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.