Signaling Media Decoding Dependency in the Session Description Protocol (SDP)
RFC 5583
Network Working Group T. Schierl
Request for Comments: 5583 Fraunhofer HHI
Category: Standards Track S. Wenger
Independent
July 2009
Signaling Media Decoding Dependency in
the Session Description Protocol (SDP)
Abstract
This memo defines semantics that allow for signaling the decoding
dependency of different media descriptions with the same media type
in the Session Description Protocol (SDP). This is required, for
example, if media data is separated and transported in different
network streams as a result of the use of a layered or multiple
descriptive media coding process.
A new grouping type "DDP" -- decoding dependency -- is defined, to be
used in conjunction with RFC 3388 entitled "Grouping of Media Lines
in the Session Description Protocol". In addition, an attribute is
specified describing the relationship of the media streams in a "DDP"
group indicated by media identification attribute(s) and media format
description(s).
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
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Schierl & Wenger Standards Track [Page 1]
RFC 5583 Signaling Media Decoding Dependency in SDP July 2009
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
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Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................4
3. Definitions .....................................................4
4. Motivation, Use Cases, and Architecture .........................5
4.1. Motivation .................................................5
4.2. Use Cases ..................................................7
5. Signaling Media Dependencies ....................................7
5.1. Design Principles ..........................................7
5.2. Semantics ..................................................8
5.2.1. SDP Grouping Semantics for Decoding Dependency ......8
5.2.2. "depend" Attribute for Dependency Signaling
per Media-Stream ....................................8
6. Usage of New Semantics in SDP ..................................10
6.1. Usage with the SDP Offer/Answer Model .....................10
6.2. Declarative usage .........................................12
6.3. Usage with AVP and SAVP RTP Profiles ......................12
6.4. Usage with Capability Negotiation .........................12
6.5. Examples ..................................................12
7. Security Considerations ........................................15
8. IANA Considerations ............................................15
9. Informative Note on "The SDP (Session Description Protocol)
Grouping Framework" ............................................16
10. References ....................................................16
10.1. Normative References .....................................16
10.2. Informative References ...................................17
Appendix A. Acknowledgements .....................................18
Schierl & Wenger Standards Track [Page 2]
RFC 5583 Signaling Media Decoding Dependency in SDP July 2009
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