opl.c

/*
 * Library to access OPL2/OPL3 hardware (YM3812 / YMF262)
 *
 * Copyright (C) 2015-2016 Mateusz Viste
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifdef OPL

#include <conio.h> /* inp(), out() */
#include <dos.h>
#include <i86.h>   /* delay() */
#include <stdio.h>
#include <stdlib.h> /* calloc() */
#include <string.h> /* memset() */

#include "opl.h"

#include "opl-gm.h"

struct voicealloc_t {
  unsigned short priority;
  signed short timbreid;
  signed char channel;
  signed char note;
};

struct oplstate_t {
  signed char notes2voices[16][128];    /* keeps the map of channel:notes -> voice allocations */
  unsigned short channelpitch[16];      /* per-channel pitch level */
  unsigned short channelvol[16];        /* per-channel pitch level */
  struct voicealloc_t voices2notes[18]; /* keeps the map of what voice is playing what note/channel currently */
  unsigned char channelprog[16];        /* programs (patches) assigned to channels */
  int opl3; /* flag indicating whether or not the sound module is OPL3-compatible or only OPL2 */
};

struct oplstate_t *oplmem = NULL; /* memory area holding all OPL's current states */

static unsigned short freqtable[128] = {                         /* note # */
        345, 365, 387, 410, 435, 460, 488, 517, 547, 580, 615, 651,  /*  0 */
        690, 731, 774, 820, 869, 921, 975, 517, 547, 580, 615, 651,  /* 12 */
        690, 731, 774, 820, 869, 921, 975, 517, 547, 580, 615, 651,  /* 24 */
        690, 731, 774, 820, 869, 921, 975, 517, 547, 580, 615, 651,  /* 36 */
        690, 731, 774, 820, 869, 921, 975, 517, 547, 580, 615, 651,  /* 48 */
        690, 731, 774, 820, 869, 921, 975, 517, 547, 580, 615, 651,  /* 60 */
        690, 731, 774, 820, 869, 921, 975, 517, 547, 580, 615, 651,  /* 72 */
        690, 731, 774, 820, 869, 921, 975, 517, 547, 580, 615, 651,  /* 84 */
        690, 731, 774, 820, 869, 921, 975, 517, 547, 580, 615, 651,  /* 96 */
        690, 731, 774, 820, 869, 921, 975, 517, 547, 580, 615, 651, /* 108 */
        690, 731, 774, 820, 869, 921, 975, 517};                    /* 120 */

static unsigned char octavetable[128] = {                        /* note # */
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                          /*  0 */
        0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1,                          /* 12 */
        1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2,                          /* 24 */
        2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3,                          /* 36 */
        3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4,                          /* 48 */
        4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5,                          /* 60 */
        5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6,                          /* 72 */
        6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7,                          /* 84 */
        7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8,                          /* 96 */
        8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9,                         /* 108 */
        9, 9, 9, 9, 9, 9, 9,10};                                    /* 120 */

