[ogg-dev] Header packet multiplicity

Ralph Giles giles at xiph.org
Wed Feb 13 10:09:15 PST 2008

On 13-Feb-08, at 3:40 AM, ogg.k.ogg.k at googlemail.com wrote:

> However, I was concerned about the RTP streaming case, where packets
> may be lost, and the "other" container case, where they have to be
> concatenated (and thus one needs a way to walk past them easily).
> I reckon I'll just add a "header length" to headers past the first  
> one, and
> maybe on data packets as well. I'm not clear at all on what would  
> happen
> when not in Ogg, I need to think more about this case.

There are a usually lot more data packets than header packets, so  
having an internal length there hurts your bitrate a lot more. Of  
course, it may not be significant for an uncompressed text codec.

With codecs using the 'count of decodable samples' rule to calculate  
their granulepos, the headers can often be distinguished by having a  
granulepos that maps to time zero. I know that works with theora  
(after the change in beta1).

Conrad, does this work for the other codecs as well? I vaguely  
remember libvorbis putting -1 on the header packets instead of 0.


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