Subject: [linux-audio-dev] Re: Moog VCF in SpiralSynthModular
From: Juhana Sadeharju (kouhia_AT_nic.funet.fi)
Date: Sat May 25 2002 - 14:34:16 EEST
>Any hint on how I can tune the Moog VCFs ?
Hello. Plot the freq. response and check how the parameter
changes change the response. I tuned one of moog filters
manually and it needed only slight modifications. I don't
remember well if there were problems in keeping the filter
peak contant during cut off freq. changes. If yes, it got
solved at the same effort.
I wrote a simple code for searching the peak of the frequency
response, but I never finished a part which would match
the parameter (via polynomials) to the frequency.
A look-up table could be a bad thing nowadays.
-*-
Were are all those mentioned filters available as your source code?
I checked filter.* of AMS package, but could not figure out if they
were there. Could you add documentation to your filter codes?
For the start, what filters they are, were you read about them,
and what are the parameters.
If the idea is to forbit the re-use of your code, a good start
is to not add any comments to the code.
If you mail me all your filter implementations, I will document
them myself.
-*-
It is actually a good idea to not implement LADSPA etc. plug-ins
in the first place, specially if one is not used to programming
those. I have written filters with simple API: void *filter_new(),
filter_init(), filter_set_parameter(), float filter_do(float) etc.
This way the programming is done fast. Any plug-in envelope can be
build over the filter in no time. Re-usability is high because
only the essential is in the filter code (no need for KDE for
compiling, for example). An optimized versions can be written later
by others if absolutely necessary.
Best regards,
Juhana
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