[Theora-dev] ogg and keyframes

Ralph Giles giles at xiph.org
Tue Sep 28 10:24:26 PDT 2004

On Tue, Sep 28, 2004 at 10:12:27AM +0200, Wim Taymans wrote:

> I verified and it was my own fault. libogg is doing the right thing, I
> wasn't. Well, it's fixed now, thanks.

Whew! I think our userbase might have fainted if we'd done a third 
libogg release in 3 weeks. :-D

> Ah, fine. Better than checking 'the second most significant bit of the
> first data byte'. Can you also add some method to check if it's a header
> packet or a data packet?

There's theora_packet_isheader() too. It only checks the initial bit 
though, so it's no good for bitstream identification. It seems like it 
would also be nice to have something for that but lighter-weight than 
theora_decode_header(). The problem is that we have room in the spec for 
future optional additional headers that we don't want to include the 
'theora' magic, so checking the first bit is the only reliable approach.
I'm open to suggestions here. Perhaps theora_decode_header() could just
accept NULL for the info and comment structs.

> When we find a new camera (donations welcome :)) it will be back up with
> that bug finally fixed. 

Great! What method did you end up using? Thomas and I talked about this 
a bit on #theora but neither came up with anything that was an obvious 


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