mirror of
https://github.com/TomHarte/CLK.git
synced 2026-04-21 17:16:44 +00:00
Clean up: pull out noise generation, remove code from header.
This commit is contained in:
Thomas Harte
+218
-1
@@ -18,6 +18,8 @@ SID::SID(Concurrency::AsyncTaskQueue<false> &audio_queue) :
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15000.0f
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) {}
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// MARK: - Programmer interface.
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void SID::write(const Numeric::SizedInt<5> address, const uint8_t value) {
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last_write_ = value;
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audio_queue_.enqueue([=, this] {
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@@ -111,10 +113,23 @@ void SID::update_filter() {
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type,
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1'000'000.0f,
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30.0f + float(filter_cutoff_.get()) * 5.8f,
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0.707f + float(filter_resonance_.get()) * 0.125f,
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0.707f + float(filter_resonance_.get()) * 0.2862f,
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6.0f,
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true
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);
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// Filter cutoff: the data sheet provides that it is linear, and "approximate Cutoff Frequency
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// ranges between 30Hz and 12KHz [with recommended externally-supplied capacitors]."
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//
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// It's an 11-bit number, so the above is "approximate"ly right.
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// Resonance: a complete from-thin-air guess. The data sheet says merely:
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//
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// "There are 16 Resonance settings ranging from about 0.707 (Critical Damping) for a count of 0
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// to a maximum for a count of 15"
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//
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// i.e. no information is given on the maximum. I've taken it to be 5-ish per commentary on more general sites
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// that 5 is a typical ceiling for the resonance factor.
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}
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uint8_t SID::read(const Numeric::SizedInt<5> address) {
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@@ -122,6 +137,208 @@ uint8_t SID::read(const Numeric::SizedInt<5> address) {
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return last_write_;
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}
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// MARK: - Oscillators.
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void Voice::Oscillator::reset_phase() {
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phase = PhaseReload;
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}
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bool Voice::Oscillator::did_raise_b23() const {
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return previous_phase > phase;
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}
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bool Voice::Oscillator::did_raise_b19() const {
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static constexpr int NoiseBit = 1 << (19 + 8);
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return (previous_phase ^ phase) & phase & NoiseBit;
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}
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uint16_t Voice::Oscillator::sawtooth_output() const {
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return (phase >> 20) ^ 0x800;
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}
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// MARK: - Noise generator.
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uint16_t Voice::NoiseGenerator::output() const {
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// Uses bits: 20, 18, 14, 11, 9, 5, 2 and 0, plus four more zero bits.
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return
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((noise >> 9) & 0b1000'0000'0000) | // b20 -> b11
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((noise >> 8) & 0b0100'0000'0000) | // b18 -> b10
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((noise >> 5) & 0b0010'0000'0000) | // b14 -> b9
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((noise >> 3) & 0b0001'0000'0000) | // b11 -> b8
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((noise >> 2) & 0b0000'1000'0000) | // b9 -> b7
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((noise << 1) & 0b0000'0100'0000) | // b5 -> b6
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((noise << 3) & 0b0000'0010'0000) | // b2 -> b5
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((noise << 4) & 0b0000'0001'0000); // b0 -> b4
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}
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void Voice::NoiseGenerator::update(const bool test) {
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noise =
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(noise << 1) |
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(((noise >> 17) ^ ((noise >> 22) | test)) & 1);
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}
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// MARK: - ADSR.
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void Voice::ADSR::set_phase(const Phase new_phase) {
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static constexpr uint16_t rate_prescaler[] = {
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9, 32, 63, 95, 149, 220, 267, 313, 392, 977, 1954, 3126, 3907, 11720, 19532, 31251
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};
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static_assert(sizeof(rate_prescaler) / sizeof(*rate_prescaler) == 16);
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phase = new_phase;
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switch(phase) {
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case Phase::Attack: rate_counter_target = rate_prescaler[attack.get()]; break;
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case Phase::DecayAndHold: rate_counter_target = rate_prescaler[decay.get()]; break;
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case Phase::Release: rate_counter_target = rate_prescaler[release.get()]; break;
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}
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}
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// MARK: - Voices.
