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308 lines
11 KiB
C++
308 lines
11 KiB
C++
//
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// OPLL.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 03/05/2020.
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// Copyright © 2020 Thomas Harte. All rights reserved.
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//
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#include "OPLL.hpp"
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#include <cassert>
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using namespace Yamaha::OPL;
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OPLL::OPLL(Concurrency::DeferringAsyncTaskQueue &task_queue, int audio_divider, bool is_vrc7):
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OPLBase(task_queue), audio_divider_(audio_divider), is_vrc7_(is_vrc7) {
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// Due to the way that sound mixing works on the OPLL, the audio divider may not
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// be larger than 4.
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assert(audio_divider <= 4);
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// Set up proper damping management.
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for(int c = 0; c < 9; ++c) {
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envelope_generators_[c].set_should_damp([this, c] {
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// Propagate attack mode to the modulator, and reset both phases.
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envelope_generators_[c + 9].set_key_on(true);
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phase_generators_[c + 0].reset();
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phase_generators_[c + 9].reset();
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});
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}
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}
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// MARK: - Machine-facing programmatic input.
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void OPLL::write_register(uint8_t address, uint8_t value) {
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// The OPLL doesn't have timers or other non-audio functions, so all writes
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// go to the audio queue.
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task_queue_.defer([this, address, value] {
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// The first 8 locations are used to define the custom instrument, and have
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// exactly the same format as the patch set arrays at the head of this file.
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if(address < 8) {
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custom_instrument_[address] = value;
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// Update all channels that refer to instrument 0.
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for(int c = 0; c < 9; ++c) {
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if(!channels_[c].instrument) {
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install_instrument(c);
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}
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}
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return;
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}
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// Register 0xe enables or disables rhythm mode and contains the
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// percussion key-on bits.
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if(address == 0xe) {
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rhythm_mode_enabled_ = value & 0x20;
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rhythm_generators_[0].set_key_on(value & 0x01);
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rhythm_generators_[1].set_key_on(value & 0x02);
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rhythm_generators_[2].set_key_on(value & 0x04);
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rhythm_generators_[3].set_key_on(value & 0x08);
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rhythm_generators_[4].set_key_on(value & 0x10);
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return;
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}
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// That leaves only per-channel selections, for which the addressing
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// is completely orthogonal; check that a valid channel is being requested.
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const auto index = address & 0xf;
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if(index > 8) return;
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switch(address & 0xf0) {
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default: break;
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// Address 1x sets the low 8 bits of the period for channel x.
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case 0x10:
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channels_[index].period = (channels_[index].period & ~0xff) | value;
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set_channel_period(index);
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return;
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// Address 2x Sets the octave and a single bit of the frequency, as well
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// as setting key on and sustain mode.
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case 0x20:
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channels_[index].period = (channels_[index].period & 0xff) | ((value & 1) << 8);
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channels_[index].octave = (value >> 1) & 7;
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set_channel_period(index);
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// In this implementation the first 9 envelope generators are for
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// channel carriers, and their will_attack callback is used to trigger
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// key-on for modulators. But key-off needs to be set to both envelope
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// generators now.
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if(value & 0x10) {
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envelope_generators_[index].set_key_on(true);
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} else {
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envelope_generators_[index + 0].set_key_on(false);
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envelope_generators_[index + 9].set_key_on(false);
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}
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// Set sustain bit to both the relevant operators.
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channels_[index].use_sustain = value & 0x20;
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set_use_sustain(index);
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return;
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// Address 3x selects the instrument and attenuation for a channel;
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// in rhythm mode some of the nibbles that ordinarily identify instruments
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// instead nominate additional attenuations. This code reads those back
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// from the stored instrument values.
