[ogg-dev] OGG Vorbis I

Ralph Giles giles at xiph.org
Fri Aug 24 12:03:55 PDT 2007

On Thu, Apr 26, 2007 at 04:17:35PM +0800, EmilyGao at viatech.com.cn wrote:

> I don't quite understand why vorbis I spec dictates that "Ogg stream
> must be unmultiplexed".
> Ogg can include both audio and video, that means one Ogg stream can both
> have vorbis and theora multiplexed. How vorbis I spec say could not
> allowed?

This is essentially a specification bug. The reference implementation 
(libvorbisfile versions prior to version 1.2.0) did not handle 
multiplexed streams. Rather than fix the reference implementation,
we imposed the same limitation in the Ogg Vorbis mapping profile.

Not having to support multiplexed streams does simplify (or at least 
improve the performance of) seeking, so there are some advantages for 

Nevertheless, we certainly recommend that decoders support general 
multiplexed streams and at least play the first occurring audio stream
they recognize.

Hope that helps,

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