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/*
Copyright (C) 2000 Jeff Tranter
tranter@pobox.com
(C) 1999 Stefan Westerfeld
stefan@space.twc.de
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1307, USA.
*/
#include "artsmodulessynth.h"
#include "stdsynthmodule.h"
using namespace Arts;
/*
Try this. It's a really nice 4pole. Very Moog like.
in[x] and out[x] are member variables, init to 0.0
the controls:
fc = cutoff, nearly linear [0,1] -> [0, fs/2]
res = resonance [0, 4] -> [no resonance, self-oscillation]
*/
class Synth_MOOG_VCF_impl : virtual public Synth_MOOG_VCF_skel,
virtual public StdSynthModule
{
protected:
float _frequency, _resonance;
double freqcorrect;
double in1, in2, in3, in4;
double out1, out2, out3, out4;
public:
float frequency() { return _frequency; }
void frequency(float newFrequency) { _frequency = newFrequency; }
float resonance() { return _resonance; }
void resonance(float newResonance) { _resonance = newResonance; }
void streamInit()
{
in1 = in2 = in3 = in4 = out1 = out2 = out3 = out4 = 0.0;
}
void calculateBlock(unsigned long samples)
{
freqcorrect = 1.16 / (double)(samplingRate / 2);
for (unsigned int i=0; i < samples; i++)
{
double input = invalue[i];
double fc = _frequency;
double res = _resonance;
double f = fc * freqcorrect;
double fb = res * (1.0 - 0.15 * f * f);
input -= out4 * fb;
input *= 0.35013 * (f * f) * (f * f);
out1 = input + 0.3 * in1 + (1 - f) * out1; // Pole 1
in1 = input;
out2 = out1 + 0.3 * in2 + (1 - f) * out2; // Pole 2
in2 = out1;
out3 = out2 + 0.3 * in3 + (1 - f) * out3; // Pole 3
in3 = out2;
out4 = out3 + 0.3 * in4 + (1 - f) * out4; // Pole 4
in4 = out3;
outvalue[i] = out4;
}
}
};
REGISTER_IMPLEMENTATION(Synth_MOOG_VCF_impl);
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