[vorbis-dev] Trivial 12% performance gain in encoding

[Timothy J. Wood]

  (well, YMMV, but it got me 12% on Mac OS X Public Beta on my test case).

In vorbis/lib/scales.h, add the following after fromdB()

#define sqrt_fromdB(x) (exp((x)*.11512925*0.5))

In vorbis/lib/psy.c at the bottom of bark_noise(), do:

<      noise[i]=sqrt(fromdB(v));

>      noise[i]=sqrt_fromdB(v);

  This avoids the sqrt() call entirely by just doing it as part of the exp().

  (I'd send a patch, but my local source tree is severely mauled with timing instrumentation code :)

-tim

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