static unsigned short pitchtable[256] = {                   /* pitch wheel */
         29193U,29219U,29246U,29272U,29299U,29325U,29351U,29378U,  /* -128 */
         29405U,29431U,29458U,29484U,29511U,29538U,29564U,29591U,  /* -120 */
         29618U,29644U,29671U,29698U,29725U,29752U,29778U,29805U,  /* -112 */
         29832U,29859U,29886U,29913U,29940U,29967U,29994U,30021U,  /* -104 */
         30048U,30076U,30103U,30130U,30157U,30184U,30212U,30239U,  /*  -96 */
         30266U,30293U,30321U,30348U,30376U,30403U,30430U,30458U,  /*  -88 */
         30485U,30513U,30541U,30568U,30596U,30623U,30651U,30679U,  /*  -80 */
         30706U,30734U,30762U,30790U,30817U,30845U,30873U,30901U,  /*  -72 */
         30929U,30957U,30985U,31013U,31041U,31069U,31097U,31125U,  /*  -64 */
         31153U,31181U,31209U,31237U,31266U,31294U,31322U,31350U,  /*  -56 */
         31379U,31407U,31435U,31464U,31492U,31521U,31549U,31578U,  /*  -48 */
         31606U,31635U,31663U,31692U,31720U,31749U,31778U,31806U,  /*  -40 */
         31835U,31864U,31893U,31921U,31950U,31979U,32008U,32037U,  /*  -32 */
         32066U,32095U,32124U,32153U,32182U,32211U,32240U,32269U,  /*  -24 */
         32298U,32327U,32357U,32386U,32415U,32444U,32474U,32503U,  /*  -16 */
         32532U,32562U,32591U,32620U,32650U,32679U,32709U,32738U,  /*   -8 */
         32768U,32798U,32827U,32857U,32887U,32916U,32946U,32976U,  /*    0 */
         33005U,33035U,33065U,33095U,33125U,33155U,33185U,33215U,  /*    8 */
         33245U,33275U,33305U,33335U,33365U,33395U,33425U,33455U,  /*   16 */
         33486U,33516U,33546U,33576U,33607U,33637U,33667U,33698U,  /*   24 */
         33728U,33759U,33789U,33820U,33850U,33881U,33911U,33942U,  /*   32 */
         33973U,34003U,34034U,34065U,34095U,34126U,34157U,34188U,  /*   40 */
         34219U,34250U,34281U,34312U,34343U,34374U,34405U,34436U,  /*   48 */
         34467U,34498U,34529U,34560U,34591U,34623U,34654U,34685U,  /*   56 */
         34716U,34748U,34779U,34811U,34842U,34874U,34905U,34937U,  /*   64 */
         34968U,35000U,35031U,35063U,35095U,35126U,35158U,35190U,  /*   72 */
         35221U,35253U,35285U,35317U,35349U,35381U,35413U,35445U,  /*   80 */
         35477U,35509U,35541U,35573U,35605U,35637U,35669U,35702U,  /*   88 */
         35734U,35766U,35798U,35831U,35863U,35895U,35928U,35960U,  /*   96 */
         35993U,36025U,36058U,36090U,36123U,36155U,36188U,36221U,  /*  104 */
         36254U,36286U,36319U,36352U,36385U,36417U,36450U,36483U,  /*  112 */
         36516U,36549U,36582U,36615U,36648U,36681U,36715U,36748U}; /*  120 */


/* tables below provide register offsets for each voice. note, that these are
 * NOT the registers IDs, but their direct offsets instead - this for simpler
 * and faster computations. */
const unsigned short op1offsets[18] = {0x00,0x01,0x02,0x08,0x09,0x0a,0x10,0x11,0x12,0x100,0x101,0x102,0x108,0x109,0x10a,0x110,0x111,0x112};
const unsigned short op2offsets[18] = {0x03,0x04,0x05,0x0b,0x0c,0x0d,0x13,0x14,0x15,0x103,0x104,0x105,0x10b,0x10c,0x10d,0x113,0x114,0x115};

/* number of melodic voices: 9 by default (OPL2), can go up to 18 (OPL3) */
static int voicescount = 9;


/* function used to write into a register 'reg' of the OPL chip located at
 * port 'port', writing byte 'data' into it. this function supports also OPL3.
 * to write into the secondary address of an OPL3, just OR your register with
 * the 0x100 value (the 0x100 flag will be removed then, and the data will be
 * written into port+3). */
static void oplregwr(unsigned short port, unsigned short reg, unsigned char data) {
  int i;
  /* remap 'high' registers to second port (OPL3) */
  if ((reg & 0x100) != 0) {
    reg &= 0xff;
    port += 2;
  }
  /* select the register we want to write to, via the index register */
  outp(port, reg);
  /* OPL2 requires 3.3us to pass before writing to the data port. AdLib
   * recommends reading 6 times from the index register to make time pass. */
  i = 6;
  while (i--) inp(port);
  /* write the data to the data register */
  outp(port+1, data);
  /* OPL2 requires 23us to pass before writing to the data port. AdLib
   * recommends reading 35 times from the index register to make time pass. */
  i = 35;
  while (i--) inp(port);
}


/* 'volume' is in range 0..127 - take care to change only the 'attenuation'
 * part of the register, and never touch the KSL bits */
static void calc_vol(unsigned char *regbyte, int volume) {
  int level;
  /* invert bits and strip out the KSL header */
  level = ~(*regbyte);
  level &= 0x3f;

  /* adjust volume */
  level = (level * volume) / 127;

