[PD] algorithms for drawing filter response curves

[Hans-Christoph Steiner]

On Feb 7, 2011, at 12:43 PM, Hans-Christoph Steiner wrote:

>
> On Feb 7, 2011, at 6:12 AM, volker böhm wrote:
>
>>
>> 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
>>
>> <queryBiquad.js>
>
> Thanks, that helped.  Here's what I have so far: I got the mouse  
> interaction almost completed, now I'm just starting the plotting  
> part, which has a ways to go.
>
> .hc
> <filterview.tcl>


I also just pushed my git to a public repo:

https://github.com/pd-projects/filterview

.hc


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