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 "common/scummsys.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 {
public:
    SID();
    ~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);
    void reset();

    // Read/write registers.
    reg8 read(reg8 offset);
    void write(reg8 offset, reg8 value);

    // 16-bit output (AUDIO OUT).
    int output();

protected:
    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;
};

}

#endif // not AUDIO_SOFTSYNTH_SID_H