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sed -i 's/^\s\+]]>/]]>/g' xep-*.xml
276 lines
9.9 KiB
XML
276 lines
9.9 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>Multiparty Jingle (Muji)</title>
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<abstract>
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This specification defines an XMPP protocol extension for initiating and
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managing multiparty voice and video conferences within an XMPP MUC
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</abstract>
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&LEGALNOTICE;
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<number>0272</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>XMPP Core</spec>
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<spec>XEP-0045</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>muji</shortname>
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<author>
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<firstname>Sjoerd</firstname>
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<surname>Simons</surname>
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<email>sjoerd.simons@collabora.co.uk</email>
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<jid>sjoerd.simons@collabora.co.uk</jid>
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</author>
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<author>
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<firstname>Dafydd</firstname>
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<surname>Harries</surname>
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<email>dafydd.harries@collabora.co.uk</email>
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<jid>dafydd.harries@collabora.co.uk</jid>
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</author>
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<revision>
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<version>0.1</version>
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<date>2009-09-11</date>
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<initials>psa</initials>
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<remark><p>Initial published version as accepted for publication by the XMPP Council.</p></remark>
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</revision>
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<revision>
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<version>0.0.0.2</version>
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<date>2009-06-09</date>
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<initials>sjoerd</initials>
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<remark><p>Second rough 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>
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&xep0166; is used to negotiate peer to peer media sessions.
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Muji (short for Multiparty Jingle) is a way to coordinate Jingle sessions
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between a group of people.
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Muji conferences are held in &xep0045; rooms.
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</p>
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</section1>
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<section1 topic="How it Works" anchor="howitworks">
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<p>
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A Muji conference has a number of contents, each of which has unique name,
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content type, and an encoding.
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Each participant may provide a stream for each content, and communicates
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which contents they are willing to provide streams for, along with encoding
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information, in their MUC presence.
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This serves two purposes. Firstly, so that each participant knows which
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contents every other participant provides.
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Secondly, so that there is a global payload type (PT) mapping for the
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various contents, so that clients only need to encode and payload each
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content that they provide once.
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</p>
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<p>
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Participants are not required to participate all the contents that are
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available.
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For example, a Muji client might choose to only request audio streams.
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</p>
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</section1>
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<section1 topic='Joining a Conference' anchor='joining'>
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<p>
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Joining a conference is done in two stages. The first step is to
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declare that preparations are being done to either join or start a muji
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session inside the MUC. This is indicated by the client sending a presence
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stanza to the MUC with a preparing element in muji section.
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</p>
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<code><![CDATA[
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<presence from='wiccarocks@shakespeare.lit/laptop'
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to='darkcave@chat.shakespeare.lit/oldhag'>
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<c xmlns="http://jabber.org/protocol/caps"
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node="http://telepathy.freedesktop.org/wiki/Muji"
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ver="48QdBuXRCJFb8qIzgy1FOHSGO0U="
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hash="sha-1" />
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<muji xmlns='http://telepathy.freedesktop.org/muji'>
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<preparing />
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</muji>
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</presence>
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]]></code>
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<p>
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The client MUST then wait until the MUC rebroadcasts its presence message,
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after which it MUST wait for all other participants that had a preparing
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element in their presence to finish preparation. Afterwards it should finish
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it's own preparation by updating its presence with the contents it wants to
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take part in.
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</p>
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<code><![CDATA[
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<presence from='wiccarocks@shakespeare.lit/laptop'
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to='darkcave@chat.shakespeare.lit/oldhag'>
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<c xmlns="http://jabber.org/protocol/caps"
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node="http://telepathy.freedesktop.org/wiki/Muji"
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ver="48QdBuXRCJFb8qIzgy1FOHSGO0U="
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hash="sha-1" />
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<muji xmlns='http://telepathy.freedesktop.org/muji'>
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<content name='video'>
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<description xmlns='urn:xmpp:jingle:apps:rtp:0' media='video'>
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<payload-type id='97' name='theora' clockrate='90000'/>
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</description>
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</content>
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<content creator='initiator' name='voice'>
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<description xmlns='urn:xmpp:jingle:apps:rtp:0' media='audio'>
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<payload-type id='97' name='speex' clockrate='8000'/>
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<payload-type id='18' name='G729'/>
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</description>
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</content>
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</muji>
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</presence>
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]]></code>
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<p>
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When a client adds a payload ID to a content description, it MUST have the
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same codec name and receiving parameters as the corresponding entries in
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other participants' payload maps for that content. For instance, if Alice
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defines a payload type with ID 98, codec Speex and a a clock rate of 8000
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for a content called “voice0”, then Bob must define payload type 98
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identically or not at all for that content.
