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audio/softsynth/sid.h

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/*
+ *  This file is based on reSID, a MOS6581 SID emulator engine.
+ *  Copyright (C) 2004  Dag Lem <resid@nimrod.no>
+ */
+
+#ifndef AUDIO_SOFTSYNTH_SID_H
+#define AUDIO_SOFTSYNTH_SID_H
+
+#include "audio/sid.h"
+
+// Inlining on/off.
+#define RESID_INLINE inline
+
+namespace Resid {
+
+// We could have used the smallest possible data type for each SID register,
+// however this would give a slower engine because of data type conversions.
+// An int is assumed to be at least 32 bits (necessary in the types reg24,
+// cycle_count, and sound_sample). GNU does not support 16-bit machines
+// (GNU Coding Standards: Portability between CPUs), so this should be
+// a valid assumption.
+
+typedef unsigned int reg4;
+typedef unsigned int reg8;
+typedef unsigned int reg12;
+typedef unsigned int reg16;
+typedef unsigned int reg24;
+
+typedef int cycle_count;
+typedef int sound_sample;
+
+typedef unsigned char data8;
+typedef unsigned short data16;
+typedef unsigned short fc_point[2];
+
+
+class WaveformGenerator {
+public:
+	WaveformGenerator();
+
+	void set_sync_source(WaveformGenerator *);
+
+	void updateClock(cycle_count delta_t);
+	void synchronize();
+	void reset();
+
+	void writeFREQ_LO(reg8);
+	void writeFREQ_HI(reg8);
+	void writePW_LO(reg8);
+	void writePW_HI(reg8);
+	void writeCONTROL_REG(reg8);
+	reg8 readOSC();
+
+	// 12-bit waveform output.
+	reg12 output();
+
+protected:
+	const WaveformGenerator* sync_source;
+	WaveformGenerator* sync_dest;
+
+	// Tell whether the accumulator MSB was set high on this cycle.
+	bool msb_rising;
+
+	reg24 accumulator;
+	reg24 shift_register;
+
+	// Fout  = (Fn*Fclk/16777216)Hz
+	reg16 freq;
+	// PWout = (PWn/40.95)%
+	reg12 pw;
+
+	// The control register right-shifted 4 bits; used for output function
+	// table lookup.
+	reg8 waveform;
+
+	// The remaining control register bits.
+	reg8 test;
+	reg8 ring_mod;
+	reg8 sync;
+	// The gate bit is handled by the EnvelopeGenerator.
+
+	// 16 possible combinations of waveforms.
+	reg12 output____();
+	reg12 output___T();
+	reg12 output__S_();
+	reg12 output__ST();
+	reg12 output_P__();
+	reg12 output_P_T();
+	reg12 output_PS_();
+	reg12 output_PST();
+	reg12 outputN___();
+	reg12 outputN__T();
+	reg12 outputN_S_();
+	reg12 outputN_ST();
+	reg12 outputNP__();
+	reg12 outputNP_T();
+	reg12 outputNPS_();
+	reg12 outputNPST();
+
+	// Sample data for combinations of waveforms.
+	static const data8 wave6581__ST[];
+	static const data8 wave6581_P_T[];
+	static const data8 wave6581_PS_[];
+	static const data8 wave6581_PST[];
+
+	friend class Voice;
+	friend class SID;
+};
+
+class Filter {
+public:
+	Filter();
+
+	void enable_filter(bool enable);
+
+	void updateClock(cycle_count delta_t,
+		sound_sample voice1, sound_sample voice2, sound_sample voice3);
+	void reset();
+
+	// Write registers.
+	void writeFC_LO(reg8);
+	void writeFC_HI(reg8);
+	void writeRES_FILT(reg8);
+	void writeMODE_VOL(reg8);
+
+	// SID audio output (16 bits).
+	sound_sample output();
+
+protected:
+	void set_w0();
+	void set_Q();
+
+	// Filter enabled.
+	bool enabled;
+
+	// Filter cutoff frequency.
+	reg12 fc;
+
+	// Filter resonance.
+	reg8 res;
+
+	// Selects which inputs to route through filter.
+	reg8 filt;
+
+	// Switch voice 3 off.
+	reg8 voice3off;
+
+	// Highpass, bandpass, and lowpass filter modes.
+	reg8 hp_bp_lp;
+
+	// Output master volume.
+	reg4 vol;
+
+	// Mixer DC offset.
+	sound_sample mixer_DC;
+
+	// State of filter.
+	sound_sample Vhp; // highpass
+	sound_sample Vbp; // bandpass
+	sound_sample Vlp; // lowpass
+	sound_sample Vnf; // not filtered
+
+	// Cutoff frequency, resonance.
