[theora-dev] What sort of math i required?

Christoph Lampert chl at math.uni-bonn.de
Thu Dec 11 05:05:55 PST 2003

On Thu, 11 Dec 2003, Martin Jeppesen wrote:
> Does there excist a wavelet codec today?
> > Wavelets could almost certainly provide better compression than the
> > vanilla DCT Theora uses, but also carry an increased computational cost.
> > They'd also break backwards compatibility.
> Interesting indeed! It seams to me, that wavelets are the state of the
> art.


the (main) problem with wavelet based codecs is that wavelets aren't
localized in the image space, so you cannot just use the very 
successful block-based motion estimation as for all DCT-based codecs. 
For JPEG2000 that wasn't a problem, because JPEG is for still images only,
but for video, it's bad. 
There are some workarounds, IIRC, grouping pictures together and using 3D
wavelets for ME, but it seems that's not going to hit the market until
next generation codecs (or, depending on what you consider the
current) the one after next. 


P.S. I'm a mathematician, and seen from that position, implementation 
of video encoding/decoding needs hardly any maths at all, because
in the maths part, you usually just follow some specs. Creation of a video
encoding standard is more challanging, but few people do that. 
But both needs lots of engineers' skills, like making dirty compromises,
based on "heuristics", just for speedup etc. ;-) 

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