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Code Issues Releases Wiki Activity

1.1rc1

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Peter Saint-Andre 2013-03-01 14:27:24 -07:00
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xep-0266.xml
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@ -11,6 +11,7 @@
&LEGALNOTICE;
<number>0266</number>
<status>Draft</status>
<interim/>
<type>Standards Track</type>
<sig>Standards</sig>
<approver>Council</approver>
@ -23,6 +24,12 @@
<shortname>N/A</shortname>
<discuss>jingle</discuss>
&stpeter;
<revision>
<version>1.1rc1</version>
<date>2013-03-01</date>
<initials>psa</initials>
<remark><p>Updated to reflect standardization of the Opus codec; changed client conformance to also recommend (but not require) support for Opus.</p></remark>
</revision>
<revision>
<version>1.0</version>
<date>2011-10-04</date>
@ -92,7 +99,7 @@
</header>
<section1 topic='Introduction' anchor='intro'>
<p>&xep0167; defines the &xep0166; signalling exchanges needed to establish voice chat and other audio sessions using the Real-time Transport Protocol &rfc3550;; however, it does not say which audio codecs are mandatory-to-implement, since the state of codec technologies is more fluid than the signalling interactions. This document fills that gap by providing guidance to Jingle developers regarding audio codecs.</p>
<p>&xep0167; defines the &xep0166; signalling exchanges needed to establish voice chat and other audio sessions using the Real-time Transport Protocol &rfc3550;; however, it does not specify which audio codecs are mandatory-to-implement, since the state of codec technologies is more fluid than the signalling interactions. This document fills that gap by providing guidance to Jingle developers regarding audio codecs.</p>
<p>Because codec technologies are typically subject to patents, the topics discussed here are controversial. This document attempts to steer a middle path between (1) specifying mandatory-to-implement technologies that realistically will not be implemented and deployed and (2) providing guidelines that, while realistic, do not encourage the implementation and deployment of patent-clear technologies.</p>
</section1>
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</table>
</section2>
<section2 topic='Opus' anchor='codecs-opus'>
<p>The Opus codec is under development within the IETF's <link url='http://tools.ietf.org/wg/codec/'>Codec Working Group</link>. In essence it combines the best features of CELT (developed by Jean-Marc Valin, the creator of Speex) and SILK (created by and widely used in the Skype service). The following table summarizes the available information about Opus.</p>
<p>The Opus codec was developed within the IETF's <link url='http://tools.ietf.org/wg/codec/'>Codec Working Group</link> and has been published as &rfc6716;. In essence it combines the best features of CELT (developed by Jean-Marc Valin, the creator of Speex) and SILK (created by and widely used in the Skype service). The following table summarizes the available information about Opus.</p>
<table caption='Codec Considerations for Opus'>
<tr>
<th>Quality</th>
@ -136,10 +143,10 @@
<th>Patents</th>
</tr>
<tr>
<td>Extremely high quality; can be used for wide-band audio.</td>
<td>Extremely high quality; can be used for wide-band audio; very robust in the face of packet loss.</td>
<td>See &opusrtp;.</td>
<td>Covered under IETF IPR rules, the intent is for the codec to be covered under a simplified BSD license. See <link url='http://tools.ietf.org/html/draft-ietf-codec-opus'>http://tools.ietf.org/html/draft-ietf-codec-opus</link> for details. Not commonly deployed yet, but the SILK codec on which it is partly based is very widely deployed.</td>
<td>Designed to be patent-clear, but IPR claims have been filed.</td>
<td>In accordance with IETF IPR rules, the codec is covered under a simplified BSD license. See RFC 6716 for details. Starting to be more commonly deployed, and the SILK codec on which it is partly based is very widely deployed.</td>
<td>Designed to be patent-clear, although IPR claims have been filed.</td>
</tr>
</table>
</section2>
@ -164,13 +171,13 @@
<section1 topic='Guidance for Implementers' anchor='impl'>
<p>This section is non-normative.</p>
<p>Given that both Speex and G.711 are patent-clear, freely implementable, and commonly deployed, implementers are encouraged to consider including support for both codecs in audio applications of Jingle RTP sessions. Discussion on the jingle@xmpp.org mailing list indicates a slight preference for G.711 because it is easily available and so widely deployed (e.g., in SIP networks and the PSTN). The Opus codec is not yet widely deployed (or even fully developed), but it might become the "codec of the future" for audio applications over the Internet.</p>
<p>Given that Opus and G.711 are patent-clear, freely implementable, and commonly deployed, implementers are encouraged to consider including support for both codecs in audio applications of Jingle RTP sessions. Discussion on the jingle@xmpp.org mailing list indicates a slight preference for G.711 because it is easily available and so widely deployed (e.g., in SIP networks and the PSTN). Opus has effectively superseded Speex, and implementers are strongly encouraged to include support for Opus rather than Speex among the "open" codecs.</p>
</section1>
<section1 topic='Mandatory-to-Implement Codecs' anchor='mti'>
<p>As of June 2011, this document makes the following recommendations:</p>
<p>As of January 2013, this document makes the following recommendations:</p>
<ol>
<li>Jingle clients MUST implement both PCMU and PCMA.</li>
<li>Jingle clients MUST implement G.711 (i.e., both PCMU and PCMA) and SHOULD implement Opus.</li>
<li>Gateways between Jingle networks and other networks (e.g., SIP networks and the PSTN) MUST implement either PCMU or PCMA (and preferably both).</li>
</ol>
<p>Naturally, clients and gateways can implement additional codecs, such as those listed in this document.</p>
@ -189,6 +196,6 @@
</section1>
<section1 topic='Acknowledgements' anchor='ack'>
<p>Thanks to Olivier Crête, Dave Cridland, Florian Jensen, Justin Karneges, Evgeniy Khramtsov, Marcus Lundblad, Tobias Markmann, Pedro Melo, Jack Moffitt, Jeff Muller, Jehan Pagès, Arc Riley, Kevin Smith, Remko Tronçon, Justin Uberti, and Paul Witty for their feedback.</p>
<p>Thanks to Olivier Crête, Dave Cridland, Florian Jensen, Justin Karneges, Evgeniy Khramtsov, Marcus Lundblad, Tobias Markmann, Jean-Marc Valin, Pedro Melo, Jack Moffitt, Jeff Muller, Jehan Pagès, Arc Riley, Kevin Smith, Remko Tronçon, Justin Uberti, and Paul Witty for their feedback.</p>
</section1>
</xep>