+	sound_sample w0, w0_ceil_1, w0_ceil_dt;
+	sound_sample _1024_div_Q;
+
+	// Cutoff frequency tables.
+	// FC is an 11 bit register.
+	sound_sample f0_6581[2048];
+	sound_sample* f0;
+	static const fc_point f0_points_6581[];
+	const fc_point* f0_points;
+	int f0_count;
+
+	friend class SID;
+};
+
+class EnvelopeGenerator {
+public:
+	EnvelopeGenerator();
+
+	enum State { ATTACK, DECAY_SUSTAIN, RELEASE };
+
+	void updateClock(cycle_count delta_t);
+	void reset();
+
+	void writeCONTROL_REG(reg8);
+	void writeATTACK_DECAY(reg8);
+	void writeSUSTAIN_RELEASE(reg8);
+	reg8 readENV();
+
+	// 8-bit envelope output.
+	reg8 output();
+
+protected:
+	reg16 rate_counter;
+	reg16 rate_period;
+	reg8 exponential_counter;
+	reg8 exponential_counter_period;
+	reg8 envelope_counter;
+	bool hold_zero;
+
+	reg4 attack;
+	reg4 decay;
+	reg4 sustain;
+	reg4 release;
+
+	reg8 gate;
+
+	State state;
+
+	// Lookup table to convert from attack, decay, or release value to rate
+	// counter period.
+	static const data16 rate_counter_period[];
+
+	// The 16 selectable sustain levels.
+	static const data8 sustain_level[];
+
+	friend class SID;
+};
+
+class ExternalFilter {
+public:
+	ExternalFilter();
+
+	void enable_filter(bool enable);
+	void set_sampling_parameter(double pass_freq);
+
+	void updateClock(cycle_count delta_t, sound_sample Vi);
+	void reset();
+
+	// Audio output (20 bits).
+	sound_sample output();
+
+protected:
+	// Filter enabled.
+	bool enabled;
+
+	// Maximum mixer DC offset.
+	sound_sample mixer_DC;
+
+	// State of filters.
+	sound_sample Vlp; // lowpass
+	sound_sample Vhp; // highpass
+	sound_sample Vo;
+
+	// Cutoff frequencies.
+	sound_sample w0lp;
+	sound_sample w0hp;
+
+	friend class SID;
+};
+
+class Voice {
+public:
+	Voice();
+
+	void set_sync_source(Voice *);
+	void reset();
+
+	void writeCONTROL_REG(reg8);
+
+	// Amplitude modulated waveform output.
+	// Range [-2048*255, 2047*255].
+	sound_sample output() {
+		// Multiply oscillator output with envelope output.
+		return (wave.output() - wave_zero)*envelope.output() + voice_DC;
+	}
+
+protected:
+	WaveformGenerator wave;
+	EnvelopeGenerator envelope;
+
+	// Waveform D/A zero level.
+	sound_sample wave_zero;
+
+	// Multiplying D/A DC offset.
+	sound_sample voice_DC;
+
+	friend class SID;
+};
+
+
+class SID final : public ::SID::SID, public Audio::EmulatedChip {
+public:
+	SID(::SID::Config::SidType videoSystem);
+	~SID();
+
+	void enable_filter(bool enable);
+	void enable_external_filter(bool enable);
+	bool set_sampling_parameters(double clock_freq,
+		double sample_freq, double pass_freq = -1,
+		double filter_scale = 0.97);
+
+	void updateClock(cycle_count delta_t);
+	int updateClock(cycle_count& delta_t, short* buf, int n, int interleave = 1);
+
+	bool init() override;
+	void reset() override;
+
+	// Read/write registers.
+	reg8 read(reg8 offset);
+	void writeReg(int offset, int value) override;
+
+	// 16-bit output (AUDIO OUT).
+	int output();
+
+	bool isStereo() const override { return false; }
+
+protected:
+	void generateSamples(int16 *buffer, int numSamples) override;
+
+	Voice voice[3];
+	Filter filter;
+	ExternalFilter extfilt;
+
+	reg8 bus_value;
+	cycle_count bus_value_ttl;
+
+	double clock_frequency;
+
+	// Fixpoint constants.
+	static const int FIXP_SHIFT;
+	static const int FIXP_MASK;
+
+	// Sampling variables.
+	cycle_count cycles_per_sample;
+	cycle_count sample_offset;
+	short sample_prev;
+
+	::SID::Config::SidType _videoSystem;
+	cycle_count _cpuCyclesLeft;
+};
+
+}
+
+#endif // not AUDIO_SOFTSYNTH_SID_H