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</p>
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<p>
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Furthermore, each content description MUST include at least one payload type
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that every other participant supports. In other words, the intersection of
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payload type mappings in descriptions for a content must not be the empty
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set. This avoids clients having to encode the same stream multiple times,
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which can be very costly, and also allows sending the encoded data only once
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where the transport makes this possible (e.g. IP multicast).
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</p>
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<p>
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Once a client has constructed content descriptions and advertised them in
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its MUC presence, it MUST initiate a Jingle session with every other
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participant. The requirement that it is the joining participant that
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initiates sessions avoids race conditions.
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</p>
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<p>
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Jingle sessions are initiated between the MUC JIDs of participants. That is,
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the Jingle session-initiate stanza is sent from one MUC JID to another. This
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allows participants to easily identify sessions as belonging to a Muji
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conference. Content names inside Muji-related Jingle sessions always refer
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to the content with the same name inside the Muji conference.
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</p>
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</section1>
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<section1 topic='Leaving a Conference' anchor='leaving'>
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<p>
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To leave a conference the Muji information MUST first be removed from the
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participant's presence; subsequently it SHOULD terminate all Jingle sessions
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related to that conference. Updating the presence first reduces the
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likelihood of situations where new participants initiate sessions with
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participants who are leaving the conference.
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</p>
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</section1>
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<section1 topic='Adding a Content Type' anchor='addcontent'>
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<p>
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Adding a stream follows a process similar to the joining a conference. As a
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first step an updated presence stanza MUST be send which contains a
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preparing element as part of the Muji section.
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</p>
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<code><![CDATA[
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<presence from='wiccarocks@shakespeare.lit/laptop'
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to='darkcave@chat.shakespeare.lit/oldhag'>
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<c xmlns="http://jabber.org/protocol/caps"
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node="http://telepathy.freedesktop.org/wiki/Muji"
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ver="48QdBuXRCJFb8qIzgy1FOHSGO0U="
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hash="sha-1" />
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<muji xmlns='http://telepathy.freedesktop.org/muji'>
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<content creator='initiator' name='voice'>
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<description xmlns='urn:xmpp:jingle:apps:rtp:0' media='audio'>
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<payload-type id='97' name='speex' clockrate='8000'/>
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<payload-type id='18' name='G729'/>
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</description>
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</content>
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<preparing/>
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</muji>
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</presence>
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]]></code>
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<p>
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The client MUST then wait until the MUC rebroadcasts its presence message,
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after which it MUST wait for all other participants that had a preparing
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element in their presence to finish their changes.
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</p>
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<p>
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Afterwards the client should add the new content to the muji section of its
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presence and add the content to all the Jingle sessions it had with
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participants it shared the content with.
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</p>
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<code><![CDATA[
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<presence from='wiccarocks@shakespeare.lit/laptop'
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to='darkcave@chat.shakespeare.lit/oldhag'>
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<c xmlns="http://jabber.org/protocol/caps"
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node="http://telepathy.freedesktop.org/wiki/Muji"
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ver="48QdBuXRCJFb8qIzgy1FOHSGO0U="
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hash="sha-1" />
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<muji xmlns='http://telepathy.freedesktop.org/muji'>
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<content name='video'>
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<description xmlns='urn:xmpp:jingle:apps:rtp:0' media='video'>
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<payload-type id='97' name='theora' clockrate='90000'/>
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</description>
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</content>
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<content creator='initiator' name='voice'>
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<description xmlns='urn:xmpp:jingle:apps:rtp:0' media='audio'>
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<payload-type id='97' name='speex' clockrate='8000'/>
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<payload-type id='18' name='G729'/>
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</description>
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</content>
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</muji>
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</presence>
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]]></code>
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</section1>
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<section1 topic='Removing a Content Type' anchor='removecontent'>
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<p>
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To remove a content type the participant SHOULD first sent an updated presence
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without the content in its muji section. Afterwards it MUST the content from
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all the Jingle sessions it has open.
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</p>
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</section1>
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<section1 topic='Relays and Mixers' anchor='relaysmixer'>
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<p>
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When scaling to conferences with a big number of participants
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it's no longer viable for all participants to have direct
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connections.
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On connections where upstream bandwidth is the limiting factor, an RTP
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relay which is able to relay the stream to multiple participants on
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the behalf of the clients and which forwards the streams of other
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participants back to the client can be used.
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If the limiting factor is either CPU or downstream bandwidth then a mixer
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can be used, which receives the media streams from other participants and
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mixes them on behalf of the client, so that the client only has to deal
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with receiving and decoding a single stream for each media type. On the
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sending side a mixer acts like a relay and relays the clients stream to all
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other participants.
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Both these services can either be provided by dedicated services or by
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other clients.
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</p>
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</section1>
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</xep>
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