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void Voice::set_control(const uint8_t new_control) {
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const bool old_gate = gate();
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control = new_control;
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if(gate() && !old_gate) {
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adsr.set_phase(ADSR::Phase::Attack);
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} else if(!gate() && old_gate) {
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adsr.set_phase(ADSR::Phase::Release);
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}
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}
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bool Voice::noise() const { return control.bit<7>(); }
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bool Voice::pulse() const { return control.bit<6>(); }
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bool Voice::sawtooth() const { return control.bit<5>(); }
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bool Voice::triangle() const { return control.bit<4>(); }
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bool Voice::test() const { return control.bit<3>(); }
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bool Voice::ring_mod() const { return control.bit<2>(); }
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bool Voice::sync() const { return control.bit<1>(); }
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bool Voice::gate() const { return control.bit<0>(); }
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void Voice::update() {
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// Oscillator.
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oscillator.previous_phase = oscillator.phase;
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if(test()) {
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oscillator.phase = 0;
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} else {
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oscillator.phase += oscillator.pitch;
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if(oscillator.did_raise_b19()) {
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noise_generator.update(test());
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}
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}
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// ADSR.
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// First prescalar, which is a function of the programmer-set rate.
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++ adsr.rate_counter;
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if(adsr.rate_counter == adsr.rate_counter_target) {
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adsr.rate_counter = 0;
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// Second prescalar, which approximates an exponential.
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static constexpr uint8_t exponential_prescaler[] = {
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1, // 0
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30, 30, 30, 30, 30, 30, // 1–6
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16, 16, 16, 16, 16, 16, 16, 16, // 7–14
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8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, // 15–26
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4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
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4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, // 27–54
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // 55–94
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1,
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};
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static_assert(sizeof(exponential_prescaler) == 256);
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static_assert(exponential_prescaler[0] == 1);
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static_assert(exponential_prescaler[1] == 30);
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static_assert(exponential_prescaler[6] == 30);
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static_assert(exponential_prescaler[7] == 16);
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static_assert(exponential_prescaler[14] == 16);
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static_assert(exponential_prescaler[15] == 8);
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static_assert(exponential_prescaler[26] == 8);
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static_assert(exponential_prescaler[27] == 4);
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static_assert(exponential_prescaler[54] == 4);
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static_assert(exponential_prescaler[55] == 2);
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static_assert(exponential_prescaler[94] == 2);
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static_assert(exponential_prescaler[95] == 1);
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static_assert(exponential_prescaler[255] == 1);
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if(adsr.phase == ADSR::Phase::Attack) {
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++adsr.envelope;
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// TODO: what really resets the exponential counter? If anything?
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adsr.exponential_counter = 0;
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if(adsr.envelope == 0xff) {
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adsr.set_phase(ADSR::Phase::DecayAndHold);
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}
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} else {
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++adsr.exponential_counter;
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if(adsr.exponential_counter == exponential_prescaler[adsr.envelope]) {
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adsr.exponential_counter = 0;
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if(adsr.envelope && (adsr.envelope != adsr.sustain || adsr.phase != ADSR::Phase::DecayAndHold)) {
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--adsr.envelope;
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}
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}
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}
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}
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}
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void Voice::synchronise(const Voice &prior) {
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// Only oscillator work to do here.
