completed after |
| | | reaching maximum recording |
| | | time specified in record |
| | | method. |
| 002 | noinput-timeout | RECORD failed due to no |
| | | input |
| 003 | uri-failure | Failure accessing the record |
| | | URI. |
| 004 | error | RECORD request terminated |
| | | prematurely due to a |
| | | recorder error. |
+------------+-----------------------+------------------------------+
10.4.4. Completion Reason
This header field MAY be present in a RECORD-COMPLETE event coming
from the recorder resource to the client. It contains the reason
text behind the RECORD request completion. This header field
communicates text describing the reason for the failure.
The completion reason text is provided for client use in logs and for
debugging and instrumentation purposes. Clients MUST NOT interpret
the completion reason text.
completion-reason = "Completion-Reason" ":"
quoted-string CRLF
10.4.5. Failed URI
When a recorder method needs to post the audio to a URI and access to
the URI fails, the server MUST provide the failed URI in this header
field in the method response.
failed-uri = "Failed-URI" ":" absoluteURI CRLF
10.4.6. Failed URI Cause
When a recorder method needs to post the audio to a URI and access to
the URI fails, the server MAY provide the URI specific or protocol
specific response code through this header field in the method
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response. The value encoding is UTF-8 to accommodate any access
protocol, some of which might have a response string instead of a
numeric response code.
failed-uri-cause = "Failed-URI-Cause" ":" 1*UTFCHAR
CRLF
10.4.7. Record URI
When a recorder method contains this header field the server MUST
capture the audio and store it. If the header field is present but
specified with no value, the server MUST store the content locally
and generate a URI that points to it. This URI is then returned in
either the "STOP" response or the RECORD-COMPLETE event. If the
header field in the RECORD method specifies a URI, the server MUST
attempt to capture and store the audio at that location. If this
header field is not specified in the RECORD request, the server MUST
capture the audio and send it in the "STOP" response or the RECORD-
COMPLETE event as a message body. In this case, the response
carrying the audio content would have this header field with a cid
value pointing to the Content-ID in the message body.
The server MUST also return the size in octets and the duration in
milliseconds of the recorded audio wave-form as parameters associated
with the header field.
Only HTTP, HTTPS, and FILE are permitted as valid schemes in the URI.
Note, however, that implementations already exist that support other
schemes.
record-uri = "Record-URI" ":" ["<" uri ">"
";" "size" "=" 1*19DIGIT
";" "duration" "=" 1*19DIGIT] CRLF
10.4.8. Media Type
A RECORD method MUST contain this header field, which specifies to
the server the Media Type of the captured audio or video.
media-type = "Media-Type" ":" media-type-value
CRLF
10.4.9. Max Time
When recording is started this specifies the maximum length of the
recording in milliseconds, calculated from the time the actual
capture and store begins and is not necessarily the time the RECORD
method is received. It specifies the duration before silence
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suppression, if any, has been applied by the recorder resource.
After this time, the recording stops and the server MUST return a
RECORD-COMPLETE event to the client having a request-state of
"COMPLETE". This header field MAY occur in RECORD, "SET-PARAMS" or
"GET-PARAMS". The value for this header field ranges from 0 to an
implementation specific maximum value. A value of zero means
infinity and hence the recording continues until one or more of the
other stop conditions are met. The default value for this header
field is 0.
max-time = "Max-Time" ":" 1*19DIGIT CRLF
10.4.10. Trim-Length
This header field MAY be sent on a STOP method and specifies the
length of audio to be trimmed from the end of the recording after the
stop. The length is interpreted to be in milliseconds. The default
value for this header field is 0.
trim-length = "Trim-Length" ":" 1*19DIGIT CRLF
10.4.11. Final Silence
When recorder is started and the actual capture begins, this header
field specifies the length of silence in the audio that is to be
interpreted as the end of the recording. This header field MAY occur
in RECORD, "SET-PARAMS" or "GET-PARAMS". The value for this header
field ranges from 0 to an implementation specific maximum value and
is interpreted to be in milliseconds. A value of zero means infinity
and hence the recording will continue until one of the other stop
conditions are met. The default value for this header field is
implementation specific.
final-silence = "Final-Silence" ":" 1*19DIGIT CRLF
10.4.12. Capture On Speech
If false, the recorder MUST start capturing immediately when started.
If true, the recorder MUST wait for the endpointing functionality to
detect speech before it starts capturing. This header field MAY
occur in the RECORD, "SET-PARAMS" or "GET-PARAMS". The value for
this header field is a Boolean. The default value for this header
field is false.
capture-on-speech = "Capture-On-Speech " ":" BOOLEAN CRLF
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10.4.13. Ver-Buffer-Utterance
This header field is the same as the one described for the verifier
resource (see Section 11.4.14). This tells the server to buffer the
utterance associated with this recording request into the
verification buffer. Sending this header field is permitted only if
the verification buffer is for the session. This buffer is shared
across resources within a session. It gets instantiated when a
verifier resource is added to this session and is released when the
verifier resource is released from the session.
10.4.14. Start Input Timers
This header field MAY be sent as part of the RECORD request. A value
of false tells the recorder resource to start the operation, but not
to start the no-input timer until the client sends a START-INPUT-
TIMERS request to the recorder resource. This is useful in the
scenario when the recorder and synthesizer resources are not part of
the same session. When a kill-on-barge-in prompt is being played,
the client may want the RECORD request to be simultaneously active so
that it can detect and implement kill-on-barge-in (see
Section 8.4.2). But at the same time the client doesn't want the
recorder resource to start the no-input timers until the prompt is
finished. The default value is "true".
start-input-timers = "Start-Input-Timers" ":"
BOOLEAN CRLF
10.4.15. New Audio Channel
This header field is the same as the one described for the Recognizer
resource (see Section 9.4.23).
10.5. Recorder Message Body
If the RECORD request did not have a Record-Uri header field, the
"STOP" response or the RECORD-COMPLETE event MUST contain a message
body carrying the captured audio. In this case, the message carrying
the audio content has a Record-Uri header field with a cid value
pointing to the message body entity that contains the recorded audio.
10.6. RECORD
The RECORD request places the recorder resource in the Recording
state. Depending on the header fields specified in the RECORD
method, the resource may start recording the audio immediately or
wait for the end pointing functionality to detect speech in the
audio. The audio is then made available to the client either in the
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message body or as specified by Record-URI.
The server MUST support the HTTPS URI scheme and MAY support other
schemes. Note that due to the sensitive nature of voice recordings,
any protocols used for dereferencing SHOULD employ integrity and
confidentiality, unless other means, such as physical security, are
employed.
If a RECORD operation is already in progress, invoking this method
causes the server to issue a response having a status code of 402,
"Method not valid in this state", and a COMPLETE request state.
If the recording-uri is not valid, a status code of 404, "Illegal
Value for Header Field", is returned in the response. If it is
impossible for the server to create the requested stored content, a
status code of 407, "Method or Operation Failed", is returned.
If the type specified in the Media-Type header field is not
supported, the server MUST respond with a status code of 409,
"Unsupported Header Field Value", with the Media-Type header field in
its response.
When the recording operation is initiated, the response indicates an
IN-PROGRESS request state. The server MAY generate a subsequent
START-OF-INPUT event when speech is detected. Upon completion of the
recording operation, the server generates a RECORD-COMPLETE event.
C->S: MRCP/2.0 ... RECORD 543257
Channel-Identifier:32AECB23433802@recorder
Record-URI:<file://mediaserver/recordings/myfile.wav>
Media-Type:audio/wav
Capture-On-Speech:true
Final-Silence:300
Max-Time:6000
S->C: MRCP/2.0 ... 456234 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@recorder
S->C: MRCP/2/0 ... START-OF-INPUT 456234 IN-PROGRESS
Channel-Identifier:32AECB23433802@recorder
S->C: MRCP/2.0 ... RECORD-COMPLETE 456234 COMPLETE
Channel-Identifier:32AECB23433802@recorder
Completion-Cause:000 success-silence
Record-URI:<file://mediaserver/recordings/myfile.wav>;
size=242552;duration=25645
RECORD Example
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10.7. STOP
The "STOP" method moves the recorder from the recording state back to
the idle state. If a RECORD request is active and the "STOP" request
successfully terminated it, then the STOP response MUST contain an
active-request-id-list header field containing the "RECORD"
request-id that was terminated. In this case, no RECORD-COMPLETE
event is sent for the terminated request. If there was no recording
active, then the response MUST NOT contain an active-request-id-list
header field. If the recording was a success the "STOP" response
MUST contain a Record-URI header field pointing to the recorded audio
content or to an typed entity in the body of the "STOP" response
containing the recorded audio. The "STOP" method may have a Trim-
Length header field, in which case the specified length of audio is
trimmed from the end of the recording after the stop. In any case,
the response MUST contain a status of 200 (Success).
C->S: MRCP/2.0 ... RECORD 543257
Channel-Identifier:32AECB23433802@recorder
Record-URI:<file://mediaserver/recordings/myfile.wav>
Capture-On-Speech:true
Final-Silence:300
Max-Time:6000
S->C: MRCP/2.0 ... 456234 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@recorder
S->C: MRCP/2/0 ... START-OF-INPUT 456234 IN-PROGRESS
Channel-Identifier:32AECB23433802@recorder
C->S: MRCP/2.0 ... STOP 543257
Channel-Identifier:32AECB23433802@recorder
Trim-Length:200
S->C: MRCP/2.0 ... 456234 200 COMPLETE
Channel-Identifier:32AECB23433802@recorder
Record-URI:<file://mediaserver/recordings/myfile.wav>;
size=324253;duration=24561
Active-Request-Id-List:543257
STOP Example
10.8. RECORD-COMPLETE
If the recording completes due to no-input, silence after speech, or
max-time, the server MUST generate the RECORD-COMPLETE event to the
client with a request-state of "COMPLETE". If the recording was a
success the RECORD-COMPLETE event contains a Record-URI header field
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pointing to the recorded audio file on the server or to a typed
entity in the message body containing the recorded audio .
C->S: MRCP/2.0 ... RECORD 543257
Channel-Identifier:32AECB23433802@recorder
Record-URI:<file://mediaserver/recordings/myfile.wav>
Capture-On-Speech:true
Final-Silence:300
Max-Time:6000
S->C: MRCP/2.0 ... 456234 200 IN-PROGRESS
Channel-Identifier:32AECB23433802@recorder
S->C: MRCP/2/0 ... START-OF-INPUT 456234 IN-PROGRESS
Channel-Identifier:32AECB23433802@recorder
S->C: MRCP/2.0 ... RECORD-COMPLETE 456234 COMPLETE
Channel-Identifier:32AECB23433802@recorder
Completion-Cause:000 success
Record-URI:<file://mediaserver/recordings/myfile.wav>;
size=325325;duration=24652
RECORD-COMPLETE Example
10.9. START-INPUT-TIMERS
This request is sent from the client to the recorder resource when it
discovers that a kill-on-barge-in prompt has finished playing (see
Section 8.4.2). This is useful in the scenario when the recorder and
synthesizer resources are not in the same MRCPv2 session. When a
kill-on-barge-in prompt is being played, the client wants the RECORD
request to be simultaneously active so that it can detect and
implement kill on barge-in. But at the same time the client doesn't
want the recorder resource to start the no-input timers until the
prompt is finished. The Start-Input-Timers header field in the
RECORD request allows the client to say if the timers should be
started or not. In the above case the recorder resource does not
start the timers until the client sends a START-INPUT-TIMERS method
to the recorder.
10.10. START-OF-INPUT
The START-OF-INPUT event is returned from the server to the client
once the server has detected speech. This event is always returned
by the recording resource when speech has been detected. The
recorder resource also MUST send a Proxy-Sync-Id header field with a
unique value for this event.
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S->C: MRCP/2.0 ... START-OF-INPUT 543259 IN-PROGRESS
Channel-Identifier:32AECB23433801@recorder
Proxy-Sync-Id:987654321
11. Speaker Verification and Identification
This section describes the methods, responses and events employed by
MRCPv2 for doing Speaker Verification / Identification.
Speaker verification is a voice authentication methodology that can
be used to identify the speaker in order to grant the user access to
sensitive information and transactions. Because speech is a
biometric, a number of essential security considerations related to
biometric authentication technologies apply to its implementation and
usage. Implementers should carefully read Section 12 in this
document and the corresponding section of Speechsc Requirements
[RFC4313].
In speaker verification, a recorded utterance is compared to a
previously stored voiceprint which is in turn associated with a
claimed identity for that user. Verification typically consists of
two phases: a designation phase to establish the claimed identity of
the caller and an execution phase in which a voiceprint is either
created (training) or used to authenticate the claimed identity
(verification).
Speaker identification is the process of associating an unknown
speaker with a member in a population. It does not employ a claim of
identity. When an individual claims to belong to a group (e.g., one
of the owners of a joint bank account) a group authentication is
performed. This is generally implemented as a kind of verification
involving comparison with more than one voice model. It is sometimes
called 'multi-verification.' If the individual speaker can be
identified from the group, this may be useful for applications where
multiple users share the same access privileges to some data or
application. Speaker identification and group authentication are
also done in two phases, a designation phase and an execution phase.
Note that from a functionality standpoint identification can be
thought of as a special case of group authentication (if the
individual is identified) where the group is the entire population,
although the implementation of speaker identification may be
different from the way group authentication is performed. To
accommodate single-voiceprint verification, verification against
multiple voiceprints, group authentication, and identification, this
specification provides a single set of methods that can take a list
of identifiers, called "voiceprint identifiers", and return a list of
identifiers, with a score for each representing how well the input
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speech matched each identifier. The input and output lists of
identifiers do not have to match, allowing a vendor-specific group
identifier to be used as input to indicate that identification is to
be performed. In this specification, the terms "Identification" and
"Multi-verification" are used to indicate that the input represents a
group (potentially the entire population) and that results for
multiple voiceprints may be returned.
It is possible for a verifier resource to share the same session with
a recognizer resource or to operate independently. In order to share
the same session, the verifier and recognizer resources MUST be
allocated from within the same SIP dialog. Otherwise, an independent
verifier resource, running on the same physical server or a separate
one, will be set up. Note that in addition to allowing both
resources to be allocated in the same INVITE, it is possible to
allocate one initially and the other later via a re-INVITE.
Some of the speaker verification methods, described below, apply only
to a specific mode of operation.
The verifier resource has a verification buffer associated with it
(see Section 11.4.14). This allows the storage of speech utterances
for the purposes of verification, identification or training from the
buffered speech. This buffer is owned by the verifier resource but
other input resources such as the recognition resource or recorder
resource may write to it. This allows the speech received as part of
a recognition or recording operation to be later used for
verification, identification or training. Access to the buffer is
limited to one operation at time. Hence when the resource is doing
read, write or delete operation such as a RECOGNIZE with ver-buffer-
utterance turned on, another operation involving the buffer fails
with a status of 402. The verification buffer can be cleared by a
CLEAR-BUFFER request from the client and is freed when the verifier
resource is deallocated or the session with the server terminates.
The verification buffer is different from collecting waveforms and
processing them using either the real time audio stream or stored
audio, because this buffering mechanism does not simply accumulate
speech to a buffer. The verification buffer may contain additional
information gathered by the recognition resource that serves to
improve verification performance.
11.1. Speaker Verification State Machine
Speaker verification may operate in a training or a verification
session. Starting one of these sessions does not change the state of
the verifier resource, i.e. it remains idle. Once a verification or
training session is started, then utterances are trained or verified
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by calling the VERIFY or VERIFY-FROM-BUFFER method. The state of the
verifier resources goes from IDLE to VERIFYING state each time VERIFY
or VERIFY-FROM-BUFFER is called.
