Internet Engineering Task Force Audio/Video Transport Working Group INTERNET-DRAFT S. Casner draft-ietf-avt-rfc3555bis-01.txt Packet Design October 19, 2005 Expires: April 19, 2006 MIME Type Registration of RTP Payload Formats Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 10, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document defines the procedure to register RTP Payload Formats as audio, video or other MIME subtype names. This is useful in a text-based format or control protocol to identify the type of an RTP transmission. This document also registers all the RTP payload formats defined in the RTP Profile for Audio and Video Conferences as MIME subtypes. Some of these may also be used for transfer modes other than RTP. Expires April 2006 [Page 1]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Table of Contents 1. Introduction .................................................. 3 1.1. IANA Considerations ...................................... 3 1.2. Terminology .............................................. 4 2. Procedure For Registering MIME Types for RTP Payload Types .... 4 2.1. Restrictions on Sharing a Type ........................... 6 3. Mapping to SDP Parameters ..................................... 6 4. Registrations for "Audio/Video Profile" ....................... 8 4.1. Audio Type Registrations ................................. 8 4.2. Video Type Registrations ................................. 28 5. Changes from RFC 3555 ......................................... 38 6. Security Considerations ....................................... 38 7. Normative References .......................................... 39 8. Author's Address .............................................. 39 9. Intellectual Property Statement ............................... 40 10. Disclaimer of Validity ........................................ 40 11. Copyright Statement ........................................... 41 Expires April 2006 [Page 2]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 1. Introduction The MIME registration procedure described in RFC 2048 [1] was originally designed for transport of multimedia information via asynchronous Internet mail, but the MIME namespace now provides identification for other transport modes as well. Updated registration procedures are specified in [2]. This document defines the procedure to register MIME subtype names for use with the Real-time Transport Protocol (RTP), RFC 3550 [3], to identify RTP payload formats. This document also registers all the RTP payload formats defined in the RTP Profile for Audio and Video Conferences, RFC 3551 [4], as MIME subtypes under the "audio" and "video" MIME types. 1.1. IANA Considerations This document registers the following MIME subtypes: audio/DVI4 audio/G722 audio/G723 audio/G726-16 audio/G726-24 audio/G726-32 audio/G726-40 audio/G728 audio/G729 audio/G729D audio/G729E audio/GSM audio/GSM-EFR audio/L8 audio/L16 audio/LPC audio/MPA audio/PCMA audio/PCMU audio/QCELP audio/RED audio/VDVI Expires April 2006 [Page 3]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 video/BT656 video/CelB video/JPEG video/H261 video/H263 video/H263-1998 video/H263-2000 video/MPV video/MP2T video/MP1S video/MP2P video/BMPEG video/nv MIME subtype audio/L16 has already been registered via RFC 2586 for transports other than RTP. That registration is incorporated here and augmented with additional information for RTP transport. 1.2. Terminology 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 RFC 2119 [5] and indicate requirement levels for implementations compliant with this specification. 2. Procedure For Registering MIME Types for RTP Payload Types Registering an RTP payload type as a MIME type follows the same procedures as described in [2] and uses the registration template shown in Section 10 of [2]. Some additional parameters are required to specify how a particular payload format is transported over RTP: Published specification A description of the media encoding and a specification of the payload format must be provided, usually by reference to an RTP payload format specification RFC. That RFC may be separate, or the MIME subtype registration may be incorporated into the payload format specification RFC. The payload format specification MUST include the RTP timestamp clock rate (or multiple rates for audio encodings with multiple sampling rates). A reference to a further description of the data compression format itself should be provided, if available. Expires April 2006 [Page 4]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Required parameters If the payload format does not have a fixed RTP timestamp clock rate, then a "rate" parameter is required to specify the RTP timestamp clock rate. A particular payload format may have additional required parameters. Optional parameters Most audio payload formats can have an optional "channels" parameter to specify the number of audio channels included in the transmission. Any payload format, but most likely audio formats, may also include the optional parameters "ptime", to specify the recommended length of time in milliseconds represented by the media in a packet, and/or "maxptime" to specify the maximum amount of media which can be encapsulated in each packet, expressed as time in