mirror of
https://github.com/moparisthebest/xeps
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341 lines
12 KiB
XML
Executable File
341 lines
12 KiB
XML
Executable File
<?xml version='1.0' encoding='UTF-8'?>
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<!DOCTYPE xep SYSTEM 'xep.dtd' [
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<!ENTITY % ents SYSTEM 'xep.ent'>
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%ents;
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]>
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<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
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<xep>
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<header>
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<title>Jingle RTP Feedback Negotiation</title>
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<abstract>This specification defines an XMPP extension to negotiate
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the use of the Extended RTP Profile for Real-time Transport Control
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Protocol (RTCP)-Based Feedback (RTP/AVPF) with Jingle RTP
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sessions</abstract>
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&LEGALNOTICE;
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<number>0293</number>
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<status>Deferred</status>
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<type>Standards Track</type>
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<sig>Standards</sig>
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<approver>Council</approver>
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<dependencies>
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<spec>XEP-0167</spec>
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<spec>RFC 4585</spec>
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</dependencies>
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<author>
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<firstname>Olivier</firstname>
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<surname>Crête</surname>
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<email>olivier.crete@collabora.co.uk</email>
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<jid>olivier.crete@collabora.co.uk</jid>
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</author>
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<discuss>jingle</discuss>
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<revision>
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<version>0.1</version>
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<date>2011-03-24</date>
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<initials>psa</initials>
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<remark><p>Initial published version.</p></remark>
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</revision>
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<revision>
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<version>0.0.1</version>
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<date>2011-01-10</date>
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<initials>oc</initials>
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<remark><p>First draft.</p></remark>
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</revision>
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</header>
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<section1 topic='Introduction' anchor='introduction'>
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<p>This documents specifies how to negotiate the use of the Extended
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RTP Profile for Real-time Transport Control Protocol (RTCP)-Based
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Feedback (RTP/AVPF) with Jingle RTP sessions.</p>
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</section1>
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<section1 topic='Requirements' anchor='requirements'>
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<p>The Jingle extension defined herein is designed to meet the following requirements:</p>
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<ol>
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<li>Enable negotiations of the required parameters for the
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transmissions of RTP Feedback messages as defined in &rfc4585;.</li>
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<li>Map these parameters to Session Description Protocol (SDP; see
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&rfc4566;) to enable interoperability.</li>
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</ol>
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</section1>
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<section1 topic='New elements' anchor='elements'>
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<p>This specification defines two new elements, <rtcp-fb/> and
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<rtcp-fb-trr-int/>, that can be inserted in the
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<description/> or the <payload-type/> elements of
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&xep0167;. The presence of any of these elements in a
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content's description means that the RTP/AVPF profile should be used
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for the whole content. If any of these elements are inside the
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<payload-type/> element, the parameters specified apply only to
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that payload type, if they are directly inside the
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<description/> tag, then the specified parameters apply to the
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whole content.</p>
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<p>The attributes of the <rtcp-fb/> element are:</p>
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<table caption='rtcp-fb attributes'>
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<tr>
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<th>Attribute</th>
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<th>Description</th>
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<th>Inclusion</th>
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<th>Possible values</th>
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</tr>
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<tr>
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<td>type</td>
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<td>The type of feedback</td>
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<td>REQUIRED</td>
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<td>ack, nack, ccm, app, etc..</td>
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</tr>
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<tr>
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<td>subtype</td>
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<td>The subtype (depends on the type)</td>
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<td>OPTIONAL (possibly REQUIRED depending on the type)</td>
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<td>
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ack: rpsi, app<br/>
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nack: sli, pli, rpsi, app, rai<br/>
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ccm: fir, tmmbr, tstr, vbcm<br/>
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app: depends on the application<br/>
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</td>
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</tr>
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</table>
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<p>Any type or subtype of feedback message that requires extra
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parameters in the a=b form can use the <parameter/> element to
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describe it. Any other form of parameter can be store in the CDATA
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inside the <rtcp-fb/> element.</p>
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<p>The element <rtcp-fb-trr-int/> is used to specify the minimum
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interval between two Regular (full compound) RTCP packets in
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milliseconds for this media session. It corresponds to the
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"a=rtcp-fb:* trr-int" line in SDP. The attributes of the
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<rtcp-fb-trr-int/> element are:</p>
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<table caption='rtcp-fb-trr-int attributes'>
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<tr>
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<th>Attribute</th>
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<th>Description</th>
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<th>Inclusion</th>
