[vorbis-dev] here's the test case, possible solution

[Segher Boessenkool]

Hello all,

Finally I succeeded in uploading the test case I promised.
It's at http://home.wanadoo.nl/segher/test1.wav.bz2 (It is a wav,
the headers are a bit inconsistent, but encoder_example will be
ok with it, as it just skips them).

I did some thinking, and a possible solution is decreasing the
ATH_Bark_dB[] for the lower frequencies. As the comments say,
it's not really an ATH, but this table is limiting the maximum
quantizer step (or something like that, I still don't fully
understand the psymodel). I overdid it a bit (changing everything
to zero, until the first zero in the original), and it helps a lot.
Maybe this is the right spot for the change, in which case it needs
to be tuned, or otherwise, it can help hunt down the problem. Btw,
all these zeroes is too much; high freqs suffer.

Maybe this table shouldn't be static, but instead calculated every
frame. I'll do some more testing.

Oh, vorbis is not doing anything to compensate for mdct aliasing
effects, or am I missing something? I'll try to hack some in as
well.

Dagdag,

Segher

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