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Minor layout and commenting improvements.

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This commit is contained in:
Thomas Harte 2020-04-21 23:35:48 -04:00
parent 676dcf7fbb
commit c7ad6b1b50
1 changed files with 12 additions and 2 deletions
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14
Components/OPL2/Implementation/Operator.cpp
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@ -13,6 +13,8 @@
using namespace Yamaha::OPL;
// MARK: - Setters
int OperatorState::level() {
return power_two(attenuation);
}
@ -44,7 +46,10 @@ void Operator::set_am_vibrato_hold_sustain_ksr_multiple(uint8_t value) {
frequency_multiple_ = value & 0xf;
}
// MARK: - Getter
bool Operator::is_audible(OperatorState &state, OperatorOverrides *overrides) {
// TODO: (i) do I actually want to support this functionality? (ii) if so, fix below.
if(state.adsr_phase_ == OperatorState::ADSRPhase::Release) {
if(overrides) {
if(overrides->attenuation == 0xf) return false;
@ -55,6 +60,8 @@ bool Operator::is_audible(OperatorState &state, OperatorOverrides *overrides) {
return state.adsr_attenuation_ != 511;
}
// MARK: - Update logic.
void Operator::update(OperatorState &state, bool key_on, int channel_period, int channel_octave, OperatorState *phase_offset, OperatorOverrides *overrides) {
// Per the documentation:
//
@ -74,7 +81,7 @@ void Operator::update(OperatorState &state, bool key_on, int channel_period, int
// Hence calculate phase (TODO: by also taking account of vibrato).
constexpr int waveforms[4][4] = {
{1023, 1023, 1023, 1023}, // Sine: don't mask in any quadrant.
{511, 511, 0, 0}, // Half sine: keep the first half in tact, lock to 0 in the second half.
{511, 511, 0, 0}, // Half sine: keep the first half intact, lock to 0 in the second half.
{511, 511, 511, 511}, // AbsSine: endlessly repeat the first half of the sine wave.
{255, 0, 255, 0}, // PulseSine: act as if the first quadrant is in the first and third; lock the other two to 0.
};
@ -142,9 +149,12 @@ void Operator::update(OperatorState &state, bool key_on, int channel_period, int
// A rate of 2 means increase 2 per cycle.
// A rate of 3 means increase 1 per cycle.
// A rate of 4 means increase 1 every other cycle.
// (etc)
// A rate of 5 means increase once every fourth cycle.
// etc.
// eighth, sixteenth, 32nd, 64th, 128th, 256th, 512th, 1024th, 2048th, 4096th, 8192th
const int decrease_rate = key_scaling_rate + ((state.adsr_phase_ == OperatorState::ADSRPhase::Decay) ? decay_rate_ : release_rate_);
if(decrease_rate) {
// TODO: don't throw away KSR bits.
switch(decrease_rate >> 2) {