[theora-dev] A/V sync in Theora

David Kuehling dvdkhlng at gmx.de
Fri Jun 13 11:19:34 PDT 2003

> Theora will work just as well as AVI.  There are no arbitrary
> timestamps in AVI or MPEG; there are frame numbers and a global
> framerate (MPEG doesn't even have the option of a fractional framerate
> other than drop frame = 23.997). 

It is well known that AVI is an old and deficient format.  Does it make
sense to justify Ogg/Theora design desisions with missing features in

I accept that weird things need to be done, to get an AVI file sync
correctly.  After all AVI is wide-spread.  People just learned how to
work around some of AVIs limitation.  If I can choose between
compatability and innovation, I choose compatability in this case.

But who will choose Ogg?  The whole standards is contradicting.  If it's
a format intended for streaming, why would people want to adjust the
header fields, after the stream was created?  There's no interface for
such kind of operation in libtheora.  Everything that could be done
would be considered an ugly hack.  Keep in mind that resampling audio
without too much loss of quality is not a simple operation.

You've placed a heavy burden on the shoulders of developers willing to
integrate Theora with their applications.  The A/V sync issue is not the
only one.  Other problems include missing logical separation of Ogg
container and Theora codec and underspecification of Ogg for multimedia
content, introducing diverse methods (hacks?) for Ogg contained video
(ie .ogm) which are already in use.

In spite of all my negative comments on the topics, I still acknoledge
the potential of Ogg/Theora.  But it seems IMHO more limited than it
would be necessary. 


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