commit db2756d00fddced77b20b704ed367081e3d3851b
parent f8dcc25131537c341bfa7da7827f2a0b8b88adf5
Author: Johannes Lorenz <j.git@lorenz-ho.me>
Date: Sat, 2 Nov 2019 17:10:53 +0100
add a moog filter type
Diffstat:
9 files changed, 294 insertions(+), 19 deletions(-)
diff --git a/src/DSP/CMakeLists.txt b/src/DSP/CMakeLists.txt
@@ -4,6 +4,7 @@ set(zynaddsubfx_dsp_SRCS
DSP/Filter.cpp
DSP/FormantFilter.cpp
DSP/SVFilter.cpp
+ DSP/MoogFilter.cpp
DSP/Unison.cpp
DSP/Value_Smoothing_Filter.cpp
PARENT_SCOPE
diff --git a/src/DSP/Filter.cpp b/src/DSP/Filter.cpp
@@ -19,6 +19,7 @@
#include "AnalogFilter.h"
#include "FormantFilter.h"
#include "SVFilter.h"
+#include "MoogFilter.h"
#include "../Params/FilterParams.h"
#include "../Misc/Allocator.h"
@@ -52,6 +53,10 @@ Filter *Filter::generate(Allocator &memory, const FilterParams *pars,
if(filter->outgain > 1.0f)
filter->outgain = sqrt(filter->outgain);
break;
+ case 3:
+ filter = memory.alloc<MoogFilter>(Ftype, 1000.0f, pars->getq(), srate, bufsize);
+ filter->setgain(pars->getgain());
+ break;
default:
filter = memory.alloc<AnalogFilter>(Ftype, 1000.0f, pars->getq(), Fstages, srate, bufsize);
if((Ftype >= 6) && (Ftype <= 8))
diff --git a/src/DSP/MoogFilter.cpp b/src/DSP/MoogFilter.cpp
@@ -0,0 +1,174 @@
+#include <cassert>
+#include <cstdio>
+#include <cmath>
+#include <stdio.h>
+
+#include "../Misc/Util.h"
+#include "MoogFilter.h"
+
+// theory from "THE ART OF VA FILTER DESIGN"
+// by Vadim Zavalishin
+
+namespace zyn{
+
+MoogFilter::MoogFilter(unsigned char Ftype, float Ffreq, float Fq,
+ unsigned int srate, int bufsize)
+ :Filter(srate, bufsize), sr(srate), gain(1.0f), type(Ftype)
+{
+ setfreq_and_q(Ffreq/srate, Fq);
+ settype(type); // q must be set before
+ for (unsigned int i = 0; i<(sizeof(state)/sizeof(*state)); i++)
+ {
+ state[i] = 0.0f;
+ }
+}
+
+MoogFilter::~MoogFilter(void)
+{
+
+}
+
+inline float MoogFilter::tan_2(const float x)
+{
+ //Pade approximation tan(x) hand tuned to map fCutoff
+ float x2 = x*x;
+ return ((9.5f*(11.15f*x - x2*x))/(105.0f - 45.0f*x2 + x2*x2));
+}
+
+inline float MoogFilter::tanhX(const float x)
+{
+ // Pade approximation of tanh(x) bound to [-1 .. +1]
+ // https://mathr.co.uk/blog/2017-09-06_approximating_hyperbolic_tangent.html
+ float x2 = x*x;
+ return (x*(105.0f+10.0f*x2)/(105.0f+(45.0f+x2)*x2)); //
+}
+
+
+inline float MoogFilter::tanhXdivX(float x)
+{
+ // Pade approximation for tanh(x)/x used in filter stages
+ float x2 = x*x;
+ return ((x2 + 105.0f)*x2 + 945.0f) / ((15.0f*x2 + 420.0f)*x2 + 945.0f);
+}
+
+inline float MoogFilter::step(float input)
+{
+ // transconductance
+ // gM(vIn) = tanh( vIn ) / vIn
+ float gm0 = tanhXdivX(state[0]);
+ float gm1 = tanhXdivX(state[1]);
+ float gm2 = tanhXdivX(state[2]);
+ float gm3 = tanhXdivX(state[3]);
+
+ // pre calc often used terms