Idle Session Opened Verifying/Training
State State State
| | |
|--START-SESSION--->| |
| | |
| |----------| |
| | START-SESSION |
| |<---------| |
| | |
|<--END-SESSION-----| |
| | |
| |---------VERIFY--------->|
| | |
| |---VERIFY-FROM-BUFFER--->|
| | |
| |----------| |
| | VERIFY-ROLLBACK |
| |<---------| |
| | |
| | |--------|
| | GET-INTERMEDIATE-RESULT |
| | |------->|
| | |
| | |--------|
| | START-INPUT-TIMERS |
| | |------->|
| | |
| | |--------|
| | START-OF-INPUT |
| | |------->|
| | |
| |<-VERIFICATION-COMPLETE--|
| | |
| |<--------STOP------------|
| | |
| |----------| |
| | STOP |
| |<---------| |
| | |
|----------| | |
| STOP | |
|<---------| | |
| |----------| |
| | CLEAR-BUFFER |
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| |<---------| |
| | |
|----------| | |
| CLEAR-BUFFER | |
|<---------| | |
| | |
| |----------| |
| | QUERY-VOICEPRINT |
| |<---------| |
| | |
|----------| | |
| QUERY-VOICEPRINT | |
|<---------| | |
| | |
| |----------| |
| | DELETE-VOICEPRINT |
| |<---------| |
| | |
|----------| | |
| DELETE-VOICEPRINT | |
|<---------| | |
Verifier Resource State Machine
11.2. Speaker Verification Methods
The verifier resource supports the following methods.
verifier-method = "START-SESSION"
/ "END-SESSION"
/ "QUERY-VOICEPRINT"
/ "DELETE-VOICEPRINT"
/ "VERIFY"
/ "VERIFY-FROM-BUFFER"
/ "VERIFY-ROLLBACK"
/ "STOP"
/ "CLEAR-BUFFER"
/ "START-INPUT-TIMERS"
/ "GET-INTERMEDIATE-RESULT"
These methods allow the client to control the mode and target of
verification or identification operations within the context of a
session. All the verification input operations that occur within a
session may be used to create, update, or validate against the
voiceprint specified during the session. At the beginning of each
session the verifier resource is reset to the state it had prior to
any previous verification session.
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Verification/identification operations can be executed against live
or buffered audio. The verifier resource provides methods for
collecting and evaluating live audio data, and methods for
controlling the verifier resource and adjusting its configured
behavior.
There are no dedicated methods for collecting buffered audio data.
This is accomplished by calling VERIFY, RECOGNIZE or RECORD as
appropriate for the resource, with the header field ver-buffer-
utterance. Then, when the following method is called verification is
performed using the set of buffered audio.
1. VERIFY-FROM-BUFFER
The following methods are used for verification of live audio
utterances :
1. VERIFY
2. START-INPUT-TIMERS
The following methods are used for configuring the verifier resource
and for establishing resource states :
1. START-SESSION
2. END-SESSION
3. QUERY-VOICEPRINT
4. DELETE-VOICEPRINT
5. VERIFY-ROLLBACK
6. "STOP"
7. CLEAR-BUFFER
The following method allows the polling a Verification in progress
for intermediate results.
1. GET-INTERMEDIATE-RESULT
11.3. Verification Events
The verifier resource generates the following events.
verifier-event = "VERIFICATION-COMPLETE"
/ "START-OF-INPUT"
11.4. Verification Header Fields
A verifier resource message may contain header fields containing
request options and information to augment the Request, Response or
Event message it is associated with.
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verification-header = repository-uri
/ voiceprint-identifier
/ verification-mode
/ adapt-model
/ abort-model
/ min-verification-score
/ num-min-verification-phrases
/ num-max-verification-phrases
/ no-input-timeout
/ save-waveform
/ media-type
/ waveform-uri
/ voiceprint-exists
/ ver-buffer-utterance
/ input-waveform-uri
/ completion-cause
/ completion-reason
/ speech-complete-timeout
/ new-audio-channel
/ abort-verification
/ start-input-timers
11.4.1. Repository-URI
This header field specifies the voiceprint repository to be used or
referenced during speaker verification or identification operations.
This header field is required in the START-SESSION, QUERY-VOICEPRINT
and DELETE-VOICEPRINT methods.
repository-uri = "Repository-URI" ":" uri CRLF
11.4.2. Voiceprint-Identifier
This header field specifies the claimed identity for verification
applications. The claimed identity may be used to specify an
existing voiceprint or to establish a new voiceprint. This header
field is required in the QUERY-VOICEPRINT and DELETE-VOICEPRINT
methods. The Voiceprint-Identifier is required in the START-SESSION
method for verification operations. For Identification or Multi-
Verification operations this header field may contain a list of
voiceprint identifiers separated by semi-colons. For identification
operations the client can also specify a voiceprint group identifier
instead of a list of voiceprint identifiers.
voiceprint-identifier = "Voiceprint-Identifier" ":"
vid *[";" vid] CRLF
vid = 1*VCHAR ["." 1*VCHAR]
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11.4.3. Verification-Mode
This header field specifies the mode of the verifier resource and is
set by the START-SESSION method. Acceptable values indicate whether
the verification session will train a voiceprint ("train") or verify/
identify using an existing voiceprint ("verify").
Training and verification sessions both require the voiceprint
Repository-URI to be specified in the START-SESSION. In many usage
scenarios, however, the system does not know the speaker's claimed
identity until a recognition operation has, for example, recognized
an account number to which the user desires access. In order to
allow the first few utterances of a dialog to be both recognized and
verified, the verifier resource on the MRCPv2 server retains a
buffer. In this buffer, the MRCPv2 server accumulates recognized
utterances. The client can later execute a verification method and
apply the buffered utterances to the current verification session.
Some voice user interfaces may require additional user input that
should not be subject to verification. For example, the user's input
may have been recognized with low confidence and thus require a
confirmation cycle. In such cases, the client should not execute the
VERIFY or VERIFY-FROM-BUFFER methods to collect and analyze the
caller's input. A separate recognizer resource can analyze the
caller's response without any participation by the verifier resource.
Once the following conditions have been met:
1. Voiceprint identity has been successfully established through the
voiceprint identifier header fields of the START-SESSION method,
and
2. the verification mode has been set to one of "train" or "verify",
the verifier resource may begin providing verification information
during verification operations. If the verifier resource does not
reach one of the two major states ("train" or "verify") , it MUST
report an error condition in the MRCPv2 status code to indicate why
the verifier resource is not ready for the corresponding usage.
The value of verification-mode is persistent within a verification
session. If the client attempts to change the mode during a
verification session, the verifier resource reports an error and the
mode retains its current value.
verification-mode = "Verification-Mode" ":"
verification-mode-string
verification-mode-string = "train"
/ "verify"
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11.4.4. Adapt-Model
This header field indicates the desired behavior of the verifier
resource after a successful verification operation. If the value of
this header field is "true", the sever SHOULD use audio collected
during the verification session to update the voiceprint to account
for ongoing changes in a speaker's incoming speech characteristics,
unless local policy prohibits updating the voiceprint. If the value
is "false" (the default), the server MUST NOT update the voiceprint.
This header field MAY occur in the START-SESSION method.
adapt-model = "Adapt-Model" ":" BOOLEAN CRLF
11.4.5. Abort-Model
The Abort-Model header field indicates the desired behavior of the
verifier resource upon session termination. If the value of this
header field is "true", the server MUST discard any pending changes
to a voiceprint due to verification training or verification
adaptation. If the value is "false" (the default), the server MUST
commit any pending changes for a training session or a successful
verification session to the voiceprint repository. A value of "true"
for Abort-Model overrides a value of "true" for the Adapt-Model
header field. This header field MAY occur in the END-SESSION method.
abort-model = "Abort-Model" ":" BOOLEAN CRLF
11.4.6. Min-Verification-Score
The Min-Verification-Score header field, when used with a verifier
resource through a "SET-PARAMS", "GET-PARAMS" or START-SESSION
method, determines the minimum verification score for which a
verification decision of "accepted" may be declared by the server.
This is a float value between -1.0 and 1.0 that determines the
minimum verification score for which a verification decision of
"accepted" may be declared by the server. The default value for this
header field is implementation specific.
min-verification-score = "Min-Verification-Score" ":"
[ %x2D ] FLOAT CRLF
11.4.7. Num-Min-Verification-Phrases
The Num-Min-Verification-Phrases header field is used to specify the
minimum number of valid utterances before a positive decision is
given for verification. The value for this header field is an
integer and the default value is 1. The verifier resource MUST NOT
declare a verification 'accepted' unless Num-Min-Verification-Phrases
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valid utterances have been received. The minimum value is 1. This
header field MAY occur in START-SESSION, "SET-PARAMS" or
"GET-PARAMS".
num-min-verification-phrases = "Num-Min-Verification-Phrases" ":"
1*19DIGIT CRLF
11.4.8. Num-Max-Verification-Phrases
The Num-Max-Verification-Phrases header field is used to specify the
number of valid utterances required before a decision is forced for
verification. The verifier resource MUST NOT return a decision of
'undecided' once Num-Max-Verification-Phrases have been collected and
used to determine a verification score. The value for this header
field is an integer and the minimum value is 1. The default value is
implementation-specific. This header field MAY occur in START-
SESSION, "SET-PARAMS" or "GET-PARAMS".
num-max-verification-phrases = "Num-Max-Verification-Phrases" ":"
1*19DIGIT CRLF
11.4.9. No-Input-Timeout
The No-Input-Timeout header field sets the length of time from the
start of the verification timers (see START-INPUT-TIMERS) until the
declaration of a no-input event in the VERIFICATION-COMPLETE server
event message. The value is in milliseconds. This header field MAY
occur in VERIFY, "SET-PARAMS" or "GET-PARAMS". The value for this
header field ranges from 0 to an implementation specific maximum
value. The default value for this header field is implementation
specific.
no-input-timeout = "No-Input-Timeout" ":" 1*19DIGIT CRLF
11.4.10. Save-Waveform
This header field allows the client to request that the verifier
resource save the audio stream that was used for verification/
identification. The verifier resource MUST attempt to record the
audio and make it available to the client in the form of a URI
returned in the Waveform-URI header field in the VERIFICATION-
COMPLETE event. If there was an error in recording the stream or the
audio content is otherwise not available, the verifier resource MUST
return an empty Waveform-URI header field. The default value for
this header field is "false". This header field MAY appear in the
VERIFY method. Note that this header field does not appear in the
VERIFY-FROM-BUFFER method since it only controls whether or not to
save the waveform for live verification / identification operations.
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save-waveform = "Save-Waveform" ":" BOOLEAN CRLF
11.4.11. Media Type
This header field MAY be specified in the SET-PARAMS, GET-PARAMS or
the VERIFY methods and tells the server resource the Media Type of
the captured audio or video such as the one captured and returned by
the Waveform-URI header field.
media-type = "Media-Type" ":" media-type-value
CRLF
11.4.12. Waveform-URI
If the Save-Waveform header field is set to true, the verifier
resource MUST attempt to record the incoming audio stream of the
verification into a file and provide a URI for the client to access
it. This header field MUST be present in the VERIFICATION-COMPLETE
event if the Save-Waveform header field was set to true by the
client. The value of the header field MUST be empty if there was
some error condition preventing the server from recording.
Otherwise, the URI generated by the server MUST be globally unique
across the server and all its verification sessions. The content
MUST be available via the URI until the verification session ends.
Since the Save-Waveform header field applies only to live
verification / identification operations, the server can return the
Waveform-URI only in the VERIFICATION-COMPLETE event for live
verification / identification operations.
The server MUST also return the size in octets and the duration in
milliseconds of the recorded audio wave-form as parameters associated
with the header field.
waveform-uri = "Waveform-URI" ":" ["<" uri ">"
";" "size" "=" 1*19DIGIT
";" "duration" "=" 1*19DIGIT] CRLF
11.4.13. Voiceprint-Exists
This header field MUST be returned in QUERY-VOICEPRINT and DELETE-
VOICEPRINT responses. This is the status of the voiceprint specified
in the QUERY-VOICEPRINT method. For the DELETE-VOICEPRINT method
this header field indicates the status of the voiceprint at the
moment the method execution started.
voiceprint-exists = "Voiceprint-Exists" ":" BOOLEAN CRLF
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11.4.14. Ver-Buffer-Utterance
This header field is used to indicate that this utterance could be
later considered for Speaker Verification. This way, a client can
request the server to buffer utterances while doing regular
recognition or verification activities and speaker verification can
later be requested on the buffered utterances. This header field is
OPTIONAL in the RECOGNIZE, VERIFY and RECORD methods. The default
value for this header field is "false".
ver-buffer-utterance = "Ver-Buffer-Utterance" ":" BOOLEAN
CRLF
11.4.15. Input-Waveform-Uri
This header field specifies stored audio content that the client
requests the server to fetch and process according to the current
verification mode, either to train the voiceprint or verify a claimed
identity. This header field enables the client to implement the
buffering use case where the recognizer and verifier resources are in
different sessions and the verification buffer technique cannot be
used. It MAY be specified on the VERIFY request.
input-waveform-uri = "Input-Waveform-URI" ":" uri CRLF
11.4.16. Completion-Cause
This header field MUST be part of a VERIFICATION-COMPLETE event from
the verifier resource to the client. This indicates the cause of
VERIFY or VERIFY-FROM-BUFFER method completion. This header field
MUST be sent in the VERIFY, VERIFY-FROM-BUFFER, and QUERY-VOICEPRINT
responses, if they return with a failure status and a COMPLETE state.
completion-cause = "Completion-Cause" ":" 3DIGIT SP
1*VCHAR CRLF
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+------------+--------------------------+---------------------------+
| Cause-Code | Cause-Name | Description |
+------------+--------------------------+---------------------------+
| 000 | success | VERIFY or |
| | | VERIFY-FROM-BUFFER |
| | | request completed |
| | | successfully. The verify |
| | | decision can be |
| | | "accepted", "rejected", |
| | | or "undecided". |
| 001 | error | VERIFY or |
| | | VERIFY-FROM-BUFFER |
| | | request terminated |
| | | prematurely due to a |
| | | verifier resource or |
| | | system error. |
| 002 | no-input-timeout | VERIFY request completed |
| | | with no result due to a |
| | | no-input-timeout. |
| 003 | too-much-speech-timeout | VERIFY request completed |
| | | with no result due to too |
| | | much speech. |
| 004 | speech-too-early | VERIFY request completed |
| | | with no result due to |
| | | spoke too soon. |
| 005 | buffer-empty | VERIFY-FROM-BUFFER |
| | | request completed with no |
| | | result due to empty |
| | | buffer. |
| 006 | out-of-sequence | Verification operation |
| | | failed due to |
| | | out-of-sequence method |
| | | invocations. For example |
| | | calling VERIFY before |
| | | QUERY-VOICEPRINT. |
| 007 | repository-uri-failure | Failure accessing |
| | | Repository URI. |
| 008 | repository-uri-missing | Repository-uri is not |
| | | specified. |
| 009 | voiceprint-id-missing | Voiceprint-identification |
| | | is not specified. |
| 010 | voiceprint-id-not-exist | Voiceprint-identification |
| | | does not exist in the |
| | | voiceprint repository. |
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| 011 | speech-not-usable | VERIFY request completed |
| | | with no result because |
| | | the speech was not usable |
| | | (too noisy, too short, |
| | | etc.) |
+------------+--------------------------+---------------------------+
11.4.17. Completion Reason
This header field MAY be specified in a VERIFICATION-COMPLETE event
coming from the verifier resource to the client. It contains the
reason text behind the VERIFY request completion. This header field
communicates text describing the reason for the failure.
The completion reason text is provided for client use in logs and for
debugging and instrumentation purposes. Clients MUST NOT interpret
the completion reason text.
completion-reason = "Completion-Reason" ":"
quoted-string CRLF
11.4.18. Speech Complete Timeout
This header field is the same as the one described for the Recognizer
resource. See Section 9.4.15. This header field MAY occur in
VERIFY, SET-PARAMS, or GET-PARAMS.
11.4.19. New Audio Channel
This header field is the same as the one described for the Recognizer
resource. See Section 9.4.23. This header field MAY be specified in
a VERIFY request.
11.4.20. Abort-Verification
This header field MUST be sent in a "STOP" request to indicate
whether or not to abort a VERIFY method in progress. A value of
"true" requests the server to discard the results. A value of
"false" requests the server to return in the "STOP" response the
verification results obtained up to the point it received the "STOP"
request.
Abort-verification = "Abort-Verification " ":" BOOLEAN CRLF
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11.4.21. Start Input Timers
This header field MAY be sent as part of a VERIFY request. A value
of false tells the verifier resource to start the VERIFY operation,
but not to start the no-input timer yet. The verifier resource MUST
NOT start the timers until the client sends a START-INPUT-TIMERS
request to the resource. This is useful in the scenario when the
verifier and synthesizer resources are not part of the same session.
