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Looking towards rhythm mode, and in search of bugs: factors out ADSR.

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Further factorings to come.
This commit is contained in:
Thomas Harte 2020-04-24 18:48:32 -04:00
parent 983c32bf75
commit b3979e2fda
3 changed files with 73 additions and 37 deletions
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86
Components/OPL2/Implementation/Operator.cpp
View File

@ -62,45 +62,13 @@ bool Operator::is_audible(OperatorState &state, OperatorOverrides *overrides) {
// MARK: - Update logic.
void Operator::update(
void Operator::update_adsr(
OperatorState &state,
const OperatorState *phase_offset,
const LowFrequencyOscillator &oscillator,
bool key_on,
int channel_period,
int channel_octave,
const OperatorOverrides *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]);
// Key-on logic: any time it is false, be in the release state.
// On the leading edge of it becoming true, enter the attack state.
if(!key_on) {
@ -194,6 +162,50 @@ void Operator::update(
break;
}
++state.attack_time_;
}
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]);
// 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
@ -214,22 +226,22 @@ void Operator::update(
};
assert((channel_period >> 6) < 16);
assert(channel_octave < 8);
state.attenuation.log += (key_level_scales[channel_octave][channel_period >> 6] >> key_level_scale_shifts[key_level_scaling_]) << 7;
state.attenuation += (key_level_scales[channel_octave][channel_period >> 6] >> key_level_scale_shifts[key_level_scaling_]) << 7;
// 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
// attenuations of 24db to 3db; the main envelope generator is stated to have a resolution of
// 0.325db (which I've assumed is supposed to say 0.375db).
state.attenuation.log += (state.adsr_attenuation_ << 3) + (overrides->attenuation << 7);
state.attenuation += (state.adsr_attenuation_ << 3) + (overrides->attenuation << 7);
} else {
// Overrides here represent per-channel volume on an OPLL. The bits are defined to represent
// attenuations of 24db to 0.75db.
state.attenuation.log += (state.adsr_attenuation_ << 3) + (attenuation_ << 5);
state.attenuation += (state.adsr_attenuation_ << 3) + (attenuation_ << 5);
}
// Add optional tremolo.
state.attenuation.log += int(apply_amplitude_modulation_) * oscillator.tremolo << 4;
state.attenuation += int(apply_amplitude_modulation_) * oscillator.tremolo << 4;
}
// TODO: both the tremolo and ADSR envelopes should be half-resolution on an OPLL.

8
Components/OPL2/Implementation/Operator.hpp
View File

@ -135,6 +135,14 @@ class Operator {
enum class Waveform {
Sine, HalfSine, AbsSine, PulseSine
} waveform_ = Waveform::Sine;
void update_adsr(
OperatorState &state,
const LowFrequencyOscillator &oscillator,
bool key_on,
int channel_period,
int channel_octave,
const OperatorOverrides *overrides);
};
}

16
Components/OPL2/Implementation/Tables.hpp
View File

@ -28,6 +28,22 @@ namespace OPL {
struct LogSign {
int log;
int sign;
void reset() {
log = 0;
sign = 1;
}
LogSign &operator +=(int attenuation) {
log += attenuation;
return *this;
}
LogSign &operator +=(LogSign log_sign) {
log += log_sign.log;
sign *= log_sign.sign;
return *this;
}
};
/*!