codec optimization

[salsaman at xs4all.nl]

John (J5) Palmieri wrote:

>On Sun, 2007-02-25 at 14:20 -0500, Albert Cahalan wrote:
>
>>John (J5) Palmieri writes:
>>
>>>Ogg Theora for video and Ogg Vorbis for audio are the
>>>main codecs.  Code can be found at http://xiph.org/.
>>
>>Dan Williams writes:
>>
>>>It's likely Ogg Theora (video) and Ogg Vorbis (audio).
>>>They are in need to some optimization help, so anything
>>>you could provide would be great.
>>
>>Ogg (audio) is a surviver. That Theora thing was stillborn,
>>which is good because you can't decently share a file
>>extension between different media types.
>
>
>Ogg is just the container format. Can you elaborate on why Theora is
>"stillborn"?  The code is known not to be optimized so if it is running
>slow on the XO it may just take someone looking into it.
>
>>The fast low-compression choice is MJPEG. Perhaps
>>the XO can even create this in real-time.
>
>
>Are there any legality issues with using mjpeg?
>
>>For heavy compression, we have Snow and Dirac.
>>Both of these use wavelet compression and thus,
>>if we hurry, have a tiny chance to become the next
>>common real-world standard. (we're up against both
>>the ISO's "reasonable licensing" gang and Microsoft)
>
>
>It is my impression that Dirac was a high quality archival format which
>is not suitable for real time streaming playback.  I have no knowledge
>of Snow.
>
>

Dirac is not yet ready for production use. We (LiVES users) did some
comparisons last year, and there were very visible artifacts in the dirac
encoding. Snow is better, but still not really usable. High quality theora
is still the way to go for now for free codecs.

Does the OLPC use mmx ? If so, there is a theora-mmx extension, which is
several times faster than the standard theora encoder.

Also, matroska is a better container than ogg. It uses the same format as
ogg, but is slightly more compressed, which can result in ~10% smaller
files.

Gabriel.
http://lives.sourceforge.net