In this scenario, when a kill-on-barge-in prompt is being played, the
client may want the VERIFY request to be simultaneously active so
that it can detect and implement kill-on-barge-in (see
Section 8.4.2). But at the same time the client doesn't want the
verifier resource to start the no-input timers until the prompt is
finished. The default value is "true".
start-input-timers = "Start-Input-Timers" ":"
BOOLEAN CRLF
11.5. Verification Message Body
A verification response or event message may carry additional data as
described in the following subsection.
11.5.1. Verification Result Data
Verification results are returned to the client in the message body
of the VERIFICATION-COMPLETE event or the GET-INTERMEDIATE-RESULT
response message as described in Section 6.3). Element and attribute
descriptions for the verification portion of the NLSML format are
provided in Section 11.5.2 with a normative definition of the schema
in Section 16.3.
11.5.2. Verification Result Elements
All verification elements are contained within a single
<verification-result> element under <result>. The elements are
described below and have the schema defined in Section 16.2. The
following elements are defined:
1. Voiceprint
2. Incremental
3. Cumulative
4. Decision
5. Utterance-Length
6. Device
7. Gender
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8. Adapted
9. Verification-Score
10. Vendor-Specific-Results
11.5.2.1. Voiceprint
This element in the verification results provides information on how
the speech data matched a single voiceprint. The result data
returned may have more than one such entity in the case of
Identification or Multi-Verification. Each "<voiceprint>" element
and the XML data within the element describe verification result
information for how well the speech data matched that particular
voiceprint. The list of voiceprint element data are ordered
according to their cumulative verification match scores, with the
highest score first.
11.5.2.2. Cumulative
Within each "<voiceprint>" element there MUST be a "<cumulative>"
element with the cumulative scores of how well multiple utterances
matched the voiceprint.
11.5.2.3. Incremental
The first "<voiceprint>" element MAY contain an "<incremental>"
element with the incremental scores of how well the last utterance
matched the voiceprint.
11.5.2.4. Decision
This element is found within the "<incremental>" or "<cumulative>"
element within the verification results. Its value indicates the
verification decision. It can have the values of "accepted",
"rejected" or "undecided".
11.5.2.5. Utterance-Length
This element MAY occur within either the "<incremental>" or
"<cumulative>" elements within the first "<voiceprint>" element. Its
value indicates the size in milliseconds, respectively, of the last
utterance or the cumulated set of utterances.
11.5.2.6. Device
This element is found within the incremental or cumulative element
within the verification results. Its value indicates the apparent
type of device used by the caller as determined by the verifier
resource. It can have the values of "cellular-phone", "electret-
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phone", "carbon-button-phone", or "unknown".
11.5.2.7. Gender
This element is found within the incremental or cumulative element
within the verification results. Its value indicates the apparent
gender of the speaker as determined by the verifier resource. It can
have the values of "male", "female" or "unknown".
11.5.2.8. Adapted
This element is found within the first "<voiceprint>" element within
the verification results. When verification is trying to confirm the
voiceprint, this indicates if the voiceprint has been adapted as a
consequence of analyzing the source utterances. It is not returned
during verification training. The value can be "true" or "false".
11.5.2.9. Verification-Score
This element is found within the incremental or cumulative element
within the verification results. Its value indicates the score of
the last utterance as determined by verification.
During verification, the higher the score the more likely it is that
the speaker is the same one as the one who spoke the voiceprint
utterances. During training, the higher the score the more likely
the speaker is to have spoken all of the analyzed utterances. The
value is a floating point between -1.0 and 1.0. If there are no such
utterances the score is -1. Note that the verification score is not
a probability value.
11.5.2.10. Vendor-Specific-Results
Verification results may contain implementation specific data which
augment the information provided by the MRCPv2-defined elements.
These may be useful to clients who have private knowledge of how to
interpret these schema extensions. Implementation specific additions
to the verification results schema MUST belong to the vendor's own
namespace. In the result structure, they must either be indicated by
a namespace prefix declared within the result or must be children of
an element identified as belonging to the respective namespace.
The following example shows the results of three voiceprints. Note
that the first one has crossed the verification score threshold, and
the speaker has been accepted. The voiceprint was also adapted with
the most recent utterance.
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<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
grammar="What-Grammar-URI">
<verification-result>
<voiceprint id="johnsmith">
<adapted> true </adapted>
<incremental>
<utterance-length> 500 </utterance-length>
<device> cellular-phone </device>
<gender> male </gender>
<decision> accepted </decision>
<verification-score> 0.98514 </verification-score>
</incremental>
<cumulative>
<utterance-length> 10000 </utterance-length>
<device> cellular-phone </device>
<gender> male </gender>
<decision> accepted </decision>
<verification-score> 0.96725</verification-score>
</cumulative>
</voiceprint>
<voiceprint id="marysmith">
<cumulative>
<verification-score> 0.93410 </verification-score>
</cumulative>
</voiceprint>
<voiceprint uri="juniorsmith">
<cumulative>
<verification-score> 0.74209 </verification-score>
</cumulative>
</voiceprint>
</verification-result>
</result>
Verification Results Example 1
In this next example, the verifier has enough information to decide
to reject the speaker.
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<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:xmpl="http://www.example.org/2003/12/mrcpv2"
grammar="What-Grammar-URI">
<verification-result>
<voiceprint id="johnsmith">
<incremental>
<utterance-length> 500 </utterance-length>
<device> cellular-phone </device>
<gender> male </gender>
<verification-score> 0.88514 </verification-score>
<xmpl:raspiness> high </xmpl:raspiness>
<xmpl:emotion> sadness </xmpl:emotion>
</incremental>
<cumulative>
<utterance-length> 10000 </utterance-length>
<device> cellular-phone </device>
<gender> male </gender>
<decision> rejected </decision>
<verification-score> 0.9345 </verification-score>
</cumulative>
</voiceprint>
</verification-result>
</result>
Verification Results Example 2
11.6. START-SESSION
The START-SESSION method starts a Speaker Verification or
Identification session. Execution of this method places the verifier
resource into its initial state. If this method is called during an
ongoing verification session, the previous session is implicitly
aborted. If this method is invoked when VERIFY or VERIFY-FROM-BUFFER
is active, the method fails and the server returns a status code of
402.
Upon completion of the START-SESSION method, the verifier resource
MUST have terminated any ongoing verification session, and cleared
any voiceprint designation.
A verification session is associated with the voiceprint repository
to be used during the session. This is specified through the
"Repository-URI" header field (see Section 11.4.1).
The START-SESSION method also establishes, through the Voiceprint-
Identifier header field, which voiceprints are to be matched or
trained during the verification session. If this is an
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Identification session or if the client wants to do Multi-
Verification, the Voiceprint-Identifier header field contains a list
of semi-colon separated voiceprint identifiers.
The header field "Adapt-Model" may also be present in the START-
SESSION request to indicate whether or not to adapt a voiceprint
based on data collected during the session (if the voiceprint
verification phase succeeds). By default, the voiceprint model MUST
NOT be adapted with data from a verification session.
The START-SESSION also determines whether the session is for a train
or verify of a voiceprint. Hence the Verification-Mode header field
MUST be sent in every START-SESSION request. The value of the
Verification-Mode header field MUST be one of either "train" or
"verify".
Before a verification/identification session is started, only VERIFY-
ROLLBACK and generic "SET-PARAMS" and "GET-PARAMS" operations may be
performed on the verifier resource. The server MUST return 402
"Method not valid in this state" for all other verification
operations.
A verifier resource may only have a single session active at one
time.
C->S: MRCP/2.0 ... START-SESSION 314161
Channel-Identifier:32AECB23433801@speakverify
Repository-URI:http://www.example.com/voiceprintdbase/
Voiceprint-Mode:verify
Voiceprint-Identifier:johnsmith.voiceprint
Adapt-Model:true
S->C: MRCP/2.0 ... 314161 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
11.7. END-SESSION
The END-SESSION method terminates an ongoing verification session and
releases the verification voiceprint resources. The session may
terminate in one of three ways:
1. abort - the voiceprint adaptation or creation may be aborted so
that the voiceprint remains unchanged (or is not created).
2. commit - when terminating a voiceprint training session, the new
voiceprint is committed to the repository.
3. adapt - an existing voiceprint is modified using a successful
verification.
The header field "Abort-Model" MAY be included in the END-SESSION to
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control whether or not to abort any pending changes to the
voiceprint. The default behavior is to commit (not abort) any
pending changes to the designated voiceprint.
The END-SESSION method may be safely executed multiple times without
first executing the START-SESSION method. Any additional executions
of this method without an intervening use of the START-SESSION method
have no effect on the verifier resource.
The following example assumes there is either a training session or a
verification session in progress.
C->S: MRCP/2.0 ... END-SESSION 314174
Channel-Identifier:32AECB23433801@speakverify
Abort-Model:true
S->C: MRCP/2.0 ... 314174 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
11.8. QUERY-VOICEPRINT
The QUERY-VOICEPRINT method is used to get status information on a
particular voiceprint and can be used by the client to ascertain if a
voiceprint or repository exists and if it contains trained
voiceprints.
The response to the QUERY-VOICEPRINT request contains an indication
of the status of the designated voiceprint in the "Voiceprint-Exists"
header field, allowing the client to determine whether to use the
current voiceprint for verification, train a new voiceprint, or
choose a different voiceprint.
A voiceprint is completely specified by providing a repository
location and a voiceprint identifier. The particular voiceprint or
identity within the repository is specified by a string identifier
that is unique within the repository. The "Voiceprint-Identifier"
header field carries this unique voiceprint identifier within a given
repository.
The following example assumes a verification session is in progress
and the voiceprint exists in the voiceprint repository.
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C->S: MRCP/2.0 ... QUERY-VOICEPRINT 314168
Channel-Identifier:32AECB23433801@speakverify
Repository-URI:http://www.example.com/voiceprints/
Voiceprint-Identifier:johnsmith.voiceprint
S->C: MRCP/2.0 ... 314168 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
Repository-URI:http://www.example.com/voiceprints/
Voiceprint-Identifier:johnsmith.voiceprint
Voiceprint-Exists:true
The following example assumes that the URI provided in the
'Repository-URI' header field is a bad URI.
C->S: MRCP/2.0 ... QUERY-VOICEPRINT 314168
Channel-Identifier:32AECB23433801@speakverify
Repository-URI:http://www.example.com/bad-uri/
Voiceprint-Identifier:johnsmith.voiceprint
S->C: MRCP/2.0 ... 314168 405 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
Repository-URI:http://www.example.com/bad-uri/
Voiceprint-Identifier:johnsmith.voiceprint
Completion-Cause:007 repository-uri-failure
11.9. DELETE-VOICEPRINT
The DELETE-VOICEPRINT method removes a voiceprint from a repository.
This method MUST carry the Repository-URI and Voiceprint-Identifier
header fields.
If the corresponding voiceprint does not exist, the DELETE-VOICEPRINT
method MUST return a 200 status code.
The following example demonstrates a DELETE-VOICEPRINT operation to
remove a specific voiceprint.
C->S: MRCP/2.0 ... DELETE-VOICEPRINT 314168
Channel-Identifier:32AECB23433801@speakverify
Repository-URI:http://www.example.com/bad-uri/
Voiceprint-Identifier:johnsmith.voiceprint
S->C: MRCP/2.0 ... 314168 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
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11.10. VERIFY
The VERIFY method is used to request that the verifier resource
either train/adapt the voiceprint or verify/identify a claimed
identity. If the voiceprint is new or was deleted by a previous
DELETE-VOICEPRINT method, the VERIFY method trains the voiceprint.
If the voiceprint already exits, it is adapted and not retrained by
the VERIFY command.
C->S: MRCP/2.0 ... VERIFY 543260
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... 543260 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speakverify
When the VERIFY request is completes, the MRCPv2 server MUST send a
'VERIFICATION-COMPLETE' event to the client.
11.11. VERIFY-FROM-BUFFER
The VERIFY-FROM-BUFFER method directs the verifier resource to verify
buffered audio against a voiceprint. Only one VERIFY or VERIFY-FROM-
BUFFER method may be active for a verifier resource at a time.
The buffered audio is not consumed by this method and thus VERIFY-
FROM-BUFFER may be invoked multiple times by the client to attempt
verification against different voiceprints.
For the VERIFY-FROM-BUFFER method, the server MAY optionally return
an "IN-PROGRESS" response before the "VERIFICATION-COMPLETE" event.
When the VERIFY-FROM-BUFFER method is invoked and the verification
buffer is in use by another resource sharing it, the server MUST
return an IN-PROGRESS response and wait until the buffer is available
to it. The verification buffer is owned by the verifier resource but
is shared with write access from other input resources on the same
session. Hence, it is considered to be in use if there is a read or
write operation such as a RECORD or RECOGNIZE with the Ver-Buffer-
Utterance header field set to "true" on a resource that shares this
buffer. Note that if a RECORD or RECOGNIZE method returns with a
failure cause code, the VERIFY-FROM-BUFFER request waiting to process
that buffer MUST also fail with a Completion-Cause of 005 (buffer-
empty).
The following example illustrates the usage of some buffering
methods. In this scenario the client first performed a live
verification, but the utterance had been rejected. In the meantime,
the utterance is also saved to the audio buffer. Then, another
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voiceprint is used to do verification against the audio buffer and
the utterance is accepted. For the example, we assume both Num-Min-
Verification-Phrases and Num-Max-Verification-Phrases are 1.
C->S: MRCP/2.0 ... START-SESSION 314161
Channel-Identifier:32AECB23433801@speakverify
Verification-Mode:verify
Adapt-Model:true
Repository-URI:http://www.example.com/voiceprints
Voiceprint-Identifier:johnsmith.voiceprint
S->C: MRCP/2.0 ... 314161 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
C->S: MRCP/2.0 ... VERIFY 314162
Channel-Identifier:32AECB23433801@speakverify
Ver-buffer-utterance:true
S->C: MRCP/2.0 ... 314164 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... VERIFICATION-COMPLETE 314162 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
Completion-Cause:000 success
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
grammar="What-Grammar-URI">
<verification-result>
<voiceprint id="johnsmith">
<incremental>
<utterance-length> 500 </utterance-length>
<device> cellular-phone </device>
<gender> female </gender>
<decision> rejected </decision>
<verification-score> 0.05465 </verification-score>
</incremental>
<cumulative>
<utterance-length> 500 </utterance-length>
<device> cellular-phone </device>
<gender> female </gender>
<decision> rejected </decision>
<verification-score> 0.05465 </verification-score>
</cumulative>
</voiceprint>
</verification-result>
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</result>
C->S: MRCP/2.0 ... QUERY-VOICEPRINT 314163
Channel-Identifier:32AECB23433801@speakverify
Repository-URI:http://www.example.com/voiceprints/
Voiceprint-Identifier:johnsmith
S->C: MRCP/2.0 ... 314163 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
Repository-URI:http://www.example.com/voiceprints/
Voiceprint-Identifier:johnsmith.voiceprint
Voiceprint-Exists:true
C->S: MRCP/2.0 ... START-SESSION 314164
Channel-Identifier:32AECB23433801@speakverify
Verification-Mode:verify
Adapt-Model:true
Repository-URI:http://www.example.com/voiceprints
Voiceprint-Identifier:marysmith.voiceprint
S->C: MRCP/2.0 ... 314164 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
C->S: MRCP/2.0 ... VERIFY-FROM-BUFFER 314165
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... 314165 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... VERIFICATION-COMPLETE 314165 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
Completion-Cause:000 success
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
grammar="What-Grammar-URI">
<verification-result>
<voiceprint id="marysmith">
<incremental>
<utterance-length> 1000 </utterance-length>
<device> cellular-phone </device>
<gender> female </gender>
<decision> accepted </decision>
<verification-score> 0.98 </verification-score>
</incremental>
<cumulative>
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<utterance-length> 1000 </utterance-length>
<device> cellular-phone </device>
<gender> female </gender>
<decision> accepted </decision>
<verification-score> 0.98 </verification-score>
</cumulative>
</voiceprint>
</verification-result>
</result>
C->S: MRCP/2.0 ... END-SESSION 314166
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... 314166 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
VERIFY-FROM-BUFFER example
11.12. VERIFY-ROLLBACK
The VERIFY-ROLLBACK method discards the last buffered utterance or
discards the last live utterances (when the mode is "train" or
"verify"). The client should invoke this method when the user
provides undesirable input such as non-speech noises, side-speech,
out-of-grammar utterances, commands, etc. Note that this method does
not provide a stack of rollback states. Executing VERIFY-ROLLBACK
twice in succession without an intervening recognition operation has
no effect on the second attempt.
