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Fully separates updates and outputs in operators; takes a shot at the snare.

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This commit is contained in:
Thomas Harte 2020-04-26 00:18:09 -04:00
parent a424e867f9
commit ee10fe3d2c
6 changed files with 126 additions and 80 deletions
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21
Components/OPL2/Implementation/Channel.cpp
View File

@ -34,22 +34,27 @@ void Channel::set_feedback_mode(uint8_t value) {
}
int Channel::update_melodic(const LowFrequencyOscillator &oscillator, Operator *modulator, Operator *carrier, bool force_key_on, OperatorOverrides *modulator_overrides, OperatorOverrides *carrier_overrides) {
modulator->update(modulator_state_, oscillator, key_on_ || force_key_on, period_ << frequency_shift_, octave_, modulator_overrides);
carrier->update(carrier_state_, oscillator, key_on_ || force_key_on, period_ << frequency_shift_, octave_, carrier_overrides);
if(use_fm_synthesis_) {
// Get modulator level, use that as a phase-adjusting input to the carrier and then return the carrier level.
modulator->update(modulator_state_, nullptr, oscillator, key_on_ || force_key_on, period_ << frequency_shift_, octave_, modulator_overrides);
carrier->update(carrier_state_, &modulator_state_, oscillator, key_on_ || force_key_on, period_ << frequency_shift_, octave_, carrier_overrides);
return carrier_state_.level();
const LogSign modulator_output = modulator->melodic_output(modulator_state_);
return carrier->melodic_output(carrier_state_, &modulator_output).level();
} else {
// Get modulator and carrier levels separately, return their sum.
modulator->update(modulator_state_, nullptr, oscillator, key_on_ || force_key_on, period_ << frequency_shift_, octave_, modulator_overrides);
carrier->update(carrier_state_, nullptr, oscillator, key_on_ || force_key_on, period_ << frequency_shift_, octave_, carrier_overrides);
return (modulator_state_.level() + carrier_state_.level()) >> 1;
return (carrier->melodic_output(carrier_state_).level() + modulator->melodic_output(carrier_state_).level()) >> 1;
}
}
int Channel::update_tom_tom(const LowFrequencyOscillator &oscillator, Operator *modulator, bool force_key_on, OperatorOverrides *modulator_overrides) {
modulator->update(modulator_state_, nullptr, oscillator, key_on_ || force_key_on, period_ << frequency_shift_, octave_, modulator_overrides);
return modulator_state_.level();
modulator->update(modulator_state_, oscillator, key_on_ || force_key_on, period_ << frequency_shift_, octave_, modulator_overrides);
return modulator->melodic_output(modulator_state_).level();
}
int Channel::update_snare(const LowFrequencyOscillator &oscillator, Operator *carrier, bool force_key_on, OperatorOverrides *carrier_overrides) {
carrier->update(carrier_state_, oscillator, key_on_ || force_key_on, period_ << frequency_shift_, octave_, carrier_overrides);
return carrier->snare_output(modulator_state_).level();
}
bool Channel::is_audible(Operator *carrier, OperatorOverrides *carrier_overrides) {

4
Components/OPL2/Implementation/Channel.hpp
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@ -46,10 +46,10 @@ class Channel {
int update_tom_tom(const LowFrequencyOscillator &oscillator, Operator *modulator, bool force_key_on, OperatorOverrides *modulator_overrides = nullptr);
/// Updates this channel, using the carrier to produce a snare drum and the modulator to produce a tom tom.
int update_snare_tom_tom(const LowFrequencyOscillator &oscillator, Operator *modulator, Operator *carrier, OperatorOverrides *modulator_overrides = nullptr, OperatorOverrides *carrier_overrides = nullptr);
int update_snare(const LowFrequencyOscillator &oscillator, Operator *carrier, bool force_key_on, OperatorOverrides *carrier_overrides = nullptr);
/// Updates this channel, using the carrier to produce a cymbal and the modulator to produce a high-hat.
int update_symbal_high_hat(const LowFrequencyOscillator &oscillator, Operator *modulator, Operator *carrier, OperatorOverrides *modulator_overrides = nullptr, OperatorOverrides *carrier_overrides = nullptr);
int update_cymbal_high_hat(const LowFrequencyOscillator &oscillator, Operator *modulator, Operator *carrier, OperatorOverrides *modulator_overrides = nullptr, OperatorOverrides *carrier_overrides = nullptr);
/// @returns @c true if this channel is currently producing any audio; @c false otherwise;
bool is_audible(Operator *carrier, OperatorOverrides *carrier_overrides = nullptr);

