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Attempts to move forward in defining what the parts of an OPL are meant to do.
This commit is contained in:
Thomas Harte
parent
a0d14f4030
commit
84b115f15f
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@ -157,38 +157,37 @@ void OPLL::write_register(uint8_t address, uint8_t value) {
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return;
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}
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// Locations 0x30 to 0x38: select an instrument in the top nibble, set a channel volume in the lower.
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if(address >= 0x30 && address <= 0x38) {
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const auto index = address - 0x30;
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const auto instrument = value >> 4;
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channels_[index].output_level = value & 0xf;
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channels_[index].modulator = &operators_[instrument * 2];
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return;
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}
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// Register 0xe is a cut-down version of the OPLL's register 0xbd.
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if(address == 0xe) {
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depth_rhythm_control_ = value & 0x3f;
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return;
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}
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// Registers 0x10 to 0x18 set the bottom part of the channel frequency.
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if(address >= 0x10 && address <= 0x18) {
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const auto index = address - 0x10;
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channels_[index].frequency = (channels_[index].frequency & ~0xff) | value;
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return;
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}
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const auto index = address & 0xf;
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if(index > 8) return;
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// 0x20 to 0x28 set sustain on/off, key on/off, octave and a single extra bit of frequency.
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// So they're a lot like OPLL registers 0xb0 to 0xb8, but not identical.
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if(address >= 0x20 && address <= 0x28) {
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const auto index = address - 0x20;
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channels_[index].frequency = (channels_[index].frequency & 0xff) | (value & 1);
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channels_[index].octave = (value >> 1) & 0x7;
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channels_[index].key_on = value & 0x10;
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channels_[index].hold_sustain_level = value & 0x20;
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return;
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switch(address & 0xf0) {
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case 0x30:
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// Select an instrument in the top nibble, set a channel volume in the lower.
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channels_[index].output_level = value & 0xf;
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channels_[index].modulator = &operators_[(value >> 4) * 2];
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break;
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case 0x10:
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// Set the bottom part of the channel frequency.
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channels_[index].frequency = (channels_[index].frequency & ~0xff) | value;
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break;
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case 0x20:
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// Set sustain on/off, key on/off, octave and a single extra bit of frequency.
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// So they're a lot like OPLL registers 0xb0 to 0xb8, but not identical.
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channels_[index].frequency = (channels_[index].frequency & 0xff) | (value & 1);
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channels_[index].octave = (value >> 1) & 0x7;
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channels_[index].key_on = value & 0x10;
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channels_[index].hold_sustain_level = value & 0x20;
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break;
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default: break;
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}
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});
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}
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@ -197,21 +196,22 @@ void OPLL::setup_fixed_instrument(int number, const uint8_t *data) {
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auto modulator = &operators_[number * 2];
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auto carrier = &operators_[number * 2 + 1];
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modulator->set_am_vibrato_hold_sustain_ksr_multiple(data[0]);
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carrier->set_am_vibrato_hold_sustain_ksr_multiple(data[1]);
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modulator->set_scaling_output(data[2]);
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// Set waveforms — only sine and halfsine are available.
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carrier->waveform = Operator::Waveform((data[3] & 0x10) ? 1 : 0);
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modulator->waveform = Operator::Waveform((data[3] & 0x08) ? 1 : 0);
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carrier->set_waveform((data[3] >> 4) & 1);
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modulator->set_waveform((data[3] >> 3) & 1);
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// Set modulator amplitude and key-scale level.
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modulator->scaling_level = data[2] >> 6;
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modulator->output_level = data[2] & 0x3f;
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// TODO: data[3] b0-b2: modulator feedback level
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// TODO: data[3] b6, b7: carrier key-scale level
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// set_opl2_register(0x20 + carrier, source[0]);
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// set_opl2_register(0x20 + modulator, source[1]);
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// set_opl2_register(0x40 + carrier, source[2]);
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// set_opl2_register(0x60 + carrier, source[4]);
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// set_opl2_register(0x60 + modulator, source[5]);
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// set_opl2_register(0x80 + carrier, source[6]);
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// set_opl2_register(0x80 + modulator, source[7]);
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// Set ADSR parameters.