C->S: MRCP/2.0 ... VERIFY-ROLLBACK 314165
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... 314165 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
VERFY-ROLLBACK Example
11.13. STOP
The "STOP" method from the client to the server tells the verifier
resource to stop the VERIFY or VERIFY-FROM-BUFFER request if one is
active. If such a request is active and the "STOP" request
successfully terminated it, then the response header section contains
an active-request-id-list header field containing the request-id of
the VERIFY or VERIFY-FROM-BUFFER request that was terminated. In
this case, no VERIFICATION-COMPLETE event is sent for the terminated
request. If there was no verify request active, then the response
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MUST NOT contain an active-request-id-list header field. Either way
the response MUST contain a status of 200 (Success).
The "STOP" method can carry a "Abort-Verification" header field which
specifies if the verification result until that point should be
discarded or returned. If this header field is not present or if the
value is "true", the verification result is discarded and the "STOP"
response does not contain any result data. If the header field is
present and its value is "false", the "STOP" response MUST contain a
"Completion-Cause" header field and carry the Verification result
data in its body.
An aborted VERIFY request does an automatic roll-back and hence does
not affect the cumulative score. A VERIFY request that was stopped
with no "Abort-Verification" header field or with the "Abort-
Verification" header field set to "false" does affect cumulative
scores and would need to be explicitly rolled-back if the client does
not want the verification result considered in the cumulative scores.
The following example assumes a voiceprint identity has already been
established.
C->S: MRCP/2.0 ... VERIFY 314177
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... 314177 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speakverify
C->S: MRCP/2.0 ... STOP 314178
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... 314178 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
Active-Request-Id-List:314177
STOP verification Example
11.14. START-INPUT-TIMERS
This request is sent from the client to the verifier resource to
start the no-input timer, usually once the client has ascertained
that any audio prompts to the user have played to completion.
C->S: MRCP/2.0 ... START-INPUT-TIMERS 543260
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... 543260 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
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11.15. VERIFICATION-COMPLETE
The VERIFICATION-COMPLETE event follows a call to VERIFY or VERIFY-
FROM-BUFFER and is used to communicate the verification results to
the client. The event message body contains only verification
results.
S->C: MRCP/2.0 ... VERIFICATION-COMPLETE 543259 COMPLETE
Completion-Cause:000 success
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
grammar="What-Grammar-URI">
<verification-result>
<voiceprint id="johnsmith">
<incremental>
<utterance-length> 500 </utterance-length>
<device> cellular-phone </device>
<gender> male </gender>
<decision> accepted </decision>
<verification-score> 0.85 </verification-score>
</incremental>
<cumulative>
<utterance-length> 1500 </utterance-length>
<device> cellular-phone </device>
<gender> male </gender>
<decision> accepted </decision>
<verification-score> 0.75 </verification-score>
</cumulative>
</voiceprint>
</verification-result>
</result>
11.16. START-OF-INPUT
The START-OF-INPUT event is returned from the server to the client
once the server has detected speech. This event is always returned
by the verifier resource when speech has been detected, irrespective
of whether the recognizer and verifier resources share the same
session or not.
S->C: MRCP/2.0 ... START-OF-INPUT 543259 IN-PROGRESS
Channel-Identifier:32AECB23433801@speakverify
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11.17. CLEAR-BUFFER
The CLEAR-BUFFER method can be used to clear the verification buffer.
This buffer is used to buffer speech during a recognition, record or
verification operations that may later be used by VERIFY-FROM-BUFFER.
As noted before, the buffer associated with the verifier resource is
shared by other input resources like recognizers and recorders.
Hence, a CLEAR-BUFFER request fails if the verification buffer is in
use. This can happen when any one of the input resources that shares
this buffer has an active read or write operation such as RECORD,
RECOGNIZE or VERIFY with the Ver-Buffer-Utterance header field set to
"true".
C->S: MRCP/2.0 ... CLEAR-BUFFER 543260
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... 543260 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
11.18. GET-INTERMEDIATE-RESULT
A client can use the GET-INTERMEDIATE-RESULT method to poll for
intermediate results of a verification request that is in progress.
Invoking this method does not change the state of the resource. The
verifier resource collects the accumulated verification results and
returns the information in the method response. The message body in
the response to a GET-INTERMEDIATE-RESULT REQUEST contains only
verification results. The method response MUST NOT contain a
Completion-Cause header field as the request is not yet complete. If
the resource does not have a verification in progress the response
has a 402 failure code and no result in the body.
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C->S: MRCP/2.0 ... GET-INTERMEDIATE-RESULT 543260
Channel-Identifier:32AECB23433801@speakverify
S->C: MRCP/2.0 ... 543260 200 COMPLETE
Channel-Identifier:32AECB23433801@speakverify
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
grammar="What-Grammar-URI">
<verification-result>
<voiceprint id="marysmith">
<incremental>
<utterance-length> 50 </utterance-length>
<device> cellular-phone </device>
<gender> female </gender>
<decision> undecided </decision>
<verification-score> 0.85 </verification-score>
</incremental>
<cumulative>
<utterance-length> 150 </utterance-length>
<device> cellular-phone </device>
<gender> female </gender>
<decision> undecided </decision>
<verification-score> 0.65 </verification-score>
</cumulative>
</voiceprint>
</verification-result>
</result>
12. Security Considerations
MRCPv2 is designed to comply with the security-related requirements
documented in SpeechSC Requirements [RFC4313]. Implementers and
users of MRCPv2 are strongly encouraged to read the Security
Considerations section of [RFC4313], because that document contains
discussion of a number of important security issues associated with
the utilization of speech as biometric authentication technology, and
on the threats against systems which store recorded speech, contain
large corpora of voiceprints, and send and receive sensitive
information based on voice input to a recognizer or speech output
from a synthesizer. Specific security measures employed by MRCPv2
are summarized in the following subsections. See the corresponding
sections of this specification for how the security-related machinery
is invoked by individual protocol operations.
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12.1. Rendezvous and Session Establishment
MRCPv2 control sessions are established as media sessions described
by SDP within the context of a SIP dialog. In order to ensure secure
rendezvous between MRCPv2 clients and servers, the following are
required:
1. The SIP implementation in MRCPv2 clients and servers MUST support
digest authentication.
2. The SIP implementation in MRCPv2 clients and servers SHOULD
employ SIPS: URIs,
3. If media stream cryptographic keying is done through SDP (e.g.
using [RFC4568]), the MRCPv2 clients and servers MUST employ
SIPS:.
4. When TLS is used for SIP, the client MUST verify the identity of
the server to which it connects, following the rules and
guidelines defined in [RFC5922].
12.2. Control channel protection
Sensitive data is carried over the MRCPv2 control channel. This
includes things like the output of speech recognition operations,
speaker verification results, input to text-to-speech conversion,
personally-identifying grammars, etc. For this reason MRCPv2 servers
must be properly authenticated and the control channel must permit
the use of both confidentiality and integrity for the data. To
ensure control channel protection, MRCPv2 clients and servers MUST
support TLS and SHOULD utilize it by default unless alternative
control channel protection is used. When TLS is used, the client
MUST verify the identity of the server to which it connects,
following the rules and guidelines defined in [RFC4572]. If there
are multiple TLS-protected channels between the client and the
server, the server MUST NOT send a response to the client over a
channel for which the TLS identities of the server or client differ
from the channel over which the server received the corresponding
request. Alternative control channel protection MAY be used if
desired (e.g. IPSEC).
12.3. Media session protection
Sensitive data is also carried on media sessions terminating on
MRCPv2 servers (the other end of a media channel may or may not be on
the MRCPv2 client). This data includes the user's spoken utterances
and the output of text-to-speech operations. MRCPv2 servers MUST
support a security mechanism for protection of audio media sessions.
MRCPv2 clients that originate or consume audio similarly MUST support
a security mechanism for protection of the audio. If appropriate,
usage of the Secure Real-time Transport Protocol (SRTP) [RFC3711] is
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recommended.
12.4. Indirect Content Access
MCRPv2 employs content indirection extensively. Content may be
fetched and/or stored based on URI-addressing on systems other than
the MRCPv2 client or server. Not all of the stored content is
necessarily sensitive (e.g. XML schemas), but the majority generally
needs protection, and some indirect content, such as voice recordings
and voiceprints, are extremely sensitive and must always be
protected. MRCPv2 clients and servers MUST implement HTTPS for
indirect content access, and SHOULD employ secure access for all
sensitive indirect content. Other secure URI-schemes such as FTPS
MAY also be used. See Section 6.2.15 for the header fields used to
transfer cookie information between the MRCPv2 client and server if
needed for authentication.
MRCPv2 makes no inherent assumptions about the lifetime and access
controls associated with a URI. For example, if neither
authentication nor scheme-specific access controls are used, a leak
of the URI is equivalent to a leak of the content. Moreover, MRCPv2
makes no specific demands on the lifetime of a URI. If a server
offers a URI and the client takes a long, long time to access that
URI, the server may have removed the resource in the interim time
period. MRCPv2 deals with this case by using the URI access scheme's
resource not found error, such as 404 for HTTPS. How long a server
should keep a dynamic resource available is highly application and
context dependent. However, the server SHOULD keep the resource
available for a reasonable amount of time to make it likely the
client will have the resource available when the client needs the
resource. Conversely, to mitigate state exhaustion attacks, MRCPv2
servers are not obligated to keep resources and resource state in
perpetuity. The server SHOULD delete dynamically-generated resources
associated with an MRCPv2 session when the session ends.
One method to avoid resource leakage is for the server to use one-
time resource URIs. In this instance, there can be only a single
access to the underlying resource using the given URI. A downside to
this approach is if an attacker uses the URI before the client uses
the URI, then the client is denied the resource. Other methods would
be to adopt a mechanism similar to the URLAUTH IMAP extension
[RFC4467], where the server sets cryptographic checks on URI usage,
as well as capabilities for expiration, revocation, and so on.
Specifying such a mechanism is beyond the scope of this document.
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12.5. Protection of stored media
MRCPv2 applications often require the use of stored media. Voice
recordings are both stored (e.g. for diagnosis and system tuning),
and fetched (for replaying utterances into multiple MRCPv2
resources). Voiceprints are fundamental to the speaker
identification and verification functions. This data can be
extremely sensitive and can present substantial privacy and
impersonation risks if stolen. Systems employing MRCPv2 should be
deployed in ways that minimize these risks. The SpeechSC
Requirements [RFC4313] contains a more extensive discussion of these
risks and ways they may be mitigated.
12.6. DTMF and recognition buffers
DTMF buffers and recognition buffers may grow large enough to exceed
the capabilities of a server, and the server MUST be prepared to
gracefully handle resource consumption. A server MAY respond with
the appropriate recognition incomplete if the server is in danger of
running out of resources.
13. IANA Considerations
13.1. New registries
This section describes the name spaces (registries) for MRCPv2 that
IANA is requested to create and maintain. Assignment/registration
policies are described in RFC5226 [RFC5226].
13.1.1. MRCPv2 resource types
IANA SHALL create a new name space of "MRCPv2 resource types". All
maintenance within and additions to the contents of this name space
MUST be according to the "Standards Action" registration policy. The
initial contents of the registry, defined in Section 4.2, are given
below:
Resource type Resource description Reference
------------- -------------------- ---------
speechrecog Speech Recognizer [RFCXXXX]
dtmfrecog DTMF Recognizer [RFCXXXX]
speechsynth Speech Synthesizer [RFCXXXX]
basicsynth Basic Synthesizer [RFCXXXX]
speakverify Speaker Verifier [RFCXXXX]
recorder Speech Recorder [RFCXXXX]
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13.1.2. MRCPv2 methods and events
IANA SHALL create a new name space of "MRCPv2 methods and events".
All maintenance within and additions to the contents of this name
space MUST be according to the "Standards Action" registration
policy. The initial contents of the registry, defined by the
"method-name" and "event-name" BNF in Section 15 and explained in
Section 5.2 and Section 5.5, are given below.
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Name Resource type Method/Event Reference
---- ------------- ------------ ---------
SET-PARAMS Generic Method [RFCXXXX]
GET-PARAMS Generic Method [RFCXXXX]
SPEAK Synthesizer Method [RFCXXXX]
STOP Synthesizer Method [RFCXXXX]
PAUSE Synthesizer Method [RFCXXXX]
RESUME Synthesizer Method [RFCXXXX]
BARGE-IN-OCCURRED Synthesizer Method [RFCXXXX]
CONTROL Synthesizer Method [RFCXXXX]
DEFINE-LEXICON Synthesizer Method [RFCXXXX]
DEFINE-GRAMMAR Recognizer Method [RFCXXXX]
RECOGNIZE Recognizer Method [RFCXXXX]
INTERPRET Recognizer Method [RFCXXXX]
GET-RESULT Recognizer Method [RFCXXXX]
START-INPUT-TIMERS Recognizer Method [RFCXXXX]
STOP Recognizer Method [RFCXXXX]
START-PHRASE-ENROLLMENT Recognizer Method [RFCXXXX]
ENROLLMENT-ROLLBACK Recognizer Method [RFCXXXX]
END-PHRASE-ENROLLMENT Recognizer Method [RFCXXXX]
MODIFY-PHRASE Recognizer Method [RFCXXXX]
DELETE-PHRASE Recognizer Method [RFCXXXX]
RECORD Recorder Method [RFCXXXX]
STOP Recorder Method [RFCXXXX]
START-INPUT-TIMERS Recorder Method [RFCXXXX]
START-SESSION Verifier Method [RFCXXXX]
END-SESSION Verifier Method [RFCXXXX]
QUERY-VOICEPRINT Verifier Method [RFCXXXX]
DELETE-VOICEPRINT Verifier Method [RFCXXXX]
VERIFY Verifier Method [RFCXXXX]
VERIFY-FROM-BUFFER Verifier Method [RFCXXXX]
VERIFY-ROLLBACK Verifier Method [RFCXXXX]
STOP Verifier Method [RFCXXXX]
START-INPUT-TIMERS Verifier Method [RFCXXXX]
GET-INTERMEDIATE-RESULT Verifier Method [RFCXXXX]
SPEECH-MARKER Synthesizer Event [RFCXXXX]
SPEAK-COMPLETE Synthesizer Event [RFCXXXX]
START-OF-INPUT Recognizer Event [RFCXXXX]
RECOGNITION-COMPLETE Recognizer Event [RFCXXXX]
INTERPRETATION-COMPLETE Recognizer Event [RFCXXXX]
START-OF-INPUT Recorder Event [RFCXXXX]
RECORD-COMPLETE Recorder Event [RFCXXXX]
VERIFICATION-COMPLETE Verifier Event [RFCXXXX]
START-OF-INPUT Verifier Event [RFCXXXX]
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13.1.3. MRCPv2 header fields
IANA SHALL create a new name space of "MRCPv2 header fields". All
maintenance within and additions to the contents of this name space
MUST be according to the "Standards Action" registration policy. The
initial contents of the registry, defined by the "message-header" BNF
in Section 15 and explained in Section 5.1, are given below. Note
that the values permitted for the "Vendor-Specific-Parameters"
parameter are managed according to a different policy. See
Section 13.1.6.
