Vorbis dev - Nov 2000 - Trivial 12% performance gain in encoding

(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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on 11/26/2000 13:49, Timothy J. Wood at tjw@omnigroup.com wrote:
> (well, YMMV, but it got me 12% on Mac OS X Public Beta on my test case).
Hi Tim. I see you're working on Vorbis & Mac OS X again. I'm that
"other
guy" who tweaked your patches a bit. I noticed a few people grab them from
the web site, but as you noted, I couldn't get anyone to commit them.

Let me know if there's anything you'd like me to do -- even if it's
just do
a test build on another OS X system. Seems like you're making some pretty
terrific progress.

-- Richard

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| Richard Kiss            |
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