[PD] biquad~ formula

[Miller Puckette]

hi Nicolas and all,

I believe it's:

ff1 = c1
ff2 = c2
ff3 = c3
fb1 = -c4
fb5 = -c5

cheers
Miller

On Thu, Jan 03, 2002 at 05:16:46AM +0100, Nicolas Lhommet wrote:
> Hello,
> biquad~ formula in the PD help-patch is :
> y(n) = ff1 * w(n) + ff2 * w(n-1) + ff3 * w(n-2)
> w(n) = x(n) + fb1 * w(n-1) + fb2 * w(n-2)
> 
> biquad~ formula in Jmax is :
> y[n] = c1*x[n] + c2*x[n-1] + c3*x[n-2] - c4*y[n-1] - c5*y[n-2]
> 
> What is the mathematical relation between these two formulae (so between Pd
> and Jmax coefficients) ?
> 
> I found a nice document that explains how to get the right coeffs for
> different filters :
> http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt
> and I'm not sure how to use it with PD biquad~ object.
> 
> nicolas
> 
> 
> 
>