  /* boundaries check */
  if (level > 0x3f) level = 0x3f;
  if (level < 0) level = 0;

  /* invert the bits, as expected by the OPL registers */
  level = ~level;
  level &= 0x3f;

  /* final result computation */
  *regbyte &= 0xC0;  /* zero out all attentuation bits */
  *regbyte |= level; /* fill in the new attentuation value */
}


/* Initialize hardware upon startup - positive on success, negative otherwise
 * Returns 0 for OPL2 initialization, or 1 if OPL3 has been detected */
int opl_init(unsigned short port) {
  int x, y;

  /* make sure we're not inited yet */
  if (oplmem != NULL) return(-1);

  /* detect the hardware and return error if not found */
  oplregwr(port, 0x04, 0x60); /* reset both timers by writing 60h to register 4 */
  oplregwr(port, 0x04, 0x80); /* enable interrupts by writing 80h to register 4 (must be a separate write from the 1st one) */
  x = inp(port) & 0xE0; /* read the status register (port 388h) and store the result */
  oplregwr(port, 0x02, 0xff); /* write FFh to register 2 (Timer 1) */
  oplregwr(port, 0x04, 0x21); /* start timer 1 by writing 21h to register 4 */
  delay(90);  /* delay for at least 80 microseconds (I delay for 90ms to make
                 sure that the DOS timing resolution won't zero out my delay).
                 DO NOT perform inp() calls for delay here, some cards do not
                 initialize well then (reported for CT2760) */
  y = inp(port) & 0xE0;  /* read the upper bits of the status register */
  oplregwr(port, 0x04, 0x60); /* reset both timers and interrupts (see steps 1 and 2) */
  oplregwr(port, 0x04, 0x80); /* reset both timers and interrupts (see steps 1 and 2) */
  /* test the stored results of steps 3 and 7 by ANDing them with E0h. The result of step 3 should be */
  if (x != 0) return(-1);    /* 00h, and the result of step 7 should be C0h. If both are     */
  if (y != 0xC0) return(-2); /* ok, an AdLib-compatible board is installed in the computer   */

  /* init memory */
  oplmem = calloc(1, sizeof(struct oplstate_t));
  if (oplmem == NULL) return(-3);

  /* is it an OPL3 or just an OPL2? */
  if ((inp(port) & 0x06) == 0) oplmem->opl3 = 1;

  /* init the hardware */
  voicescount = 9; /* OPL2 provides 9 melodic voices */

  /* enable OPL3 (if detected) and put it into 36 operators mode */
  if (oplmem->opl3 != 0) {
    oplregwr(port, 0x105, 1);  /* enable OPL3 mode (36 operators) */
    oplregwr(port, 0x104, 0);  /* disable four-operator voices */
    voicescount = 18;          /* OPL3 provides 18 melodic channels */

    /* Init the secondary OPL chip
     * NOTE: this I don't do anymore, it turns my Aztech Waverider mute! */
    /* oplregwr(port, 0x101, 0x20); */ /* enable Waveform Select */
    /* oplregwr(port, 0x108, 0x40); */ /* turn off CSW mode and activate FM synth mode */
    /* oplregwr(port, 0x1BD, 0x00); */ /* set vibrato/tremolo depth to low, set melodic mode */
  }

  oplregwr(port, 0x01, 0x20);  /* enable Waveform Select */
  oplregwr(port, 0x04, 0x00);  /* turn off timers IRQs */
  oplregwr(port, 0x08, 0x40);  /* turn off CSW mode and activate FM synth mode */
  oplregwr(port, 0xBD, 0x00);  /* set vibrato/tremolo depth to low, set melodic mode */

  for (x = 0; x < voicescount; x++) {
    oplregwr(port, 0x20 + op1offsets[x], 0x1);     /* set the modulator's multiple to 1 */
    oplregwr(port, 0x20 + op2offsets[x], 0x1);     /* set the modulator's multiple to 1 */
    oplregwr(port, 0x40 + op1offsets[x], 0x10);    /* set volume of all channels to about 40 dB */
    oplregwr(port, 0x40 + op2offsets[x], 0x10);    /* set volume of all channels to about 40 dB */
  }

  opl_clear(port);

