RTP Payload Format for Vorbis Encoded Audio
RFC 5215

Approval announcement
Draft of message to be sent after approval:

From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Cc: Internet Architecture Board <iab@iab.org>,
    RFC Editor <rfc-editor@rfc-editor.org>, 
    avt mailing list <avt@ietf.org>, 
    avt chair <avt-chairs@tools.ietf.org>
Subject: Protocol Action: 'RTP Payload Format for Vorbis Encoded 
         Audio' to Proposed Standard 

The IESG has approved the following document:

- 'RTP Payload Format for Vorbis Encoded Audio '
   <draft-ietf-avt-rtp-vorbis-10.txt> as a Proposed Standard

This document is the product of the Audio/Video Transport Working Group. 

The IESG contact persons are Cullen Jennings and Jon Peterson.

A URL of this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-vorbis-10.txt

Technical Summary
This document describes an RTP payload format for transporting  Vorbis
encoded audio. It details the RTP encapsulation mechanism for raw
Vorbis data and details the delivery mechanisms for the decoder
probability model, referred to as a codebook and other setup
information.

Also included within this memo are media type registrations, and the
details necessary for the use of Vorbis with the Session Description
Protocol (SDP).


Working Group Summary
The RTP payload format for Vorbis has been under discussion since the 
50th IETF meeting and has changed author several times (which has 
delayed its progress). The main technical issue has been transport of 
configuration headers: Vorbis doesn't use statically configured code 
books, and must receive a configuration header containing appropriate 
code books for a stream before it can begin decoding. This is 
problematic for RTP sessions using unreliable transports with limited 
packet size, and required definition of both in-band and out-of-band 
access methods for configuration headers, to ensure the configured 
data can be retrieved.

Document Quality
There are a number of implementations.

The media type review request was posted 11 June 2007. During the 
media type review, Bjoern Hoehrmann and Chris Lilley expressed 
concern that this draft registers the audio/vorbis media type for use 
only with RTP. We believe this concern is misplaced, since Vorbis 
data must be framed (the application/ogg container provides the 
framing for non-RTP use) and the registration of an RTP-only media 
type is consistent with current practice, as documented in RFC 4855.


Personnel
Colin Perkins is the document shepherd. Cullen Jennings is a 
responsible area director.