JEP-0180: Jingle Video Media Description Format

This document defines a media description format for Jingle video sessions.

WARNING: This Standards-Track JEP is Experimental. Publication as a Jabber Enhancement Proposal does not imply approval of this proposal by the Jabber Software Foundation. Implementation of the protocol described herein is encouraged in exploratory implementations, but production systems should not deploy implementations of this protocol until it advances to a status of Draft.

JEP Information

Status: Experimental
Type: Standards Track
Number: 0180
Version: 0.1
Last Updated: 2006-03-23
JIG: Standards JIG
Approving Body: Jabber Council
Dependencies: XMPP Core, JEP-0166
Supersedes: None
Superseded By: None
Short Name: jingle-video
Wiki Page: <http://wiki.jabber.org/index.php/Jingle Video Media Description Format (JEP-0180)>

Author Information

Legal Notice

This Jabber Enhancement Proposal is copyright 1999 - 2006 by the Jabber Software Foundation (JSF) and is in full conformance with the JSF's Intellectual Property Rights Policy <http://www.jabber.org/jsf/ipr-policy.shtml>. This material may be distributed only subject to the terms and conditions set forth in the Creative Commons Attribution License (<http://creativecommons.org/licenses/by/2.5/>).

Discussion Venue

The preferred venue for discussion of this document is the Standards-JIG discussion list: <http://mail.jabber.org/mailman/listinfo/standards-jig>.

Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the Jabber Software Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this JEP has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Conformance Terms

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

Table of Contents

1. Introduction

Jingle [1] 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.

2. Requirements

The Jingle media description format defined herein is designed to meet the following requirements:

1. Enable negotiation of parameters necessary for video exchange.
2. Map these parameters to Session Description Protocol (SDP; see RFC 2327 [2]) to enable interoperability.
3. Define informational messages related to video exchange chat.

3. Media Description Format

A Jingle video session is described by one or more encodings contained within a wrapper <description/> element. In the language of RFC 2327 these encodings are payload-types; therefore, each <payload-type/> 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 RFC 3550 [3]) but may be used in other contexts as well. The most common encodings for the Audio/Video Profile (AVP) of RTP are listed in RFC 3551 [4] (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 RFC 3551. The 'id' attribute is REQUIRED and the 'name' attribute is RECOMMENDED. The encodings SHOULD be provided in order of preference.

Example 1. Video Description Format

    <description xmlns='http://jabber.org/protocol/jingle/media/video'>
      <payload-type id='18' name='G729'/>
      <payload-type id='97' name='IPCMWB'/>
      <payload-type id='98' name='L16' transparent='true'/>
      <payload-type id='13' name='CN'/>
    </description>
  

The <description/> element is intended to be a child of a <jingle/> element as specified in JEP-0166.

The defined attributes of the <description/> element are as follows:

Table 1: Video Description Attributes

4. Mapping to Session Description Protocol

To follow.

5. Service Discovery

If an entity supports the Jingle video media description format, it MUST advertise that fact by returning a feature of "http://jabber.org/protocol/jingle/media/video" in response to Service Discovery [5] information requests.

Example 2. Service Discovery Information Request

<iq from='romeo@montague.net/orchard' 
    id='disco1'
    to='juliet@capulet.com/balcony' 
    type='get'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
  

Example 3. Service Discovery Information Response

<iq from='juliet@capulet.com/balcony' 
    id='disco1'
    to='romeo@montague.net/orchard' 
    type='result'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
    ...
    <feature var='http://jabber.org/protocol/jingle'/>
    <feature var='http://jabber.org/protocol/jingle/media/video'/>
    ...
  </query>
</iq>
  

6. Informational Messages

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 "media-info", where the informational message is a payload element qualified by the 'http://jabber.org/protocol/jingle/info/video' namespace. No payload elements have yet been defined, but will be specified in a future version of this document.

7. Implementation Notes

8. Security Considerations

The description of a format for video sessions introduces no known security vulnerabilities.

9. IANA Considerations

This JEP requires no interaction with the Internet Assigned Numbers Authority (IANA) [7].

10. Jabber Registrar Considerations

<media>
  <name>video</name>
  <desc>Jingle sessions that support video exchanges</desc>
  <doc>JEP-xxxx</doc>
</media>
    

11. XML Schemas

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='http://jabber.org/protocol/jingle/media/video'
    xmlns='http://jabber.org/protocol/jingle/media/video'
    elementFormDefault='qualified'>

  <xs:element name='description'>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref='payload-type' minOccurs='0' maxOccurs='unbounded'/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:element name='payload-type'>
    <xs:complexType>
      <xs:simpleContent>
        <xs:extension base='empty'>
          <xs:attribute name='channels' type='xs:integer' use='optional' default='1'/>
          <xs:attribute name='height' type='xs:nonNegativeInteger' use='optional'/>
          <xs:attribute name='id' type='xs:unsignedByte' use='required'/>
          <xs:attribute name='layer' type='xs:nonNegativeInteger' use='optional'/>
          <xs:attribute name='name' type='xs:string' use='optional'/>
          <xs:attribute name='rate' type='xs:short' use='optional'/>
          <xs:attribute name='transparent' type='xs:boolean' use='optional'/>
          <xs:attribute name='width' type='xs:nonNegativeInteger' use='optional'/>
          <xs:attribute name='x' type='xs:integer' use='optional'/>
          <xs:attribute name='y' type='xs:integer' use='optional'/>
        </xs:extension>
      </xs:simpleContent>
    </xs:complexType>
  </xs:element>

  <xs:simpleType name='empty'>
    <xs:restriction base='xs:string'>
      <xs:enumeration value=''/>
    </xs:restriction>
  </xs:simpleType>

</xs:schema>
    

Notes

Revision History

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