Name Resource type Reference
---- ------------- ---------
channel-identifier Generic [RFCXXXX]
accept Generic [RFC2616]
active-request-id-list Generic [RFCXXXX]
proxy-sync-id Generic [RFCXXXX]
accept-charset Generic [RFC2616]
content-type Generic [RFCXXXX]
content-id Generic [RFC2392, RFC2046, and RFC5322]
content-base Generic [RFCXXXX]
content-encoding Generic [RFCXXXX]
content-location Generic [RFCXXXX]
content-length Generic [RFCXXXX]
fetch-timeout Generic [RFCXXXX]
cache-control Generic [RFCXXXX]
logging-tag Generic [RFCXXXX]
set-cookie Generic [RFCXXXX]
set-cookie2 Generic [RFCXXXX]
vendor-specific Generic [RFCXXXX]
jump-size Synthesizer [RFCXXXX]
kill-on-barge-in Synthesizer [RFCXXXX]
speaker-profile Synthesizer [RFCXXXX]
completion-cause Synthesizer [RFCXXXX]
completion-reason Synthesizer [RFCXXXX]
voice-parameter Synthesizer [RFCXXXX]
prosody-parameter Synthesizer [RFCXXXX]
speech-marker Synthesizer [RFCXXXX]
speech-language Synthesizer [RFCXXXX]
fetch-hint Synthesizer [RFCXXXX]
audio-fetch-hint Synthesizer [RFCXXXX]
failed-uri Synthesizer [RFCXXXX]
failed-uri-cause Synthesizer [RFCXXXX]
speak-restart Synthesizer [RFCXXXX]
speak-length Synthesizer [RFCXXXX]
load-lexicon Synthesizer [RFCXXXX]
lexicon-search-order Synthesizer [RFCXXXX]
confidence-threshold Recognizer [RFCXXXX]
sensitivity-level Recognizer [RFCXXXX]
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speed-vs-accuracy Recognizer [RFCXXXX]
n-best-list-length Recognizer [RFCXXXX]
input-type Recognizer [RFCXXXX]
no-input-timeout Recognizer [RFCXXXX]
recognition-timeout Recognizer [RFCXXXX]
waveform-uri Recognizer [RFCXXXX]
input-waveform-uri Recognizer [RFCXXXX]
completion-cause Recognizer [RFCXXXX]
completion-reason Recognizer [RFCXXXX]
recognizer-context-block Recognizer [RFCXXXX]
start-input-timers Recognizer [RFCXXXX]
speech-complete-timeout Recognizer [RFCXXXX]
speech-incomplete-timeout Recognizer [RFCXXXX]
dtmf-interdigit-timeout Recognizer [RFCXXXX]
dtmf-term-timeout Recognizer [RFCXXXX]
dtmf-term-char Recognizer [RFCXXXX]
failed-uri Recognizer [RFCXXXX]
failed-uri-cause Recognizer [RFCXXXX]
save-waveform Recognizer [RFCXXXX]
media-type Recognizer [RFCXXXX]
new-audio-channel Recognizer [RFCXXXX]
speech-language Recognizer [RFCXXXX]
ver-buffer-utterance Recognizer [RFCXXXX]
recognition-mode Recognizer [RFCXXXX]
cancel-if-queue Recognizer [RFCXXXX]
hotword-max-duration Recognizer [RFCXXXX]
hotword-min-duration Recognizer [RFCXXXX]
interpret-text Recognizer [RFCXXXX]
dtmf-buffer-time Recognizer [RFCXXXX]
clear-dtmf-buffer Recognizer [RFCXXXX]
early-no-match Recognizer [RFCXXXX]
num-min-consistent-pronunciations Recognizer [RFCXXXX]
consistency-threshold Recognizer [RFCXXXX]
clash-threshold Recognizer [RFCXXXX]
personal-grammar-uri Recognizer [RFCXXXX]
enroll-utterance Recognizer [RFCXXXX]
phrase-id Recognizer [RFCXXXX]
phrase-nl Recognizer [RFCXXXX]
weight Recognizer [RFCXXXX]
save-best-waveform Recognizer [RFCXXXX]
new-phrase-id Recognizer [RFCXXXX]
confusable-phrases-uri Recognizer [RFCXXXX]
abort-phrase-enrollment Recognizer [RFCXXXX]
sensitivity-level Recorder [RFCXXXX]
no-input-timeout Recorder [RFCXXXX]
completion-cause Recorder [RFCXXXX]
completion-reason Recorder [RFCXXXX]
failed-uri Recorder [RFCXXXX]
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failed-uri-cause Recorder [RFCXXXX]
record-uri Recorder [RFCXXXX]
media-type Recorder [RFCXXXX]
max-time Recorder [RFCXXXX]
trim-length Recorder [RFCXXXX]
final-silence Recorder [RFCXXXX]
capture-on-speech Recorder [RFCXXXX]
ver-buffer-utterance Recorder [RFCXXXX]
start-input-timers Recorder [RFCXXXX]
new-audio-channel Recorder [RFCXXXX]
repository-uri Verifier [RFCXXXX]
voiceprint-identifier Verifier [RFCXXXX]
verification-mode Verifier [RFCXXXX]
adapt-model Verifier [RFCXXXX]
abort-model Verifier [RFCXXXX]
min-verification-score Verifier [RFCXXXX]
num-min-verification-phrases Verifier [RFCXXXX]
num-max-verification-phrases Verifier [RFCXXXX]
no-input-timeout Verifier [RFCXXXX]
save-waveform Verifier [RFCXXXX]
media-type Verifier [RFCXXXX]
waveform-uri Verifier [RFCXXXX]
voiceprint-exists Verifier [RFCXXXX]
ver-buffer-utterance Verifier [RFCXXXX]
input-waveform-uri Verifier [RFCXXXX]
completion-cause Verifier [RFCXXXX]
completion-reason Verifier [RFCXXXX]
speech-complete-timeout Verifier [RFCXXXX]
new-audio-channel Verifier [RFCXXXX]
abort-verification Verifier [RFCXXXX]
start-input-timers Verifier [RFCXXXX]
input-type Verifier [RFCXXXX]
13.1.4. MRCPv2 status codes
IANA SHALL create a new name space of "MRCPv2 status codes" with the
initial values that are defined in Section 5.4 All maintenance within
and additions to the contents of this name space MUST be according to
the "Specification Required with Expert Review" registration policy.
13.1.5. Grammar Reference List Parameters
IANA SHALL create a new name space of "Grammar Reference List
Parameters". All maintenance within and additions to the contents of
this name space MUST be according to the "Specification Required with
Expert Review" registration policy. There is only one initial
parameter, "weight", which is defined in Section 13.5.1 and
Section 9.9.
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13.1.6. MRCPv2 vendor-specific parameters
IANA SHALL create a new name space of "MRCPv2 vendor-specific
parameters". All maintenance within and additions to the contents of
this name space MUST be according to the "Hierarchical Allocation"
registration policy as follows. Each name (corresponding to the
"vendor-av-pair-name" ABNF production) MUST satisfy the syntax
requirements of Internet Domain Names as described in section 2.3.1
of RFC1035 [RFC1035] (and as updated or obsoleted by successive
RFCs), with one exception, the order of the domain names is reversed.
For example, a vendor-specific parameter "foo" by example.com would
have the form "com.example.foo". The first, or top-level domain, is
restricted to exactly the set of Top-Level Internet Domains defined
by IANA and will be updated by IANA when and only when that set
changes. The second-level and all subdomains within the parameter
name MUST be allocated according to the "Expert Review" policy. The
Designated Expert MAY advise IANA to allow delegation of subdomains
to the requester. As a general guideline, the Designated Expert is
encouraged to manage the allocation of corporate, organizational, or
institutional names and delegate all subdomains accordingly. For
example, the Designated Expert MAY allocate "com.example" and
delegate all subdomains of that name to the organization represented
by the Internet domain name "example.com". For simplicity, the
Designated Expert is encouraged to perform allocations according to
the existing allocations of Internet domain names to organizations,
institutions, corporations, etc.
The registry contains a list of vendor-registered parameters, where
each defined parameter is associated with a reference to an RFC
defining it. The registry is initially empty.
13.2. NLSML-related registrations
13.2.1. application/nlsml+xml Media Type registration
IANA is requested to register the following Media Type according to
the process defined in RFC4288 [RFC4288].
To: ietf-types@iana.org
Subject: Registration of media type application/nlsml+xml
MIME media type name: application
MIME subtype name: nlsml+xml
Required parameters: none
Optional parameters:
charset: All of the considerations described in RFC3023 also
apply to the application/nlsml+xml media type.
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Encoding considerations: All of the considerations described in
RFC3023 also apply to the application/nlsml+xml media type.
Security considerations: As with HTML, NLSML documents contain links
to other data stores (grammars, verifier resources, etc.). Unlike
HTML, however, the data stores are not treated as media to be
rendered. Nevertheless, linked files may themselves have security
considerations, which would be those of the individual registered
types. Additionally, this media type has all of the security
considerations described in RFC3023.
Interoperability considerations: Although an NLSML document is
itself a complete XML document, for a fuller interpretation of the
content a receiver of an NLSML document may wish to access
resources linked to by the document. The inability of an NLSML
processor to access or process such linked resources could result
in different behavior by the ultimate consumer of the data.
Published specification: RFCXXXX
Applications which use this media type: MRCPv2 clients and servers
Additional information: none
Magic number(s): There is no single initial octet sequence that is
always present for NLSML files.
Person & email address to contact for further information: Sarvi
Shanmugham, sarvi@cisco.com
Intended usage: This media type is expected to be used only in
conjunction with MRCPv2.
13.3. NLSML XML Schema registration
IANA is requested to register and maintain the following XML Schema.
Information provided follows the template in RFC3688 [RFC3688].
XML element type: schema
URI: http://www.ietf.org/xml/schema/mrcpv2
Registrant Contact: IESG
XML: See Section 16.1.
13.4. MRCPv2 XML Namespace registration
IANA is requested to register and maintain the following XML Name
space. Information provided follows the template in RFC3688
[RFC3688].
XML element type: ns
URI: http://www.ietf.org/xml/ns/mrcpv2
Registrant Contact: IESG
XML: RFCXXXX
13.5. text Media Type Registrations
IANA is requested to register the following text Media Types
according to the process defined in RFC 4288 [RFC4288].
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13.5.1. text/grammar-ref-list
To: ietf-types@iana.org
Subject: Registration of media type text/grammar-ref-list
MIME media type name: application
MIME subtype name: text/grammar-ref-list
Required parameters: none
Optional parameters: none
Encoding considerations: Depending on the transfer protocol, a
transfer encoding may be necessary to deal with very long lines.
Security considerations: This media type contains URIs which may
represent references to external resources. As these resources
are assumed to be speech recognition grammars, similar
considerations as for the media types "application/srgs" and
"application/srgs+xml" apply.
Interoperability considerations; '>' must be percent encoded in URIs
according to RFC3986.
Published specification: The RECOGNIZE method of the MRCP protocol
performs a recognition operation that matches input against a set
of grammars. When matching against more than one grammar, it is
sometimes necessary to use different weights for the individual
grammars. These weights are not a property of the grammar
resource itself but qualify the reference to that grammar for the
particular recognition operation initiated by the RECOGNIZE
method. The format of the proposed text/grammar-ref-list media
type is as follows: body = *reference where reference = "<" uri
">" [parameters] CRLF parameters = ";" parameter *(";" parameter)
and parameter = attribute "=" value. This specification currently
only defines a 'weight' parameter, but new parameters may be added
through the "Grammar Reference List Parameters" IANA registry
established through this specification. Example:
<http://example.com/grammars/field1.gram>
<http://example.com/grammars/field2.gram>;weight="0.85"
<session:field3@form-level.store>;weight="0.9"
<http://example.com/grammars/universals.gram>;weight="0.75"
Applications which use this media type: MRCPv2 clients and servers
Additional information: none
Magic number(s): none
Person & email address to contact for further information: Sarvi
Shanmugham, sarvi@cisco.com
Intended usage: This media type is expected to be used only in
conjunction with MRCPv2.
13.6. session URL scheme registration
IANA is requested to register the following new URI scheme. The
information below follows the template given in RFC4395 [RFC4395].
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URL scheme name: "session"
URL scheme syntax: The syntax of this scheme is identical to that
defined for the "cid" scheme in section 2 of RFC2392.
Character encoding considerations: URI values are limited to the US-
ASCII character set.
Intended usage: The URI is intended to identify a data resource
previously given to the network computing resource. The purpose
of this scheme is to permit access to the specific resource for
the lifetime of the session with the entity storing the resource.
The media type of the resource CAN vary. There is no explicit
mechanism for communication of the media type. This scheme is
currently widely used internally by existing implementations, and
the registration is intended to provide information in the rare
(and unfortunate) case that the scheme is used elsewhere. The
scheme SHOULD NOT be used for open internet protocols.
Applications and/or protocols which use this URL scheme name: This
scheme name is used by MRCPv2 clients and servers.
Interoperability considerations:
The character set for URLs is restricted to US-ASCII. Note that
none of the resources are accessible after the MCRPv2 session
ends, hence the name of the scheme. For clients who establish one
MRCPv2 session only for the entire speech application being
implemented this is sufficient, but clients who create, terminate,
and recreate MRCP sessions for performance or scalability reasons
will lose access to resources established in the earlier
session(s).
Security considerations: The URIs defined here provide an
identification mechanism only. Given that the communication
channel between client and server is secure, that the server
correctly accesses the resource associated with the URI, and that
the server ensures session-only lifetime and access for each URI,
the only remaining security issues are those of the types of media
referred to by the URI.
Relevant publications: This specification, particularly sections
Section 6.2.7, Section 8.5.2, Section 9.5.1, and Section 9.9.
Contact for further information: Sarvi Shanmugham, sarvi@cisco.com
Author/Change controller: IESG
13.7. SDP parameter registrations
IANA is requested to register the following SDP parameter values.
The information for each follows the template given in RFC4566
[RFC4566], Appendix B.
13.7.1. sub-registry "proto"
"TCP/MRCPv2" value of the "proto" parameter
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Contact name, email address and telephone number: Sarvi Shanmugham,
sarvi@cisco.com, +1.408.902.3875
Name being registered (as it will appear in SDP): TCP/MRCPv2
Long-form name in English: MCRPv2 over TCP
Type of name: proto
Explanation of name: This name represents the MCRPv2 protocol
carried over TCP.
Reference to specification of name: RFCXXXX
"TCP/TLS/MRCPv2" value of the "proto" parameter
Contact name, email address and telephone number: Sarvi Shanmugham,
sarvi@cisco.com, +1.408.902.3875
Name being registered (as it will appear in SDP): TCP/TLS/MRCPv2
Long-form name in English: MCRPv2 over TLS over TCP
Type of name: proto
Explanation of name: This name represents the MCRPv2 protocol
carried over TLS over TCP.
Reference to specification of name: RFCXXXX
13.7.2. sub-registry "att-field (session-level)"
"resource" value of the "att-field" parameter
Contact name, email address and telephone number: Sarvi Shanmugham,
sarvi@cisco.com, +1.408.902.3875
Attribute name (as it will appear in SDP): resource
Long-form attribute name in English: MRCPv2 resource type
Type of attribute: media-level
Subject to charset attribute? no
Explanation of attribute: See Section 4.2 of RFCXXXX for description
and examples.
Specification of appropriate attribute values: See section
Section 13.1.1 of RFCXXXX.
"channel" value of the "att-field" parameter
Contact name, email address and telephone number: Sarvi Shanmugham,
sarvi@cisco.com, +1.408.902.3875
Attribute name (as it will appear in SDP): channel
Long-form attribute name in English: MRCPv2 resource channel
identifier
Type of attribute: media-level
Subject to charset attribute? no
Explanation of attribute: See Section 4.2 of RFCXXXX for description
and examples.
Specification of appropriate attribute values See Section 4.2 and
the "channel-id" ABNF production rules of RFCXXXX.
13.7.3. sub-registry "att-field (media-level)"
"cmid" value of the "att-field" parameter
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Contact name, email address and telephone number: Sarvi Shanmugham,
sarvi@cisco.com, +1.408.902.3875
Attribute name (as it will appear in SDP): cmid
Long-form attribute name in English: MRCPv2 resource channel media
identifier
Type of attribute: media-level
Subject to charset attribute? no
Explanation of attribute: See Section 4.4 of RFCXXXX for description
and examples.
Specification of appropriate attribute values See Section 4.4 and
the "cmid-attribute" ABNF production rules of RFCXXXX.
14. Examples
14.1. Message Flow
The following is an example of a typical MRCPv2 session of speech
synthesis and recognition between a client and a server.
The figure below illustrates opening a session to the MRCPv2 server.
This is exchange does not allocate a resource or setup media. It
simply establishes a SIP session with the MRCPv2 server.
C->S:
INVITE sip:mresources@example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg1
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:323123 INVITE
Contact:<sip:sarvi@client.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=sarvi 2614933546 2614933546 IN IP4 192.0.2.4
s=Set up MRCPv2 control and audio
i=Initial contact
c=IN IP4 192.0.2.12
S->C:
SIP/2.0 200 OK
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg1;received=192.0.32.10
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To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:323123 INVITE
Contact:<sip:mresources@server.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=- 3000000001 3000000001 IN IP4 192.0.2.4
s=Set up MRCPv2 control and audio
i=Initial contact
c=IN IP4 192.0.2.11
C->S:
ACK sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg2
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
From:Sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:323123 ACK
Content-Length:0
The client requests the server to create synthesizer resource control
channel to do speech synthesis. This also adds a media stream to
send the generated speech. Note that in this example, the client
requests a new MRCPv2 TCP stream between the client and the server.
