On Thu, 30 May 2019 at 16:15, Oleg Nesterov <o...@redhat.com> wrote: > On 05/30, Dario Sanfilippo wrote: > > > > > 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 ? > > > > > > > I must be doing something wrong with fi.tf2f but I get no response when > > testing it like this: > > > > process = f2.lpbi(1000, au.dirac), > > > > (au.dirac : fi.tf2s(0,0,1, 1/.707, 1, 2*ma.PI/ma.SR * 1000)), > ^^^^^^ > > typo. please try > > fi.tf2s(0,0,1, 1/.707, 1, 2*ma.PI * 1000) >
Yes, the three filters are identical. > > > (au.dirac : fi.resonlp(1000, .707, 1)); > > btw, you could write > > process = au.dirac <: > f2.lpbi(1000), > fi.tf2s(0,0,1, 1/.707, 1, 2*ma.PI * 1000), > i.resonlp(1000, .707, 1); > Sure :) > > this looks more simple. and au.dirac is os.impulse ;) > True that but Dirac sounds cool ;) But really, perhaps it could be moved to maths.lib rather in staying in the oscillators? > > > On the other hand, the impulse response of f2.lpbi and fi.resonlp are > > identical: > > I think tf2s() should have the same response if you remove "/ma.SR"... > > > Perhaps the zero-delay feedback design in Zavalishin is not in the Faust > > filters and it could be integrated. He claims that such filters, even at > > orders higher than 1 or 2, are more stable in time-variant configurations > > than the others. > > If you want a second order zdf please consider the code below. I did some > naive non-scientific tests and to me it really works better than even > tf2snp > when modulated. > Great, thanks for that. I'll check it out. I've achieved great sounds just by modulating the raw feedback coefficient of a normalised (a0 = 1-|b1|) one-pole system using audio signals, both directly like that or by passing the modulating signal through some nonlinear function. I was meaning to also implement the ZDF 4-pole ladder. Will Pirkle resolved it into this diagram: http://www.willpirkle.com/Downloads/AN-4VirtualAnalogFilters.2.0.pdf. D > > Oleg. > > > ------------------------------------------------------------------------------- > // http://www.cytomic.com/files/dsp/SvfLinearTrapOptimised2.pdf > import("stdfaust.lib"); > > svf = environment { > svf(T,F,Q,G) = tick ~ (_,_) : !,!,_,_,_ : si.dot(3, mix) > with { > tick(ic1eq, ic2eq, v0) = > 2*v1 - ic1eq, > 2*v2 - ic2eq, > v0, v1, v2 > with { > v1 = ic1eq + g *(v0-ic2eq) : /(1 + g*(g+k)); > 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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