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modulator->set_attack_decay(data[4]);
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carrier->set_attack_decay(data[5]);
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modulator->set_sustain_release(data[6]);
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carrier->set_sustain_release(data[7]);
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}
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/*
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@ -266,59 +266,28 @@ void OPL2::write_register(uint8_t address, uint8_t value) {
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// Operator modifications.
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//
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// The 18 operators are spreat out across 22 addresses; each group of
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// six is framed within an eight-byte area thusly:
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constexpr int operator_by_address[] = {
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0, 1, 2, 3, 4, 5, -1, -1,
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6, 7, 8, 9, 10, 11, -1, -1,
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12, 13, 14, 15, 16, 17, -1, -1
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};
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if((address >= 0x20 && address < 0xa0) || address >= 0xe0) {
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// The 18 operators are spreat out across 22 addresses; each group of
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// six is framed within an eight-byte area thusly:
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constexpr int operator_by_address[] = {
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0, 1, 2, 3, 4, 5, -1, -1,
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6, 7, 8, 9, 10, 11, -1, -1,
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12, 13, 14, 15, 16, 17, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1,
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};
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if(address >= 0x20 && address <= 0x35) {
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const auto index = operator_by_address[address - 0x20];
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const auto index = operator_by_address[address & 0x1f];
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if(index == -1) return;
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operators_[index].apply_amplitude_modulation = value & 0x80;
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operators_[index].apply_vibrato = value & 0x40;
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operators_[index].hold_sustain_level = value & 0x20;
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operators_[index].keyboard_scaling_rate = value & 0x10;
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operators_[index].frequency_multiple = value & 0xf;
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return;
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}
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switch(address & 0xe0) {
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case 0x20: operators_[index].set_am_vibrato_hold_sustain_ksr_multiple(value); break;
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case 0x40: operators_[index].set_scaling_output(value); break;
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case 0x60: operators_[index].set_attack_decay(value); break;
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case 0x80: operators_[index].set_sustain_release(value); break;
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case 0xe0: operators_[index].set_waveform(value); break;
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if(address >= 0x40 && address <= 0x55) {
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const auto index = operator_by_address[address - 0x40];
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if(index == -1) return;
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operators_[index].scaling_level = value >> 6;
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operators_[index].output_level = value & 0x3f;
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return;
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}
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if(address >= 0x60 && address <= 0x75) {
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const auto index = operator_by_address[address - 0x60];
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if(index == -1) return;
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operators_[index].attack_rate = value >> 5;
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operators_[index].decay_rate = value & 0xf;
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return;
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}
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if(address >= 0x80 && address <= 0x95) {
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const auto index = operator_by_address[address - 0x80];
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if(index == -1) return;
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operators_[index].sustain_level = value >> 5;
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operators_[index].release_rate = value & 0xf;
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return;
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}
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if(address >= 0xe0 && address <= 0xf5) {
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const auto index = operator_by_address[address - 0xe0];
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if(index == -1) return;
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operators_[index].waveform = Operator::Waveform(value & 3);
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return;
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default: break;
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}
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}
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@ -326,21 +295,25 @@ void OPL2::write_register(uint8_t address, uint8_t value) {
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// Channel modifications.
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//
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if(address >= 0xa0 && address <= 0xa8) {
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channels_[address - 0xa0].frequency = (channels_[address - 0xa0].frequency & ~0xff) | value;
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return;
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}
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if(address >= 0xa0 && address <= 0xd0) {
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const auto index = address & 0xf;
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if(index > 8) return;
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if(address >= 0xb0 && address <= 0xb8) {
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channels_[address - 0xb0].frequency = (channels_[address - 0xb0].frequency & 0xff) | ((value & 3) << 8);
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channels_[address - 0xb0].octave = (value >> 2) & 0x7;
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channels_[address - 0xb0].key_on = value & 0x20;;
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return;
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}
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switch(address & 0xf0) {
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case 0xa0:
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channels_[index].frequency = (channels_[index].frequency & ~0xff) | value;
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break;
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case 0xb0:
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channels_[index].frequency = (channels_[index].frequency & 0xff) | ((value & 3) << 8);
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channels_[index].octave = (value >> 2) & 0x7;
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channels_[index].key_on = value & 0x20;;
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break;
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case 0xc0:
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channels_[index].feedback_strength = (value >> 1) & 0x7;
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channels_[index].use_fm_synthesis = value & 1;
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break;
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}
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if(address >= 0xc0 && address <= 0xc8) {
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channels_[address - 0xc0].feedback_strength = (value >> 1) & 0x7;
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channels_[address - 0xc0].use_fm_synthesis = value & 1;
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return;
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}
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@ -18,68 +18,170 @@ namespace Yamaha {
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namespace OPL {
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struct Operator {
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/// If true then an amplitude modulation of "3.7Hz" is applied,
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/// with a depth "determined by the AM-DEPTH of the BD register"?
