Internet DRAFT - draft-guduru-ietf-rtcweb-codec-preferences
draft-guduru-ietf-rtcweb-codec-preferences
rtcweb K. Guduru
Internet-Draft Samsung Electronics
Intended status: Standards Track May 16, 2014
Expires: November 17, 2014
WebRTC Codec Preferences
draft-guduru-ietf-rtcweb-codec-preferences-00
Abstract
WebRTC working group prefers mandatory to implement codecs inside the
browser to achieve guaranteed interoperability between two WebRTC
peers. WebRTC allows browser implementors to support vendor specific
codecs apart from mandatory codecs. This document explains the way
to give preferences for media codecs in WebRTC context out of the
available codecs in browser for creating the offer / answer.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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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."
This Internet-Draft will expire on November 17, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. getSupportedAudioCodecs . . . . . . . . . . . . . . . . . . . 2
4. getSupportedVideoCodecs . . . . . . . . . . . . . . . . . . . 3
5. RTCOfferAnswerOptions . . . . . . . . . . . . . . . . . . . . 3
5.1. preferedAudioCodecs . . . . . . . . . . . . . . . . . . . . 3
5.2. preferedVideoCodecs . . . . . . . . . . . . . . . . . . . . 3
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
9. Normative References . . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
WebRTC specified mandatory to implement codecs for attaining the
interoperability between browsers and to increase the success rate
[I-D.ietf-rtcweb-audio]. Browser implementors may support other
codecs apart from mandatory to implement codecs. This specification
describes a mechanism for JavaScript application to check the
available codecs, to give preferences among the available codecs and
to remove some codecs if the application don't want to use them.
This specification extends RTCPeerConnection by adding two new
methods, getSupportedAudioCodecs and getSupportedVideoCodecs and the
offer / answer options with sequences of audio and video codec list.
This process will avoid the SDP mangling for removing and re-ordering
of codecs.
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 [RFC2119].
3. getSupportedAudioCodecs
The getSupportedAudioCodes method of RTCPeerConnection returns the
supported audio codecs. This function SHOULD be called before
calling createOffer or createAnswer mehtod.
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4. getSupportedVideoCodecs
The getSupportedVideoCodes method of RTCPeerConnection returns the
supported video codecs. This function SHOULD be called before
calling createOffer or createAnswer mehtod.
5. RTCOfferAnswerOptions
createOffer and createAnswer methods supports optional "options"
attribute. A sequence of audio and video codecs, namely
preferedAudioCodecs and preferedVideoCodecs respectively, in
applications prefered order SHOULD be included as optional
constraints in RTCOfferAnswerOptions. Next sections explain about
preferedAudioCodecs and preferdVideoCodecs.
5.1. preferedAudioCodecs
preferedAudioCodecs optional constraint is a sequence of audio codecs
in the applications prefered order. If the application does not
specify any codec preference, then this attribute MUST not be added
to RTCOfferAnswerOptions. If options attribute is not present in the
createOffer/createAnswer, browser SHOULD arrange the codecs with
previously specified preference, if specified earlier for that
session, otherwise browser MAY arrange the codecs with its own
preferences. The prefered codec sequence MAY contain the same number
of audio codecs returned by getSupportedAudioCodecs. Audio codecs
other than those supported by browser SHOULD be ignored, if present
in preferedAudioCodecs. If the preferedAudioCodecs does not contain
atleast one audio codec returned by getAudioCodecs, browser SHOULD
fire an error event UNSUPPORTED_CODECS. The offer/answer SHOULD_NOT
contain audo codecs other than those specified in preferedAudioCodecs
and the order of preference SHOULD be with high priority for the
codecs first in the preferedAudioCodecs sequence.
5.2. preferedVideoCodecs
preferedVideoCodecs optional constraint is a sequence of video codecs
in the applications prefered order. If the application does not
specify any codec preference, then this attribute MUST not be added
to RTCOfferAnswerOptions. If options attribute is not present in the
createOffer/createAnswer, browser SHOULD arrange the codecs with
previously specified preference, if specified earlier for that
session, otherwise browser MAY arrange the codecs with its own
preferences. The prefered codec sequence MAY contain the same number
of video codecs returned by getSupportedVideoCodecs. Video codecs
other than those supported by browser SHOULD be ignored, if present
in preferedVideoCodecs. If the preferedVideoCodecs does not contain
atleast one video codec returned by getVideoCodecs, browser SHOULD
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fire an error event UNSUPPORTED_CODECS. The offer/answer SHOULD_NOT
contain audo codecs other than those specified by preferedVideoCodecs
and the order of preference SHOULD be with high priority for the
codecs first in the preferedVideoCodecs sequence.
6. Security Considerations
TBD.
7. IANA Considerations
This document requires no actions from IANA.
8. Acknowledgements
TBD.
9. Normative References
[I-D.ietf-rtcweb-audio]
Valin, J. and C. Bran, "WebRTC Audio Codec and Processing
Requirements", draft-ietf-rtcweb-audio-05 (work in
progress), February 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Author's Address
Kiran Kumar Guduru
Samsung Electronics
Samsung RnD Institute India - Bangalore
Bangalore, Doddanakundi 560037
India
Phone: +91-888-4995166
Email: kiran.guduru@samsung.com
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