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Diffstat (limited to 'sc4pd/source/LPF.cpp')
| -rw-r--r-- | sc4pd/source/LPF.cpp | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/sc4pd/source/LPF.cpp b/sc4pd/source/LPF.cpp new file mode 100644 index 0000000..a11e784 --- /dev/null +++ b/sc4pd/source/LPF.cpp @@ -0,0 +1,180 @@ +/* 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 */ |