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Source-Specific Media Attributes in Jingle This specification provides an XML mapping for translating the RFC 5766 Source-Specific Media Attributes from SDP to Jingle &LEGALNOTICE; 0339 Draft 2020-05-19 Standards Track Standards Council XEP-0166 NOT_YET_ASSIGNED &fippo; 1.0.1 2021-10-23 egp

Add a XML Schema, and fix an example lacking a namespace.

 1.0.0 2020-05-26 XEP Editor (jsc)

Move to Draft as per Council vote from 2020-05-20.

 0.3 2017-09-11 XEP Editor (jwi) Defer due to lack of activity. 0.2 2015-11-09 ph

remove obsolete mslabel and label lines.

 0.1 2014-01-08 psa

Initial published version approved by the XMPP Council.

 0.0.1 2013-11-25 ph

First draft.

&rfc5576; provides a mechanism to describe attributes of individual media sources (identified by their synchronization source) within a media stream. A mapping to Jingle as an extension to &xep0167; is defined in this document.

The SDP format defined in RFC 5576 is shown below.

a=ssrc:<ssrc-id> <attribute> a=ssrc:<ssrc-id> <attribute>:<value>

This maps to Jingle as a <source/> element qualified by the 'urn:xmpp:jingle:apps:rtp:ssma:0' namespace. Since 'ssrc' is a media attribute in SDP, the <source/> element is included as child of the Jingle <description/> element.

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Each ssrc-id maps to a <source/> element whose 'ssrc' attribute is set to the ssrc-id. The associated attributes map to <parameter/> children with 'name' and 'value' attributes. If there is no value in the SDP, the value parameter shall be omitted.

An example follows:

a=ssrc:1656081975 cname:Yv/wvbCdsDW2Prgd a=ssrc:1656081975 msid:MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIv MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIva0 ]]>

The SDP format defined in RFC 5576 is shown below.

a=ssrc-group:<semantics> <ssrc-id> ...

This maps to Jingle as a <ssrc-group/> element qualified by the 'urn:xmpp:jingle:apps:rtp:ssma:0' namespace. Like the <source/> element, this is included as child of the Jingle <description/> element. The SDP 'semantics' parameter is mapped to the semantics attribute (for consistency with &xep0338;) and the list of ssrc-ids is mapped to <source/> elements whole 'ssrc' attribute is set to the ssrc-id.

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A minimal example follows:

m=video 1 RTP/SAVPF 100 116 117 a=rtpmap:100 VP8/90000 a=ssrc-group:FID 2301230316 386328120 a=ssrc:2301230316 cname:T5qvrIZj42v//eYQ a=ssrc:386328120 cname:uEYgNtStZyTF74sM a=ssrc-group:FID 3139499595 2613715171 a=ssrc:3139499595 cname:re8jhxkly9bxzuxr a=ssrc:2613715171 cname:f83avsiw6n1m7vi

This is mapped to Jingle as follows:

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If an entity supports source specific media attributes as described in RFC 5576, it MUST advertise that fact in its responses to &xep0030; information ("disco#info") requests by returning a feature of 'urn:ietf:rfc:5576':

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In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.

This document introduces no additional security considerations above and beyond those defined in the documents on which it depends.

This document requires no interaction with &IANA;.

This specification defines the following XML namespace:

  • urn:xmpp:jingle:apps:rtp:ssma:0

The ®ISTRAR; includes the foregoing namespace to the registry located at &NAMESPACES;, as described in Section 4 of &xep0053;.

 &NSVER; The protocol documented by this schema is defined in XEP-0339: http://www.xmpp.org/extensions/xep-0339.html ]]>