[theora-dev] Re: What sort of math i required?
christian at matroska.org
Sat Dec 13 04:45:04 PST 2003
Martin Jeppesen wrote:
>>even need to understand how this works. The transform in use is fixed,
>>and our VP3 compatibility goal will not let us change it. You can just
>>treat it as a black box.
> What about in the future? Must later versions of Theora always be backward
> compatible with VP3? Or will Theora be renamed when it is not compatible
> with VP3 anymore doe to competition from other codecs?
IMHO it has to leave the boundaries of VP3 pretty quickly, else it will
have huge problems to keep pace with other codecs around, and the fact
that its most likely patent free and also free to use wont help it too
much to get widespread acceptance, again IMHO.
With respect to the rest of the discussion about why most video
compression technologies are still based on Huffman :
There is CorePNG ( http://corecodec.org/projects/corepng ) as a working
VfW ( VCM ) codec now, a project that will simply compress single images
using libPNG, and even allows P frame encoding ( if the codec finds out
its better to encode the difference to the last frame instaed of the
whole frame, it will insert a P frame ). Its a lossless codec and
compresses pretty well, especially anime fans have been dancing circles
But : its HELL slow ! PNG, AFAIK, is based on either zlib or bzip2, cant
remember, and the compression speed during encoding is about 20 - 30x
slower than what modern, Huffman based codecs can achieve. Decoding is a
bit better, but still much too slow, on a modern AMD or P4 you can watch
movies with 320 x 240, and thats it, with 100% CPU of course.
About new video compression algorithms :
WARP ( http://corecodec.org/projects/warp ) was abandoned before it
really worked, but the idea behind it is quite new :
The codec will load either 64, 128 or 256 frames into RAM and then
perform a sepcial wavelet transformation on each pixel, better about the
changes of each pixel over time. The transformation, according to the
author, was inspired by bio-mechanical causalities.
This codec is not frame based at all, and this way leaves the concept
every other codecs i ever heard of. It seems to use one aspect of
Tarkin, which should perform compression over time also IIRC.
The author, Toby 'GLDM' Houdon, gave up after struggling for weeks with
the VfW interface to make a valid VCM codec for use in Virtualdub.
Knowing VfW main restriction, the 'one frame in - one frame out'
scenario, you might have guessed why ;) ....
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