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0.3
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stpeter
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xep-0266.xml
79
xep-0266.xml
@ -23,6 +23,12 @@
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<shortname>N/A</shortname>
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<discuss>jingle</discuss>
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&stpeter;
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<revision>
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<version>0.3</version>
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<date>2011-01-12</date>
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<initials>psa</initials>
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<remark><p>Added information about the Opus audio codec.</p></remark>
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</revision>
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<revision>
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<version>0.2</version>
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<date>2009-04-23</date>
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@ -81,23 +87,6 @@
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<section1 topic='Codec Summary' anchor='summary'>
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<section2 topic='Audio' anchor='audio'>
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<section3 topic='Speex' anchor='audio-speex'>
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<p>According to the speex.org website, the Speex codec is "an Open Source/Free Software patent-free audio compression format designed for speech". Speex was developed by Jean-Marc Valin and is maintained by the <link url='http://www.xiph.org/'>Xiph.org Foundation</link>. The following table summarizes the available information about Speex.</p>
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<table caption='Codec Considerations for Speex'>
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<tr>
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<th>Quality</th>
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<th>Packetization</th>
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<th>Availability</th>
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<th>Patents</th>
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</tr>
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<tr>
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<td>Good quality; optimized for voice; can be used for wide-band audio.</td>
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<td>See &rfc5574;.</td>
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<td>Freely downloadable under a revised BSD license at <<link url='http://speex.org/'>http://speex.org/</link>> and commonly deployed on Internet (VoIP) systems; not commonly deployed on non-Internet systems.</td>
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<td>Designed to be patent-clear.</td>
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</tr>
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</table>
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</section3>
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<section3 topic='G.711' anchor='audio-g711'>
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<p>G.711 refers to the Pulse Code Modulation (PCM) codec defined in &ITU; recommendation G.711, which is widely used on the public switched telephone network (PSTN) and by many voice over Internet Protocol (VoIP) providers. There are two versions: the μ-law ("U-law") version is widely deployed in North America and in Japan and the A-law version is widely deployed in the rest of the world. The following table summarizes the available information about G.711.</p>
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<table caption='Codec Considerations for G.711'>
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@ -115,11 +104,9 @@
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</tr>
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</table>
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</section3>
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</section2>
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<section2 topic='Video' anchor='video'>
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<section3 topic='Theora' anchor='video-theora'>
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<p>According to the theora.org website, the Theora codec is "a free and open video compression format". Theora is based on the VP3 codec originally developed by On2 Technologies and is now maintained by the <link url='http://www.xiph.org/'>Xiph.org Foundation</link>. The following table summarizes the available information about Theora.</p>
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<table caption='Codec Considerations for Theora'>
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<section3 topic='Opus' anchor='audio-opus'>
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<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). The following table summarizes the available information about Opus.</p>
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<table caption='Codec Considerations for Opus'>
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<tr>
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<th>Quality</th>
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<th>Packetization</th>
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@ -127,13 +114,32 @@
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<th>Patents</th>
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</tr>
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<tr>
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<td>Acceptable quality.</td>
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<td>See &rtptheora;.</td>
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<td>Freely downloadable under BSD license at <<link url='http://theora.org/'>http://theora.org/</link>>; not yet commonly deployed, especially on devices that have deployed H.264 instead.</td>
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<td>On2's patents over VP3 were contributed to the Xiph.org Foundation in 2001.</td>
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<td>Extremely high quality; can be used for wide-band audio.</td>
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<td>Not yet defined.</td>
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<td>Covered under IETF IPR rules, the intent it 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>
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<td>Designed to be patent-clear, but IPR claims have been filed.</td>
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</tr>
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</table>
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</section3>
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<section3 topic='Speex' anchor='audio-speex'>