133
Components/OPL2/Implementation/Operator.cpp
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@ -15,10 +15,6 @@ using namespace Yamaha::OPL;
// MARK: - Setters
int OperatorState::level() {
return power_two(attenuation);
}
void Operator::set_attack_decay(uint8_t value) {
attack_rate_ = (value & 0xf0) >> 2;
decay_rate_ = (value & 0x0f) << 2;
@ -167,46 +163,6 @@ void Operator::update_adsr(
++state.attack_time_;
}
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.
constexpr int key_level_scale_shifts[4] = {7, 1, 2, 0}; // '7' is just a number large enough to render all the numbers below as 0.
constexpr int key_level_scales[8][16] = {
#define _ 0
// 6 db attenuations.
{_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _},
{_, _, _, _, _, _, _, _, _, 4, 6, 8, 10, 12, 14, 16},
{_, _, _, _, _, 6, 10, 14, 16, 20, 22, 24, 26, 28, 30, 32},
{_, _, _, 10, 16, 22, 26, 30, 32, 36, 38, 40, 42, 44, 46, 48},
{_, _, 16, 26, 32, 38, 42, 46, 48, 52, 54, 56, 58, 60, 62, 64},
{_, 16, 32, 42, 48, 54, 58, 62, 64, 68, 70, 72, 74, 76, 78, 80},
{_, 32, 48, 58, 64, 70, 74, 78, 80, 84, 86, 88, 90, 92, 94, 96},
{_, 48, 64, 74, 80, 86, 90, 94, 96, 100, 102, 104, 106, 108, 110, 112},
#undef _
};
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
// 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 += (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 += (state.adsr_attenuation_ << 3) + (attenuation_ << 5);
}
// Add optional tremolo.
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:
//
@ -229,9 +185,50 @@ void Operator::update_phase(OperatorState &state, const LowFrequencyOscillator &
state.raw_phase_ += multipliers[frequency_multiple_] * (channel_period + vibrato) << channel_octave;
}
int Operator::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.
constexpr int key_level_scale_shifts[4] = {7, 1, 2, 0}; // '7' is just a number large enough to render all the numbers below as 0.
constexpr int key_level_scales[8][16] = {
#define _ 0
// 6 db attenuations.
{_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _},
{_, _, _, _, _, _, _, _, _, 4, 6, 8, 10, 12, 14, 16},
{_, _, _, _, _, 6, 10, 14, 16, 20, 22, 24, 26, 28, 30, 32},
{_, _, _, 10, 16, 22, 26, 30, 32, 36, 38, 40, 42, 44, 46, 48},
{_, _, 16, 26, 32, 38, 42, 46, 48, 52, 54, 56, 58, 60, 62, 64},
{_, 16, 32, 42, 48, 54, 58, 62, 64, 68, 70, 72, 74, 76, 78, 80},
{_, 32, 48, 58, 64, 70, 74, 78, 80, 84, 86, 88, 90, 92, 94, 96},
{_, 48, 64, 74, 80, 86, 90, 94, 96, 100, 102, 104, 106, 108, 110, 112},
#undef _
};
assert((channel_period >> 6) < 16);
assert(channel_octave < 8);
return (key_level_scales[channel_octave][channel_period >> 6] >> key_level_scale_shifts[key_level_scaling_]) << 7;
}
int Operator::attenuation_adsr(OperatorState &state, const LowFrequencyOscillator &oscillator, const OperatorOverrides *overrides) {
int attenuation = 0;
// 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).
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.
attenuation += (state.adsr_attenuation_ << 3) + (attenuation_ << 5);
}
// Add optional tremolo.
return attenuation + (int(apply_amplitude_modulation_) * oscillator.tremolo << 4);
}
void Operator::update(
OperatorState &state,
const OperatorState *phase_offset,
const LowFrequencyOscillator &oscillator,
bool key_on,
int channel_period,
@ -239,7 +236,16 @@ void Operator::update(
const OperatorOverrides *overrides) {
update_adsr(state, oscillator, key_on, channel_period, channel_octave, overrides);
update_phase(state, oscillator, channel_period, channel_octave);
state.key_level_scaling_ = key_level_scaling(state, channel_period, channel_octave);
state.channel_adsr_attenuation_ = attenuation_adsr(state, oscillator, overrides);
state.lfsr_ = oscillator.lfsr;
}
// TODO: both the tremolo and ADSR envelopes should be half-resolution on an OPLL.
// MARK: - Output Generators.
LogSign Operator::melodic_output(OperatorState &state, const LogSign *phase_offset) {
// Calculate raw attenuation level.
constexpr int waveforms[4][4] = {
{1023, 1023, 1023, 1023}, // Sine: don't mask in any quadrant.
@ -247,12 +253,39 @@ void Operator::update(
{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 scaled_phase_offset = phase_offset ? phase_offset->level(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);
LogSign result = negative_log_sin(phase & waveforms[int(waveform_)][(phase >> 8) & 3]);
result += state.key_level_scaling_;
result += state.channel_adsr_attenuation_;
return result;
}
// TODO: both the tremolo and ADSR envelopes should be half-resolution on an OPLL.
LogSign Operator::snare_output(OperatorState &state) {
LogSign result;
// If noise is 0, output is positive.
// If noise is 1, output is negative.
// If (noise ^ sign) is 0, output is 0. Otherwise it is max.
// const int angle = ((state.lfsr_ << 10) ^ (state.raw_phase_ >> 12)) & 0x100;
//
// result = negative_log_sin((state.raw_phase_ >> 11) &;
// constexpr int masks[] = {~0, 0};
// result += masks[state.lfsr_
if((state.raw_phase_ >> 11) & 0x200) {
// Result is -max if LFSR is 0, otherwise -0.
result = negative_log_sin(1024 + ((state.lfsr_^1) << 8));
} else {
// Result is +max if LFSR is 1, otherwise +0.
result = negative_log_sin(state.lfsr_ << 8);
}
// printf("%d %d: %d/%d\n", state.lfsr_, (state.raw_phase_ >> 11) & 1023, result.log, result.sign);
result += state.key_level_scaling_;
result += state.channel_adsr_attenuation_;
return result;
}

