[private] Re: [theora] support for theora in xine

Ralph Giles giles at xiph.org
Tue Apr 22 13:07:57 PDT 2003

On Tuesday, April 22, 2003, at 05:12 pm, Andreas Heinchen wrote:

> Are there other easy possibilities to see if the opp_packet is an
> syncpoint? If not, could future versions of theora set the 
> op.granulepos
> for every keyframe? That would make seeking a lot easier.

There's a hack with the granulepos to facilitate streaming: the 
lower-order bits are always zero. The field is treated something like a 
fixed-point number, with the fractional part incremented on P frames 
and the integral part incremented only for key frames. Where exactly 
the radix is is encoded as part of the packet header (the log of 
keyframe_frequency_force) so you'll still have to pass that up from the 

Hope that helps,

P.S. I've cc'd theora-dev, which is a more appropriate venue for this 

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