src/hardware/opl.h

/*
 *  Copyright (C) 2002-2020  The DOSBox Team
 *  OPL2/OPL3 emulation library
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 * 
 *  This library 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
 *  Lesser General Public License for more details.
 * 
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */


/*
 * Originally based on ADLIBEMU.C, an AdLib/OPL2 emulation library by Ken Silverman
 * Copyright (C) 1998-2001 Ken Silverman
 * Ken Silverman's official web site: "http://www.advsys.net/ken"
 */


#define fltype double

/*
        define Bits, Bitu, Bit32s, Bit32u, Bit16s, Bit16u, Bit8s, Bit8u here
*/
/*
#include <stdint.h>
typedef uintptr_t       Bitu;
typedef intptr_t        Bits;
typedef uint32_t        Bit32u;
typedef int32_t         Bit32s;
typedef uint16_t        Bit16u;
typedef int16_t         Bit16s;
typedef uint8_t         Bit8u;
typedef int8_t          Bit8s;
*/


/*
        define attribution that inlines/forces inlining of a function (optional)
*/
#define OPL_INLINE INLINE


#undef NUM_CHANNELS
#if defined(OPLTYPE_IS_OPL3)
#define NUM_CHANNELS    18
#else
#define NUM_CHANNELS    9
#endif

#define MAXOPERATORS    (NUM_CHANNELS*2)


#define FL05    ((fltype)0.5)
#define FL2             ((fltype)2.0)
#define PI              ((fltype)3.1415926535897932384626433832795)


#define FIXEDPT                 0x10000         // fixed-point calculations using 16+16
#define FIXEDPT_LFO             0x1000000       // fixed-point calculations using 8+24

#define WAVEPREC                1024            // waveform precision (10 bits)

#define INTFREQU                ((fltype)(14318180.0 / 288.0))          // clocking of the chip


#define OF_TYPE_ATT                     0
#define OF_TYPE_DEC                     1
#define OF_TYPE_REL                     2
#define OF_TYPE_SUS                     3
#define OF_TYPE_SUS_NOKEEP      4
#define OF_TYPE_OFF                     5

#define ARC_CONTROL                     0x00
#define ARC_TVS_KSR_MUL         0x20
#define ARC_KSL_OUTLEV          0x40
#define ARC_ATTR_DECR           0x60
#define ARC_SUSL_RELR           0x80
#define ARC_FREQ_NUM            0xa0
#define ARC_KON_BNUM            0xb0
#define ARC_PERC_MODE           0xbd
#define ARC_FEEDBACK            0xc0
#define ARC_WAVE_SEL            0xe0

#define ARC_SECONDSET           0x100   // second operator set for OPL3


#define OP_ACT_OFF                      0x00
#define OP_ACT_NORMAL           0x01    // regular channel activated (bitmasked)
#define OP_ACT_PERC                     0x02    // percussion channel activated (bitmasked)

#define BLOCKBUF_SIZE           512


// vibrato constants
#define VIBTAB_SIZE                     8
#define VIBFAC                          70/50000                // no braces, integer mul/div

// tremolo constants and table
#define TREMTAB_SIZE            53
#define TREM_FREQ                       ((fltype)(3.7))                 // tremolo at 3.7hz


/* operator struct definition
     For OPL2 all 9 channels consist of two operators each, carrier and modulator.
     Channel x has operators x as modulator and operators (9+x) as carrier.
     For OPL3 all 18 channels consist either of two operators (2op mode) or four
     operators (4op mode) which is determined through register4 of the second
     adlib register set.
     Only the channels 0,1,2 (first set) and 9,10,11 (second set) can act as
     4op channels. The two additional operators for a channel y come from the
     2op channel y+3 so the operatorss y, (9+y), y+3, (9+y)+3 make up a 4op
     channel.
*/
typedef struct operator_struct {
        Bit32s cval, lastcval;                  // current output/last output (used for feedback)
        Bit32u tcount, wfpos, tinc;             // time (position in waveform) and time increment
        fltype amp, step_amp;                   // and amplification (envelope)
        fltype vol;                                             // volume
        fltype sustain_level;                   // sustain level
        Bit32s mfbi;                                    // feedback amount
        fltype a0, a1, a2, a3;                  // attack rate function coefficients
        fltype decaymul, releasemul;    // decay/release rate functions
        Bit32u op_state;                                // current state of operator (attack/decay/sustain/release/off)
        Bit32u toff;
        Bit32s freq_high;                               // highest three bits of the frequency, used for vibrato calculations
        Bit16s* cur_wform;                              // start of selected waveform
        Bit32u cur_wmask;                               // mask for selected waveform
        Bit32u act_state;                               // activity state (regular, percussion)
        bool sus_keep;                                  // keep sustain level when decay finished
        bool vibrato,tremolo;                   // vibrato/tremolo enable bits
        
        // variables used to provide non-continuous envelopes
        Bit32u generator_pos;                   // for non-standard sample rates we need to determine how many samples have passed
        Bits cur_env_step;                              // current (standardized) sample position
        Bits env_step_a,env_step_d,env_step_r;  // number of std samples of one step (for attack/decay/release mode)
        Bit8u step_skip_pos_a;                  // position of 8-cyclic step skipping (always 2^x to check against mask)
        Bits env_step_skip_a;                   // bitmask that determines if a step is skipped (respective bit is zero then)

#if defined(OPLTYPE_IS_OPL3)
        bool is_4op,is_4op_attached;    // base of a 4op channel/part of a 4op channel
        Bit32s left_pan,right_pan;              // opl3 stereo panning amount
#endif
} op_type;

// per-chip variables
Bitu chip_num;
op_type op[MAXOPERATORS];

Bits int_samplerate;
        
Bit8u status;
Bit32u opl_index;
#if defined(OPLTYPE_IS_OPL3)
Bit8u adlibreg[512];    // adlib register set (including second set)
Bit8u wave_sel[44];             // waveform selection
#else
Bit8u adlibreg[256];    // adlib register set
Bit8u wave_sel[22];             // waveform selection
#endif


// vibrato/tremolo increment/counter
Bit32u vibtab_pos;
Bit32u vibtab_add;
Bit32u tremtab_pos;
Bit32u tremtab_add;


// enable an operator
void enable_operator(Bitu regbase, op_type* op_pt);

// functions to change parameters of an operator
void change_frequency(Bitu chanbase, Bitu regbase, op_type* op_pt);

void change_attackrate(Bitu regbase, op_type* op_pt);
void change_decayrate(Bitu regbase, op_type* op_pt);
void change_releaserate(Bitu regbase, op_type* op_pt);
void change_sustainlevel(Bitu regbase, op_type* op_pt);
void change_waveform(Bitu regbase, op_type* op_pt);
void change_keepsustain(Bitu regbase, op_type* op_pt);
void change_vibrato(Bitu regbase, op_type* op_pt);
void change_feedback(Bitu chanbase, op_type* op_pt);

// general functions
void adlib_init(Bit32u samplerate);
void adlib_write(Bitu idx, Bit8u val);
void adlib_getsample(Bit16s* sndptr, Bits numsamples);

Bitu adlib_reg_read(Bitu port);
void adlib_write_index(Bitu port, Bit8u val);

static Bit32u generator_add;    // should be a chip parameter