mirror of
https://github.com/moparisthebest/xeps
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29bee13867
git-svn-id: file:///home/ksmith/gitmigration/svn/xmpp/trunk@320 4b5297f7-1745-476d-ba37-a9c6900126ab
245 lines
10 KiB
XML
245 lines
10 KiB
XML
<?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 Video Content Description Format</title>
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<abstract>This document defines a content description format for Jingle video sessions.</abstract>
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&LEGALNOTICE;
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<number>0180</number>
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<status>Experimental</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>XMPP Core</spec>
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<spec>XEP-0166</spec>
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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>TO BE ASSIGNED</shortname>
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&stpeter;
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<author>
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<firstname>Milton</firstname>
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<surname>Chen</surname>
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<email>Milton.Chen@vseelab.com</email>
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</author>
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<revision>
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<version>0.4</version>
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<date>2006-12-21</date>
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<initials>psa</initials>
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<remark><p>Modified spec to use provisional namespace before advancement to Draft (per XEP-0053).</p></remark>
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</revision>
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<revision>
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<version>0.3</version>
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<date>2006-08-23</date>
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<initials>psa</initials>
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<remark><p>Modified namespace to track XEP-0166.</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>2006-07-12</date>
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<initials>psa</initials>
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<remark><p>Updated to use content type instead of media type.</p></remark>
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</revision>
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<revision>
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<version>0.1</version>
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<date>2006-03-23</date>
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<initials>psa/mc</initials>
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<remark><p>Initial 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>2006-03-20</date>
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<initials>psa/mc</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='intro'>
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<p>&xep0166; can be used to initiate and negotiate a wide range of peer-to-peer sessions. One session type of interest is video exchange. This document specifies a format for describing Jingle video sessions.</p>
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</section1>
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<section1 topic='Requirements' anchor='reqs'>
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<p>The Jingle content description format defined herein is designed to meet the following requirements:</p>
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<ol>
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<li>Enable negotiation of parameters necessary for video exchange.</li>
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<li>Map these parameters to Session Description Protocol (SDP; see &rfc4566;) to enable interoperability.</li>
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<li>Define informational messages related to video exchange chat.</li>
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</ol>
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</section1>
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<section1 topic='Content Description Format' anchor='format'>
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<p>A Jingle video session is described by one or more encodings contained within a wrapper &DESCRIPTION; element. In the language of <cite>RFC 4566</cite> these encodings are payload-types; therefore, each <payload-type/> child element specifies an encoding that can be used for the video stream. Such encodings are often used in the context of the Real-time Transfer Protocol (RTP; see &rfc3550;) but may be used in other contexts as well. The most common encodings for the Audio/Video Profile (AVP) of RTP are listed in &rfc3551; (these "static" types are reserved from payload ID 0 through payload ID 96), although other encodings are allowed (these "dynamic" types use payload IDs 97 to 127) in accordance with the dynamic assignment rules described in Section 3 of <cite>RFC 3551</cite>. The &PAYLOADTYPE; element's 'id' attribute is REQUIRED and its 'name' attribute is RECOMMENDED. The encodings SHOULD be provided in order of preference.</p>
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<example caption="Video Description Format"><![CDATA[
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<description xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns/description/video'>
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<payload-type id='18' name='G729'/>
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<payload-type id='97' name='IPCMWB'/>
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<payload-type id='98' name='L16' transparent='true'/>
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<payload-type id='13' name='CN'/>
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</description>
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]]></example>
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<p>The &DESCRIPTION; element is intended to be a child of a &JINGLE; element as specified in <cite>XEP-0166</cite>.</p>
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<p>The defined attributes of the &PAYLOADTYPE; element are as follows:</p>
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<table caption='Video Description 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>Datatype/Units</th>
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</tr>
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<tr>
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<td>channels</td>
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<td>The number of channels (e.g., 2 for stereoscopic video)</td>
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<td>positiveInteger (defaults to 1)</td>
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</tr>
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<tr>
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<td>height</td>
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<td>The vertical extent of the displayed video, in pixels</td>
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<td>positiveInteger</td>
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</tr>
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<tr>
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<td>id</td>
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<td>A unique identifier for the payload type</td>
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<td>positiveInteger</td>
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</tr>
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<tr>
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<td>layer</td>
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<td>The relationship of a layer to the "bottom" of the stack, where 0 = bottom (the first layer)</td>
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<td>nonNegativeInteger</td>
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</tr>
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<tr>
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<td>name</td>
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<td>A name for the payload type</td>
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<td>string</td>
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</tr>
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<tr>
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<td>transparent</td>
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<td>Whether or not a layer is transparent</td>
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<td>boolean</td>
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</tr>
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<tr>
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<td>width</td>
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<td>The horizontal extent of the displayed video, in pixels</td>
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<td>positiveInteger</td>
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</tr>
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<tr>
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<td>x</td>
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<td>The horizontal starting point of a tile, in pixels from the origin point</td>
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<td>positiveInteger</td>
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</tr>
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<tr>
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<td>y</td>
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<td>The vertical starting point of a tile, in pixels from the origin point</td>
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<td>positiveInteger</td>
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</tr>
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</table>
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</section1>
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<section1 topic='Mapping to Session Description Protocol' anchor='sdp'>
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<p>To follow.</p>
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</section1>
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<section1 topic='Service Discovery' anchor='disco'>
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<p>If an entity supports the Jingle video content description format, it MUST advertise that fact by returning a feature of "http://www.xmpp.org/extensions/xep-0166.html#ns/description/video" in response to &xep0030; information requests.</p>
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<example caption="Service Discovery Information Request"><![CDATA[
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<iq from='romeo@montague.net/orchard'
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id='disco1'
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to='juliet@capulet.com/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.com/balcony'
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id='disco1'
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to='romeo@montague.net/orchard'
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type='result'>
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<query xmlns='http://jabber.org/protocol/disco#info'>
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...
