initial triplex procedural reimplementation
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286
synth/triplex.h
Normal file
286
synth/triplex.h
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#pragma once
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#include <cmath>
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#include <random>
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namespace trnr {
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//////////////
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// SINE OSC //
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//////////////
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struct tx_sineosc {
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bool phase_reset;
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double samplerate;
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float phase_resolution;
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float phase;
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float history;
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};
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inline void tx_randomize_phase(float& phase)
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{
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std::random_device random;
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std::mt19937 gen(random());
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std::uniform_real_distribution<> dis(0.0, 1.0);
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phase = dis(gen);
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}
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inline void tx_sineosc_init(tx_sineosc& s, double samplerate)
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{
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s.phase_reset = false;
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s.samplerate = samplerate;
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s.phase_resolution = 16.f;
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s.phase = 0.f;
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s.history = 0.f;
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tx_randomize_phase(s.phase);
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}
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inline float tx_wrap(float& phase)
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{
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while (phase < 0.) phase += 1.;
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while (phase >= 1.) phase -= 1.;
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return phase;
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}
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inline float tx_sineosc_process_sample(tx_sineosc& s, bool trigger, float frequency, float phase_modulation = 0.f)
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{
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if (trigger) {
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if (s.phase_reset) s.phase = 0.f;
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else tx_randomize_phase(s.phase);
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}
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float lookup_phase = s.phase + phase_modulation;
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tx_wrap(lookup_phase);
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s.phase += frequency / s.samplerate;
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tx_wrap(s.phase);
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// redux
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s.phase = static_cast<int>(s.phase * s.phase_resolution) / s.phase_resolution;
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// x is scaled 0<=x<4096
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float output;
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float x = lookup_phase;
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const float a = -0.40319426317E-08;
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const float b = 0.21683205691E+03;
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const float c = 0.28463350538E-04;
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const float d = -0.30774648337E-02;
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float y;
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bool negate = false;
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if (x > 2048) {
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negate = true;
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x -= 2048;
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}
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if (x > 1024) x = 2048 - x;
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y = (a + x) / (b + c * x * x) + d * x;
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if (negate) output = (-y);
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else output = y;
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// filter
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output = 0.5 * (output + s.history);
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s.history = output;
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return output;
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}
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//////////////
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// ENVELOPE //
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//////////////
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enum tx_env_state {
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idle = 0,
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attack1,
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attack2,
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hold,
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decay1,
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decay2,
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sustain,
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release1,
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release2
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};
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struct tx_envelope {
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tx_env_state state = idle;
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float attack1_rate = 0;
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float attack1_level = 0;
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float attack2_rate = 0;
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float hold_rate = 0;
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float decay1_rate = 0;
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float decay1_level = 0;
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float decay2_rate = 0;
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float sustain_level = 0;
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float release1_rate = 0;
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float release1_level = 0;
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float release2_rate = 0;
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bool skip_sustain = false;
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double samplerate = 44100.;
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size_t phase = 0;
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float level = 0.f;
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float start_level = 0.f;
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float h1 = 0.f;
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float h2 = 0.f;
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float h3 = 0.f;
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bool retrigger;
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};
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inline void tx_envelope_init(tx_envelope& e, double samplerate, bool retrigger = false)
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{
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e.samplerate = samplerate;
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e.retrigger = retrigger;
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}
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inline size_t tx_mtos(float ms, double samplerate) { return static_cast<size_t>(ms * samplerate / 1000.f); }
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inline float tx_lerp(float x1, float y1, float x2, float y2, float x)
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{
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return y1 + (((x - x1) * (y2 - y1)) / (x2 - x1));
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}
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inline float tx_enveloope_process_sample(tx_envelope& e, bool gate, bool trigger, float _attack_mod, float _decay_mod)
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{
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size_t attack_mid_x1 = tx_mtos(e.attack1_rate + (float)_attack_mod, e.samplerate);
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size_t attack_mid_x2 = tx_mtos(e.attack2_rate + (float)_attack_mod, e.samplerate);
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size_t hold_samp = tx_mtos(e.hold_rate, e.samplerate);
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size_t decay_mid_x1 = tx_mtos(e.decay1_rate + (float)_decay_mod, e.samplerate);
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size_t decay_mid_x2 = tx_mtos(e.decay2_rate + (float)_decay_mod, e.samplerate);
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size_t release_mid_x1 = tx_mtos(e.release1_rate + (float)_decay_mod, e.samplerate);
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size_t release_mid_x2 = tx_mtos(e.release2_rate + (float)_decay_mod, e.samplerate);
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// if note on is triggered, transition to attack phase
