[vorbis-dev] Different floor, quality improvement

Segher Boessenkool segher at wanadoo.nl
Fri Dec 22 06:43:00 PST 2000



Hello all,

Please try this "patch". It changes the way the noise floor is used
for quantization in a not-so-subtle way.

At the very end of _vp_compute_mask, add the lines:

        for(i=0;i<n;i++)
                flr[i]=.01f*sqrt(flr[i]);

The .01 is there to ensure the current codebooks will work. We will
really need different, newly-trained codebooks with this change; then
the .01 can probably go away, though it won't hurt (I think).

Be warned that the bitstreams increase roughly 50% in size with this
change, so you should compare 128kbps new with 192kbps old etc.

Please try this on tracks you find difficult to encode, especially
very tonal stuff,

I'll explain later what this really does, it's a bunch of math so
I'll make a TeX file of it,

Cheers && happy coding,

Segher

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