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/* sc4pd
LPF~
Copyright (c) 2004 Tim Blechmann.
This code is derived from:
SuperCollider real time audio synthesis system
Copyright (c) 2002 James McCartney. All rights reserved.
http://www.audiosynth.com
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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
Based on:
PureData by Miller Puckette and others.
http://www.crca.ucsd.edu/~msp/software.html
FLEXT by Thomas Grill
http://www.parasitaere-kapazitaeten.net/ext
SuperCollider by James McCartney
http://www.audiosynth.com
Coded while listening to: Peter Kowald & Tatsuya Nakatani:
13 Definitions of Truth
*/
#include "sc4pd.hpp"
/* ------------------------ LPF~ -------------------------------*/
class LPF_ar:
public sc4pd_dsp
{
FLEXT_HEADER(LPF_ar,sc4pd_dsp);
public:
LPF_ar(int argc, t_atom *argv);
protected:
virtual void m_signal(int n, t_sample *const *in, t_sample *const *out);
virtual void m_dsp(int n, t_sample *const *in, t_sample *const *out)
{
mRadiansPerSample = sc_radianspersample();
mFilterSlope = sc_filterslope();
mFilterLoops = sc_filterloops();
mFilterRemain = sc_filterremain();
}
void m_set_freq(float f)
{
m_freq=f;
changed = true;
}
private:
float m_y1, m_y2, m_a0, m_b1, m_b2, m_freq;
bool changed;
float mRadiansPerSample, mFilterSlope;
int mFilterLoops, mFilterRemain;
FLEXT_CALLBACK_F(m_set_freq);
};
FLEXT_LIB_DSP_V("LPF~",LPF_ar);
LPF_ar::LPF_ar(int argc, t_atom *argv)
{
FLEXT_ADDMETHOD_(0,"kfreq",m_set_freq);
//parse arguments
AtomList Args(argc,argv);
m_freq = sc_getfloatarg(Args,0);
changed = true;
AddOutSignal();
m_a0 = 0.f;
m_b1 = 0.f;
m_b2 = 0.f;
m_y1 = 0.f;
m_y2 = 0.f;
}
void LPF_ar::m_signal(int n, t_sample *const *in,
t_sample *const *out)
{
t_sample *nin = *in;
t_sample *nout = *out;
float y0;
float y1 = m_y1;
float y2 = m_y2;
float a0 = m_a0;
float b1 = m_b1;
float b2 = m_b2;
if (changed)
{
float pfreq = m_freq * mRadiansPerSample * 0.5;
float C = 1.f / tan(pfreq);
float C2 = C * C;
float sqrt2C = C * sqrt2;
float next_a0 = 1.f / (1.f + sqrt2C + C2);
float next_b1 = -2.f * (1.f - C2) * next_a0 ;
float next_b2 = -(1.f - sqrt2C + C2) * next_a0;
float a0_slope = (next_a0 - a0) * mFilterSlope;
float b1_slope = (next_b1 - b1) * mFilterSlope;
float b2_slope = (next_b2 - b2) * mFilterSlope;
for (int i = 0; i!= mFilterLoops;++i)
{
y0 = ZXP(nin) + b1 * y1 + b2 * y2;
ZXP(nout) = a0 * (y0 + 2.f * y1 + y2);
y2 = ZXP(nin) + b1 * y0 + b2 * y1;
ZXP(nout) = a0 * (y2 + 2.f * y0 + y1);
y1 = ZXP(nin) + b1 * y2 + b2 * y0;
ZXP(nout) = a0 * (y1 + 2.f * y2 + y0);
a0 += a0_slope;
b1 += b1_slope;
b2 += b2_slope;
}
for (int i = 0; i!= mFilterRemain;++i)
{
y0 = ZXP(nin) + b1 * y1 + b2 * y2;
ZXP(nout) = a0 * (y0 + 2.f * y1 + y2);
y2 = y1;
y1 = y0;
}
m_a0 = a0;
m_b1 = b1;
m_b2 = b2;
changed = false;
}
else
{
for (int i = 0; i!= mFilterLoops;++i)
{
y0 = ZXP(nin) + b1 * y1 + b2 * y2;
ZXP(nout) = a0 * (y0 + 2.f * y1 + y2);
y2 = ZXP(nin) + b1 * y0 + b2 * y1;
ZXP(nout) = a0 * (y2 + 2.f * y0 + y1);
y1 = ZXP(nin) + b1 * y2 + b2 * y0;
ZXP(nout) = a0 * (y1 + 2.f * y2 + y0);
}
for (int i = 0; i!= mFilterRemain;++i)
{
y0 = ZXP(nin) + b1 * y1 + b2 * y2;
ZXP(nout) = a0 * (y0 + 2.f * y1 + y2);
y2 = y1;
y1 = y0;
}
}
m_y1 = zapgremlins(y1);
m_y2 = zapgremlins(y2);
}
/* no control rate LPF filter */
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