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if (trigger) {
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if (e.retrigger) e.start_level = 0.f;
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else e.start_level = e.level;
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e.phase = 0;
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e.state = attack1;
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}
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// attack 1st half
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if (e.state == attack1) {
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// while in attack phase
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if (e.phase < attack_mid_x1) {
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e.level = tx_lerp(0, e.start_level, (float)attack_mid_x1, e.attack1_level, (float)e.phase);
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e.phase += 1;
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}
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// reset phase if parameter was changed
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if (e.phase > attack_mid_x1) { e.phase = attack_mid_x1; }
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// if attack phase is done, transition to decay phase
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if (e.phase == attack_mid_x1) {
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e.state = attack2;
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e.phase = 0;
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}
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}
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// attack 2nd half
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if (e.state == attack2) {
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// while in attack phase
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if (e.phase < attack_mid_x2) {
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e.level = tx_lerp(0, e.attack1_level, (float)attack_mid_x2, 1, (float)e.phase);
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e.phase += 1;
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}
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// reset phase if parameter was changed
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if (e.phase > attack_mid_x2) { e.phase = attack_mid_x2; }
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// if attack phase is done, transition to decay phase
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if (e.phase == attack_mid_x2) {
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e.state = hold;
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e.phase = 0;
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}
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}
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// hold
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if (e.state == hold) {
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if (e.phase < hold_samp) {
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e.level = 1.0;
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e.phase += 1;
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}
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if (e.phase > hold_samp) { e.phase = hold_samp; }
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if (e.phase == hold_samp) {
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e.state = decay1;
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e.phase = 0;
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}
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}
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// decay 1st half
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if (e.state == decay1) {
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// while in decay phase
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if (e.phase < decay_mid_x1) {
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e.level = tx_lerp(0, 1, (float)decay_mid_x1, e.decay1_level, (float)e.phase);
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e.phase += 1;
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}
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// reset phase if parameter was changed
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if (e.phase > decay_mid_x1) { e.phase = decay_mid_x1; }
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// if decay phase is done, transition to sustain phase
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if (e.phase == decay_mid_x1) {
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e.state = decay2;
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e.phase = 0;
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}
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}
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// decay 2nd half
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if (e.state == decay2) {
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// while in decay phase
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if (e.phase < decay_mid_x2) {
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e.level = tx_lerp(0, e.decay1_level, (float)decay_mid_x2, e.sustain_level, (float)e.phase);
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e.phase += 1;
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}
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// reset phase if parameter was changed
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if (e.phase > decay_mid_x2) { e.phase = decay_mid_x2; }
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// if decay phase is done, transition to sustain phase
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if (e.phase == decay_mid_x2) {
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e.state = sustain;
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e.phase = 0;
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e.level = e.sustain_level;
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}
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}
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// while sustain phase: if note off is triggered, transition to release phase
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if (e.state == sustain && (!gate || e.skip_sustain)) {
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e.state = release1;
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e.level = e.sustain_level;
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}
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// release 1st half
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if (e.state == release1) {
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// while in release phase
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if (e.phase < release_mid_x1) {
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e.level = tx_lerp(0, e.sustain_level, (float)release_mid_x1, e.release1_level, (float)e.phase);
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e.phase += 1;
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}
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// reset phase if parameter was changed
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if (e.phase > release_mid_x1) { e.phase = release_mid_x1; }
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// transition to 2nd release half
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if (e.phase == release_mid_x1) {
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e.phase = 0;
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e.state = release2;
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}
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}
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// release 2nd half
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if (e.state == release2) {
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// while in release phase
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if (e.phase < release_mid_x2) {
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e.level = tx_lerp(0, e.release1_level, (float)release_mid_x2, 0, (float)e.phase);
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e.phase += 1;
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}
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// reset phase if parameter was changed
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if (e.phase > release_mid_x2) { e.phase = release_mid_x2; }
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// reset
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if (e.phase == release_mid_x2) {
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e.phase = 0;
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e.state = idle;
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e.level = 0;
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}
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}
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// smooth output
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e.h3 = e.h2;
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e.h2 = e.h1;
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e.h1 = e.level;
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return (e.h1 + e.h2 + e.h3) / 3.f;
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}
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//////////////
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// OPERATOR //
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//////////////
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struct tx_operator {
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tx_envelope envelope;
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tx_sineosc oscillator;
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float ratio;
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float amplitude;
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};
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} // namespace trnr
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