sid.h

/* 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