  /* all done */
  return(oplmem->opl3);
}


/* close OPL device */
void opl_close(unsigned short port) {
  int x;

  /* turns all notes 'off' */
  opl_clear(port);

  /* set volume to lowest level on all voices */
  for (x = 0; x < voicescount; x++) {
    oplregwr(port, 0x40 + op1offsets[x], 0x1f);
    oplregwr(port, 0x40 + op2offsets[x], 0x1f);
  }

  /* if OPL3, switch the chip back into its default OPL2 mode */
  if (oplmem->opl3 != 0) oplregwr(port, 0x105, 0);

  /* free state memory */
  free(oplmem);
  oplmem = NULL;
}


/* turns off all notes */
void opl_clear(unsigned short port) {
  int x, y;
  for (x = 0; x < voicescount; x++) opl_noteoff(port, x);

  /* reset the percussion bits at the 0xBD register */
  oplregwr(port, 0xBD, 0);

  /* mark all voices as unused */
  for (x = 0; x < voicescount; x++) {
    oplmem->voices2notes[x].channel = -1;
    oplmem->voices2notes[x].note = -1;
    oplmem->voices2notes[x].timbreid = -1;
  }

  /* mark all notes as unallocated */
  for (x = 0; x < 16; x++) {
    for (y = 0; y < 128; y++) oplmem->notes2voices[x][y] = -1;
  }

  /* pre-set emulated channel patches to default GM ids and reset all
   * per-channel volumes */
  for (x = 0; x < 16; x++) {
    opl_midi_changeprog(x, x);
    oplmem->channelvol[x] = 127;
  }
}


void opl_noteoff(unsigned short port, unsigned short voice) {
  /* if voice is one of the OPL3 set, adjust it and route over secondary OPL port */
  if (voice >= 9) {
    oplregwr(port, 0x1B0 + voice - 9, 0);
  } else {
    oplregwr(port, 0xB0 + voice, 0);
  }
}


void opl_noteon(unsigned short port, unsigned short voice, unsigned int note, int pitch) {
  unsigned int freq = freqtable[note];
  unsigned int octave = octavetable[note];

  if (pitch != 0) {
    if (pitch > 127) {
      pitch = 127;
    } else if (pitch < -128) {
      pitch = -128;
    }
    freq = ((unsigned long)freq * pitchtable[pitch + 128]) >> 15;
    if (freq >= 1024) {
      freq >>= 1;
      octave++;
    }
  }
  if (octave > 7) octave = 7;

  /* if voice is one of the OPL3 set, adjust it and route over secondary OPL port */
  if (voice >= 9) {
    voice -= 9;
    voice |= 0x100;
  }

  oplregwr(port, 0xA0 + voice, freq & 0xff); /* set lowfreq */
  oplregwr(port, 0xB0 + voice, (freq >> 8) | (octave << 2) | 32); /* KEY ON + hifreq + octave */
}


void opl_midi_pitchwheel(unsigned short oplport, int channel, int pitchwheel) {
  /*int x;*/
  /* update the new pitch value for channel (used by newly played notes) */
  oplmem->channelpitch[channel] = pitchwheel;
  /* check all active voices to see who is playing on given channel now, and
   * recompute all playing notes for this channel with the new pitch TODO */
  /*for (x = 0; x < voicescount; x++) {
    if (oplmem->voices2notes[x].channel != channel) continue;
    opl_noteon(oplport, x, oplmem->voices2notes[x].note, pitchwheel + gmtimbres[oplmem->voices2notes[x].timbreid].finetune);
  }*/
}


void opl_midi_controller(unsigned short oplport, int channel, int id, int value) {
  int x;
  switch (id) {
    case 11: /* "Expression" (meaning "channel volume") */
      oplmem->channelvol[channel] = value;
      break;
    case 123: /* 'all notes off' */
    case 120: /* 'all sound off' - I map it to 'all notes off' for now, not perfect but better than not handling it at all */
      for (x = 0; x < voicescount; x++) {
        if (oplmem->voices2notes[x].channel != channel) continue;
        opl_midi_noteoff(oplport, channel, oplmem->voices2notes[x].note);
      }
      break;
  }
}


