[PD] algorithms for drawing filter response curves

[cyrille henry]

Le 07/02/2011 18:40, Hans-Christoph Steiner a écrit :
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> On Feb 7, 2011, at 6:36 AM, cyrille henry wrote:
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>> 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~.
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>> or use bq~ from nusmuk-audio lib.
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> I like that [bq~] has audio inputs,
yep, that's very useful.
> but can you send a list of them to the first inlet, like [biquad~]?
no, you need an unpack f f f f f...
i think to add this functionality should not be to hard, but do you really need it?

C

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