[theora-dev] A/V sync in Theora

Sam Leitch sam.l at usask.ca
Thu Jun 12 12:32:30 PDT 2003

My apologies for the double post. I was just looking over the Ogg 
standard (RFC 3533).

granule_position is not an absolute, which means timing information must 
be stored and processed at a higher level.

That begs the question. Who is responsible for synchronization? Ogg, 
Vorbis/Theora, or the player software.

Vorbis and Theora are independent streams, which require timing 
information(arguably), but no synchronization.
The player requires synchronization, but requires feedback on if it's 
still on track (which is what granule-position is designed for)
The most logical method would be to include common 
timing/synchronization in Ogg encapsulation. That's the job of the 
format, is it not?

This is more a question for the entire Xiph crew, not Theora alone, but 
I couldn't find the correct place to present it.

Sam Leitch wrote:

> Why does Ogg\Theora require constant frame rate? From what understand 
> lurking for a while, there's no reason to.
> Why not encode absolute time in granulepos (or likewise 
> keyframe/offset time)?
> This could really give theora an advantage over the competition. (I'm 
> thinking animation)

Sam Leitch
* * * * * * * * * * * * * * *
Graduate Student
Department of Physics and Engineering Physics
University of Saskatchewan
* * * * * * * * * * * * * * *

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