milliseconds. The "ptime" and "maxptime" parameters are defined in the Session Description Protocol (SDP) [6]. A particular payload format may have additional optional parameters. Encoding considerations Most RTP payload formats include binary or framed data as described in Section 4.8 of [2]. The appropriate encoding considerations MUST be noted. Restrictions on usage: The fact that the type is defined for transfer via RTP MUST be noted, in particular if the transfer depends on RTP framing and hence the type is only defined for transfer via RTP. Depending on whether the type has already been registered for transfer with a non-RTP protocol (e.g. MIME mail or http) or not, several different cases can occur: a) Not yet registered as a MIME type A new registration should be constructed using the MIME registration template. The registration may specify transfer via other means in addition to RTP if that is feasible and desired. The appropriate encoding considerations must be specified, and the restrictions on usage must specify whether the type is only defined for transfer via RTP or via other modes as well. Optional parameters may be defined as needed, and it must be clearly stated to which mode(s) of transfer the parameters apply. Expires April 2006 [Page 5]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 b) MIME type exists for a non-RTP protocol The restrictions on usage of the existing type should be changed, if present, or added, if not, to indicate that the type can also be transferred via RTP. RTP-specific parameters may be added, and it must be clearly stated that these are only to be used when the media type is transmitted via RTP transport. c) Update an existing MIME type for RTP to be used for a non-RTP protocol The restrictions on usage of the existing type should be changed to indicate that the type can also be transferred via a non-RTP protocol (e.g. SMTP, HTTP). Non-RTP-specific parameters can be added, and it must be clearly stated that these are only to be used when the media type is transmitted via a non-RTP transport. 2.1. Restrictions on Sharing a Type The same MIME type MUST NOT be shared for RTP and non-RTP (file-based) transfer methods unless the data format is the same for both methods. The data format is considered to be same if the file format is equivalent to a concatenated sequence of payloads from RTP packets not including the RTP header or any RTP payload-format header. The file format MAY include a magic number or other header at the start of the file that is not included when the data is transferred via RTP. A second requirement for sharing a MIME type is that the sets of required parameters must be the same for both methods. For cases where the data format or required parameters cannot be the same for RTP and non-RTP transfer methods, then the data formats MUST be registered as separate types. It is RECOMMENDED that the type names be related, such as by using a common root plus a suffix. 3. Mapping to SDP Parameters The representation of a MIME media type is specified in the syntax of the Content-Type header field in RFC 2045 [7] as follows: type "/" subtype *(";" parameter) Expires April 2006 [Page 6]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Parameters may be required for a particular type or subtype or they may be optional. For media types which represent RTP payload formats, the parameters "rate", "channels", "ptime", and "maxptime" have general definitions (given above) that may apply across types and subtypes. The format for a parameter is specified in RFC 2045 as attribute "=" value where attribute is the parameter name and the permissible values are specified for each parameter. The value may need to be a quoted string if it contains any of the special characters listed in RFC 2045. The information carried in the media type string has a specific mapping to fields in the Session Description Protocol (SDP) [6], which is commonly used to describe RTP sessions. The mapping is as follows: o The MIME type (e.g., audio) goes in SDP "m=" as the media name. o The MIME subtype (payload format) goes in SDP "a=rtpmap" as the encoding name. o The general (possibly optional) parameters "rate" and "channels" also go in "a=rtpmap" as clock rate and encoding parameters, respectively. o The general (and optional) parameters "ptime" and "maxptime" go in the SDP "a=ptime" and "a=maxptime" attributes, respectively. o Any payload-format-specific parameters go in the SDP "a=fmtp" attribute. The set of allowed parameters is defined by the RFC that specifies the payload format and MUST NOT be extended by the MIME subtype registration without a corresponding revision of the payload format specification. The format and syntax of these parameters may also be defined by the payload format specification, but it is suggested that the parameters be copied directly from the MIME media type string as a semicolon separated list of parameter=value pairs. For payload formats that specify some other syntax for the fmtp parameters, the registration of that payload format as a MIME subtype must specify what the parameters are in MIME format and how to map them to the SDP "a=fmtp" attribute. See Section 4.1.21 for an example. An example mapping is as follows: Expires April 2006 [Page 7]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 audio/L16; rate=48000; channels=2; ptime=5; emphasis=50-15 m=audio 49170 RTP/AVP 97 a=rtpmap:97 L16/48000/2 a=fmtp:97 emphasis=50-15 a=ptime:5 Note that the payload format (encoding) names defined in the RTP Profile are commonly shown in upper case. MIME subtypes are commonly shown in lower case. These names are case-insensitive in both places. Similarly, parameter names are case-insensitive both in MIME types and in the default mapping to the SDP a=fmtp attribute. 