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<th>Possible values</th>
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</tr>
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<tr>
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<td>value</td>
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<td>Number of milliseconds between regular RTCP reports</td>
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<td>REQUIRED</td>
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<td>0 to MAXUINT (default to 0)</td>
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</tr>
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</table>
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</section1>
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<section1 topic='Negotiation' anchor='negotiation'>
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<p>Feedback messages are negotiated along the codecs. They follow
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the same Offer/Answer mechanism based on SDP Offer/Answer. The
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initiator signals which feedback messages it wants to send or
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receive in the the <session-initiate/> iq stanza. If the
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responder does not understand the type or subtype of a feedback
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message, it MUST remove the element from the reply. If the responder
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does not wish to provide or receive some kind of feedback, it MUST
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remove the relevant element. It MUST then send the remaining
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elements it wants to keep as-is without modifying them in the
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<session-accept/></p>
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<p>The responder MUST send any <rtcp-fb/> element as-is if it
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accepts it. It MUST NOT change any parameter to conform the the
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negotiation defined in <cite>RFC 4585</cite> Section 4. It MUST NOT add any
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<rtcp-fb/> element that was not offered by the initiator. It
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MUST NOT modify the 'value' of any <rtcp-fb-trr-int/>
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element. It can only remove the <rtcp-fb-trr-int/> element or
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reject the content. If all the feedback messages are removed but the
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responder wants to stay in the RTP/AVPF profile, it MUST put a
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<rtcp-fb-trr-int/> element with the same 'value' that it
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received from the intiator, if the initiator did not provide a
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<rtcp-fb-trr-int/> element, then this value is "0".</p>
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<p>Example negotiation where the initiator requests Packet Loss
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Indications (pli) as defined in <cite>RFC 4585</cite> on both H.263 and H.264,
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but also requests Slice Loss Indications for H.264 with a minimum
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interval between regular full compound RTCP packets of 100 milliseconds.</p>
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<example caption='Initiator sends description inside session-initiate'><![CDATA[
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<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
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<rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack' subtype='pli'/>
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<payload-type id='96' name='H264' clockrate='90000'>
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<rtcp-fb-trr-int xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' value='100'/>
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<rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack' subtype='sli'/>
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</payload-type>
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<payload-type id='34' name='H263' clockrate='90000'/>
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</description>
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]]></example>
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<p>Example reply where the responder rejects the "sli" but
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accepts the "pli".</p>
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<example caption='Reponder sends description inside session-accept'><![CDATA[
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<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
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<rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack' subtype='pli'/>
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<payload-type id='96' name='H264' clockrate='90000'>
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<rtcp-fb-trr-int xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' value='100'/>
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</payload-type>
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<payload-type id='34' name='H263' clockrate='90000'/>
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</description>
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]]></example>
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<p>Another reply to the same request where the responder wishes to
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stay in the AVPF profile but rejects all specific feedback messages
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by using the <rtcp-fb-trr-int/> with the default value.</p>
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<example caption='Responder sends description inside session-accept without any feedback message'><![CDATA[
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<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
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<rtcp-fb-trr-int xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' value='0'/>
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<payload-type id='96' name='H264' clockrate='90000'/>
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<payload-type id='34' name='H263' clockrate='90000'/>
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</description>
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]]></example>
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</section1>
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<section1 topic='Mapping to Session Description Protocol' anchor='sdp-mapping'>
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<p>The <rtcp-fb/> element maps to the a:rtcp-fb= SDP line with
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the exception of the 'trr-int' parameter which is mapped into it's
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own element (<rtcp-fb-trr-int/>) in XMPP. The payload types
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are also not explicitly written in the <rtcp-fb/> and
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<rtcp-fb-trr-int/> elements. Instead, each payload type has its own
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set of <rtcp-fb/> and <rtcp-fb-trr-int/> elements if
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they do not apply to the whole content.</p>
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<p>Example conversion of a sample fragment of a SDP containing an
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audio session using the RTP/AVP profile for audio and the RTP/AVPF
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profile for video:</p>
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<example caption='SDP fragment'><![CDATA[
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v=0
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o=remeo 3203093520 3203093520 IN IP4 host.example.com
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s=Video call with feedback
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t=3203130148 3203137348
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m=audio 49170 RTP/AVP 0
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c=IN IP4 10.0.1.1
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a=rtpmap:0 PCMU/8000
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m=video 59172 RTP/AVPF 98 99
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c=IN IP4 10.0.1.1
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a=rtpmap:98 H263-1998/90000
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a=rtpmap:99 H261/90000
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a=rtcp-fb:* nack
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a=rtcp-fb:98 nack rpsi
