On 08/22, Julius Smith wrote:
>
> Hey, thanks for posting. I made a faust2octave test program
> (attached). Everything looks good to me, assuming I guessed all the
> names right.
Great, thanks.
do you think it can live in filters.lib? If yes, then I think
"svf = environment" makes sense, so that you can use it like
process = fi.svf.lp(f,q);
See the code below. Note that this version differs a little bit, it uses
the second version described in that paper (see "algorithm using v1 to
compute v2").
iow
v2 = ic2eq + g*v1; (2)
instead of
v2 = ic2eq + a2*ic1eq + a3*v3; (1)
I think it makes more sense for faust because it is simpler, and because
quite possibly faust will turn (2) into (1) after aterm/mterm normalization
anyway.
I even verified that "all pass" generates the same code with this change.
Oleg.
-------------------------------------------------------------------------------
svf = environment {
svf(T,F,Q,G) = tick ~ (_,_) : !,!,_,_,_ : si.dot(3, mix)
with {
a1 = 1/(1 + g*(g + k));
a2 = g*a1;
tick(ic1eq, ic2eq, v0) =
2*v1 - ic1eq,
2*v2 - ic2eq,
v0, v1, v2
with {
v1 = a1*ic1eq + a2*(v0 - ic2eq);
v2 = ic2eq + g*v1;
};
A = pow(10.0, G / 40.0);
g = tan(F * ma.PI / ma.SR) : case {
(7) => /(sqrt(A));
(8) => *(sqrt(A));
(t) => _;
} (T);
k = case {
(6) => 1/(Q*A);
(t) => 1/Q;
} (T);
mix = case {
(0) => 0, 0, 1;
(1) => 0, 1, 0;
(2) => 1, -k, -1;
(3) => 1, -k, 0;
(4) => 1, -k, -2;
(5) => 1, -2*k, 0;
(6) => 1, k*(A*A - 1), 0;
(7) => 1, k*(A-1), A*A - 1;
(8) => A*A, k*(1-A)*A, 1-A*A;
} (T);
};
lp(f,q) = svf(0, f,q,0);
bp(f,q) = svf(1, f,q,0);
hp(f,q) = svf(2, f,q,0);
notch(f,q) = svf(3, f,q,0);
peak(f,q) = svf(4, f,q,0);
ap(f,q) = svf(5, f,q,0);
bell(f,q,g) = svf(6, f,q,g);
ls(f,q,g) = svf(7, f,q,g);
hs(f,q,g) = svf(8, f,q,g);
};
------------------------------------------------------------------------------
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