4. Registrations for "Audio/Video Profile" In the following sections, all RTP payload formats described in the RTP Profile for Audio and Video Conferences, RFC 3551 [4], are registered as MIME subtypes. 4.1. Audio Type Registrations The following sections register all of the RTP audio payload types defined in RFC 3551 as MIME types. For most audio payload formats, the RTP timestamp clock rate is equal to the sampling rate. Some payload formats operate only at one fixed sampling rate, while others are adjustable. 4.1.1. Registration of MIME media type audio/DVI4 MIME media type name: audio MIME subtype name: DVI4 Required parameters: rate The RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000, but other rates may be specified. Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Expires April 2006 [Page 8]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.2. Registration of MIME media type audio/G722 MIME media type name: audio MIME subtype name: G722 Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Expires April 2006 [Page 9]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.3. Registration of MIME media type audio/G723 MIME media type name: audio MIME subtype name: G723 Required parameters: None Optional parameters: ptime, maxptime bitrate: the data rate in kb/s used or preferred for the audio bit stream, with permissible values 5.3 or 6.3. If unspecified, the bitrate may change from frame to frame as indicated inband. annexa: indicates that Annex A, voice activity detection, is used or preferred. Permissible values are "yes" and "no" (without the quotes); "yes" is implied if this parameter is omitted. Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Expires April 2006 [Page 10]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.4. Registration of MIME media type audio/G726-16 MIME media type name: audio MIME subtype name: G726-16 Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.5. Registration of MIME media type audio/G726-24 MIME media type name: audio Expires April 2006 [Page 11]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 MIME subtype name: G726-24 Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.6. Registration of MIME media type audio/G726-32 MIME media type name: audio MIME subtype name: G726-32 Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Expires April 2006 [Page 12]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.7. Registration of MIME media type audio/G726-40 MIME media type name: audio MIME subtype name: G726-40 Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Expires April 2006 [Page 13]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.8. Registration of MIME media type audio/G728 MIME media type name: audio MIME subtype name: G728 Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.9. Registration of MIME media type audio/G729 MIME media type name: audio Expires April 2006 [Page 14]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 MIME subtype name: G729 Required parameters: None Optional parameters: ptime, maxptime annexb: indicates that Annex B, voice activity detection, is used or preferred. Permissible values are "yes" and "no" (without the quotes); "yes" is implied if this parameter is omitted. Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.10. Registration of MIME media type audio/G729D MIME media type name: audio MIME subtype name: G729D Required parameters: None Optional parameters: ptime, maxptime Expires April 2006 [Page 15]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 annexb: indicates that Annex B, voice activity detection, is used or preferred. Permissible values are "yes" and "no" (without the quotes); "yes" is implied if this parameter is omitted. Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.11. Registration of MIME media type audio/G729E MIME media type name: audio MIME subtype name: G729E Required parameters: None Optional parameters: ptime, maxptime annexb: indicates that Annex B, voice activity detection, is used or preferred. Permissible values are "yes" and "no" (without the quotes); "yes" is implied if this parameter is omitted. Expires April 2006 [Page 16]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.12. Registration of MIME media type audio/GSM MIME media type name: audio MIME subtype name: GSM Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Expires April 2006 [Page 17]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.13. Registration of MIME media type audio/GSM-EFR MIME media type name: audio MIME subtype name: GSM-EFR Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner Expires April 2006 [Page 18]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 4.1.14. Registration of MIME media type audio/L8 MIME media type name: audio MIME subtype name: L8 Required