[theora] NHW Image codec - Compression Performance

Raphael Canut nhwcodec at gmail.com
Wed Aug 28 06:52:46 PDT 2013


Definitely not any (constructive) comments on the NHW Image codec?

According to my tests, it can compare good with reference codecs like
x264 intra and WebP.

Yes, the codec is still experimental and is optimized for visual
(subjective) evaluation, not PSNR.Its main feature is again that it would
have a little more neatness/sharpness and a little less precision (residual
coding is applied on "sub" wavelet images or orders and I take advantage
then of the neatness the wavelet 5/3 filterbank can have).The entropy
coding schemes for each parts: wavelet coefficients, residuals, are also
near optimal as with the best (binarization +) context modeling +
arithmetic coders, except for the DC parts where the compression scheme is
not optimal, can win 0.7Ko per file in average with the best arithmetic

The NHW codec is also (really) faster in return, -it also uses a "direct"
discrete wavelet 5/3 transform which is very fast, also associated with a
fast segmentation algorithm-.

So I would have been really interested to have some opinion about the
performance and limitations of the NHW algorithm? Any comment from the Xiph
core members on the NHW algorithm? If you could find time, do you plan to
study the NHW algorithm deeper, or not? -I would also understand that you
could not find time and/or could not go further with it, would also help me
to know if I put it on pause for now-.

Many thanks again,
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