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if(
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sync() &&
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prior.oscillator.did_raise_b23()
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) {
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oscillator.phase = Oscillator::PhaseReload;
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}
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}
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uint16_t Voice::pulse_output() const {
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return (
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(oscillator.phase ^ 0x8000'0000) < oscillator.pulse_width
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) ? 0 : MaxWaveformValue;
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}
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uint16_t Voice::triangle_output(const Voice &prior) const {
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const uint16_t sawtooth = oscillator.sawtooth_output();
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const uint16_t xor_mask1 = sawtooth;
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const uint16_t xor_mask2 = ring_mod() ? prior.sawtooth() : 0;
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const uint16_t xor_mask = ((xor_mask1 ^ xor_mask2) & 0x800) ? 0xfff : 0x000;
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return ((sawtooth << 1) ^ xor_mask) & 0xfff;
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}
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uint16_t Voice::output(const Voice &prior) const {
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// TODO: true composite waves.
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//
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// My current understanding on this: if multiple waveforms are enabled, the pull to zero beats the
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// pull to one on any line where the two compete. But the twist is that the lines are not necessarily
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// one per bit since they lead to a common ground. Ummm, I think.
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//
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// Anyway, first pass: logical AND. It's not right. It will temporarily do.
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uint16_t output = MaxWaveformValue;
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if(pulse()) output &= pulse_output();
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if(sawtooth()) output &= oscillator.sawtooth_output();
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if(triangle()) output &= triangle_output(prior);
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if(noise()) output &= noise_generator.output();
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return (output * adsr.envelope) / 255;
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}
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// MARK: - Wave generation
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void SID::set_sample_volume_range(const std::int16_t range) {
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range_ = range;
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}
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+31
-196
@@ -32,40 +32,11 @@ struct Voice {
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static constexpr uint32_t PhaseReload = 0x8000'0000;
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uint32_t phase = PhaseReload;
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uint32_t previous_phase = PhaseReload;
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void reset_phase() {
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phase = PhaseReload;
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}
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static constexpr uint32_t NoiseReload = 0x7'ffff;
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uint32_t noise = NoiseReload;
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bool did_raise_b23() const {
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return previous_phase > phase;
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}
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bool did_raise_b19() const {
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static constexpr int NoiseBit = 1 << (19 + 8);
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return (previous_phase ^ phase) & phase & NoiseBit;
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}
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uint16_t sawtooth_output() const {
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return (phase >> 20) ^ 0x800;
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}
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uint16_t noise_output() const {
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// Uses bits: 20, 18, 14, 11, 9, 5, 2 and 0, plus four more zero bits.
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return
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((noise >> 9) & 0b1000'0000'0000) | // b20 -> b11
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((noise >> 8) & 0b0100'0000'0000) | // b18 -> b10
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((noise >> 5) & 0b0010'0000'0000) | // b14 -> b9
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((noise >> 3) & 0b0001'0000'0000) | // b11 -> b8
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((noise >> 2) & 0b0000'1000'0000) | // b9 -> b7
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((noise << 1) & 0b0000'0100'0000) | // b5 -> b6
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((noise << 3) & 0b0000'0010'0000) | // b2 -> b5
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((noise << 4) & 0b0000'0001'0000); // b0 -> b4
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}
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void update_noise(const bool test) {
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noise =
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(noise << 1) |
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(((noise >> 17) ^ ((noise >> 22) | test)) & 1);
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}
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void reset_phase();
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bool did_raise_b23() const;
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bool did_raise_b19() const;
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uint16_t sawtooth_output() const;
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} oscillator;
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struct ADSR {
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// Programmer inputs.
