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Continues factoring this apart, albeit with a decision on whether to retain update-and-output still pending.

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This commit is contained in:
Thomas Harte 2020-04-25 23:07:40 -04:00
parent f52b40396a
commit a424e867f9
2 changed files with 64 additions and 50 deletions
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101
Components/OPL2/Implementation/Operator.cpp
View File

@ -74,12 +74,11 @@ void Operator::update_adsr(
if(!key_on) {
state.adsr_phase_ = OperatorState::ADSRPhase::Release;
} else if(!state.last_key_on_) {
// printf("---\n");
state.adsr_phase_ = OperatorState::ADSRPhase::Attack;
state.attack_time_ = 0;
// TODO: should this happen only if current ADSR attenuation is 511?
// state.raw_phase_ = 0;
state.raw_phase_ = 0;
}
state.last_key_on_ = key_on;
@ -166,55 +165,9 @@ void Operator::update_adsr(
break;
}
++state.attack_time_;
// if(key_on) {
// printf("%d\n", state.adsr_attenuation_);
// }
}
void Operator::update(
OperatorState &state,
const OperatorState *phase_offset,
const LowFrequencyOscillator &oscillator,
bool key_on,
int channel_period,
int channel_octave,
const OperatorOverrides *overrides) {
state.attenuation.reset();
update_adsr(state, oscillator, key_on, channel_period, channel_octave, overrides);
// Per the documentation:
//
// Delta phase = ( [desired freq] * 2^19 / [input clock / 72] ) / 2 ^ (b - 1)
//
// After experimentation, I think this gives rate calculation as formulated below.
// This encodes the MUL -> multiple table given on page 12,
// multiplied by two.
constexpr int multipliers[] = {
1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 20, 24, 24, 30, 30
};
const int top_freq = channel_period >> 7;
assert(top_freq < 8);
constexpr int vibrato_shifts[8] = {3, 1, 0, 1, 3, 1, 0, 1};
constexpr int vibrato_signs[2] = {1, -1};
const int vibrato = (top_freq >> vibrato_shifts[oscillator.vibrato]) * vibrato_signs[oscillator.vibrato >> 2] * int(apply_vibrato_);
// Update the raw phase.
state.raw_phase_ += multipliers[frequency_multiple_] * (channel_period + vibrato) << channel_octave;
// Hence calculate phase.
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 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.
};
const int scaled_phase_offset = phase_offset ? power_two(phase_offset->attenuation, 11) : 0;
const int phase = (state.raw_phase_ + scaled_phase_offset) >> 11;
state.attenuation += negative_log_sin(phase & waveforms[int(waveform_)][(phase >> 8) & 3]);
void Operator::apply_key_level_scaling(OperatorState &state, int channel_period, int channel_octave) {
// Calculate key-level scaling. Table is as per p14 of the YM3812 application manual,
// converted into a fixed-point scheme. Compare with https://www.smspower.org/Development/RE12
// and apologies for the highly ad hoc indentation.
@ -235,7 +188,9 @@ void Operator::update(
assert((channel_period >> 6) < 16);
assert(channel_octave < 8);
state.attenuation += (key_level_scales[channel_octave][channel_period >> 6] >> key_level_scale_shifts[key_level_scaling_]) << 7;
}
void Operator::apply_attenuation_adsr(OperatorState &state, const LowFrequencyOscillator &oscillator, const OperatorOverrides *overrides) {
// Combine the ADSR attenuation and overall channel attenuation.
if(overrides) {
// Overrides here represent per-channel volume on an OPLL. The bits are defined to represent
@ -252,4 +207,52 @@ void Operator::update(
state.attenuation += int(apply_amplitude_modulation_) * oscillator.tremolo << 4;
}
void Operator::update_phase(OperatorState &state, const LowFrequencyOscillator &oscillator, int channel_period, int channel_octave) {
// Per the documentation:
//
// Delta phase = ( [desired freq] * 2^19 / [input clock / 72] ) / 2 ^ (b - 1)
//
// After experimentation, I think this gives rate calculation as formulated below.
// This encodes the MUL -> multiple table given on page 12,
// multiplied by two.
constexpr int multipliers[] = {
1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 20, 24, 24, 30, 30
};
const int top_freq = channel_period >> 7;
assert(top_freq < 8);
constexpr int vibrato_shifts[8] = {3, 1, 0, 1, 3, 1, 0, 1};
constexpr int vibrato_signs[2] = {1, -1};
const int vibrato = (top_freq >> vibrato_shifts[oscillator.vibrato]) * vibrato_signs[oscillator.vibrato >> 2] * int(apply_vibrato_);
// Update the raw phase.
state.raw_phase_ += multipliers[frequency_multiple_] * (channel_period + vibrato) << channel_octave;
}
void Operator::update(
OperatorState &state,
const OperatorState *phase_offset,
const LowFrequencyOscillator &oscillator,
bool key_on,
int channel_period,
int channel_octave,
const OperatorOverrides *overrides) {
update_adsr(state, oscillator, key_on, channel_period, channel_octave, overrides);
update_phase(state, oscillator, channel_period, channel_octave);
// Calculate raw attenuation level.
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 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.
};
const int scaled_phase_offset = phase_offset ? power_two(phase_offset->attenuation, 11) : 0;
const int phase = (state.raw_phase_ + scaled_phase_offset) >> 11;
state.attenuation = negative_log_sin(phase & waveforms[int(waveform_)][(phase >> 8) & 3]);
apply_key_level_scaling(state, channel_period, channel_octave);
apply_attenuation_adsr(state, oscillator, overrides);
}
// TODO: both the tremolo and ADSR envelopes should be half-resolution on an OPLL.

13
Components/OPL2/Implementation/Operator.hpp
View File

@ -136,13 +136,24 @@ class Operator {
Sine, HalfSine, AbsSine, PulseSine
} waveform_ = Waveform::Sine;
void update_adsr(
/// Updates the ADSR envelope.
void update_adsr(
OperatorState &state,
const LowFrequencyOscillator &oscillator,
bool key_on,
int channel_period,
int channel_octave,
const OperatorOverrides *overrides);
/// Updates the phase generator.
void update_phase(OperatorState &state, const LowFrequencyOscillator &oscillator, int channel_period, int channel_octave);
/// Adds key-level scaling to the current output state.
void apply_key_level_scaling(OperatorState &state, int channel_period, int channel_octave);
/// Adds ADSR and general channel attenuations to the output state.
void apply_attenuation_adsr(OperatorState &state, const LowFrequencyOscillator &oscillator, const OperatorOverrides *overrides);
};
}