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bool apply_amplitude_modulation = false;
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/*!
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Models an operator.
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/// If true then a vibrato of '6.4 Hz' is applied, with a depth
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/// "determined by VOB_DEPTH of the BD register"?
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bool apply_vibrato = false;
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In Yamaha FM terms, an operator is a combination of a few things:
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/// Selects between an ADSR envelope that holds at the sustain level
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/// for as long as this key is on, releasing afterwards, and one that
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/// simply switches straight to the release rate once the sustain
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/// level is hit, getting back to 0 regardless of an ongoing key-on.
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bool hold_sustain_level = false;
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* an oscillator, producing one of a handful of sine-derived waveforms;
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* an ADSR output level envelope; and
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* a bunch of potential adjustments to those two things:
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* optional tremolo and/or vibrato (the rates of which are global);
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* the option to skip 'sustain' in ADSR and go straight to release (since no sustain period is supplied,
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it otherwise runs for as long as the programmer leaves a channel enabled);
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* an attenuation for the output level; and
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* a factor by which to speed up the ADSR envelope as a function of frequency.
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/// Provides a potential faster step through the ADSR envelope. Cf. p12.
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bool keyboard_scaling_rate = false;
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Oscillator frequency isn't set directly, it's a multiple of the owning channel, in which
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frequency is set as a combination of f-num and octave.
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*/
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class Operator {
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public:
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/// Sets this operator's attack rate as the top nibble of @c value, its decay rate as the bottom nibble.
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void set_attack_decay(uint8_t value) {
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attack_rate = value >> 4;
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decay_rate = value & 0xf;
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}
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/// Indexes a lookup table to determine what multiple of the channel's frequency
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/// this operator is advancing at.
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int frequency_multiple = 0;
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/// Sets this operator's sustain level as the top nibble of @c value, its release rate as the bottom nibble.
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void set_sustain_release(uint8_t value) {
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sustain_level = value >> 4;
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release_rate = value & 0xf;
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}
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/// Sets the current output level of this modulator, as an attenuation.
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int output_level = 0;
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/// Sets this operator's key scale level as the top two bits of @c value, its total output level as the low six bits.
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void set_scaling_output(uint8_t value) {
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scaling_level = value >> 6;
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output_level = value & 0x3f;
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}
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/// Selects attenuation that is applied as a function of interval. Cf. p14.
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int scaling_level = 0;
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/// Sets this operator's waveform using the low two bits of @c value.
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void set_waveform(uint8_t value) {
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waveform = Operator::Waveform(value & 3);
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}
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/// Sets the ADSR rates.
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int attack_rate = 0;
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int decay_rate = 0;
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int sustain_level = 0;
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int release_rate = 0;
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/// From the top nibble of @c value sets the AM, vibrato, hold/sustain level and keyboard sampling rate flags;
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/// uses the bottom nibble to set the frequency multiplier.
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void set_am_vibrato_hold_sustain_ksr_multiple(uint8_t value) {
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apply_amplitude_modulation = value & 0x80;
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apply_vibrato = value & 0x40;
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hold_sustain_level = value & 0x20;
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keyboard_scaling_rate = value & 0x10;
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frequency_multiple = value & 0xf;
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}
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/// Selects the generated waveform.
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enum class Waveform {
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Sine, HalfSine, AbsSine, PulseSine
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} waveform = Waveform::Sine;
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void update(int channel_frequency, int channel_octave) {
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// Per the documentation:
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// F-Num = Music Frequency * 2^(20-Block) / 49716
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//
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// Given that a 256-entry table is used to store a quarter of a sine wave,
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// making 1024 steps per complete wave, add what I've called frequency
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// to an accumulator and move on whenever that exceeds 2^(10 - octave).
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//
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// ... subject to each operator having a frequency multiple.
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//
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// Or: 2^19?
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// This encodes the MUL -> multiple table given on page 12,
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// multiplied by two.
