[PD] algorithms for drawing filter response curves

Hans-Christoph Steiner hans at at.or.at
Mon Feb 7 20:50:25 CET 2011


On Feb 7, 2011, at 2:39 PM, cyrille henry wrote:

>
>
> Le 07/02/2011 18:40, Hans-Christoph Steiner a écrit :
>>
>> On Feb 7, 2011, at 6:36 AM, cyrille henry wrote:
>>
>>>
>>>
>>> Le 07/02/2011 12:12, volker böhm a écrit :
>>>>
>>>> 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~.
>>>
>>> or use bq~ from nusmuk-audio lib.
>>
>>
>> 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?


Its what [biquad~] uses, so other objects expect that, like the filter  
calcs in ggee.  Plus this new filterview object I'm working on would  
output a list, and using a list means making just a single connection  
rather than 5.

.hc


----------------------------------------------------------------------------

I spent 33 years and four months in active military service and during  
that period I spent most of my time as a high class muscle man for Big  
Business, for Wall Street and the bankers.      - General Smedley Butler





More information about the Pd-list mailing list