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case 0x30:
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channels_[index].instrument = value >> 4;
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channels_[index].attenuation = value >> 4;
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install_instrument(index);
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return;
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}
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});
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}
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void OPLL::set_channel_period(int channel) {
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phase_generators_[channel + 0].set_period(channels_[channel].period, channels_[channel].octave);
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phase_generators_[channel + 9].set_period(channels_[channel].period, channels_[channel].octave);
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envelope_generators_[channel + 0].set_period(channels_[channel].period, channels_[channel].octave);
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envelope_generators_[channel + 9].set_period(channels_[channel].period, channels_[channel].octave);
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key_level_scalers_[channel + 0].set_period(channels_[channel].period, channels_[channel].octave);
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key_level_scalers_[channel + 9].set_period(channels_[channel].period, channels_[channel].octave);
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}
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const uint8_t *OPLL::instrument_definition(int instrument) {
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// Instrument 0 is the custom instrument.
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if(!instrument) return custom_instrument_;
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// Instruments other than 0 are taken from the fixed set.
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const int index = (instrument - 1) * 8;
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return is_vrc7_ ? &vrc7_patch_set[index] : &opll_patch_set[index];
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}
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void OPLL::install_instrument(int channel) {
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auto &carrier_envelope = envelope_generators_[channel + 0];
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auto &carrier_phase = phase_generators_[channel + 0];
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auto &carrier_scaler = key_level_scalers_[channel + 0];
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auto &modulator_envelope = envelope_generators_[channel + 9];
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auto &modulator_phase = phase_generators_[channel + 9];
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auto &modulator_scaler = key_level_scalers_[channel + 9];
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const uint8_t *const instrument = instrument_definition(channels_[channel].instrument);
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// Bytes 0 (modulator) and 1 (carrier):
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//
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// b0-b3: multiplier;
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// b4: key-scale rate enable;
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// b5: sustain-level enable;
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// b6: vibrato enable;
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// b7: tremolo enable.
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modulator_phase.set_multiple(instrument[0] & 0xf);
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channels_[channel].modulator_key_rate_scale_multiplier = (instrument[0] >> 4) & 1;
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modulator_phase.set_vibrato_enabled(instrument[0] & 0x40);
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modulator_envelope.set_tremolo_enabled(instrument[0] & 0x80);
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carrier_phase.set_multiple(instrument[1] & 0xf);
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channels_[channel].carrier_key_rate_scale_multiplier = (instrument[1] >> 4) & 1;
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carrier_phase.set_vibrato_enabled(instrument[1] & 0x40);
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carrier_envelope.set_tremolo_enabled(instrument[1] & 0x80);
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// Pass off bit 5.
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set_use_sustain(channel);
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// Byte 2:
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//
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// b0–b5: modulator attenuation;
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// b6–b7: modulator key-scale level.
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modulator_scaler.set_key_scaling_level(instrument[3] >> 6);
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channels_[channel].modulator_attenuation = instrument[2] & 0x3f;
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// Byte 3:
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//
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// b0–b2: modulator feedback level;
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// b3: modulator waveform selection;
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// b4: carrier waveform selection;
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// b5: [unused]
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// b6–b7: carrier key-scale level.
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channels_[channel].modulator_feedback = instrument[3] & 7;
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channels_[channel].modulator_waveform = Waveform((instrument[3] >> 3) & 1);
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channels_[channel].carrier_waveform = Waveform((instrument[3] >> 4) & 1);
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carrier_scaler.set_key_scaling_level(instrument[3] >> 6);
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// Bytes 4 (modulator) and 5 (carrier):
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//
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// b0–b3: decay rate;
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// b4–b7: attack rate.
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modulator_envelope.set_decay_rate(instrument[4] & 0xf);
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modulator_envelope.set_attack_rate(instrument[4] >> 4);
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carrier_envelope.set_decay_rate(instrument[5] & 0xf);
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carrier_envelope.set_attack_rate(instrument[5] >> 4);
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// Bytes 6 (modulator) and 7 (carrier):
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//
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// b0–b3: release rate;
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// b4–b7: sustain level.
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modulator_envelope.set_release_rate(instrument[6] & 0xf);
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modulator_envelope.set_sustain_level(instrument[6] >> 4);
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carrier_envelope.set_release_rate(instrument[7] & 0xf);
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carrier_envelope.set_release_rate(instrument[7] >> 4);
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}
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void OPLL::set_use_sustain(int channel) {
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const uint8_t *const instrument = instrument_definition(channels_[channel].instrument);
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envelope_generators_[channel + 0].set_sustain_level((instrument[1] & 0x20) || channels_[channel].use_sustain);
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envelope_generators_[channel + 9].set_sustain_level((instrument[0] & 0x20) || channels_[channel].use_sustain);
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}
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// MARK: - Output generation.
