[PD] algorithms for drawing filter response curves

[volker böhm]

On 07.02.2011, at 00:12, Hans-Christoph Steiner wrote:

> 
> 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.
> 
> .hc

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~.

vb

-------------- next part --------------
A non-text attachment was scrubbed...
Name: queryBiquad.js
Type: application/x-javascript
Size: 1354 bytes
Desc: not available
URL: <http://lists.puredata.info/pipermail/pd-list/attachments/20110207/8b45784a/attachment.bin>
-------------- next part --------------