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Simplifies the phase counter.

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This commit is contained in:
Thomas Harte 2020-04-19 00:30:14 -04:00
parent cdfd7de221
commit 020c760976
3 changed files with 5 additions and 10 deletions
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12
Components/OPL2/Implementation/Operator.cpp
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@ -64,14 +64,7 @@ void Operator::update(OperatorState &state, bool key_on, int channel_period, int
};
// 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 = 4096 >> channel_octave;
state.divider_ %= octave_divider;
state.divider_ += channel_period;
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.
state.raw_phase_ += multipliers[frequency_multiple_] * channel_period << channel_octave;
// Hence calculate phase (TODO: by also taking account of vibrato).
constexpr int waveforms[4][4] = {
@ -80,7 +73,8 @@ void Operator::update(OperatorState &state, bool key_on, int channel_period, int
{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.
};
state.phase = state.raw_phase_ & waveforms[int(waveform_)][(state.raw_phase_ >> 8) & 3];
const int phase = state.raw_phase_ >> 11;
state.phase = 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.

1
Components/OPL2/Implementation/Operator.hpp
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@ -23,7 +23,6 @@ struct OperatorState {
int attenuation = 1023; // Will be in the range [0, 1023].
private:
int divider_ = 0;
int raw_phase_ = 0;
enum class ADSRPhase {

2
Components/OPL2/OPL2.cpp
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@ -195,6 +195,8 @@ void OPLL::update_all_chanels() {
channels_[c].level = (channels_[c].update() * total_volume_) >> 14;
}
}
// channels_[2].level = (channels_[2].update() * total_volume_) >> 14;
}
/*