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87 lines
3.4 KiB
C++
87 lines
3.4 KiB
C++
//
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// Channel.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 15/04/2020.
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// Copyright © 2020 Thomas Harte. All rights reserved.
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//
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#ifndef Channel_hpp
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#define Channel_hpp
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#include "LowFrequencyOscillator.hpp"
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#include "Operator.hpp"
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namespace Yamaha {
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namespace OPL {
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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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TODO: make this a template on period counter size in bits?
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*/
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class Channel {
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public:
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/// Sets the low 8 bits of frequency control.
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void set_frequency_low(uint8_t value);
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/// Sets the high two bits of a 10-bit frequency control, along with this channel's
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/// block/octave, and key on or off.
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void set_10bit_frequency_octave_key_on(uint8_t value);
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/// Sets the high two bits of a 9-bit frequency control, along with this channel's
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/// block/octave, and key on or off.
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void set_9bit_frequency_octave_key_on(uint8_t value);
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/// Sets the amount of feedback provided to the first operator (i.e. the modulator)
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/// associated with this channel, and whether FM synthesis is in use.
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void set_feedback_mode(uint8_t value);
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/// Updates this channel, using the operators for melodic output.
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int update_melodic(const LowFrequencyOscillator &oscillator, Operator *modulator, Operator *carrier, bool force_key_on = false, OperatorOverrides *modulator_overrides = nullptr, OperatorOverrides *carrier_overrides = nullptr);
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/// Updates this channel's modulator state, to produce a tom tom.
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int update_tom_tom(const LowFrequencyOscillator &oscillator, Operator *modulator, bool force_key_on, OperatorOverrides *modulator_overrides = nullptr);
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/// Updates this channel, using the carrier to produce a snare drum and the modulator to produce a tom tom.
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int update_snare(const LowFrequencyOscillator &oscillator, Operator *carrier, bool force_key_on, OperatorOverrides *carrier_overrides = nullptr);
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/// Updates this channel, using the carrier to produce a cymbal and the modulator to produce a high-hat.
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int update_cymbal_high_hat(const LowFrequencyOscillator &oscillator, Operator *modulator, Operator *carrier, OperatorOverrides *modulator_overrides = nullptr, OperatorOverrides *carrier_overrides = nullptr);
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/// @returns @c true if this channel is currently producing any audio; @c false otherwise;
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bool is_audible(Operator *carrier, OperatorOverrides *carrier_overrides = nullptr);
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private:
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/// 'F-Num' in the spec; this plus the current octave determines channel frequency.
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int period_ = 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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/// Used internally to make both the 10-bit OPL2 frequency selection and 9-bit OPLL/VRC7 frequency
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/// selections look the same when passed to the operators.
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int frequency_shift_ = 0;
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// Stored separately because carrier/modulator may not be unique per channel —
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// on the OPLL there's an extra level of indirection.
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OperatorState carrier_state_, modulator_state_;
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};
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}
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}
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#endif /* Channel_hpp */
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