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a=rtcp-fb:98 trr-int 100
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]]></example>
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<example caption='The same description in XMPP format'><![CDATA[
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<iq from='romeo@montague.lit/orchard'
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id='ph37a419'
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to='juliet@capulet.lit/balcony'
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type='set'>
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<jingle xmlns='urn:xmpp:jingle:1'>
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action='session-initiate'
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initiator='romeo@montague.lit/orchard'
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sid='a73sjjvkla37jfea'>
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<content creator='initiator' name='voice'>
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<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'>
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<payload-type id='0' name='PCMU' />
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</description>
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<transport xmlns='urn:xmpp:jingle:transports:raw-udp:1'>
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<candidate component='1'
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generation='0'
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id='a9j3mnbtu1'
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ip='10.0.1.1'
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port='49170'/>
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<candidate component='2'
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generation='0'
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id='a9j3mnbtu1'
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ip='10.0.1.1'
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port='49171'/>
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</transport>
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</content>
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<content creator='initiator' name='face'>
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<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
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<rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack'/>
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<payload-type id='98' name='H263-1998'>
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<rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack'
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subtype='rpsi'/>
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<rtcp-fb-trr-int xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' value='100'/>
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</payload-type>
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<payload-type id='99' name='H264' />
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</description>
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<transport xmlns='urn:xmpp:jingle:transports:raw-udp:1'>
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<candidate component='1'
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generation='0'
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id='a9j3mnbtu1'
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ip='10.0.1.1'
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port='49172'/>
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<candidate component='2'
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generation='0'
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id='a9j3mnbtu1'
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ip='10.0.1.1'
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port='49173'/>
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</transport>
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</content>
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</jingle>
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</iq>
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]]></example>
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</section1>
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<section1 topic='Determining support' anchor='determining-support'>
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<p>To advertise its support for Extended RTCP Feedback in Jingle RTP
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Sessions and a minimum interval between regular RTCP packets, when
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replying to &xep0030; information requests an entity MUST return the
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following features:</p>
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<ol>
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<li>URNs for any version of this protocol that the entity
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supports -- e.g., "urn:xmpp:jingle:apps:rtp:rtcp-fb:0" for the
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current version</li>
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</ol>
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<p>An example follows:</p>
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<example caption="Service discovery information request"><![CDATA[
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<iq from='romeo@montague.lit/orchard'
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id='bh3vd715'
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to='juliet@capulet.lit/balcony'
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type='get'>
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<query xmlns='http://jabber.org/protocol/disco#info'/>
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</iq>
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]]></example>
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<example caption="Service discovery information response"><![CDATA[
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<iq from='juliet@capulet.lit/balcony'
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id='bh3vd715'
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to='romeo@montague.lit/orchard'
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type='result'>
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<query xmlns='http://jabber.org/protocol/disco#info'>
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<feature var='urn:xmpp:jingle:1'/>
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<feature var='urn:xmpp:jingle:apps:rtp:1'/>
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<feature var='urn:xmpp:jingle:apps:rtp:video'/>
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<feature var='urn:xmpp:jingle:apps:rtp:rtcp-fb:0'/>
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</query>
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</iq>
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]]></example>
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</section1>
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<section1 topic='IANA Considerations' anchor='iana-considerations'>
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<p>This document requires no interaction with the Internet Assigned
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Numbers Authority (IANA).</p>
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</section1>
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<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
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<section2 topic='Protocol Namespaces' anchor='registrar-ns'>
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<p>This specification defines the following XML namespaces:</p>
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<ul>
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<li>urn:xmpp:jingle:apps:rtp:rtcp-fb:0</li>
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</ul>
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<p>The ®ISTRAR; includes the foregoing namespaces in its
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registry at &NAMESPACES;, as governed by &xep0053;.</p>
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</section2>
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<section2 topic='Namespace Versioning' anchor='registrar-versioning'>
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&NSVER;
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</section2>
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</section1>
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<section1 topic='XML Schemas'>
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<p>TODO: Write actual schema</p>
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</section1>
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<section1 topic='Acknowledgements' anchor='ack'>
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<p>Thanks to Youness Alaoui for his feedback.</p>
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</section1>
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</xep>
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