225 lines
6.4 KiB
C++
225 lines
6.4 KiB
C++
/*
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Peacock-8 VA polysynth
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Copyright 2025 Gordon JC Pearce <gordonjcp@gjcp.net>
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Permission to use, copy, modify, and/or distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <math.h>
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#include <stdio.h>
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#include "module.hpp"
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#include "tables.hpp"
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// antialiasing using polybleps, as described in KVRAudio forum by Mystran
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static inline float poly3blep0(float t) {
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float t2 = t * t;
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return 2 * (t * t2 - 0.5f * t2 * t2);
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}
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static inline float poly3blep1(float t) {
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return -poly3blep0(1 - t);
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}
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Voice::Voice() {
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omega = 0.0;
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theta = 0.0;
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env = 0;
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}
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void Voice::on(uint8_t midiNote) {
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while (midiNote < 24) midiNote += 12;
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while (midiNote > 108) midiNote -=12;
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note = midiNote - 24;
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envPhase = 1;
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}
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void Voice::off() {
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envPhase = 0;
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}
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// tanh(x)/x approximation, flatline at very high inputs
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// so might not be safe for very large feedback gains
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// [limit is 1/15 so very large means ~15 or +23dB]
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double tanhXdX(double x) {
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return 1-0.1*abs(x);
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double a = x*x;
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// IIRC I got this as Pade-approx for tanh(sqrt(x))/sqrt(x)
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return ((a + 105)*a + 945) / ((15*a + 420)*a + 945);
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}
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void Voice::run(Module* m, float* buffer, uint32_t samples) {
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// carry out per-voice calculations for each block of samples
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float out, t, fb;
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double zi;
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// calculate cutoff frequency
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float cut = 248.0f * (powf(2, (vcfCut - 0x1880) / 1143.0f));
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cut = M_PI * cut / sampleRate;
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cut = cut / (1 + cut); // correct tuning warp
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// printf("%f\n", cut);
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//if (cut > 0.5) cut = 0.5;
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// double f = tan(cut);
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//printf("cut = %4f f = %4f\n", cut, f);
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double r = (40.0/9.0) * m->res;
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float amp = vcaEnv / 4096.0f;
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for (uint32_t i = 0; i < samples; i++) {
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out = delay;
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delay = 0;
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theta += omega;
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while (true) {
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if (pulseStage == 0) {
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if (theta < m->pwmBuf[i]) break;
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t = (theta - m->pwmBuf[i]) / (lastpw - m->pwmBuf[i] + omega);
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out -= poly3blep0(t) * m->square;
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delay -= poly3blep1(t) * m->square;
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pulseStage = 1;
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}
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if (pulseStage == 1) {
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if (theta < 1) break; // no need to blep yet
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t = (theta - 1) / omega; // scaled remainder of phase
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out += poly3blep0(t) * (m->saw + m->square);
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delay += poly3blep1(t) * (m->saw + m->square);
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out -= poly3blep0(t) * (m->subBuf[i] * subosc);
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delay -= poly3blep1(t) * (m->subBuf[i] * subosc);
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pulseStage = 0;
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subosc = -subosc;
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theta -= 1;
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}
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}
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// FIXME DC offset removal
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delay += m->saw * (1 - (2 * theta));
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delay += m->square * ((pulseStage ? -1.f : 1.f) - m->pwmBuf[i] + 0.5);
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delay += m->subBuf[i] * subosc ;
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out += m->noise * (0.8 - 1.6 * (rand() & 0xffff) / 65536.0);
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out *= 0.01;
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// same time constant for both VCF and VCF RC circuits
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vcfRC = (cut - vcfRC) * m->vcaTC + vcfRC;
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#if 1
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//// LICENSE TERMS: Copyright 2012 Teemu Voipio
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//
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// You can use this however you like for pretty much any purpose,
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// as long as you don't claim you wrote it. There is no warranty.
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//
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// Distribution of substantial portions of this code in source form
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// must include this copyright notice and list of conditions.
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//
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// input delay and state for member variables
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// cutoff as normalized frequency (eg 0.5 = Nyquist)
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// resonance from 0 to 1, self-oscillates at settings over 0.9
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//void transistorLadder(
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// double cutoff, double resonance,
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// double * in, double * out, unsigned nsamples)
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//{
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// tuning and feedback
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//------------------------------------------------------------------------------ sample loop
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//for(unsigned n = 0; n < nsamples; ++n)
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//{
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// input with half delay, for non-linearities
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double ih = 0.5 * (out + zi); zi = out;
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//double ih = out;
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// evaluate the non-linear gains
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double t0 = tanhXdX((ih * (r+1))- r * s[3]);
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double t1 = tanhXdX(s[0]);
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double t2 = tanhXdX(s[1]);
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double t3 = tanhXdX(s[2]);
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double t4 = tanhXdX(s[3]);
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double f = vcfRC;
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// g# the denominators for solutions of individual stages
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double g0 = 1 / (1 + f*t1), g1 = 1 / (1 + f*t2);
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double g2 = 1 / (1 + f*t3), g3 = 1 / (1 + f*t4);
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// f# are just factored out of the feedback solution
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double f3 = f*t3*g3, f2 = f*t2*g2*f3, f1 = f*t1*g1*f2, f0 = f*t0*g0*f1;
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// solve feedback
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double y3 = (g3*s[3] + f3*g2*s[2] + f2*g1*s[1] + f1*g0*s[0] + f0*out) / (1 + r*f0);
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// then solve the remaining outputs (with the non-linear gains here)
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double xx = t0*((out * (r+1)) - r*y3);
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double y0 = t1*g0*(s[0] + f*xx);
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double y1 = t2*g1*(s[1] + f*y0);
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double y2 = t3*g2*(s[2] + f*y1);
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// update state
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s[0] += 2*f * (xx - y0);
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s[1] += 2*f * (y0 - y1);
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s[2] += 2*f * (y1 - y2);
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s[3] += 2*f * (y2 - t4*y3);
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//out[n] = y3;
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// }
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#else
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for (uint8_t ovs = 0; ovs < 4; ovs++) {
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fb = y3;
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// hard clip
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fb = ((out * 0.5) - fb) * m->res;
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if (fb > 4) fb = 4;
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if (fb < -4) fb = -4;
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// fb = 1.5 * fb - 0.5 * fb * fb * fb;
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//
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y0 = ((out + fb - y0) * vcfRC) + y0;
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y1 = ((y0 - y1) * vcfRC) + y1;
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y2 = ((y1 - y2) * vcfRC) + y2;
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y3 = ((y2 - y3) * vcfRC) + y3;
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}
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#endif
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vcaRC = (amp - vcaRC) * m->vcaTC + vcaRC;
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buffer[i] += 1 * m->vcaBuf[i] * vcaRC * y3;
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lastpw = m->pwmBuf[i];
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}
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// buffer[0] += 1;
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}
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