[theora] Indexing Ogg files for faster seeking
chris at pearce.org.nz
Wed Sep 23 15:52:26 PDT 2009
On 24/09/09 05:49, Conrad Parker wrote:
> OTOH, one thing I'm worried about is the cost of adding the index to
> the beginning of a long file, which then requires rewriting the entire
If you can't bear that cost for your server side seeking solution, you
could store the index in a separate file, and use that to speed up your
client side seeking. And/or you could splice the index into the
bitstream when you serve it.
The index really needs to be in the Ogg header packets at the start of
the media for it to be useful for web video.
We discussed on #theora about indexing at encode time. You can reserve
space for n indexed keyframes in the headers packets, and once you're
done encoding you can choose n keyframes to put into the index. If you
know the duration of the media in advance, you can guess how many
keyframes you'll have and allocate space accordingly. My indexer
currently only indexes keyframes which are more than 500ms after the
previously indexed keyframe anyway.
> Could you transfer your spec to the Xiph wiki? we also need to discuss
> implementation for Dirac etc.
Any content type for which seeking to and playing from a target time
requires you to decode forwards from a pre-determinable Ogg page can be
All the best,
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