/* assign a new instrument to emulated MIDI channel */
void opl_midi_changeprog(int channel, int program) {
  if (channel == 9) return; /* do not allow to change channel 9, it is for percussions only */
  oplmem->channelprog[channel] = program;
}


void opl_loadinstrument(unsigned short oplport, unsigned short voice, struct timbre_t *timbre) {
  /* KSL (key level scaling) / attenuation */
  oplregwr(oplport, 0x40 + op1offsets[voice], timbre->modulator_40);
  oplregwr(oplport, 0x40 + op2offsets[voice], timbre->carrier_40 | 0x3f); /* force volume to 0, it will be reajusted during 'note on' */

  /* select waveform on both operators */
  oplregwr(oplport, 0xE0 + op1offsets[voice], timbre->modulator_E862 >> 24);
  oplregwr(oplport, 0xE0 + op2offsets[voice], timbre->carrier_E862 >> 24);

  /* sustain / release */
  oplregwr(oplport, 0x80 + op1offsets[voice], (timbre->modulator_E862 >> 16) & 0xff);
  oplregwr(oplport, 0x80 + op2offsets[voice], (timbre->carrier_E862 >> 16) & 0xff);

  /* attack rate / decay */
  oplregwr(oplport, 0x60 + op1offsets[voice], (timbre->modulator_E862 >> 8) & 0xff);
  oplregwr(oplport, 0x60 + op2offsets[voice], (timbre->carrier_E862 >> 8) & 0xff);

  /* AM / vibrato / envelope */
  oplregwr(oplport, 0x20 + op1offsets[voice], timbre->modulator_E862 & 0xff);
  oplregwr(oplport, 0x20 + op2offsets[voice], timbre->carrier_E862 & 0xff);

  /* feedback / connection */
  if (voice >= 9) {
    voice -= 9;
    voice |= 0x100;
  }
  if (oplmem->opl3 != 0) { /* on OPL3 make sure to enable LEFT/RIGHT unmute bits */
    oplregwr(oplport, 0xC0 + voice, timbre->feedconn | 0x30);
  } else {
    oplregwr(oplport, 0xC0 + voice, timbre->feedconn);
  }

}


/* adjust the volume of the voice (in the usual MIDI range of 0..127) */
static void voicevolume(unsigned short port, unsigned short voice, int program, int volume) {
  unsigned char carrierval = gmtimbres[program].carrier_40;
  if (volume == 0) {
    carrierval |= 0x3f;
  } else {
    calc_vol(&carrierval, volume);
  }
  oplregwr(port, 0x40 + op2offsets[voice], carrierval);
}


/* get the id of the instrument that relates to channel/note pair */
static int getinstrument(int channel, int note) {
  if ((note < 0) || (note > 127) || (channel > 15)) return(-1);
  if (channel == 9) { /* the percussion channel requires special handling */
    return(128 | note);
  }
  return(oplmem->channelprog[channel]);
}


void opl_midi_noteon(unsigned short port, int channel, int note, int velocity) {
  int x, voice = -1;
  int lowestpriorityvoice = 0;
  int instrument;

  /* get the instrument to play */
  instrument = getinstrument(channel, note);
  if (instrument < 0) return;

  /* if note already playing, then reuse its voice to avoid leaving a stuck voice */
  if (oplmem->notes2voices[channel][note] >= 0) {
    voice = oplmem->notes2voices[channel][note];
  } else {
    /* else find a free voice, possibly with the right timbre, or at least locate the oldest note */
    for (x = 0; x < voicescount; x++) {
      if (oplmem->voices2notes[x].channel < 0) {
        voice = x; /* preselect this voice, but continue looking */
        /* if the instrument is right, do not look further */
        if (oplmem->voices2notes[x].timbreid == instrument) {
          break;
        }
      }
      if (oplmem->voices2notes[x].priority < oplmem->voices2notes[lowestpriorityvoice].priority) lowestpriorityvoice = x;
    }
    /* if no free voice available, then abort the oldest one */
    if (voice < 0) {
      voice = lowestpriorityvoice;
      opl_midi_noteoff(port, oplmem->voices2notes[voice].channel, oplmem->voices2notes[voice].note);
    }
  }