In the following requests, the client will ask to use the existing
connection.
C->S:
INVITE sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg3
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:323124 INVITE
Contact:<sip:sarvi@client.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=sarvi 2614933546 2614933547 IN IP4 192.0.2.4
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s=Set up MRCPv2 control and audio
i=Add TCP channel, synthesizer and one-way audio
c=IN IP4 192.0.2.12
m=application 9 TCP/MRCPv2 1
a=setup:active
a=connection:new
a=resource:speechsynth
a=cmid:1
m=audio 49170 RTP/AVP 0 96
a=rtpmap:0 pcmu/8000
a=recvonly
a=mid:1
S->C:
SIP/2.0 200 OK
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg3;received=192.0.32.10
To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:323124 INVITE
Contact:<sip:mresources@server.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=- 3000000001 3000000002 IN IP4 192.0.2.4
s=Set up MRCPv2 control and audio
i=Add TCP channel, synthesizer and one-way audio
c=IN IP4 192.0.2.11
m=application 32416 TCP/MRCPv2 1
a=setup:passive
a=connection:new
a=channel:32AECB23433801@speechsynth
a=cmid:1
m=audio 48260 RTP/AVP 0
a=rtpmap:0 pcmu/8000
a=sendonly
a=mid:1
C->S:
ACK sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg4
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
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From:Sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:323124 ACK
Content-Length:0
This exchange allocates an additional resource control channel for a
recognizer. Since a recognizer would need to receive an audio stream
for recognition, this interaction also updates the audio stream to
sendrecv making it a 2-way audio stream.
C->S:
INVITE sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg5
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:323125 INVITE
Contact:<sip:sarvi@client.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=sarvi 2614933546 2614933548 IN IP4 192.0.2.4
s=Set up MRCPv2 control and audio
i=Add recognizer and duplex the audio
c=IN IP4 192.0.2.12
m=application 9 TCP/MRCPv2 1
a=setup:active
a=connection:existing
a=resource:speechsynth
a=cmid:1
m=audio 49170 RTP/AVP 0 96
a=rtpmap:0 pcmu/8000
a=recvonly
a=mid:1
m=application 9 TCP/MRCPv2 1
a=setup:active
a=connection:existing
a=resource:speechrecog
a=cmid:2
m=audio 49180 RTP/AVP 0 96
a=rtpmap:0 pcmu/8000
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-15
a=sendonly
a=mid:2
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S->C:
SIP/2.0 200 OK
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg5;received=192.0.32.10
To:MediaServer <sip:mresources@example.com>;tag=62784
From:sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:323125 INVITE
Contact:<sip:mresources@server.example.com>
Content-Type:application/sdp
Content-Length:...
v=0
o=- 3000000001 3000000003 IN IP4 192.0.2.4
s=Set up MRCPv2 control and audio
i=Add recognizer and duplex the audio
c=IN IP4 192.0.2.11
m=application 32416 TCP/MRCPv2 1
a=channel:32AECB23433801@speechsynth
a=cmid:1
m=audio 48260 RTP/AVP 0
a=rtpmap:0 pcmu/8000
a=sendonly
a=mid:1
m=application 32416 TCP/MRCPv2 1
a=channel:32AECB23433801@speechrecog
a=cmid:2
m=audio 48260 RTP/AVP 0
a=rtpmap:0 pcmu/8000
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-15
a=recvonly
a=mid:2
C->S:
ACK sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg6
Max-Forwards:6
To:MediaServer <sip:mresources@example.com>;tag=62784
From:Sarvi <sip:sarvi@example.com>;tag=1928301774
Call-ID:a84b4c76e66710
CSeq:323125 ACK
Content-Length:0
A MRCPv2 "SPEAK" request initiates speech.
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C->S:
MRCP/2.0 ... SPEAK 543257
Channel-Identifier:32AECB23433801@speechsynth
Kill-On-Barge-In:false
Voice-gender:neutral
Voice-age:25
Prosody-volume:medium
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>You have 4 new messages.</s>
<s>The first is from Stephanie Williams
<mark name="Stephanie"/>
and arrived at <break/>
<say-as interpret-as="vxml:time">0345p</say-as>.</s>
<s>The subject is <prosody
rate="-20%">ski trip</prosody></s>
</p>
</speak>
S->C:
MRCP/2.0 ... 543257 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechsynth
Speech-Marker:timestamp=857205015059
The synthesizer hits the special marker in the message to be spoken
and faithfully informs the client of the event.
S->C: MRCP/2.0 ... SPEECH-MARKER 543257 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechsynth
Speech-Marker:timestamp=857206027059;Stephanie
The synthesizer finishes with the "SPEAK" request.
S->C: MRCP/2.0 ... SPEAK-COMPLETE 543257 COMPLETE
Channel-Identifier:32AECB23433801@speechsynth
Speech-Marker:timestamp=857207685213;Stephanie
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The recognizer is issued a request to listen for the customer
choices.
C->S: MRCP/2.0 ... RECOGNIZE 543258
Channel-Identifier:32AECB23433801@speechrecog
Content-Type:application/srgs+xml
Content-Length:...
<?xml version="1.0"?>
<!-- the default grammar language is US English -->
<grammar xmlns="http://www.w3.org/2001/06/grammar"
xml:lang="en-US" version="1.0" root="request">
<!-- single language attachment to a rule expansion -->
<rule id="request">
Can I speak to
<one-of xml:lang="fr-CA">
<item>Michel Tremblay</item>
<item>Andre Roy</item>
</one-of>
</rule>
</grammar>
S->C: MRCP/2.0 ... 543258 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
The client issues the next MRCPv2 "SPEAK" method. It is generally
RECOMMENDED when playing a prompt to the user with kill-on-barge-in
and asking for input, that the client issue the RECOGNIZE request
ahead of the "SPEAK" request for optimum performance and user
experience. This way, it is guaranteed that the recognizer is online
before the prompt starts playing and the user's speech will not be
truncated at the beginning (especially for power users).
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C->S: MRCP/2.0 ... SPEAK 543259
Channel-Identifier:32AECB23433801@speechsynth
Kill-On-Barge-In:true
Content-Type:application/ssml+xml
Content-Length:...
<?xml version="1.0"?>
<speak version="1.0"
xmlns="http://www.w3.org/2001/10/synthesis"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/10/synthesis
http://www.w3.org/TR/speech-synthesis/synthesis.xsd"
xml:lang="en-US">
<p>
<s>Welcome to ABC corporation.</s>
<s>Who would you like Talk to.</s>
</p>
</speak>
S->C: MRCP/2.0 ... 543259 200 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechsynth
Speech-Marker:timestamp=857207696314
Since the last "SPEAK" request had Kill-On-Barge-In set to "true",
the speech synthesizer is interrupted when the user starts speaking.
And the client is notified.
Now, since the recognition and synthesizer resources are on the same
session, they may have worked with each other to deliver kill-on-
barge-in. Whether the synthesizer and recognizer are in the same
session or not the recognizer MUST generate the START-OF-INPUT event
to the client.
The client MUST then blindly turn around and issued a BARGE-IN-
OCCURRED method to the synthesizer resource (if a "SPEAK" request was
active). The synthesizer, if kill-on-barge-in was enabled on the
current "SPEAK" request, would have then interrupted it and issued a
"SPEAK"-COMPLETE event to the client.
The completion-cause code differentiates if this is normal completion
or a kill-on-barge-in interruption.
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S->C: MRCP/2.0 ... START-OF-INPUT 543258 IN-PROGRESS
Channel-Identifier:32AECB23433801@speechrecog
Proxy-Sync-Id:987654321
C->S: MRCP/2.0 ... BARGE-IN-OCCURRED 543259
Channel-Identifier:32AECB23433801@speechsynth
Proxy-Sync-Id:987654321
S->C: MRCP/2.0 ... 543259 200 COMPLETE
Channel-Identifier:32AECB23433801@speechsynth
Active-Request-Id-List:543258
Speech-Marker:timestamp=857206096314
S->C: MRCP/2.0 ... SPEAK-COMPLETE 543259 COMPLETE
Channel-Identifier:32AECB23433801@speechsynth
Completion-Cause:001 barge-in
Speech-Marker:timestamp=857207685213
The recognition resource matched the spoken stream to a grammar and
generated results. The result of the recognition is returned by the
server as part of the RECOGNITION-COMPLETE event.
S->C: MRCP/2.0 ... RECOGNITION-COMPLETE 543258 COMPLETE
Channel-Identifier:32AECB23433801@speechrecog
Completion-Cause:000 success
Waveform-URI:<http://web.media.com/session123/audio.wav>;
size=423523;duration=25432
Content-Type:application/nlsml+xml
Content-Length:...
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="session:request1@form-level.store">
<interpretation>
<instance name="Person">
<ex:Person>
<ex:Name> Andre Roy </ex:Name>
</ex:Person>
</instance>
<input> may I speak to Andre Roy </input>
</interpretation>
</result>
When the client wants to tear down the whole session and all its
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resources, it MUST issue a SIP BYE to close the SIP session. This
will de-allocate all the control channels and resources allocated
under the session.
C->S: BYE sip:mresources@server.example.com SIP/2.0
Via:SIP/2.0/TCP client.atlanta.example.com:5060;
branch=z9hG4bK74bg7
Max-Forwards:6
From:Sarvi <sip:sarvi@example.com>;tag=1928301774
To:MediaServer <sip:mresources@example.com>;tag=62784
Call-ID:a84b4c76e66710
CSeq:323126 BYE
Content-Length:0
14.2. Recognition Result Examples
14.2.1. Simple ASR Ambiguity
System: To which city will you be traveling?
User: I want to go to Pittsburgh.
<?xml version="1.0"?>
<result xmlns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns:ex="http://www.example.com/example"
grammar="http://www.example.com/flight">
<interpretation confidence="0.6">
<instance>
<ex:airline>
<ex:to_city>Pittsburgh</ex:to_city>
<ex:airline>
<instance>
<input mode="speech">
I want to go to Pittsburgh
</input>
</interpretation>
<interpretation confidence="0.4"
<instance>
<ex:airline>
<ex:to_city>Stockholm</ex:to_city>
</ex:airline>
</instance>
<input>I want to go to Stockholm</input>
</interpretation>
</result>
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14.2.2. Mixed Initiative
System: What would you like?
User: I would like 2 pizzas, one with pepperoni and cheese,
one with sausage and a bottle of coke, to go.
This example includes an order object which in turn contains objects
named "food_item", "drink_item" and "delivery_method". The
representation assumes there are no ambiguities in the speech or
natural language processing. Note that this representation also
assumes some level of intra-sentential anaphora resolution, i.e., to
resolve the two "one's" as "pizza".
<?xml version="1.0"?>
<nl:result xmlns:nl="http://www.ietf.org/xml/ns/mrcpv2"
xmlns="http://www.example.com/example"
grammar="http://www.example.com/foodorder">
<nl:interpretation confidence="1.0" >
<nl:instance>
<order>
<food_item confidence="1.0">
<pizza>
<ingredients confidence="1.0">
pepperoni
</ingredients>
<ingredients confidence="1.0">
cheese
</ingredients>
</pizza>
<pizza>
<ingredients>sausage</ingredients>
</pizza>
</food_item>
<drink_item confidence="1.0">
<size>2-liter</size>
</drink_item>
<delivery_method>to go</delivery_method>
</order>
</nl:instance>
<nl:input mode="speech">I would like 2 pizzas,
one with pepperoni and cheese, one with sausage
and a bottle of coke, to go.
</nl:input>
</nl:interpretation>
</nl:result>
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14.2.3. DTMF Input
A combination of DTMF input and speech is represented using nested
input elements. For example:
User: My pin is (dtmf 1 2 3 4)
<input>
<input mode="speech" confidence ="1.0"
timestamp-start="2000-04-03T0:00:00"
timestamp-end="2000-04-03T0:00:01.5">My pin is
</input>
<input mode="dtmf" confidence ="1.0"
timestamp-start="2000-04-03T0:00:01.5"
timestamp-end="2000-04-03T0:00:02.0">1 2 3 4
</input>
</input>
Note that grammars that recognize mixtures of speech and DTMF are not
currently possible in VoiceXML; however this representation may be
needed for other applications of NLSML, and it may be introduced in
future versions of VoiceXML.
14.2.4. Interpreting Meta-Dialog and Meta-Task Utterances
Natural language communication makes use of meta-dialog and meta-task
utterances. This specification is flexible enough so that meta
utterances can be represented on an application-specific basis
without requiring other standard markup.
Here are two examples of how meta-task and meta-dialog utterances
might be represented.
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System: What toppings do you want on your pizza?
User: What toppings do you have?
<interpretation grammar="http://www.example.com/toppings">
<instance>
<question>
<questioned_item>toppings<questioned_item>
<questioned_property>
availability
</questioned_property>
</question>
</instance>
<input mode="speech">
what toppings do you have?
</input>
</interpretation>
User: slow down.
<interpretation grammar="http://www.example.com/generalCommandsGrammar">
<instance>
<command>
<action>reduce speech rate</action>
<doer>system</doer>
</command>
</instance>
<input mode="speech">slow down</input>
</interpretation>
14.2.5. Anaphora and Deixis
This specification can be used on an application-specific basis to
represent utterances that contain unresolved anaphoric and deictic
references. Anaphoric references, which include pronouns and
definite noun phrases that refer to something that was mentioned in
the preceding linguistic context, and deictic references, which refer
to something that is present in the non-linguistic context, present
similar problems in that there may not be sufficient unambiguous
linguistic context to determine what their exact role in the
interpretation should be. In order to represent unresolved anaphora
and deixis using this specification, one strategy would be for the
developer to define a more surface-oriented representation that
leaves the specific details of the interpretation of the reference
open. (This assumes that a later component is responsible for
actually resolving the reference).
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Example: (ignoring the issue of representing the input from the
pointing gesture.)
System: What do you want to drink?
User: I want this (clicks on picture of large root beer.)
<?xml version="1.0"?>
<nl:result xmlns:nl="http://www.ietf.org/xml/ns/mrcpv2"
xmlns="http://www.example.com/example"
grammar="http://www.example.com/beverages.grxml">
<nl:interpretation>
<nl:instance>
<doer>I</doer>
<action>want</action>
<object>this</object>
</nl:instance>
<nl:input mode="speech">I want this</nl:input>
</nl:interpretation>
</nl:result>
14.2.6. Distinguishing Individual Items from Sets with One Member
For programming convenience, it is useful to be able to distinguish
between individual items and sets containing one item in the XML
representation of semantic results. For example, a pizza order might
consist of exactly one pizza, but a pizza might contain zero or more
toppings. Since there is no standard way of marking this distinction
directly in XML, in the current framework, the developer is free to
adopt any conventions that would convey this information in the XML
markup. One strategy would be for the developer to wrap the set of
items in a grouping element, as in the following example.
<order>
<pizza>
<topping-group>
<topping>mushrooms</topping>
</topping-group>
</pizza>
<drink>coke</drink>
</order>
In this example, the programmer can assume that there is supposed to
be exactly one pizza and one drink in the order, but the fact that
there is only one topping is an accident of this particular pizza
order.
Note that the client controls both the grammar and the semantics to
be returned upon grammar matches, so the user of the MRCP protocol is
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fully empowered to cause results to be returned in NLSML in such a
way that the interpretation is clear to that user.
14.2.7. Extensibility
Extensibility in NLSML is provided via result content flexibility, as
discussed in the discussions of meta utterances and anaphora. NLSML
can easily be used in sophisticated systems to convey application-
specific information that more basic systems would not make use of,
for example defining speech acts.
15. ABNF Normative Definition
The following productions make use of the core rules defined in
Section 6.1 of RFC 2234 [RFC2234].