+ float ctgm0 = c*gm0;
+ float ctgm1 = c*gm1;
+ float ctgm2 = c*gm2;
+ float ctgm3 = c*gm3;
+
+ // denominators
+ float d0 = 1.0f / (1.0f + ctgm0);
+ float d1 = 1.0f / (1.0f + ctgm1);
+ float d2 = 1.0f / (1.0f + ctgm2);
+ float d3 = 1.0f / (1.0f + ctgm3);
+
+ // pre calc often used term
+ float gm1td2tgm2td3 = gm1 * d2 * gm2 * d3;
+
+ // instantaneous response estimate
+ float y3Estimate =
+ cp4 * d0 * gm0 * d1 * gm1td2tgm2td3 * input +
+ cp3 * gm0 * d1 * gm1td2tgm2td3 * d0 * state[0] +
+ cp2 * gm1td2tgm2td3 * d1 * state[1] +
+ c * gm2 * d3 * d2 * state[2] +
+ d3 * state[3];
+
+ // instantaneous gain coefficient
+ float z0 = ctgm0 * d0;
+ float z1 = ctgm1 * d1;
+ float z2 = ctgm2 * d2;
+ float z3 = ctgm3 * d3;
+ float instantaneousgain = 1.0f / (1.0f + feedbackGain * z0*z1*z2*z3);
+
+ // input for the fist stage
+ float u = input - tanhX(feedbackGain * y3Estimate) * instantaneousgain;
+ // output of all stages
+ float y0 = gm0 * d0 * (state[0] + c * u);
+ float y1 = gm1 * d1 * (state[1] + c * y0);
+ float y2 = gm2 * d2 * (state[2] + c * y1);
+ float y3 = gm3 * d3 * (state[3] + c * y2);
+
+ // update state
+ state[0] += ct2 * (u - y0);
+ state[1] += ct2 * (y0 - y1);
+ state[2] += ct2 * (y1 - y2);
+ state[3] += ct2 * (y2 - y3);
+
+ // calculate multimode filter output
+ return (a0 * u
+ + a1 * y0
+ + a2 * y1
+ + a3 * y2
+ + a4 * y3);
+}
+
+void MoogFilter::filterout(float *smp)
+{
+ for (int i = 0; i < buffersize; i ++)
+ {
+ smp[i] = step(tanhX(smp[i]*gain));
+ smp[i] *= outgain;
+ }
+}
+
+void MoogFilter::setfreq_and_q(float frequency, float q_)
+{
+ setfreq(frequency/sr);
+ setq(q_);
+}
+
+void MoogFilter::setfreq(float ff)
+{
+ // limit cutoff to prevent overflow
+ ff = limit(ff,0.0002f,0.48f);
+ // pre warp cutoff to map to reality
+ c = tan_2(PI * ff);
+ // pre calculate some stuff outside the hot zone
+ ct2 = c * 2.0f;
+ cp2 = c * c;
+ cp3 = cp2 * c;
+ cp4 = cp2 * cp2;
+}
+
+void MoogFilter::setq(float q)
+{
+ // flattening the Q input
+ feedbackGain = cbrtf(q/1000.0f)*4.0f + 0.1f;
+ // compensation factor for passband reduction by the negative feedback
+ passbandCompensation = 1.0f + limit(feedbackGain, 0.0f, 1.0f);
+}
+
+void MoogFilter::setgain(float dBgain)
+{
+ gain = dB2rap(dBgain);
+}
+
+void MoogFilter::settype(unsigned char type_)
+{
+ type = type_;
+ switch (type)
+ {
+ case 1:
+ a0 = 0.0f; a1 = 0.0f; a2 = 4.0f; a3 =-8.0f; a4 = 4.0f;
+ break;
+ case 0:
+ a0 = 1.0f; a1 =-4.0f; a2 = 6.0f; a3 =-4.0f; a4 = 1.0f;
+ break;
+ case 2:
+ default:
+ a0 = 0.0f; a1 = 0.0f; a2 = 0.0f; a3 = 0.0f; a4 = passbandCompensation;
+ break;
+ }
+}
+
+};
diff --git a/src/DSP/MoogFilter.h b/src/DSP/MoogFilter.h
@@ -0,0 +1,53 @@
+/*
+ ZynAddSubFX - a software synthesizer
+
+ Moog Filter.h - Several analog filters (lowpass, highpass...)
