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+/* sc4pd
+ HPF~
+
+ 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"
+
+/* ------------------------ HPF~ -------------------------------*/
+
+class HPF_ar:
+ public sc4pd_dsp
+{
+ FLEXT_HEADER(HPF_ar,sc4pd_dsp);
+
+public:
+ HPF_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("HPF~",HPF_ar);
+
+HPF_ar::HPF_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 HPF_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 = 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 HPF filter */