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@@ -87,173 +58,36 @@ struct Voice {
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uint8_t exponential_counter;
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uint8_t envelope;
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void set_phase(const Phase new_phase) {
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static constexpr uint16_t rate_prescaler[] = {
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9, 32, 63, 95, 149, 220, 267, 313, 392, 977, 1954, 3126, 3907, 11720, 19532, 31251
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};
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static_assert(sizeof(rate_prescaler) / sizeof(*rate_prescaler) == 16);
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phase = new_phase;
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switch(phase) {
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case Phase::Attack: rate_counter_target = rate_prescaler[attack.get()]; break;
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case Phase::DecayAndHold: rate_counter_target = rate_prescaler[decay.get()]; break;
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case Phase::Release: rate_counter_target = rate_prescaler[release.get()]; break;
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}
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}
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void set_phase(const Phase);
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} adsr;
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struct NoiseGenerator {
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static constexpr uint32_t NoiseReload = 0x7'ffff;
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uint32_t noise = NoiseReload;
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uint16_t output() const;
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void update(const bool test);
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} noise_generator;
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void set_control(const uint8_t);
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void update();
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void synchronise(const Voice &prior);
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uint16_t output(const Voice &prior) const;
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private:
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Numeric::SizedInt<8> control;
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void set_control(const uint8_t new_control) {
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const bool old_gate = gate();
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control = new_control;
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if(gate() && !old_gate) {
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adsr.set_phase(ADSR::Phase::Attack);
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} else if(!gate() && old_gate) {
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adsr.set_phase(ADSR::Phase::Release);
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}
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}
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bool noise() const { return control.bit<7>(); }
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bool pulse() const { return control.bit<6>(); }
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bool sawtooth() const { return control.bit<5>(); }
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bool triangle() const { return control.bit<4>(); }
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bool test() const { return control.bit<3>(); }
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bool ring_mod() const { return control.bit<2>(); }
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bool sync() const { return control.bit<1>(); }
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bool gate() const { return control.bit<0>(); }
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void update() {
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// Oscillator.
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oscillator.previous_phase = oscillator.phase;
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if(test()) {
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oscillator.phase = 0;
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} else {
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oscillator.phase += oscillator.pitch;
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|
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if(oscillator.did_raise_b19()) {
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oscillator.update_noise(test());
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}
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}
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// ADSR.
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|
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// First prescalar, which is a function of the programmer-set rate.
|
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++ adsr.rate_counter;
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if(adsr.rate_counter == adsr.rate_counter_target) {
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adsr.rate_counter = 0;
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// Second prescalar, which approximates an exponential.
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static constexpr uint8_t exponential_prescaler[] = {
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1, // 0
|
||||
30, 30, 30, 30, 30, 30, // 1–6
|
||||
16, 16, 16, 16, 16, 16, 16, 16, // 7–14
|
||||
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, // 15–26
|
||||
4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
|
||||
4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, // 27–54
|
||||
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
|
||||
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
|
||||
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // 55–94
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
||||
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
|
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1,
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};
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static_assert(sizeof(exponential_prescaler) == 256);
|
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static_assert(exponential_prescaler[0] == 1);
|
||||
static_assert(exponential_prescaler[1] == 30);
|
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static_assert(exponential_prescaler[6] == 30);
|
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static_assert(exponential_prescaler[7] == 16);
|
||||
static_assert(exponential_prescaler[14] == 16);
|
||||
static_assert(exponential_prescaler[15] == 8);
|
||||
static_assert(exponential_prescaler[26] == 8);
|
||||
static_assert(exponential_prescaler[27] == 4);
|
||||
static_assert(exponential_prescaler[54] == 4);
|
||||
static_assert(exponential_prescaler[55] == 2);
|
||||
static_assert(exponential_prescaler[94] == 2);
|
||||
static_assert(exponential_prescaler[95] == 1);
|
||||
static_assert(exponential_prescaler[255] == 1);
|
||||
|
||||
if(adsr.phase == ADSR::Phase::Attack) {
|
||||
++adsr.envelope;
|
||||
// TODO: what really resets the exponential counter? If anything?
|
||||
adsr.exponential_counter = 0;
|
||||
|
||||
if(adsr.envelope == 0xff) {
|
||||
adsr.set_phase(ADSR::Phase::DecayAndHold);
|
||||
}
|
||||
} else {
|
||||
++adsr.exponential_counter;
|
||||
if(adsr.exponential_counter == exponential_prescaler[adsr.envelope]) {
|
||||
adsr.exponential_counter = 0;
|
||||
|
||||
if(adsr.envelope && (adsr.envelope != adsr.sustain || adsr.phase != ADSR::Phase::DecayAndHold)) {
|
||||
--adsr.envelope;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
void synchronise(const Voice &prior) {
|
||||
// Only oscillator work to do here.
