[theora-dev] bitstream versioning

Ralph Giles giles at xiph.org
Sun Jun 8 15:17:55 PDT 2003

On Sunday, June 8, 2003, at 09:10 pm, Dan Miller wrote:

> as per yesterday's discussion at #theora --

Another thing derf and I discussed is adding additional (optional) 
header packets. Monty used a nice scheme where header packets being 
with a 1 bit, and data begin with a 0. Thus it would be easy to have 
the codec ignore unexpected headers.

The hard part with this idea is the api design. Currently the client 
knows it has to pass exactly three packets before decoding can start. 
Furthermore, it is a very nice simplicity of the theora codec that it's 
one decoded frame per packet for the rest of the stream.

So we could change that and make decode_packetin() ignore extra 
headers. The best we could come up with at the time was that the client 
had to peek at the first byte of the packets and terminate the header 
decode loop on the first data packet. Given that we're planning to 
write an 'OggFile' convenience layer to handle the demux and and 
decode, either of those might be ok if we want to go that direction.


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