135 lines
4.0 KiB
C++
135 lines
4.0 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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float tanhXdX(float x) {
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return 1 - 0.05 * abs(x);
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float s = 0.0333, d = 30.0;
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return 1.0f - s * (d + 1.0f) * x * x / (d + x * x);
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}
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void Voice::run(Module* m, float* buffer, uint32_t framePos, 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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// calculate cutoff frequency
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float cut = 261.0f * (powf(2, (vcfCut - 0x1880) / 1143.0f)); // FIXME explain magic numbers
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cut = M_PI * cut / sampleRate;
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cut = cut / (1 + cut); // correct tuning warp
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if (cut > 0.7) cut = 0.7;
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float r = 5 * 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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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 * m->noiseBuf[i + framePos];
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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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for (uint8_t ovs = 0; ovs < 2; ovs++) {
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fb = y3;
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// hard clip
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fb = ((out * 0.5) - fb) * r;
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if (fb > 2) fb = 2;
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if (fb < -2) fb = -2;
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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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vcaRC = (amp - vcaRC) * m->vcaTC + vcaRC;
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buffer[framePos + i] += m->vcaBuf[i] * vcaRC * y3;
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lastpw = m->pwmBuf[i];
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}
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// buffer[0] += 1; // buzzing noise to test
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}
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