parameters: rate, the RTP timestamp clock rate Optional parameters: channels, ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.15. Registration of MIME media type audio/L16 MIME subtype audio/L16 has already been registered via RFC 2586 for transports other than RTP. That registration is incorporated here and augmented with additional information for RTP transport. MIME media type name: audio MIME subtype name: L16 Required parameters rate: number of samples per second -- For non-RTP transport, Expires April 2006 [Page 19]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 the permissible values for rate are 8000, 11025, 16000, 22050, 24000, 32000, 44100, and 48000 samples per second. For RTP transport, other values are permissible but the aforementioned values are RECOMMENDED. For RTP, the rate parameter indicates the RTP timestamp clock rate, which is equal to the sample rate. Optional parameters channels: how many audio streams are interleaved -- defaults to 1; stereo would be 2, etc. Interleaving takes place between individual two-byte samples. emphasis: analog preemphasis applied to the signal before quantization. The only emphasis value defined here is emphasis=50-15 to indicate the 50/15 microsecond preemphasis used with Compact Disks. This parameter MUST be omitted if no analog preemphasis was applied. channel-order: specifies the sample interleaving order for multiple-channel audio streams (see [8] Section 7). Permissible values are DV.LRLsRs, DV.LRCS, DV.LRCWo, DV.LRLsRsC, DV.LRLsRsCS, DV.LmixRmixTWoQ1Q2, DV.LRCWoLsRsLmixRmix, DV.LRCWoLs1Rs1Ls2Rs2, DV.LRCWoLsRsLcRc. For interoperation with DV video systems, only a subset of these channel combinations is specified for use with 20-bit linear encoding in the DV video specification [5]; those are DV.LRLsRs, DV.LRCS, DV.LmixRmixTWoQ1Q2. This parameter MUST be omitted when the AIFF-C channel order convention (see RFC 3551) is in use. For RTP, ptime: RECOMMENDED duration of each packet in milliseconds. For RTP, maxptime: maximum duration of each packet in milliseconds. Encoding considerations Audio data is binary data, and must be encoded for non-binary transport; the Base64 encoding is suitable for Email. Note that audio data does not compress easily using lossless compression. Security considerations Audio data is believed to offer no security risks. See Section 5 of RFC 3555. Interoperability considerations This type is compatible with the encoding used in the WAV Expires April 2006 [Page 20]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 (Microsoft Windows RIFF) and Apple AIFF union types, and with the public domain "sox" and "rateconv" programs. Published specification RFC 2586 for non-RTP transports, RFC 3551 for RTP Applications which use this media The public domain "sox" and "rateconv" programs accept this type. 1. Magic number(s) : None 2. File extension(s) : WAV L16 3. Macintosh file type code : AIFF Person to contact for further information 1. Name : James Salsman 2. E-mail : jps-L16@bovik.org Intended usage Common It is expected that many audio and speech applications will use this type. Already the most popular platforms provide this type with the rate=11025 parameter referred to as "radio quality speech." Restrictions on usage In addition to file-based transfer methods, this type is also defined for transfer via RTP [RFC 3550]. Author/Change controller James Salsman for non-RTP transports. Stephen Casner for RTP transport. 4.1.16. Registration of MIME media type audio/LPC MIME media type name: audio MIME subtype name: LPC Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Expires April 2006 [Page 21]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.17. Registration of MIME media type audio/MPA MIME media type name: audio MIME subtype name: MPA (MPEG audio) Required parameters: None Optional parameters: layer: which layer of MPEG audio encoding; permissible values are 1, 2, 3. samplerate: the rate at which audio is sampled. MPEG-1 audio supports sampling rates of 32, 44.1, and 48 kHz; MPEG-2 supports sampling rates of 16, 22.05 and 24 kHz. This parameter is separate from the RTP timestamp clock rate which is always 90000 Hz for MPA. mode: permissible values are "stereo", "joint_stereo", "single_channel", "dual_channel". The "channels" parameter does not apply to MPA. It is undefined to put a number of channels in the SDP rtpmap attribute for MPA. bitrate: the data rate for the audio bit stream. Expires April 2006 [Page 22]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 ptime: RECOMMENDED duration of each packet in milliseconds. maxptime: maximum duration of each packet in milliseconds. Parameters which are omitted are left to the encoder to choose based on the session bandwidth, configuration information, or other constraints. The selected layer as well as the sampling rate and mode are indicated in the payload so receivers can process the data without these parameters being specified externally. Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.18. Registration of MIME media type audio/PCMA MIME media type name: audio MIME subtype name: PCMA Required parameters: rate The RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000, but other rates may be specified. Expires April 2006 [Page 23]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Optional parameters: channels, ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.19. Registration of MIME media type audio/PCMU MIME media type name: audio MIME subtype name: PCMU Required parameters: rate The RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000, but other rates may be specified. Optional parameters: channels, ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Expires April 2006 [Page 24]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.20. Registration of MIME media type audio/QCELP MIME media type name: audio MIME subtype name: QCELP Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2658 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Expires April 2006 [Page 25]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.21. Registration of MIME media type audio/RED MIME media type name: audio MIME subtype name: RED Required parameters: pt: a comma-separated list of RTP payload types. Because comma is a special character, the list must be a quoted-string (enclosed in double quotes). For static payload types, each list element is simply the type number. For dynamic payload types, each list element is a mapping of the dynamic payload type number to an embedded MIME content-type specification for the payload format corresponding to the dynamic payload type. The format of the mapping is: dynamic-payload-type "=" content-type If the content-type string includes a comma, then the content- type string MUST be a quoted-string. If the content-type string does not include a comma, it MAY still be quoted. Since it is part of the list which must itself be a quoted- string, that means the quotation marks MUST be quoted with backslash quoting as specified in RFC 2045. If the content- type string itself contains a quoted-string, then the requirement for backslash quoting is recursively applied. To specify the audio/RED payload format in SDP, the pt parameter is mapped to an a=fmtp attribute by eliminating the parameter name (pt) and changing the commas to slashes. For example, 'pt="0,5"' maps to 'a=fmtp:99 0/5'. A more complicated example, with a dynamic payload type, is: pt = "0, 103 = \"audio/G729D;annexb=yes\" " m=audio 49170 RTP/AVP 99 0 103 a=rtpmap:99 RED/8000 a=fmtp:99 0/103 a=rtpmap:103 G729D/8000 a=fmtp:103 annexb=yes Expires April 2006 [Page 26]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2198 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.1.22. Registration of MIME media type audio/VDVI MIME media type name: audio MIME subtype name: VDVI Required parameters: None Optional parameters: ptime, maxptime Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Expires April 2006 [Page 27]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2. Video Type Registrations For all of the video payload formats registered here, the RTP timestamp clock rate is always 90000 Hz, so the "rate" parameter is not applicable. Likewise, the "channel" parameter is not used with video, and while "ptime" and "maxptime" could be used with video, they typically are not. 4.2.1. Registration of MIME media type video/BT656 MIME media type name: video MIME subtype name: BT656 Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2431 Applications which use this media type: Audio and video streaming and conferencing tools. Expires April 2006 [Page 28]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2.2. Registration of MIME media type video/CelB MIME media type name: video MIME subtype name: CelB Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2029 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner Expires April 2006 [Page 29]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 4.2.3. Registration of MIME media type video/JPEG MIME media type name: video MIME subtype name: JPEG Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2435 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2.4. Registration of MIME media type video/H261 MIME media type name: video MIME subtype name: H261 Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in Expires April 2006 [Page 30]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2032 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2.5. Registration of MIME media type video/H263 MIME media type name: video MIME subtype name: H263 Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2190 Applications which use this media type: Audio and video streaming and conferencing tools. Expires April 2006 [Page 31]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2.6. Registration of MIME media type video/H263-1998 MIME media type name: video MIME subtype name: H263-1998 Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2429 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner Expires April 2006 [Page 32]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 4.2.7. Registration of MIME media type video/H263-2000 MIME media type name: video MIME subtype name: H263-2000 Required parameters: None Optional parameters: profile: H.263 profile number, in the range 0 through 10, specifying the supported H.263 annexes/subparts. level: Level of bitstream operation, in the range 0 through 100, specifying the level of computational complexity of the decoding process. Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2429 The specific values for the profile and level parameters and their meaning are defined in Annex X of ITU-T Recommendation H.263, "Video coding for low bit rate communication". Note that the RTP payload format for H263-2000 is the same as for H263-1998, but additional annexes/subparts are specified along with the profiles and levels. Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner Expires April 2006 [Page 33]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 4.2.8. Registration of MIME media type video/MPV MIME media type name: video MIME subtype name: MPV MPEG-1 or -2 Elementary Streams Required parameters: None Optional parameters: type: the type of MPEG video, from the set "mpeg1", "mpeg2-halfd1", or "mpeg2-fulld1". The default is "mpeg1". The mapping to a=fmtp is identity. Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2250 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2.9. Registration of MIME media type video/MP2T MIME media type name: video MIME subtype name: MP2T MPEG-2 Transport Streams Expires April 2006 [Page 34]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2250 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2.10. Registration of MIME media type video/MP1S MIME media type name: video MIME subtype name: MP1S MPEG-1 Systems Streams Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Expires April 2006 [Page 35]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Interoperability considerations: none Published specification: RFC 2250 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2.11. Registration of MIME media type video/MP2P MIME media type name: video MIME subtype name: MP2P MPEG-2 Program Streams Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2250 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Expires April 2006 [Page 36]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2.12. Registration of MIME media type video/BMPEG MIME media type name: video MIME subtype name: BMPEG Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 2343 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 4.2.13. Registration of MIME media type video/nv MIME media type name: video Expires April 2006 [Page 37]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 MIME subtype name: nv Required parameters: None Optional parameters: None Encoding considerations: This media type is framed binary data (see section 4.8 in [2]). Security considerations: See Section 5 of RFC 3555 Interoperability considerations: none Published specification: RFC 3551 Applications which use this media type: Audio and video streaming and conferencing tools. Additional information: none Person & email address to contact for further information: Stephen Casner <casner@acm.org> Intended usage: COMMON Restrictions on usage: This type is only defined for transfer via RTP [RFC 3550]. Author/Change controller: Stephen Casner 5. Changes from RFC 3555 This document updates RFC 3555 to conform to the revised MIME type registration procedures in [2]. Whereas RFC 3555 required the encoding considerations to specify transfer via RTP, that is now specified under restrictions on usage. This document also adds a new Section 2.1 to clarify the requirements for sharing a MIME type among RTP and non-RTP transfer methods. Philipp Hoschka is a co-author of RFC 3555; his contributions to the foundation of this document are appreciated. 6. Security Considerations The MIME subtype registration procedure specified in this memo does not impose any security considerations on its own. This memo also contains Expires April 2006 [Page 38]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 several MIME type registrations. The registrations themselves do not impose security risks, but some may state security considerations specific to the particular registration. Several audio and video encodings are perfect for hiding data using steganography. The RTP specification, RFC 3550, provides security considerations for the transport of audio and video data over RTP, including the use of encryption where confidentiality is required. 7. Normative References [1] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 2048, November 1996. [2] Freed, N. and J. Klensin, "Media Type Specifications and Registration Procedures", draft-freed-media-type-reg-04, April 2005. [3] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", RFC 3550, July 2003. [4] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video Conferences with Minimal Control", RFC 3551, July 2003. [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [6] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998. [7] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. [8] Kobayashi, K., Ogawa, A., Casner, S. and C. Bormann, "RTP Payload Format for 12-bit DAT Audio and 20- and 24-bit Linear Sampled Audio", RFC 3190, January 2002. 8. Author's Address Stephen L. Casner Packet Design 3400 Hillview Avenue, Building 3 Palo Alto, CA 94304 Expires April 2006 [Page 39]
Internet Draft draft-ietf-avt-rfc3555bis-01.txt October 19, 2005 United States Phone: +1 650 739-1843 EMail: casner@acm.org 9. Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. 10. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 11. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Expires April 2006 [Page 40]