|
||||
if(
|
||||
sync() &&
|
||||
prior.oscillator.did_raise_b23()
|
||||
) {
|
||||
oscillator.phase = Oscillator::PhaseReload;
|
||||
}
|
||||
}
|
||||
bool noise() const;
|
||||
bool pulse() const;
|
||||
bool sawtooth() const;
|
||||
bool triangle() const;
|
||||
bool test() const;
|
||||
bool ring_mod() const;
|
||||
bool sync() const;
|
||||
bool gate() const;
|
||||
|
||||
static constexpr uint16_t MaxWaveformValue = (1 << 12) - 1;
|
||||
|
||||
uint16_t sawtooth_output() const {
|
||||
return oscillator.sawtooth_output();
|
||||
}
|
||||
|
||||
uint16_t pulse_output() const {
|
||||
return (
|
||||
(oscillator.phase ^ 0x8000'0000) < oscillator.pulse_width
|
||||
) ? 0 : MaxWaveformValue;
|
||||
}
|
||||
|
||||
uint16_t triangle_output(const Voice &prior) const {
|
||||
const uint16_t sawtooth = oscillator.sawtooth_output();
|
||||
const uint16_t xor_mask1 = sawtooth;
|
||||
const uint16_t xor_mask2 = ring_mod() ? prior.sawtooth() : 0;
|
||||
const uint16_t xor_mask = ((xor_mask1 ^ xor_mask2) & 0x800) ? 0xfff : 0x000;
|
||||
return ((sawtooth << 1) ^ xor_mask) & 0xfff;
|
||||
}
|
||||
|
||||
uint16_t noise_output() const {
|
||||
return oscillator.noise_output();
|
||||
}
|
||||
|
||||
uint16_t output(const Voice &prior) const {
|
||||
// TODO: true composite waves.
|
||||
//
|
||||
// My current understanding on this: if multiple waveforms are enabled, the pull to zero beats the
|
||||
// pull to one on any line where the two compete. But the twist is that the lines are not necessarily
|
||||
// one per bit since they lead to a common ground. Ummm, I think.
|
||||
//
|
||||
// Anyway, first pass: logical AND. It's not right. It will temporarily do.
|
||||
|
||||
uint16_t output = MaxWaveformValue;
|
||||
|
||||
if(pulse()) output &= pulse_output();
|
||||
if(sawtooth()) output &= sawtooth_output();
|
||||
if(triangle()) output &= triangle_output(prior);
|
||||
if(noise()) output &= noise_output();
|
||||
|
||||
return (output * adsr.envelope) / 255;
|
||||
}
|
||||
uint16_t pulse_output() const;
|
||||
uint16_t triangle_output(const Voice &prior) const;
|
||||
};
|
||||
|
||||
class SID: public Outputs::Speaker::BufferSource<SID, false> {
|
||||
@@ -271,12 +105,13 @@ public:
|
||||
|
||||
private:
|
||||
Concurrency::AsyncTaskQueue<false> &audio_queue_;
|
||||
Voice voices_[3];
|
||||
|
||||
// TODO: an emulator thread copy of voices needs to be kept too, to do the digital stuff, as
|
||||
// the current output of voice 3 can be read. Probably best if the audio thread posts its most
|
||||
// recent copy atomically and the emulator thread just catches up from whatever it has? I don't
|
||||
// think that spinning on voice 3 is common.
|
||||
Voice voices_[3];
|
||||
|
||||
uint8_t last_write_;
|
||||
|
||||
int16_t range_ = 0;
|
||||
|
||||
Reference in New Issue
Block a user