LWS = [*WSP CRLF] 1*WSP ; linear whitespace
SWS = [LWS] ; sep whitespace
UTF8-NONASCII = %xC0-DF 1UTF8-CONT
/ %xE0-EF 2UTF8-CONT
/ %xF0-F7 3UTF8-CONT
/ %xF8-FB 4UTF8-CONT
/ %xFC-FD 5UTF8-CONT
UTF8-CONT = %x80-BF
UTFCHAR = %x21-7E
/ UTF8-NONASCII
param = *pchar
quoted-string = SWS DQUOTE *(qdtext / quoted-pair )
DQUOTE
qdtext = LWS / %x21 / %x23-5B / %x5D-7E
/ UTF8-NONASCII
quoted-pair = "\" (%x00-09 / %x0B-0C / %x0E-7F)
token = 1*(alphanum / "-" / "." / "!" / "%" / "*"
/ "_" / "+" / "`" / "'" / "~" )
reserved = ";" / "/" / "?" / ":" / "@" / "&" / "="
/ "+" / "$" / ","
mark = "-" / "_" / "." / "!" / "~" / "*" / "'"
/ "(" / ")"
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unreserved = alphanum / mark
pchar = unreserved / escaped
/ ":" / "@" / "&" / "=" / "+" / "$" / ","
alphanum = ALPHA / DIGIT
BOOLEAN = "true" / "false"
FLOAT = *DIGIT ["." *DIGIT]
escaped = "%" HEXDIG HEXDIG
fragment = *uric
uri = [ absoluteURI / relativeURI ]
[ "#" fragment ]
absoluteURI = scheme ":" ( hier-part / opaque-part )
relativeURI = ( net-path / abs-path / rel-path )
[ "?" query ]
hier-part = ( net-path / abs-path ) [ "?" query ]
net-path = "//" authority [ abs-path ]
abs-path = "/" path-segments
rel-path = rel-segment [ abs-path ]
rel-segment = 1*( unreserved / escaped / ";" / "@"
/ "&" / "=" / "+" / "$" / "," )
opaque-part = uric-no-slash *uric
uric = reserved / unreserved / escaped
uric-no-slash = unreserved / escaped / ";" / "?" / ":"
/ "@" / "&" / "=" / "+" / "$" / ","
path-segments = segment *( "/" segment )
segment = *pchar *( ";" param )
scheme = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
authority = srvr / reg-name
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srvr = [ [ userinfo "@" ] hostport ]
reg-name = 1*( unreserved / escaped / "$" / ","
/ ";" / ":" / "@" / "&" / "=" / "+" )
query = *uric
userinfo = ( user ) [ ":" password ] "@"
user = 1*( unreserved / escaped
/ user-unreserved )
user-unreserved = "&" / "=" / "+" / "$" / "," / ";"
/ "?" / "/"
password = *( unreserved / escaped
/ "&" / "=" / "+" / "$" / "," )
hostport = host [ ":" port ]
host = hostname / IPv4address / IPv6reference
hostname = *( domainlabel "." ) toplabel [ "." ]
domainlabel = alphanum / alphanum *( alphanum / "-" )
alphanum
toplabel = ALPHA / ALPHA *( alphanum / "-" )
alphanum
IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "."
1*3DIGIT
IPv6reference = "[" IPv6address "]"
IPv6address = hexpart [ ":" IPv4address ]
hexpart = hexseq / hexseq "::" [ hexseq ] / "::"
[ hexseq ]
hexseq = hex4 *( ":" hex4)
hex4 = 1*4HEXDIG
port = 1*19DIGIT
; generic-message is the top-level rule
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generic-message = start-line message-header CRLF
[ message-body ]
message-body = *OCTET
start-line = request-line / response-line / event-line
request-line = mrcp-version SP message-length SP method-name
SP request-id CRLF
response-line = mrcp-version SP message-length SP request-id
SP status-code SP request-state CRLF
event-line = mrcp-version SP message-length SP event-name
SP request-id SP request-state CRLF
method-name = generic-method
/ synthesizer-method
/ recognizer-method
/ recorder-method
/ verifier-method
generic-method = "SET-PARAMS"
/ "GET-PARAMS"
request-state = "COMPLETE"
/ "IN-PROGRESS"
/ "PENDING"
event-name = synthesizer-event
/ recognizer-event
/ recorder-event
/ verifier-event
message-header = 1*(generic-header / resource-header / generic-field)
generic-field = field-name ":" [ field-value ]
field-name = token
field-value = *LWS field-content *( CRLF 1*LWS field-content)
field-content = <the OCTETs making up the field-value
and consisting of either *TEXT or combinations
of token, separators, and quoted-string>
resource-header = synthesizer-header
/ recognizer-header
/ recorder-header
/ verifier-header
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generic-header = channel-identifier
/ accept
/ active-request-id-list
/ proxy-sync-id
/ accept-charset
/ content-type
/ content-id
/ content-base
/ content-encoding
/ content-location
/ content-length
/ fetch-timeout
/ cache-control
/ logging-tag
/ set-cookie
/ set-cookie2
/ vendor-specific
; -- content-id is as defined in RFC2392, RFC2046 and RFC5322
; -- accept and accept-charset are as defined in RFC2616
mrcp-version = "MRCP" "/" 1*2DIGIT "." 1*2DIGIT
message-length = 1*19DIGIT
request-id = 1*10DIGIT
status-code = 3DIGIT
channel-identifier = "Channel-Identifier" ":"
channel-id CRLF
channel-id = 1*alphanum "@" 1*alphanum
active-request-id-list = "Active-Request-Id-List" ":"
request-id *("," request-id) CRLF
proxy-sync-id = "Proxy-Sync-Id" ":" 1*VCHAR CRLF
content-base = "Content-Base" ":" absoluteURI CRLF
content-length = "Content-Length" ":" 1*19DIGIT CRLF
content-type = "Content-Type" ":" media-type-value CRLF
media-type-value = type "/" subtype *( ";" parameter )
type = token
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subtype = token
parameter = attribute "=" value
attribute = token
value = token / quoted-string
content-encoding = "Content-Encoding" ":"
*WSP content-coding
*(*WSP "," *WSP content-coding *WSP )
CRLF
content-coding = token
content-location = "Content-Location" ":"
( absoluteURI / relativeURI ) CRLF
cache-control = "Cache-Control" ":"
[*WSP cache-directive
*( *WSP "," *WSP cache-directive *WSP )]
CRLF
fetch-timeout = "Fetch-Timeout" ":" 1*19DIGIT CRLF
cache-directive = "max-age" "=" delta-seconds
/ "max-stale" ["=" delta-seconds ]
/ "min-fresh" "=" delta-seconds
delta-seconds = 1*19DIGIT
logging-tag = "Logging-Tag" ":" 1*UTFCHAR CRLF
vendor-specific = "Vendor-Specific-Parameters" ":"
[vendor-specific-av-pair
*(";" vendor-specific-av-pair)] CRLF
vendor-specific-av-pair = vendor-av-pair-name "="
value
vendor-av-pair-name = 1*UTFCHAR
set-cookie = "Set-Cookie:" cookies CRLF
cookies = cookie *("," *LWS cookie)
cookie = attribute "=" value *(";" cookie-av)
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cookie-av = "Comment" "=" value
/ "Domain" "=" value
/ "Max-Age" "=" value
/ "Path" "=" value
/ "Secure"
/ "Version" "=" 1*19DIGIT
/ "Age" "=" delta-seconds
set-cookie2 = "Set-Cookie2:" cookies2 CRLF
cookies2 = cookie2 *("," *LWS cookie2)
cookie2 = attribute "=" value *(";" cookie-av2)
cookie-av2 = "Comment" "=" value
/ "CommentURL" "=" DQUOTE uri DQUOTE
/ "Discard"
/ "Domain" "=" value
/ "Max-Age" "=" value
/ "Path" "=" value
/ "Port" [ "=" DQUOTE portlist DQUOTE ]
/ "Secure"
/ "Version" "=" 1*19DIGIT
/ "Age" "=" delta-seconds
portlist = portnum *("," *LWS portnum)
portnum = 1*19DIGIT
; Synthesizer ABNF
synthesizer-method = "SPEAK"
/ "STOP"
/ "PAUSE"
/ "RESUME"
/ "BARGE-IN-OCCURRED"
/ "CONTROL"
/ "DEFINE-LEXICON"
synthesizer-event = "SPEECH-MARKER"
/ "SPEAK-COMPLETE"
synthesizer-header = jump-size
/ kill-on-barge-in
/ speaker-profile
/ completion-cause
/ completion-reason
/ voice-parameter
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/ prosody-parameter
/ speech-marker
/ speech-language
/ fetch-hint
/ audio-fetch-hint
/ failed-uri
/ failed-uri-cause
/ speak-restart
/ speak-length
/ load-lexicon
/ lexicon-search-order
jump-size = "Jump-Size" ":" speech-length-value CRLF
speech-length-value = numeric-speech-length
/ text-speech-length
text-speech-length = 1*UTFCHAR SP "Tag"
numeric-speech-length = ("+" / "-") positive-speech-length
positive-speech-length = 1*19DIGIT SP numeric-speech-unit
numeric-speech-unit = "Second"
/ "Word"
/ "Sentence"
/ "Paragraph"
kill-on-barge-in = "Kill-On-Barge-In" ":" BOOLEAN
CRLF
speaker-profile = "Speaker-Profile" ":" uri CRLF
completion-cause = "Completion-Cause" ":" 3DIGIT SP
1*VCHAR CRLF
completion-reason = "Completion-Reason" ":"
quoted-string CRLF
voice-parameter = voice-gender
/ voice-age
/ voice-variant
/ voice-name
voice-gender = "Voice-Gender:" voice-gender-value CRLF
voice-gender-value = "male"
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/ "female"
/ "neutral"
voice-age = "Voice-Age:" 1*3DIGIT CRLF
voice-variant = "Voice-Variant:" 1*19DIGIT CRLF
voice-name = "Voice-Name:"
1*UTFCHAR *(1*WSP 1*UTFCHAR) CRLF
prosody-parameter = "Prosody-" prosody-param-name ":"
prosody-param-value CRLF
prosody-param-name = 1*VCHAR
prosody-param-value = 1*VCHAR
timestamp = "timestamp" "=" time-stamp-value
time-stamp-value = 1*20DIGIT
speech-marker = "Speech-Marker" ":"
timestamp
[";" 1*(UTFCHAR / %x20)] CRLF
speech-language = "Speech-Language" ":" 1*VCHAR CRLF
fetch-hint = "Fetch-Hint" ":" ("prefetch" / "safe") CRLF
audio-fetch-hint = "Audio-Fetch-Hint" ":"
("prefetch" / "safe" / "stream") CRLF
failed-uri = "Failed-URI" ":" absoluteURI CRLF
failed-uri-cause = "Failed-URI-Cause" ":" 1*UTFCHAR CRLF
speak-restart = "Speak-Restart" ":" BOOLEAN CRLF
speak-length = "Speak-Length" ":" positive-length-value
CRLF
positive-length-value = positive-speech-length
/ text-speech-length
load-lexicon = "Load-Lexicon" ":" BOOLEAN CRLF
lexicon-search-order = "Lexicon-Search-Order" ":"
"<" absoluteURI ">" *(" " "<" absoluteURI ">") CRLF
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; Recognizer ABNF
recognizer-method = recog-only-method
/ enrollment-method
recog-only-method = "DEFINE-GRAMMAR"
/ "RECOGNIZE"
/ "INTERPRET"
/ "GET-RESULT"
/ "START-INPUT-TIMERS"
/ "STOP"
enrollment-method = "START-PHRASE-ENROLLMENT"
/ "ENROLLMENT-ROLLBACK"
/ "END-PHRASE-ENROLLMENT"
/ "MODIFY-PHRASE"
/ "DELETE-PHRASE"
recognizer-event = "START-OF-INPUT"
/ "RECOGNITION-COMPLETE"
/ "INTERPRETATION-COMPLETE"
recognizer-header = recog-only-header
/ enrollment-header
recog-only-header = confidence-threshold
/ sensitivity-level
/ speed-vs-accuracy
/ n-best-list-length
/ input-type
/ no-input-timeout
/ recognition-timeout
/ waveform-uri
/ input-waveform-uri
/ completion-cause
/ completion-reason
/ recognizer-context-block
/ start-input-timers
/ speech-complete-timeout
/ speech-incomplete-timeout
/ dtmf-interdigit-timeout
/ dtmf-term-timeout
/ dtmf-term-char
/ failed-uri
/ failed-uri-cause
/ save-waveform
/ media-type
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/ new-audio-channel
/ speech-language
/ ver-buffer-utterance
/ recognition-mode
/ cancel-if-queue
/ hotword-max-duration
/ hotword-min-duration
/ interpret-text
/ dtmf-buffer-time
/ clear-dtmf-buffer
/ early-no-match
enrollment-header = num-min-consistent-pronunciations
/ consistency-threshold
/ clash-threshold
/ personal-grammar-uri
/ enroll-utterance
/ phrase-id
/ phrase-nl
/ weight
/ save-best-waveform
/ new-phrase-id
/ confusable-phrases-uri
/ abort-phrase-enrollment
confidence-threshold = "Confidence-Threshold" ":"
FLOAT CRLF
sensitivity-level = "Sensitivity-Level" ":" FLOAT
CRLF
speed-vs-accuracy = "Speed-Vs-Accuracy" ":" FLOAT
CRLF
n-best-list-length = "N-Best-List-Length" ":" 1*19DIGIT
CRLF
input-type = "Input-Type" ":" inputs CRLF
inputs = "speech" / "dtmf"
no-input-timeout = "No-Input-Timeout" ":" 1*19DIGIT
CRLF
recognition-timeout = "Recognition-Timeout" ":" 1*19DIGIT
CRLF
waveform-uri = "Waveform-URI" ":" ["<" uri ">"
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";" "size" "=" 1*19DIGIT
";" "duration" "=" 1*19DIGIT] CRLF
recognizer-context-block = "Recognizer-Context-Block" ":"
[1*VCHAR] CRLF
start-input-timers = "Start-Input-Timers" ":"
BOOLEAN CRLF
speech-complete-timeout = "Speech-Complete-Timeout" ":"
1*19DIGIT CRLF
speech-incomplete-timeout = "Speech-Incomplete-Timeout" ":"
1*19DIGIT CRLF
dtmf-interdigit-timeout = "DTMF-Interdigit-Timeout" ":"
1*19DIGIT CRLF
dtmf-term-timeout = "DTMF-Term-Timeout" ":" 1*19DIGIT
CRLF
dtmf-term-char = "DTMF-Term-Char" ":" VCHAR CRLF
save-waveform = "Save-Waveform" ":" BOOLEAN CRLF
new-audio-channel = "New-Audio-Channel" ":"
BOOLEAN CRLF
recognition-mode = "Recognition-Mode" ":" 1*ALPHA CRLF
cancel-if-queue = "Cancel-If-Queue" ":" BOOLEAN CRLF
hotword-max-duration = "Hotword-Max-Duration" ":"
1*19DIGIT CRLF
hotword-min-duration = "Hotword-Min-Duration" ":"
1*19DIGIT CRLF
interpret-text = "Interpret-Text" ":" 1*VCHAR CRLF
dtmf-buffer-time = "DTMF-Buffer-Time" ":" 1*19DIGIT CRLF
clear-dtmf-buffer = "Clear-DTMF-Buffer" ":" BOOLEAN CRLF
early-no-match = "Early-No-Match" ":" BOOLEAN CRLF
num-min-consistent-pronunciations =
"Num-Min-Consistent-Pronunciations" ":" 1*19DIGIT CRLF
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consistency-threshold = "Consistency-Threshold" ":" FLOAT
CRLF
clash-threshold = "Clash-Threshold" ":" FLOAT CRLF
personal-grammar-uri = "Personal-Grammar-URI" ":" uri CRLF
enroll-utterance = "Enroll-Utterance" ":" BOOLEAN CRLF
phrase-id = "Phrase-ID" ":" 1*VCHAR CRLF
phrase-nl = "Phrase-NL" ":" 1*UTFCHAR CRLF
weight = "Weight" ":" weight-value CRLF
weight-value = FLOAT
save-best-waveform = "Save-Best-Waveform" ":"
BOOLEAN CRLF
new-phrase-id = "New-Phrase-ID" ":" 1*VCHAR CRLF
confusable-phrases-uri = "Confusable-Phrases-URI" ":"
uri CRLF
abort-phrase-enrollment = "Abort-Phrase-Enrollment" ":"
BOOLEAN CRLF
; Recorder ABNF
recorder-method = "RECORD"
/ "STOP"
/ "START-INPUT-TIMERS"
recorder-event = "START-OF-INPUT"
/ "RECORD-COMPLETE"
recorder-header = sensitivity-level
/ no-input-timeout
/ completion-cause
/ completion-reason
/ failed-uri
/ failed-uri-cause
/ record-uri
/ media-type
/ max-time
/ trim-length
/ final-silence
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/ capture-on-speech
/ ver-buffer-utterance
/ start-input-timers
/ new-audio-channel
record-uri = "Record-URI" ":" [ "<" uri ">"
";" "size" "=" 1*19DIGIT
";" "duration" "=" 1*19DIGIT] CRLF
media-type = "Media-Type" ":" media-type-value CRLF
max-time = "Max-Time" ":" 1*19DIGIT CRLF
trim-length = "Trim-Length" ":" 1*19DIGIT CRLF
final-silence = "Final-Silence" ":" 1*19DIGIT CRLF
capture-on-speech = "Capture-On-Speech " ":"
BOOLEAN CRLF
; Verifier ABNF
verifier-method = "START-SESSION"
/ "END-SESSION"
/ "QUERY-VOICEPRINT"
/ "DELETE-VOICEPRINT"
/ "VERIFY"
/ "VERIFY-FROM-BUFFER"
/ "VERIFY-ROLLBACK"
/ "STOP"
/ "CLEAR-BUFFER"
/ "START-INPUT-TIMERS"
/ "GET-INTERMEDIATE-RESULT"
verifier-event = "VERIFICATION-COMPLETE"
/ "START-OF-INPUT"
verifier-header = repository-uri
/ voiceprint-identifier
/ verification-mode
/ adapt-model
/ abort-model
/ min-verification-score
/ num-min-verification-phrases
/ num-max-verification-phrases
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/ no-input-timeout
/ save-waveform
/ media-type
/ waveform-uri
/ voiceprint-exists
/ ver-buffer-utterance
/ input-waveform-uri
/ completion-cause
/ completion-reason
/ speech-complete-timeout
/ new-audio-channel
/ abort-verification
/ start-input-timers
/ input-type
repository-uri = "Repository-URI" ":" uri CRLF
voiceprint-identifier = "Voiceprint-Identifier" ":"
vid *[";" vid] CRLF
vid = 1*VCHAR ["." 1*VCHAR]
verification-mode = "Verification-Mode" ":"
verification-mode-string
verification-mode-string = "train" / "verify"
adapt-model = "Adapt-Model" ":" BOOLEAN CRLF
abort-model = "Abort-Model" ":" BOOLEAN CRLF
min-verification-score = "Min-Verification-Score" ":"
[ %x2D ] FLOAT CRLF
num-min-verification-phrases = "Num-Min-Verification-Phrases"
":" 1*19DIGIT CRLF
num-max-verification-phrases = "Num-Max-Verification-Phrases"
":" 1*19DIGIT CRLF
voiceprint-exists = "Voiceprint-Exists" ":"
BOOLEAN CRLF
ver-buffer-utterance = "Ver-Buffer-Utterance" ":"
BOOLEAN CRLF
input-waveform-uri = "Input-Waveform-URI" ":" uri CRLF
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abort-verification = "Abort-Verification " ":"
BOOLEAN CRLF
The following productions add a new SDP session-level attribute. See
Section 13.7.3.
