Subject: Re: [linux-audio-dev] wcnt linear filters
From: Tim Goetze (tim_AT_quitte.de)
Date: Tue Feb 03 2004 - 15:21:53 EET
James W. Morris wrote:
>Is it possible to code resonant linear filters which use an array as I do,
>or will I have to go on a higher mathamatics course and get my head round
>fancy bi-carbonated equations?
resonant filters use recursion; the algorithm sometimes is coded as
'take this input sample and give me an output sample' for readability
but is easily adapted to arrays. the maths behind them are intricate
(to me at least), but you don't need too firm an understanding of the
theory to actually use them. you'll find code examples for the
algorithm and the computation of the recursion coefficients in almost
every major audio synthesis/processing package or at musicdsp.org .
steve's ladspa set has a very nice state-variable filter (svf) which
lends itself well for resonance and reasonably quick parameter
changes. you may want to try it first before resorting to coding your
own.
tim
ps: the svf sounds better to me with the 'very slight waveshape for
extra stability' removed.
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