On 05/29, Dario Sanfilippo wrote:
>
> Dear list,
>
> it's only been a couple of months into working with Faust but I've written
> some stuff and they are now available on Github:
> https://github.com/dariosanfilippo/faust.
interesting... Thanks for sharing!
So far I quickly glanced at filters2.lib, and I am not sure I understand the
purpose of biquad filters... Lets look at biquad lowpass:
lpbi(cf, in) = biquad(a0, a1, a2, b1, b2, in)
with {
cf1 = st.clip(5, m2.ny-5, cf);
q1 = .707;
alpha = sin(m2.w(cf1))/(2*q1);
norm = 1+alpha;
a0 = ((1-cos(m2.w(cf1)))/2)/norm;
a1 = 1-cos(m2.w(cf1))/norm;
a2 = ((1-cos(m2.w(cf1)))/2)/norm;
b1 = cos(m2.w(cf1))*-2/norm;
b2 = (1-alpha)/norm;
};
Firstly, "a1" doesn't look right. It should be
a1 = (1 - cos(...)) / norm;
not
a1 = 1 - cos(...) / norm;
And. It seems that the implementation above is "equal" to
lpbi(cf) = fi.tf2s(0,0,1, 1/.707, 1, 2*ma.PI/ma.SR * cf);
?
or simply
lpbi(cf) = resonlp(cf, .707, 1);
no ?
Oleg.
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