+ Copyright (C) 2018-2018 Mark McCurry
+ Author: Mark McCurry
+
+ 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.
+*/
+
+#pragma once
+#include "Filter.h"
+
+namespace zyn {
+
+class MoogFilter:public Filter
+{
+ public:
+ //! @param Fq resonance, range [0.1,1000], logscale
+ MoogFilter(unsigned char Ftype, float Ffreq, float Fq,
+ unsigned int srate, int bufsize);
+ ~MoogFilter() override;
+ void filterout(float *smp) override;
+ void setfreq(float /*frequency*/) override;
+ void setfreq_and_q(float frequency, float q_) override;
+ void setq(float /*q_*/) override;
+ void setgain(float dBgain) override;
+ void settype(unsigned char type); //
+
+ private:
+ unsigned sr;
+ float gain;
+ unsigned char type;
+
+ float step(float x);
+
+ float tanhXdivX(const float x);
+ float tanhX(const float x);
+ float tan_2(const float x);
+
+ float feedbackGain;
+ // aN: multimode coefficients for LP,BP,HP configurations
+ float a0, a1, a2, a3, a4;
+ float state[4] = {0.0f,0.0f,0.0f,0.0f};
+ float passbandCompensation;
+ // c*: cutoff frequency c and precalced products (times t) and powers(p) of it
+ float c, ct2, cp2, cp3, cp4;
+};
+
+}
diff --git a/src/Params/FilterParams.cpp b/src/Params/FilterParams.cpp
@@ -69,7 +69,7 @@ const rtosc::Ports FilterParams::ports = {
rOptions(ad_global_filter, ad_voice_filter, sub_filter, in_effect),
"location of the filter"),
rOption(Pcategory, rShort("class"),
- rOptions(analog, formant, st.var.), rDefault(analog),
+ rOptions(analog, formant, st.var., moog), rDefault(analog),
"Class of filter"),
rOption(Ptype, rShort("type"),
rOptions(LP1, HP1, LP2, HP2, BP, notch, peak, l.shelf, h.shelf),
@@ -131,7 +131,9 @@ const rtosc::Ports FilterParams::ports = {
{"type-svf::i", rProp(parameter) rShort("type")
rOptions(low, high, band, notch)
rDoc("Filter Type"), 0, rOptionCb(Ptype)},
-
+ {"type-moog::i", rProp(parameter) rShort("type")
+ rOptions(HP, BP, LP)
+ rDoc("Filter Type"), 0, rOptionCb(Ptype)},
//UI reader
{"Pvowels:", rDoc("Get Formant Vowels"), NULL,
[](const char *, RtData &d) {
diff --git a/src/Synth/ModFilter.cpp b/src/Synth/ModFilter.cpp
@@ -19,6 +19,7 @@
#include "../DSP/SVFilter.h"
#include "../DSP/AnalogFilter.h"
#include "../DSP/FormantFilter.h"
+#include "../DSP/MoogFilter.h"
#include <cassert>
namespace zyn {
@@ -124,6 +125,8 @@ static int current_category(Filter *f)
return 1;
else if(dynamic_cast<SVFilter*>(f))
return 2;
+ else if(dynamic_cast<MoogFilter*>(f))
+ return 3;
assert(false);
return -1;
@@ -146,6 +149,8 @@ void ModFilter::paramUpdate(Filter *&f)
svParamUpdate(*sv);
else if(auto *an = dynamic_cast<AnalogFilter*>(f))
anParamUpdate(*an);
+ else if(auto *mg = dynamic_cast<MoogFilter*>(f))
+ mgParamUpdate(*mg);
}
void ModFilter::svParamUpdate(SVFilter &sv)
@@ -161,4 +166,10 @@ void ModFilter::anParamUpdate(AnalogFilter &an)
an.setgain(pars.getgain());
}
+void ModFilter::mgParamUpdate(MoogFilter &mg)
+{
+ mg.settype(pars.Ptype);
+ mg.setgain(pars.getgain());
+}
+
}
diff --git a/src/Synth/ModFilter.h b/src/Synth/ModFilter.h
