XEP-xxxx: Mandatory-to-Implement Technologies for Jingle RTP Sessions

Copyright (c) 1999 - 2009 XMPP Standards Foundation. See Legal Notices.


This specification defines mandatory-to-implement technologies for Jingle RTP sessions, in particular codecs for voice and video chat.

WARNING: This document has not yet been accepted for consideration or approved in any official manner by the XMPP Standards Foundation, and this document must not be referred to as an XMPP Extension Protocol (XEP). If this document is accepted as a XEP by the XMPP Council, it will be published at <http://www.xmpp.org/extensions/> and announced on the <standards@xmpp.org> mailing list.


Table of Contents


1. Introduction
2. Requirements
3. Summary of Considered Codecs
    3.1. Audio
       3.1.1. Speex
       3.1.2. G.711
    3.2. Video
       3.2.1. Theora
       3.2.2. H.264
4. Security Considerations
5. IANA Considerations
6. XMPP Registrar Considerations
7. Acknowledgements

Appendices
    A: Document Information
    B: Author Information
    C: Legal Notices
    D: Relation to XMPP
    E: Discussion Venue
    F: Requirements Conformance
    G: Notes
    H: Revision History


1. Introduction

Jingle RTP Sessions [1] defines the Jingle [2] signalling exchanges needed to establish voice and video chat using the Real-time Transport Protocol RFC 3550 [3]; however, it does not specify the recommended voice and video codecs, since the state of codec technologies is more fluid than the signalling interactions. This specification defines the recommended codecs for the sake of interoperability between Jingle voice and video applications.

2. Requirements

The following requirements apply to codec recommendations.

  1. The encoding quality of the codec MUST be acceptable for use among XMPP users.
  2. The codec specification MUST clearly define packetization of data for sending over the Realtime Transport Protocol (RTP).
  3. The codec SHOULD be widely used in Internet or other systems, thus enabling interoperability between Jingle applications and non-Jingle applications.
  4. The codec SHOULD NOT be patent-encumbered or, at the least, SHOULD be available under royalty-free licenses.

3. Summary of Considered Codecs

3.1 Audio

3.1.1 Speex

The Speex codec is an open source / free software, patent-free, audio compression format for the encoding of human speech; it is developed and maintained by xiph.org. The following table summarizes the available information about Speex.

Table 1: Requirements Conformance of the Speex Codec

Quality RTP Packetization Availability Patent Encumbrance
Good quality; optimized for voice; can be used for wide-band audio. See RTP Payload Format for the Speex Codec [4]. Widely available and freely downloadable under a revised BSD license at <http://speex.org/>. Designed to be patent-free.

3.1.2 G.711

G.711 refers to the Pulse Code Modulation (PCM) codec defined in International Telecommunication Union (ITU) [5] recommendation G.711, which is widely used on the public switched telephone network (PSTN) and by many voice over Internet Protocol (VoIP) providers. There are two versions: the μ-law ("U-law") version is widely deployed in North America and in Japan and the A-law version is widely deployed in the rest of the world. The following table summarizes the available information about G.711.

Table 2: Requirements Conformance of the G.711 Codec

Quality RTP Packetization Availability Patent Encumbrance
Good quality; no wide-band mode. See RFC 5391 [6]. Widely supported in PSTN and VoIP systems. Developed in 1972; patents have expired.

3.2 Video

3.2.1 Theora

The Theora codec is an open source / free software, patent-free, video compression format developed and maintained by xiph.org. The following table summarizes the available information about Theora.

Table 3: Requirements Conformance of the Theora Codec

Quality RTP Packetization Availability Patent Encumbrance
Unknown. See RTP Payload Format for Theora Encoded Video [7]. Widely available and freely downloadable under a revised BSD license at <http://theora.org/>. Designed to be patent-free.

3.2.2 H.264

H.264 is a technology for video compression jointly designed by the ITU and the International Organization for Standardization (ISO) [8]. The following table summarizes the available information about Theora.

Table 4: Requirements Conformance of the H.264 Codec

Quality RTP Packetization Availability Patent Encumbrance
Unknown. See RFC 3984 [9]. Unknown. Patented.

4. Security Considerations

For security considerations, refer to XEP-0167.

5. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [10].

6. XMPP Registrar Considerations

This document requires no interaction with the XMPP Registrar [11].

7. Acknowledgements

Thanks to Olivier Crête, Dave Cridland, Justin Karneges, Tobias Markmann, Jeff Muller, Arc Riley, Kevin Smith, Justin Uberti, and Paul Witty for their feedback.


Appendices


Appendix A: Document Information

Series: XEP
Number: xxxx
Publisher: XMPP Standards Foundation
Status: ProtoXEP
Type: Standards Track
Version: 0.0.2
Last Updated: 2009-03-04
Approving Body: XMPP Council
Dependencies: XMPP Core, XEP-0167
Supersedes: None
Superseded By: None
Short Name: N/A


Appendix B: Author Information

Peter Saint-Andre

JabberID: stpeter@jabber.org
URI: https://stpeter.im/


Appendix C: Legal Notices

Copyright

This XMPP Extension Protocol is copyright (c) 1999 - 2009 by the XMPP Standards Foundation (XSF).

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. In no event shall the XMPP Standards Foundation or the authors of this Specification be liable for any claim, damages, or other liability, whether in an action of contract, tort, or otherwise, arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising out of the use or inability to use the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which may be found at <http://xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA).

Appendix D: 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 XMPP Standards 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 document 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.


Appendix E: Discussion Venue

There exists a special venue for discussion related to the technology described in this document: the <jingle@xmpp.org> mailing list.

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.

Errata may be sent to <editor@xmpp.org>.


Appendix F: Requirements Conformance

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


Appendix G: Notes

1. XEP-0167: Jingle RTP Sessions <http://xmpp.org/extensions/xep-0167.html>.

2. XEP-0166: Jingle <http://xmpp.org/extensions/xep-0166.html>.

3. RFC 3550: RTP: A Transport Protocol for Real-Time Applications <http://tools.ietf.org/html/rfc3550>.

4. RTP Payload Format for the Speex Codec <http://tools.ietf.org/html/draft-ietf-avt-rtp-speex>. Work in progress.

5. The International Telecommunication Union develops technical and operating standards (such as H.323) for international telecommunication services. For further information, see <http://www.itu.int/>.

6. RFC 5391: RTP Payload Format for ITU-T Recommendation G.711.1 <http://tools.ietf.org/html/rfc5391>.

7. RTP Payload Format for Theora Encoded Video <http://tools.ietf.org/html/draft-barbato-avt-rtp-theora>. Work in progress.

8. The International Organization for Standardization develops standards a wide variety of technical domains. For further information, see <http://www.iso.org/>.

9. RFC 3984: RTP Payload Format for H.264 Video <http://tools.ietf.org/html/rfc3984>.

10. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.

11. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <http://xmpp.org/registrar/>.


Appendix H: Revision History

Version 0.0.2 (2009-03-04)

Added more information about video codecs.

(psa)

Version 0.0.1 (2009-03-04)

First draft, copied from XEP-0167 with slight revisions and addition of requirements section.

(psa)

END