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<feature var='http://www.xmpp.org/extensions/xep-0166.html#ns'/>
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<feature var='http://www.xmpp.org/extensions/xep-0166.html#ns/description/video'/>
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...
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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='Informational Messages' anchor='info'>
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<p>Informational messages may be sent by either party within the context of Jingle to communicate the status of a Jingle video session, device, or principal. The informational message MUST be an IQ-set containing a &JINGLE; element of type "content-info", where the informational message is a payload element qualified by the 'http://www.xmpp.org/extensions/xep-0166.html#ns/info/video' namespace. No payload elements have yet been defined, but will be specified in a future version of this document.</p>
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</section1>
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<section1 topic='Implementation Notes' anchor='impl'>
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<section2 topic='Codecs' anchor='impl-codecs'>
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<p>Support for the Theora codec <note>See <<link url='http://www.theora.org/'>http://www.theora.org/</link>>.</note> is RECOMMENDED.</p>
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</section2>
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</section1>
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<section1 topic='Security Considerations' anchor='security'>
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<p>The description of a format for video sessions introduces no known security vulnerabilities.</p>
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</section1>
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<section1 topic='IANA Considerations' anchor='iana'>
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<p>This document requires no interaction with &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='ns'>
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<p>Until this specification advances to a status of Draft, its associated namespaces shall be "http://www.xmpp.org/extensions/xep-0180.html#ns" and "http://www.xmpp.org/extensions/xep-0180.html#ns-info"; upon advancement of this specification, the ®ISTRAR; shall issue permanent namespaces in accordance with the process defined in Section 4 of &xep0053;.</p>
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</section2>
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<section2 topic='Jingle Content Description Formats' anchor='registrar-content'>
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<p>The XMPP Registrar shall include "video" in its registry of Jingle content description formats. The registry submission is as follows:</p>
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<code><![CDATA[
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<content>
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<name>video</name>
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<desc>Jingle sessions that support video exchanges</desc>
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<doc>XEP-0180</doc>
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</content>
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]]></code>
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</section2>
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</section1>
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<section1 topic='XML Schemas' anchor='schema'>
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<section2 topic='Content Description Format' anchor='schema-content'>
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<code><![CDATA[
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<?xml version='1.0' encoding='UTF-8'?>
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<xs:schema
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xmlns:xs='http://www.w3.org/2001/XMLSchema'
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targetNamespace='http://www.xmpp.org/extensions/xep-0166.html#ns/description/video'
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xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns/description/video'
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elementFormDefault='qualified'>
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<xs:element name='description'>
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<xs:complexType>
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<xs:sequence>
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<xs:element ref='payload-type' minOccurs='0' maxOccurs='unbounded'/>
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</xs:sequence>
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</xs:complexType>
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</xs:element>
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<xs:element name='payload-type'>
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<xs:complexType>
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<xs:simpleContent>
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<xs:extension base='empty'>
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<xs:attribute name='channels' type='xs:integer' use='optional' default='1'/>
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<xs:attribute name='height' type='xs:nonNegativeInteger' use='optional'/>
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<xs:attribute name='id' type='xs:unsignedByte' use='required'/>
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<xs:attribute name='layer' type='xs:nonNegativeInteger' use='optional'/>
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<xs:attribute name='name' type='xs:string' use='optional'/>
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<xs:attribute name='rate' type='xs:short' use='optional'/>
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<xs:attribute name='transparent' type='xs:boolean' use='optional'/>
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<xs:attribute name='width' type='xs:nonNegativeInteger' use='optional'/>
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<xs:attribute name='x' type='xs:integer' use='optional'/>
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<xs:attribute name='y' type='xs:integer' use='optional'/>
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</xs:extension>
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</xs:simpleContent>
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</xs:complexType>
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</xs:element>
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<xs:simpleType name='empty'>
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<xs:restriction base='xs:string'>
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<xs:enumeration value=''/>
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</xs:restriction>
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</xs:simpleType>
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</xs:schema>
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]]></code>
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</section2>
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<section2 topic='Informational Messages' anchor='schema-info'>
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<p>To follow.</p>
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</section2>
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</section1>
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</xep>
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