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constexpr int multipliers[] = {
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1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 20, 24, 24, 30, 30
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};
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// Update the raw phase.
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const int octave_divider = (10 - channel_octave) << 9;
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divider_ += multipliers[frequency_multiple] * channel_frequency;
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raw_phase_ += divider_ / octave_divider;
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divider_ %= octave_divider;
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// Hence calculate phase (TODO: by also taking account of vibrato).
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constexpr int waveforms[4][4] = {
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{1023, 1023, 1023, 1023}, // Sine: don't mask in any quadrant.
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{511, 511, 0, 0}, // Half sine: keep the first half in tact, lock to 0 in the second half.
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{511, 511, 511, 511}, // AbsSine: endlessly repeat the first half of the sine wave.
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{255, 0, 255, 0}, // PulseSine: act as if the first quadrant is in the first and third; lock the other two to 0.
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};
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phase = raw_phase_ & waveforms[int(waveform)][(raw_phase_ >> 8) & 3];
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// TODO: calculate output volume properly; apply: ADSR and amplitude modulation (tremolo, I assume?)
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volume = output_level;
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}
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// Outputs.
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int phase = 0; // Will be in the range [0, 1023], mapping into a 1024-unit sine curve.
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int volume = 0;
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private:
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/// If true then an amplitude modulation of "3.7Hz" is applied,
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/// with a depth "determined by the AM-DEPTH of the BD register"?
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bool apply_amplitude_modulation = false;
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/// If true then a vibrato of '6.4 Hz' is applied, with a depth
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/// "determined by VOB_DEPTH of the BD register"?
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bool apply_vibrato = false;
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/// Selects between an ADSR envelope that holds at the sustain level
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/// for as long as this key is on, releasing afterwards, and one that
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/// simply switches straight to the release rate once the sustain
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/// level is hit, getting back to 0 regardless of an ongoing key-on.
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bool hold_sustain_level = false;
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/// Provides a potential faster step through the ADSR envelope. Cf. p12.
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bool keyboard_scaling_rate = false;
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/// Indexes a lookup table to determine what multiple of the channel's frequency
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/// this operator is advancing at.
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int frequency_multiple = 0;
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/// Sets the current output level of this modulator, as an attenuation.
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int output_level = 0;
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/// Selects attenuation that is applied as a function of interval. Cf. p14.
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int scaling_level = 0;
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/// Sets the ADSR rates.
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int attack_rate = 0;
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int decay_rate = 0;
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int sustain_level = 0;
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int release_rate = 0;
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/// Selects the generated waveform.
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enum class Waveform {
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Sine, HalfSine, AbsSine, PulseSine
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} waveform = Waveform::Sine;
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// Ephemeral state.
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int raw_phase_ = 0;
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int divider_ = 0;
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};
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/*!
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Models an L-type two-operator channel.
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Assuming FM synthesis is enabled, the channel modulates the output of the carrier with that of the modulator.
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*/
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struct Channel {
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/// 'F-Num' in the spec; this plus the current octave determines channel frequency.
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int frequency = 0;
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/// Linked with the frequency, determines the channel frequency.
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int octave = 0;
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/// Sets sets this channel on or off, as an input to the ADSR envelope,
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bool key_on = false;
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/// Sets the degree of feedback applied to the modulator.
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int feedback_strength = 0;
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/// Selects between FM synthesis, using the modulator to modulate the carrier, or simple mixing of the two
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/// underlying operators as completely disjoint entities.
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bool use_fm_synthesis = true;
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// This should be called at a rate of around 49,716 Hz.
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void update() {
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// Per the documentation:
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// F-Num = Music Frequency * 2^(20-Block) / 49716
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//
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// Given that a 256-entry table is used to store a quarter of a sine wave,
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// making 1024 steps per complete wave, add what I've called frequency
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// to an accumulator and move on whenever that exceeds 2^(10 - octave).
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//
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// TODO: but, how does that apply to the two operator multipliers?
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//
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// Or: 2^19?
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void update(Operator *carrier, Operator *modulator) {
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modulator->update(frequency, octave);
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carrier->update(frequency, octave);
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}
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// Stateful information.
|
||||
};
|
||||
|
||||
template <typename Child> class OPLBase: public ::Outputs::Speaker::SampleSource {
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user