[pd] biquad~ yet again

[carmen]

On Mon, Nov 07, 2005 at 04:51:19PM -0500, david golightly wrote:
> Hey list,
> 
> I just did a search in the list-archive and, yes, I realize that there was 
> a dicussion on biquad~ back in April, but the thread referred to a link 
> that is now broken.  Suffice to say, it seems the programming of this 
> external could be a bit more user-friendly, targeted toward the people who 
> are likely to actually USE pd, not people with advanced degrees in math.  
> (If you fall into both categories, more power to ya).  If I could just get 
> some help here, I'd like:
> 
> f(x, a) = (ff1, ff2, ff3, fb1, fb2)
> where these are the biquad coefficients for x = notch frequency and a = 
> attenuation
> 
> While I understand how it's useful to have tools for building filters in 
> any DSP software, it's too bad this isn't also wrapped up as a more 
> straightforward notch filter. 

it is, see /externals/ggee/filters in CVS.. theres a helper object for most of the RBJ biquad types.. i also pasted his formules into a tk script, http://whats-your.name/pd/gui/filter.gif see /extensions/gui/ix/filter.wid. 


and no, i dont understand the math either, has somethign to do with rectangular-to-polar conversions i think (but for some reason at least in the commercial filter plugins which use biquad its never shown this way)..

> Or maybe I'm just being a wuss here.  I'm 
> sure there's someone out there who could implement this as an external.
> 
> Thanks,
> 
> David
> 
> 
> -  ---=---^---   -^-  -=- - - ^------ - -^---^-  -- --^^  --===
> 
> homepage:
> http://www.davidgolightly.net
> 
> 
> 
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