@@ -45,6 +45,7 @@ class ModFilter
void paramUpdate(Filter *&f);
void svParamUpdate(SVFilter &sv);
void anParamUpdate(AnalogFilter &an);
+ void mgParamUpdate(MoogFilter &mg);
const FilterParams &pars; //Parameters to Pull Updates From
diff --git a/src/UI/FilterUI.fl b/src/UI/FilterUI.fl
@@ -164,6 +164,16 @@ delete (formantparswindow);} {}
label 1NF
xywh {164 164 100 20} labelfont 1 labelsize 10
}
+ } Fl_Choice moogfiltertypechoice {
+ label FilterType
+ tooltip {The Filter type} xywh {10 50 50 15} down_box BORDER_BOX labelsize 10 align 5 textsize 10
+ code1 {o->init("Ptype");}
+ class Fl_Osc_Choice
+ } {
+ MenuItem {} {
+ label LPF
+ xywh {134 134 100 20} labelfont 1 labelsize 10
+ }
}
Fl_Choice filtertype {
label Category
@@ -184,6 +194,10 @@ delete (formantparswindow);} {}
label StVarF
xywh {70 70 100 20} labelfont 1 labelsize 10
}
+ MenuItem {} {
+ label Moog
+ xywh {80 80 100 20} labelfont 1 labelsize 10
+ }
}
Fl_Dial cfreqdial {
label {C.Freq}
@@ -436,10 +450,10 @@ formantfiltergraph->redraw();}
//formant_q_dial->value(pars->Pvowels[nvowel].formants[nformant].q);
//formant_amp_dial->value(pars->Pvowels[nvowel].formants[nformant].amp);
if (nformant<numformants->value()) formantparsgroup->activate();
- else formantparsgroup->deactivate();
+ else formantparsgroup->deactivate();
if (nseqpos<sequencesize->value()) vowel_counter->activate();
- else vowel_counter->deactivate();
+ else vowel_counter->deactivate();
//vowel_counter->value(pars->Psequence[nseqpos].nvowel);} {}
@@ -451,25 +465,38 @@ formantfiltergraph->redraw();
const int Pcategory = filtertype->value();
const int Ptype = analogfiltertypechoice->value();
-if (Pcategory==2) svfiltertypechoice->value(Ptype);
-if (Pcategory==0) analogfiltertypechoice->value(Ptype);
-
const int categ=Pcategory;
-if ((categ==0)||(categ==2)) {
- if (categ==0) {
- analogfiltertypechoice->show();
- svfiltertypechoice->hide();
- } else {
- svfiltertypechoice->show();
- analogfiltertypechoice->hide();
- };
- editbutton->hide();
+
+if (categ == 3) {
+ stcounter->hide(); // not (yet?) implemented for moog filter
+}
+else {
+ stcounter->show();
+}
+
+switch(categ)
+{
+ case 2: svfiltertypechoice->value(Ptype); break;
+ case 0: analogfiltertypechoice->value(Ptype); break;
+ case 3: moogfiltertypechoice->value(Ptype); break;
+}
+
+analogfiltertypechoice->hide();
+svfiltertypechoice->hide();
+moogfiltertypechoice->hide();
+
+if ((categ==0)||(categ==2)||(categ==3)) {
+ switch (categ)
+ {
+ case 0: analogfiltertypechoice->show(); break;
+ case 2: svfiltertypechoice->show(); break;
+ case 3: moogfiltertypechoice->show(); break;
+ }
+ editbutton->hide();
formantparswindow->hide();
cfreqdial->label("C.freq");
} else {
- analogfiltertypechoice->hide();
- svfiltertypechoice->hide();
- editbutton->show();
+ editbutton->show();
cfreqdial->label("BS.pos");
};
diff --git a/src/globals.h b/src/globals.h
@@ -67,6 +67,7 @@ class Part;
class Filter;
class AnalogFilter;
+class MoogFilter;
class SVFilter;
class FormantFilter;
class ModFilter;