27
Components/OPL2/Implementation/Operator.hpp
View File

@ -17,25 +17,24 @@ namespace Yamaha {
namespace OPL {
/*!
Describes the ephemeral state of an operator.
Opaquely describes the ephemeral state of an operator.
*/
struct OperatorState {
public:
/// @returns The linear output level for the operator with this state..
int level();
private:
LogSign attenuation;
int raw_phase_ = 0;
friend class Operator;
int raw_phase_ = 0;
enum class ADSRPhase {
Attack, Decay, Sustain, Release
} adsr_phase_ = ADSRPhase::Attack;
int attack_time_ = 0;
int adsr_attenuation_ = 511;
bool last_key_on_ = false;
int attack_time_ = 0;
friend class Operator;
int key_level_scaling_;
int channel_adsr_attenuation_;
int lfsr_;
bool last_key_on_ = false;
};
/*!
@ -86,7 +85,6 @@ class Operator {
/// Provides one clock tick to the operator, along with the relevant parameters of its channel.
void update(
OperatorState &state,
const OperatorState *phase_offset,
const LowFrequencyOscillator &oscillator,
bool key_on,
int channel_period,
@ -96,6 +94,9 @@ class Operator {
/// @returns @c true if this channel currently has a non-zero output; @c false otherwise.
bool is_audible(OperatorState &state, OperatorOverrides *overrides = nullptr);
LogSign melodic_output(OperatorState &state, const LogSign *phase_offset = nullptr);
LogSign snare_output(OperatorState &state);
private:
/// If true then an amplitude modulation of "3.7Hz" is applied,
/// with a depth "determined by the AM-DEPTH of the BD register"?
@ -149,10 +150,10 @@ class Operator {
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);
int 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);
int attenuation_adsr(OperatorState &state, const LowFrequencyOscillator &oscillator, const OperatorOverrides *overrides);
};

7
Components/OPL2/Implementation/Tables.hpp
View File

@ -44,6 +44,8 @@ struct LogSign {
sign *= log_sign.sign;
return *this;
}
int level(int fractional = 0) const;
};
/*!
@ -214,6 +216,11 @@ constexpr uint8_t percussion_patch_set[] = {
0x05, 0x01, 0x00, 0x00, 0xf8, 0xaa, 0x59, 0x55,
};
inline int LogSign::level(int fractional) const {
return power_two(*this, fractional);
}
}
}

14
Components/OPL2/OPL2.cpp
View File

@ -68,7 +68,8 @@ void OPLL::get_samples(std::size_t number_of_samples, std::int16_t *target) {
while(number_of_samples--) {
if(!audio_offset_) update_all_chanels();
if(!(audio_offset_&3)) oscillator_.update_lfsr();
if(!(audio_offset_&3))
oscillator_.update_lfsr();
*target = int16_t(output_levels_[audio_offset_ / channel_output_period]);
++target;
@ -140,7 +141,7 @@ void OPLL::write_register(uint8_t address, uint8_t value) {
// Register 0xe is a cut-down version of the OPLL's register 0xbd.
if(address == 0xe) {
depth_rhythm_control_ = value & 0x3f;
// if(depth_rhythm_control_ & 0x04)
// if(depth_rhythm_control_ & 0x08)
// printf("%02x\n", depth_rhythm_control_);
return;
}
@ -225,8 +226,9 @@ void OPLL::update_all_chanels() {
output_levels_[1] = output_levels_[14] =
VOLUME(channels_[7].update_tom_tom(oscillator_, &operators_[34], depth_rhythm_control_ & 0x04));
// TODO: snare.
output_levels_[6] = output_levels_[16] = 0;
// Use the carrier from channel 7 for the snare.
output_levels_[6] = output_levels_[16] =
VOLUME(channels_[7].update_snare(oscillator_, &operators_[35], depth_rhythm_control_ & 0x08));
// TODO: cymbal.
output_levels_[7] = output_levels_[17] = 0;
@ -250,9 +252,7 @@ void OPLL::update_all_chanels() {
// Test!
// for(int c = 0; c < 18; ++c) {
//// if(c != 1 && c != 14 && c != 2 && c != 15)
//// output_levels_[c] = 0;
// if(c != 1 && c != 14)
// if(c != 6 && c != 16)
// output_levels_[c] = 0;
// }