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void OPLL::set_sample_volume_range(std::int16_t range) {
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total_volume_ = range;
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}
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void OPLL::get_samples(std::size_t number_of_samples, std::int16_t *target) {
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// Both the OPLL and the OPL2 divide the input clock by 72 to get the base tick frequency;
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// unlike the OPL2 the OPLL time-divides the output for 'mixing'.
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const int update_period = 72 / audio_divider_;
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const int channel_output_period = 4 / audio_divider_;
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// TODO: the conditional below is terrible. Fix.
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while(number_of_samples--) {
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if(!audio_offset_) update_all_channels();
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*target = output_levels_[audio_offset_ / channel_output_period];
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++target;
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audio_offset_ = (audio_offset_ + 1) % update_period;
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}
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}
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void OPLL::update_all_channels() {
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oscillator_.update();
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// Update all phase generators. That's guaranteed.
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for(int c = 0; c < 18; ++c) {
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phase_generators_[c].update(oscillator_);
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}
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// Update the ADSR envelopes that are guaranteed to be melodic.
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for(int c = 0; c < 6; ++c) {
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envelope_generators_[c + 0].update(oscillator_);
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envelope_generators_[c + 9].update(oscillator_);
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}
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#define VOLUME(x) int16_t(((x) * total_volume_) >> 12)
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if(rhythm_mode_enabled_) {
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// Advance the rhythm envelope generators.
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// TODO: these need to be properly seeded.
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for(int c = 0; c < 5; ++c) {
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oscillator_.update_lfsr();
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rhythm_generators_[c].update(oscillator_);
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}
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// Fill in the melodic channels.
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output_levels_[3] = VOLUME(melodic_output(0));
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output_levels_[4] = VOLUME(melodic_output(1));
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output_levels_[5] = VOLUME(melodic_output(2));
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output_levels_[9] = VOLUME(melodic_output(3));
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output_levels_[10] = VOLUME(melodic_output(4));
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output_levels_[11] = VOLUME(melodic_output(5));
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// TODO: drum noises. Also subject to proper channel population.
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} else {
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for(int c = 6; c < 9; ++c) {
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envelope_generators_[c + 0].update(oscillator_);
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envelope_generators_[c + 9].update(oscillator_);
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}
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// All melodic. Fairly easy.
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output_levels_[0] = output_levels_[1] = output_levels_[2] =
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output_levels_[6] = output_levels_[7] = output_levels_[8] =
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output_levels_[12] = output_levels_[13] = output_levels_[14] = 0;
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output_levels_[3] = VOLUME(melodic_output(0));
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output_levels_[4] = VOLUME(melodic_output(1));
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output_levels_[5] = VOLUME(melodic_output(2));
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output_levels_[9] = VOLUME(melodic_output(3));
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output_levels_[10] = VOLUME(melodic_output(4));
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output_levels_[11] = VOLUME(melodic_output(5));
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output_levels_[15] = VOLUME(melodic_output(6));
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output_levels_[16] = VOLUME(melodic_output(7));
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output_levels_[17] = VOLUME(melodic_output(8));
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// TODO: advance LFSR.
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}
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#undef VOLUME
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// TODO: batch updates of the LFSR.
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// TODO: modulator feedback.
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}
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int OPLL::melodic_output(int channel) {
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// TODO: key-rate scaling.
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// TODO: proper scales of all attenuations below.
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auto modulation = WaveformGenerator<period_precision>::wave(channels_[channel].modulator_waveform, phase_generators_[channel + 9].phase());
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modulation += envelope_generators_[channel + 9].attenuation() + channels_[channel].modulator_attenuation;
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return WaveformGenerator<period_precision>::wave(channels_[channel].carrier_waveform, phase_generators_[channel].scaled_phase(), modulation).level() + channels_[channel].attenuation;
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}
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