cmid-attribute = "a=cmid:" identification-tag
identification-tag = token
16. XML Schemas
16.1. NLSML Schema Definition
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.ietf.org/xml/ns/mrcpv2"
xmlns="http://www.ietf.org/xml/ns/mrcpv2"
elementFormDefault="qualified"
attributeFormDefault="unqualified" >
<xs:annotation>
<xs:documentation> Natural Language Semantic Markup Schema
</xs:documentation>
</xs:annotation>
<xs:include schemaLocation="enrollment-schema.rng"/>
<xs:include schemaLocation="verification-schema.rng"/>
<xs:element name="result">
<xs:complexType>
<xs:sequence>
<xs:element name="interpretation" maxOccurs="unbounded">
<xs:complexType>
<xs:sequence>
<xs:element name="instance" minOccurs="0">
<xs:complexType mixed="true">
<xs:sequence minOccurs="0">
<xs:any namespace="##other" processContents="lax"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="input">
<xs:complexType mixed="true">
<xs:choice>
<xs:element name="noinput" minOccurs="0"/>
<xs:element name="nomatch" minOccurs="0"/>
<xs:element name="input" minOccurs="0"/>
</xs:choice>
<xs:attribute name="mode"
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type="xs:string"
default="speech"/>
<xs:attribute name="confidence"
type="confidenceinfo"
default="1.0"/>
<xs:attribute name="timestamp-start"
type="xs:string"/>
<xs:attribute name="timestamp-end"
type="xs:string"/>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="confidence" type="confidenceinfo"
default="1.0"/>
<xs:attribute name="grammar" type="xs:anyURI"
use="optional"/>
</xs:complexType>
</xs:element>
<xs:element name="enrollment-result"
type="enrollment-contents"/>
<xs:element name="verification-result"
type="verification-contents"/>
</xs:sequence>
<xs:attribute name="grammar" type="xs:anyURI"
use="optional"/>
</xs:complexType>
</xs:element>
<xs:simpleType name="confidenceinfo">
<xs:restriction base="xs:float">
<xs:minInclusive value="0.0"/>
<xs:maxInclusive value="1.0"/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
16.2. Enrollment Results Schema Definition
<!-- MRCP Enrollment Schema
(See http://www.oasis-open.org/committees/relax-ng/spec.html)
-->
<grammar datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes"
ns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns="http://relaxng.org/ns/structure/1.0">
<start>
<element name="enrollment-result">
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<ref name="enrollment-content"/>
</element>
</start>
<define name="enrollment-content">
<interleave>
<element name="num-clashes">
<data type="nonNegativeInteger"/>
</element>
<element name="num-good-repetitions">
<data type="nonNegativeInteger"/>
</element>
<element name="num-repetitions-still-needed">
<data type="nonNegativeInteger"/>
</element>
<element name="consistency-status">
<choice>
<value>consistent</value>
<value>inconsistent</value>
<value>undecided</value>
</choice>
</element>
<optional>
<element name="clash-phrase-ids">
<oneOrMore>
<element name="item">
<data type="token"/>
</element>
</oneOrMore>
</element>
</optional>
<optional>
<element name="transcriptions">
<oneOrMore>
<element name="item">
<text/>
</element>
</oneOrMore>
</element>
</optional>
<optional>
<element name="confusable-phrases">
<oneOrMore>
<element name="item">
<text/>
</element>
</oneOrMore>
</element>
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</optional>
</interleave>
</define>
</grammar>
16.3. Verification Results Schema Definition
<!-- MRCP Verification Results Schema
(See http://www.oasis-open.org/committees/relax-ng/spec.html)
-->
<grammar datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes"
ns="http://www.ietf.org/xml/ns/mrcpv2"
xmlns="http://relaxng.org/ns/structure/1.0">
<start>
<element name="verification-result">
<ref name="verification-contents"/>
</element>
</start>
<define name="verification-contents">
<element name="voiceprint">
<ref name="firstVoiceprintContent"/>
</element>
<zeroOrMore>
<element name="voiceprint">
<ref name="restVoiceprintContent"/>
</element>
</zeroOrMore>
</define>
<define name="firstVoiceprintContent">
<attribute name="id">
<data type="string"/>
</attribute>
<interleave>
<optional>
<element name="adapted">
<data type="boolean"/>
</element>
</optional>
<optional>
<element name="needmoredata">
<ref name="needmoredataContent"/>
</element>
</optional>
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<optional>
<element name="incremental">
<ref name="firstCommonContent"/>
</element>
</optional>
<element name="cumulative">
<ref name="firstCommonContent"/>
</element>
</interleave>
</define>
<define name="restVoiceprintContent">
<attribute name="id">
<data type="string"/>
</attribute>
<element name="cumulative">
<ref name="restCommonContent"/>
</element>
</define>
<define name="firstCommonContent">
<interleave>
<element name="decision">
<ref name="decisionContent"/>
</element>
<optional>
<element name="utterance-length">
<ref name="utterance-lengthContent"/>
</element>
</optional>
<optional>
<element name="device">
<ref name="deviceContent"/>
</element>
</optional>
<optional>
<element name="gender">
<ref name="genderContent"/>
</element>
</optional>
<zeroOrMore>
<element name="verification-score">
<ref name="verification-scoreContent"/>
</element>
</zeroOrMore>
</interleave>
</define>
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<define name="restCommonContent">
<interleave>
<optional>
<element name="decision">
<ref name="decisionContent"/>
</element>
</optional>
<optional>
<element name="device">
<ref name="deviceContent"/>
</element>
</optional>
<optional>
<element name="gender">
<ref name="genderContent"/>
</element>
</optional>
<zeroOrMore>
<element name="verification-score">
<ref name="verification-scoreContent"/>
</element>
</zeroOrMore>
</interleave>
</define>
<define name="decisionContent">
<choice>
<value>accepted</value>
<value>rejected</value>
<value>undecided</value>
</choice>
</define>
<define name="needmoredataContent">
<data type="boolean"/>
</define>
<define name="utterance-lengthContent">
<data type="nonNegativeInteger"/>
</define>
<define name="deviceContent">
<choice>
<value>cellular-phone</value>
<value>electret-phone</value>
<value>carbon-button-phone</value>
<value>unknown</value>
</choice>
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</define>
<define name="genderContent">
<choice>
<value>male</value>
<value>female</value>
<value>unknown</value>
</choice>
</define>
<define name="verification-scoreContent">
<data type="float">
<param name="minInclusive">-1</param>
<param name="maxInclusive">1</param>
</data>
</define>
</grammar>
17. References
17.1. Normative References
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time
Streaming Protocol (RTSP)", RFC 2326, April 1998.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
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June 2002.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
the Session Description Protocol (SDP)", RFC 4145,
September 2005.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572, July 2006.
[RFC3388] Camarillo, G., Eriksson, G., Holler, J., and H.
Schulzrinne, "Grouping of Media Lines in the Session
Description Protocol (SDP)", RFC 3388, December 2002.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
October 2008.
[RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource
Locators", RFC 2392, August 1998.
[RFC2109] Kristol, D. and L. Montulli, "HTTP State Management
Mechanism", RFC 2109, February 1997.
[RFC2965] Kristol, D. and L. Montulli, "HTTP State Management
Mechanism", RFC 2965, October 2000.
[RFC4646] Phillips, A. and M. Davis, "Tags for Identifying
Languages", RFC 4646, September 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
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[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 35,
RFC 4395, February 2006.
[RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session
Description Protocol (SDP) Security Descriptions for Media
Streams", RFC 4568, July 2006.
[W3C.REC-speech-synthesis-20040907]
Walker, M., Hunt, A., and D. Burnett, "Speech Synthesis
Markup Language (SSML) Version 1.0", World Wide Web
Consortium Recommendation REC-speech-synthesis-20040907,
September 2004,
<http://www.w3.org/TR/2004/REC-speech-synthesis-20040907>.
[RFC2483] Mealling, M. and R. Daniel, "URI Resolution Services
Necessary for URN Resolution", RFC 2483, January 1999.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004.
[RFC5922] Gurbani, V., Lawrence, S., and A. Jeffrey, "Domain
Certificates in the Session Initiation Protocol (SIP)",
RFC 5922, June 2010.
[W3C.REC-speech-grammar-20040316]
McGlashan, S. and A. Hunt, "Speech Recognition Grammar
Specification Version 1.0", World Wide Web Consortium
Recommendation REC-speech-grammar-20040316, March 2004,
<http://www.w3.org/TR/2004/REC-speech-grammar-20040316>.
[W3C.REC-semantic-interpretation-20070405]
Tichelen, L. and D. Burke, "Semantic Interpretation for
Speech Recognition (SISR) Version 1.0", World Wide Web
Consortium REC REC-semantic-interpretation-20070405,
April 2007, <http://www.w3.org/TR/2007/
REC-semantic-interpretation-20070405>.
[W3C.REC-xml-names11-20040204]
Layman, A., Hollander, D., Tobin, R., and T. Bray,
"Namespaces in XML 1.1", World Wide Web Consortium
FirstEdition REC-xml-names11-20040204, February 2004,
<http://www.w3.org/TR/2004/REC-xml-names11-20040204>.
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17.2. Informative References
[RFC4313] Oran, D., "Requirements for Distributed Control of
Automatic Speech Recognition (ASR), Speaker
Identification/Speaker Verification (SI/SV), and Text-to-
Speech (TTS) Resources", RFC 4313, December 2005.
[Q.23] International Telecommunications Union, "Technical
Features of Push-Button Telephone Sets", ITU-T Q.23, 1993.
[RFC4733] Schulzrinne, H. and T. Taylor, "RTP Payload for DTMF
Digits, Telephony Tones, and Telephony Signals", RFC 4733,
December 2006.
[W3C.REC-voicexml20-20040316]
Carter, J., Tryphonas, S., Rehor, K., Danielsen, P.,
Porter, B., Burnett, D., McGlashan, S., Ferrans, J.,
Lucas, B., and A. Hunt, "Voice Extensible Markup Language
(VoiceXML) Version 2.0", World Wide Web Consortium
Recommendation REC-voicexml20-20040316, March 2004,
<http://www.w3.org/TR/2004/REC-voicexml20-20040316>.
[RFC4463] Shanmugham, S., Monaco, P., and B. Eberman, "A Media
Resource Control Protocol (MRCP) Developed by Cisco,
Nuance, and Speechworks", RFC 4463, April 2006.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[refs.javaSpeechGrammarFormat]
Sun Microsystems, "Java Speech Grammar Format Version
1.0", October 1998.
[W3C.REC-emma-20090210]
Johnston, M., Baggia, P., Burnett, D., Carter, J., Dahl,
D., McCobb, G., and D. Raggett, "EMMA: Extensible
MultiModal Annotation markup language", World Wide Web
Consortium Recommendation REC-emma-20090210,
February 2009,
<http://www.w3.org/TR/2009/REC-emma-20090210>.
[RFC4467] Crispin, M., "Internet Message Access Protocol (IMAP) -
URLAUTH Extension", RFC 4467, May 2006.
[W3C.REC-pronunciation-lexicon-20081014]
Baggia, P., Bagshaw, P., Burnett, D., Carter, J., and F.
Scahill, "Pronunciation Lexicon Specification (PLS)",
World Wide Web Consortium Recommendation REC-
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pronunciation-lexicon-20081014, October 2008, <http://
www.w3.org/TR/2008/REC-pronunciation-lexicon-20081014>.
Appendix A. Contributors
Pierre Forgues
Nuance Communications Ltd.
1500 University Street
Suite 935
Montreal, Quebec
Canada H3A 3S7
Email: forgues@nuance.com
Charles Galles
Intervoice, Inc.
17811 Waterview Parkway
Dallas, Texas 75252
Email: charles.galles@intervoice.com
Klaus Reifenrath
Scansoft, Inc
Guldensporenpark 32
Building D
9820 Merelbeke
Belgium
Email: klaus.reifenrath@scansoft.com
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Appendix B. Acknowledgements
Andre Gillet (Nuance Communications)
Andrew Hunt (ScanSoft)
Andrew Wahbe (Genesys)
Aaron Kneiss (ScanSoft)
Brian Eberman (ScanSoft)
Corey Stohs (Cisco Systems Inc)
Dave Burke (VoxPilot)
Jeff Kusnitz (IBM Corp)
Ganesh N Ramaswamy (IBM Corp)
Klaus Reifenrath (ScanSoft)
Kristian Finlator (ScanSoft)
Magnus Westerlund (Ericsson)
Martin Dragomirecky (Cisco Systems Inc)
Paolo Baggia (Loquendo)
Peter Monaco (Nuance Communications)
Pierre Forgues (Nuance Communications)
Ran Zilca (IBM Corp)
Suresh Kaliannan (Cisco Systems Inc.)
Skip Cave (Intervoice Inc)
Thomas Gal (LumenVox)
The chairs of the speechsc work group are Eric Burger (Georgetown
University) and Dave Oran (Cisco Systems, Inc.).
Many thanks go in particular to Robert Sparks, Alex Agranovsky, and
Henry Phan, who were there at the end to dot all the i's and cross
all the t's.
Authors' Addresses
Daniel C. Burnett
Voxeo
189 South Orange Avenue #2050
Orlando, FL 32801
USA
Email: dburnett@voxeo.com
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Saravanan Shanmugham
Cisco Systems, Inc.
170 W. Tasman Dr.
San Jose, CA 95134
USA
Email: sarvi@cisco.com
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