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/*
wpfilters.h:
Copyright (C) 2017 Steven Yi
This file is part of Csound.
The Csound Library is free software; you can redistribute it
and/or modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
Csound 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with Csound; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
02110-1301 USA
*/
/*
Zero Delay Feedback Filters
Based on code by Will Pirkle, presented in:
http://www.willpirkle.com/Downloads/AN-4VirtualAnalogFilters.2.0.pdf
and in his book "Designing software synthesizer plug-ins in C++ : for
RackAFX, VST3, and Audio Units"
ZDF using Trapezoidal integrator by Vadim Zavalishin, presented in "The Art
of VA Filter Design" (https://www.native-instruments.com/fileadmin/ni_media/
downloads/pdf/VAFilterDesign_1.1.1.pdf)
Csound C versions by Steven Yi
*/
#include "csoundCore.h"
typedef struct {
OPDS h;
MYFLT *out;
MYFLT *in, *cutoff, *mode, *skip;
MYFLT last_cut, G;
double z1;
} ZDF_1POLE;
typedef struct {
OPDS h;
MYFLT *outlp, *outhp;
MYFLT *in, *cutoff, *skip;
MYFLT last_cut, G;
double z1;
} ZDF_1POLE_MODE;
typedef struct {
OPDS h;
MYFLT *out;
MYFLT *in, *cutoff, *q, *mode, *skip;
double last_cut, last_q, g, R;
double z1, z2;
} ZDF_2POLE;
typedef struct {
OPDS h;
MYFLT *outlp,*outbp, *outhp;
MYFLT *in, *cutoff, *q, *skip;
double last_cut, last_q, g, R;
double z1, z2;
} ZDF_2POLE_MODE;
typedef struct {
OPDS h;
MYFLT *out;
MYFLT *in, *cutoff, *q, *skip;
double last_cut, last_q, last_k, last_g, last_G, last_G2, last_G3, last_GAMMA;
double z1, z2, z3, z4;
} ZDF_LADDER;
typedef struct {
OPDS h;
MYFLT *out;
MYFLT *in, *cutoff, *kval, *nlp, *saturation, *skip;
double a[4], z[4], G[4], beta[4], delta[3], epsilon[3], gamma[3], SG[4];
double SIGMA, GAMMA, last_alpha, last_cut;
} DIODE_LADDER;
typedef struct {
OPDS h;
MYFLT *out;
MYFLT *in, *cutoff, *q, *nonlinear, *saturation, *skip;
double z1, z2, z3, last_cut, last_q, g, G, K, S35, alpha, lpf2_beta, hpf1_beta;
} K35_LPF;
typedef struct {
OPDS h;
MYFLT *out;
MYFLT *in, *cutoff, *q, *nonlinear, *saturation, *skip;
double z1, z2, z3, last_cut, last_q, g, G, K, S35, alpha, hpf2_beta, lpf1_beta;
} K35_HPF;
//typedef struct {
//
//} K35HPF;
static int32_t
zdf_ladder_perf(CSOUND * csound, ZDF_LADDER * p);
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