[theora] NHW Image codec - improvement of precision

Raphael Canut nhwcodec at gmail.com
Fri Sep 14 08:22:20 PDT 2012


Just a very quick message to let you know that I have a little improved my

About the PSNR and SSIM measurements, yes that's right that my codec has
worse results than JPEG, WebP,...
If I can try to justify it(...), my codec would have an additional "source
of error", penalizing these measurements, which is maybe that it increases,
a little, neatness of image (which also certainly includes a denoising...).

So to sum up very (very) quickly, JPEG and WebP would just decrease
neatness and my codec would decrease precision and increase neatness, but
just decreasing precision would be an error...

But I am not an expert, and do not hesitate to correct me if you think it
is necessary.I also totally agree that precision is more important than

Many thanks,

2012/7/25 Raphael Canut <nhwcodec at gmail.com>

> Hi again,
> I have improved precision of my codec (on the encoder and decoder).I have
> also improved the -h1 quality setting.-Source code and binaries at
> http://nhwcodec.blogspot.com/ -.
> I am still trying to improve precision of my codec, with keeping my
> low-complexity (fast) approach.
> I do not totally use the reference (and impressive) block prediction with
> different modes + residual coding scheme, but I just apply residual coding
> on the first order wavelet "image" (for example for a 512x512 image, I just
> code the errors on the 256x256 wavelet "high-resolution" part), hence the
> lack of precision.I try to compensate it with a little more neatness of the
> wavelet 5/3 filterbank, but that's right that precision seems visually more
> important.
> Any opinion on this approach or on the codec in general is very welcome.
> Many thanks again,
> Raphael
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