Re: [linux-audio-dev] Another Annoying "How Do I Get Started" Question

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Subject: Re: [linux-audio-dev] Another Annoying "How Do I Get Started" Question
From: Phil Burk (philburk_AT_softsynth.com)
Date: Thu Jul 12 2001 - 00:00:59 EEST

----- Original Message -----
From: "Greg Berchin" <76145.2455_AT_compuserve.com>
> >If you want to see this for yourself, take a GP implementation of a
> >lowpass filter and turn down the turnover frequency to a few Hz, unless
> >the programmer has been clever and sacrificed some quailty and speed
> >the cpu use will go up by 40% or so.

A jump in CPU usage may indicate that the FPU is getting numeric underflows
which can interrupt the CPU! This can easily happen in IIR filters where the
internal values decay exponentially closer and closer to zero. This can be
avoided by adding very small values, like alternating 1.0E-26 and -1.0E-26,
to the filter's internal values.

Phil Burk
JSyn,pForth,DSP,ASIC - http://www.softsynth.com
Portable Audio I/O - http://www.portaudio.com
Interaction Server - http://www.transjam.com

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