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With some fixes for scale, I think possibly this is close for melodic channels.

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This commit is contained in:
Thomas Harte 2020-04-15 21:27:27 -04:00
parent a7e63b61eb
commit 30ff399218
2 changed files with 17 additions and 11 deletions
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12
Components/OPL2/OPL2.cpp
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@ -403,10 +403,14 @@ void Operator::update(OperatorState &state, bool key_on, int channel_period, int
}; };
// Update the raw phase. // Update the raw phase.
// TODO: if this is the real formula (i.e. a downward shift for channel_octave), this is a highly
// suboptimal way to do this. Could just keep one accumulator and shift that downward for the result.
const int octave_divider = 2048 >> channel_octave; const int octave_divider = 2048 >> channel_octave;
state.divider_ %= octave_divider; state.divider_ %= octave_divider;
state.divider_ += multipliers[frequency_multiple] * channel_period; state.divider_ += channel_period;
state.raw_phase_ += state.divider_ / octave_divider; state.raw_phase_ += multipliers[frequency_multiple] * (state.divider_ / octave_divider);
// TODO: this last step introduces aliasing, but is a quick way to verify whether the multiplier should
// be applied also to the octave.
// Hence calculate phase (TODO: by also taking account of vibrato). // Hence calculate phase (TODO: by also taking account of vibrato).
constexpr int waveforms[4][4] = { constexpr int waveforms[4][4] = {
@ -512,9 +516,9 @@ void Operator::update(OperatorState &state, bool key_on, int channel_period, int
// Combine the ADSR attenuation and overall channel attenuation, clamping to the permitted range. // Combine the ADSR attenuation and overall channel attenuation, clamping to the permitted range.
if(overrides) { if(overrides) {
state.attenuation = state.adsr_attenuation_ + (overrides->attenuation << 6); state.attenuation = state.adsr_attenuation_ + (overrides->attenuation << 4);
} else { } else {
state.attenuation = state.adsr_attenuation_ + (attenuation_ << 3); state.attenuation = state.adsr_attenuation_ + (attenuation_ << 2);
} }
} }

16
Components/OPL2/OPL2.hpp
View File

@ -92,7 +92,7 @@ class Operator {
/// Sets this operator's waveform using the low two bits of @c value. /// Sets this operator's waveform using the low two bits of @c value.
void set_waveform(uint8_t value) { void set_waveform(uint8_t value) {
// waveform = Operator::Waveform(value & 3); waveform = Operator::Waveform(value & 3);
} }
/// From the top nibble of @c value sets the AM, vibrato, hold/sustain level and keyboard sampling rate flags; /// From the top nibble of @c value sets the AM, vibrato, hold/sustain level and keyboard sampling rate flags;
@ -204,7 +204,7 @@ class Channel {
// TODO: almost everything. This is a quick test. // TODO: almost everything. This is a quick test.
// Specifically: use lookup tables. // Specifically: use lookup tables.
const auto modulator_level = 0.0f;//level(modulator_state_, 0.0f) * 0.25f; const auto modulator_level = level(modulator_state_, 0.0f); // TODO: what's the proper scaling on this?
return int(level(carrier_state_, modulator_level) * 20'000.0f); return int(level(carrier_state_, modulator_level) * 20'000.0f);
} }
@ -218,7 +218,9 @@ class Channel {
const float phase = modulator_level + float(state.phase) / 1024.0f; const float phase = modulator_level + float(state.phase) / 1024.0f;
const float phase_attenuation = logf(1.0f + sinf(float(M_PI) * 2.0f * phase)); const float phase_attenuation = logf(1.0f + sinf(float(M_PI) * 2.0f * phase));
const float total_attenuation = phase_attenuation + float(state.attenuation) / 1023.0f; const float total_attenuation = phase_attenuation + float(state.attenuation) / 1023.0f;
return expf(total_attenuation); const float result = expf(total_attenuation / 2.0f);
return result;
} }
/// 'F-Num' in the spec; this plus the current octave determines channel frequency. /// 'F-Num' in the spec; this plus the current octave determines channel frequency.
@ -334,10 +336,10 @@ struct OPLL: public OPLBase<OPLL> {
int level = 0; int level = 0;
}; };
void update_all_chanels() { void update_all_chanels() {
// for(int c = 0; c < 6; ++ c) { // Don't do anything with channels that might be percussion for now. for(int c = 0; c < 6; ++ c) { // Don't do anything with channels that might be percussion for now.
// channels_[c].level = (channels_[c].update() * total_volume_) >> 14; channels_[c].level = (channels_[c].update() * total_volume_) >> 14;
// } }
channels_[0].level = (channels_[0].update() * total_volume_) >> 14; channels_[2].level = (channels_[2].update() * total_volume_) >> 14;
} }
Channel channels_[9]; Channel channels_[9];