[PD] algorithms for drawing filter response curves

[cyrille henry]

Le 07/02/2011 12:12, volker böhm a écrit :
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> On 07.02.2011, at 00:12, Hans-Christoph Steiner wrote:
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>> I've started to write a GUI for generating biquad coefficients (something like Max/MSP's [filtergraph~]).  I've gotten the GUI interaction working well, now I'm looking for the algorithms for generating a plot of the frequency response of a given set of biquad coefficents?  It'll end up being Tcl, but I can easily read C, Csound, Java, Perl, Python, etc.
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>> .hc
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> i've been using the attached js file to query amplitude and phase response of biquad coeffs,
> where the coeffs are expected to be of the form: y[n] = a0 * x[n] + a1 * x[n-1] + a2 * x[n-2] - b1 * y[n-1] - b2 * y[n-2] (like in maxmsp).
> so, you'd have to rearrage the coeffs and turn the sign of the fb coeffs to make it work with the pd biquad~.

or use bq~  from nusmuk-audio lib.

cyrille

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