Network Working Group C. Bran
Internet-Draft C. Jennings
Intended status: Standards Track Cisco
Expires: December 30, 2011 June 28, 2011
RTC-Web Codec and Media Processing Requirements
draft-cbran-rtcweb-codec-00
Abstract
This document outlines the codec and media processing requirements
for RTC-Web client application and endpoint devices.
Status of this Memo
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This Internet-Draft will expire on December 30, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Codec Requirements . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Audio Codec Requirements . . . . . . . . . . . . . . . . . 3
3.2. Video Codec Requirements . . . . . . . . . . . . . . . . . 4
4. RTC-Web Endpoint Device Requirements . . . . . . . . . . . . . 5
5. Legacy VoIP Interoperability . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
9. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
An integral part of the success and adoption of the Real-Time
Communications Web (RTC-WEB) will be the interoperability between
RTC-Web applications. This specification will focus on the media
processing and codec requirements for RTC-Web client applications.
Media processing and codec requirements fit into a series of
specifications have been created to address RTC-Web communications
protocols, security requirements, data transmission and use cases.
More information on the RTC-Web can be found here:
[TODO put links to supporting drafts here]
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 [RFC2119].
3. Codec Requirements
This section covers the audio and video codec requirements for RTC-
WEB client applications. To ensure a baseline level of
interoperability between RTC-Web applications, a minimum set of
required codes is specified below. While this section specifies the
codecs that will be supported by all RTC-Web application
implementations, it leaves the question of supporting additional
codecs to the will of the implementer.
3.1. Audio Codec Requirements
RTC-WEB applications are REQUIRED to implement the following audio
codecs.
o PCMA/PCMU - see section 4.5.14 of [RFC3551]
o Telephone-event - [RFC4734]
o Opus [draft-ietf-codec-opus]
Implementations of the PCMU and PMCA codecs are REQUIRED to support 1
channel with a rate of 8000 and a ptime of 20.
The following codecs are OPTIONAL for RTC-WEB application
implementations.
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o G729
o G722
o G722.1
o G723
o AMR
o AMR-WB
o iLBC
o L16
[Open Issue: minimum profile and identifying any additional mandatory
to implement audio codecs.]
3.2. Video Codec Requirements
RTC-WEB applications are REQUIRED to implement the following video
codecs.
o VP8 [I-D.webm]
The following feature list applies to all required video codecs.
Required video codecs:
o MUST support at least 10 frames per second (fps) and SHOULD
support 30 fps
o MUST support a the bilinear and none reconstruction filters
o OPTIONALLY offer support for additional color spaces
o MUST support a minimum resolution of 320X240
o SHOULD support resolutions of 1280x720, 720x480, 1024x768,
800x600, 640x480, 640 x 360 , 320x240
The following video codecs are OPTIONAL for RTC-WEB application
implementations.
o H.263
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o H.264-AVC
o H.264-SVC
4. RTC-Web Endpoint Device Requirements
It is plausible that the dominant near-to-mid term RTC-Web usage
model will be people using the RTC-Web functionality to communicate
with each other via web browsers typically running within a notebook
computer that has built-in microphone and speakers. The notebook-as-
communication-device paradigm presents challenging echo cancellation
and audio gain problems, the specific remedy of which will not be
mandated here. However, while no specific algorithm or standard will
be required by RTC-Web compatible endpoints, it has been found that
functionality such as automatic gain control, echo cancellation, and
headset detection will improve the user experience and should be
implemented by the endpoint device.
To address the problems outlined above, suitable implementations of
the functionality listed below SHOULD be available within an RTC-Web
endpoint device.
o Automatic gain control
o Echo cancellation, including acoustic echo cancelation
o Headset detection
o Auto-adjustments to gain control and echo cancelation algorithms
based on if headset or internal speakers/microphone is being used
5. Legacy VoIP Interoperability
The codec requirements above will ensure, at a minimum, voice
interoperability capabilities between RTC-Web client applications and
legacy phone systems.
Video interoperability will be dependent upon the support, natively
or through transcoding, of VP8 by the phone system vendors or the
availability of an interoperable codec, such as H.264-AVC, from
within the RTC-Web client application implementation.
6. IANA Considerations
This document makes no request of IANA.
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Note to RFC Editor: this section may be removed on publication as an
RFC.
7. Security Considerations
The codec requirements have no additional security considerations
other than those captured in
[I-D.ekr-security-considerations-for-rtc-web].
8. Acknowledgements
This draft incorporates ideas and text from various other drafts. In
particularly we would like to acknowledge, and say thanks for, work
we incorporated from Harald Alvestrand.
9. Normative References
[I-D.ekr-security-considerations-for-rtc-web]
Rescorla, E., "Security Considerations for RTC-Web",
May 2011.
[I-D.webm]
Google, Inc., "VP8 Data Format and Decoding Guide",
July 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
Video Conferences with Minimal Control", STD 65, RFC 3551,
July 2003.
[RFC4734] Schulzrinne, H. and T. Taylor, "Definition of Events for
Modem, Fax, and Text Telephony Signals", RFC 4734,
December 2006.
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Authors' Addresses
Cary Bran
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Phone: +1 206 256-3502
Email: cbran@cisco.com
Cullen Jennings
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Phone: +1 408 421-9990
Email: fluffy@cisco.com
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