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<p>According to the speex.org website, the Speex codec is "an Open Source/Free Software patent-free audio compression format designed for speech". Speex was developed by Jean-Marc Valin and is maintained by the <link url='http://www.xiph.org/'>Xiph.org Foundation</link>. The following table summarizes the available information about Speex.</p>
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<table caption='Codec Considerations for Speex'>
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<tr>
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<th>Quality</th>
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<th>Packetization</th>
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<th>Availability</th>
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<th>Patents</th>
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</tr>
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<tr>
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<td>Good quality; optimized for voice; can be used for wide-band audio.</td>
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<td>See &rfc5574;.</td>
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<td>Freely downloadable under a revised BSD license at <<link url='http://speex.org/'>http://speex.org/</link>> and commonly deployed on Internet (VoIP) systems; not commonly deployed on non-Internet systems.</td>
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<td>Designed to be patent-clear.</td>
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</tr>
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</table>
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</section3>
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</section2>
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<section2 topic='Video' anchor='video'>
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<section3 topic='Dirac' anchor='video-dirac'>
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<p>Dirac is a general-purpose video compression technology developed by the BBC that has been licensed in the open. It is used for everything from Internet streaming to HDTV. To date there is no RTP packetization deveintion for Dirac; however, such a format is under development.</p>
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<table caption='Codec Considerations for Dirac'>
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@ -168,11 +174,28 @@
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</tr>
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</table>
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</section3>
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<section3 topic='Theora' anchor='video-theora'>
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<p>According to the theora.org website, the Theora codec is "a free and open video compression format". Theora is based on the VP3 codec originally developed by On2 Technologies and is now maintained by the <link url='http://www.xiph.org/'>Xiph.org Foundation</link>. The following table summarizes the available information about Theora.</p>
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<table caption='Codec Considerations for Theora'>
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<tr>
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<th>Quality</th>
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<th>Packetization</th>
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<th>Availability</th>
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<th>Patents</th>
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</tr>
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<tr>
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<td>Acceptable quality.</td>
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<td>See &rtptheora;.</td>
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<td>Freely downloadable under BSD license at <<link url='http://theora.org/'>http://theora.org/</link>>; not yet commonly deployed, especially on devices that have deployed H.264 instead.</td>
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<td>On2's patents over VP3 were contributed to the Xiph.org Foundation in 2001.</td>
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</tr>
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</table>
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</section3>
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</section2>
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</section1>
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<section1 topic='Guidance for Implementors' anchor='guidance'>
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<p>Given that both Speex and G.711 are patent-clear, freely implementable, and commonly deployed, this document suggests that implementors strongly consider including support for both codecs in audio applications of Jingle RTP sessions.</p>
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<p>Given that both Speex and G.711 are patent-clear, freely implementable, and commonly deployed, this document suggests that implementors strongly 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 so widely deployed and easily available. 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>
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<p>The situation regarding video codecs is more murky, and implementors face difficult tradeoffs. While Theora is patent-clear and freely implementable, it is not yet commonly deployed. While Dirac is patent-clear and deployed fairly widely, no RTP packetization format has been defined for it. While deployment of H.264 is fairly common, it is not patent-clear or freely implementable. For many open-source / free software projects and smaller technology vendors, implementation of H.264 is either impossible (because of patents and licensing restrictions) or prohibitively expensive (because of royalty payments). These developers are strongly encouraged to implement Theora or Dirac and also to urge wider adoption of Theora and Dirac among larger technology vendors. However, this document acknowledges that it may take some time before Theora and Dirac are commonly deployed (especially on mobile devices) and that systems based on H.264 might be dominant in the marketplace for several years. This situation is unfortunate but cannot be directly changed by the XMPP developer community.</p>
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</section1>
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</section1>
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<section1 topic='Acknowledgements' anchor='ack'>
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<p>Thanks to Olivier Crête, Dave Cridland, Justin Karneges, Tobias Markmann, Jack Moffitt, Jeff Muller, Arc Riley, Kevin Smith, Justin Uberti, and Paul Witty for their feedback.</p>
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<p>Thanks to Olivier Crête, Dave Cridland, Florian Jensen, Justin Karneges, Evgeniy Khramtsov, Tobias Markmann, Pedro Melo, Jack Moffitt, Jeff Muller, Arc Riley, Kevin Smith, Justin Uberti, and Paul Witty for their feedback.</p>
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</section1>
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</xep>
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