  /* load the proper instrument, if not already good */
  if (oplmem->voices2notes[voice].timbreid != instrument) {
    oplmem->voices2notes[voice].timbreid = instrument;
    opl_loadinstrument(port, voice, &(gmtimbres[instrument]));
  }

  /* update states */
  oplmem->voices2notes[voice].channel = channel;
  oplmem->voices2notes[voice].note = note;
  oplmem->voices2notes[voice].priority = ((16 - channel) << 8) | 0xff; /* lower channels must have priority */
  oplmem->notes2voices[channel][note] = voice;

  /* set the requested velocity on the voice */
  voicevolume(port, voice, oplmem->voices2notes[voice].timbreid, velocity * oplmem->channelvol[channel] / 127);

  /* trigger NOTE_ON on the OPL, take care to apply the 'finetune' pitch correction, too */
  if (channel == 9) { /* percussion channel doesn't provide a real note, so I */
                      /* use a static one (MUSPLAYER uses C-5 (60), why not.  */
    opl_noteon(port, voice, 60, oplmem->channelpitch[channel] + gmtimbres[instrument].finetune);
  } else {
    opl_noteon(port, voice, note, oplmem->channelpitch[channel] + gmtimbres[instrument].finetune);
  }

  /* reajust all priorities */
  for (x = 0; x < voicescount; x++) {
    if (oplmem->voices2notes[x].priority > 0) oplmem->voices2notes[x].priority -= 1;
  }
}


void opl_midi_noteoff(unsigned short port, int channel, int note) {
  int voice = oplmem->notes2voices[channel][note];

  if (voice >= 0) {
    opl_noteoff(port, voice);
    oplmem->voices2notes[voice].channel = -1;
    oplmem->voices2notes[voice].note = -1;
    oplmem->voices2notes[voice].priority = -1;
    oplmem->notes2voices[channel][note] = -1;
  }
}


static int opl_loadbank_internal(char *file, int offset) {
  unsigned char buff[16];
  int i;
  FILE *fd;
  /* open the IBK file */
  fd = fopen(file, "rb");
  if (fd == NULL) return(-1);
  /* file must be exactly 3204 bytes long */
  fseek(fd, 0, SEEK_END);
  if (ftell(fd) != 3204) {
    fclose(fd);
    return(-2);
  }
  rewind(fd);
  /* file must start with an IBK header */
  if ((fread(buff, 1, 4, fd) != 4) || (buff[0] != 'I') || (buff[1] != 'B') || (buff[2] != 'K') || (buff[3] != 0x1A)) {
    fclose(fd);
    return(-3);
  }
  /* load 128 instruments from the IBK file */
  for (i = offset; i < 128 + offset; i++) {
    /* load instruments */
    if (fread(buff, 1, 16, fd) != 16) {
      fclose(fd);
      return(-4);
    }
    /* load modulator */
    gmtimbres[i].modulator_E862 = buff[8]; /* wave select */
    gmtimbres[i].modulator_E862 <<= 8;
    gmtimbres[i].modulator_E862 |= buff[6]; /* sust/release */
    gmtimbres[i].modulator_E862 <<= 8;
    gmtimbres[i].modulator_E862 |= buff[4]; /* attack/decay */
    gmtimbres[i].modulator_E862 <<= 8;
    gmtimbres[i].modulator_E862 |= buff[0]; /* AM/VIB... flags */
    /* load carrier */
    gmtimbres[i].carrier_E862 = buff[9]; /* wave select */
    gmtimbres[i].carrier_E862 <<= 8;
    gmtimbres[i].carrier_E862 |= buff[7]; /* sust/release */
    gmtimbres[i].carrier_E862 <<= 8;
    gmtimbres[i].carrier_E862 |= buff[5]; /* attack/decay */
    gmtimbres[i].carrier_E862 <<= 8;
    gmtimbres[i].carrier_E862 |= buff[1]; /* AM/VIB... flags */
    /* load KSL */
    gmtimbres[i].modulator_40 = buff[2];
    gmtimbres[i].carrier_40 = buff[3];
    /* feedconn & finetune */
    gmtimbres[i].feedconn = buff[10];
    gmtimbres[i].finetune = buff[12]; /* used only in some IBK files */
  }
  /* close file and return success */
  fclose(fd);
  return(0);
}

/*
static void dump2file(void) {
  FILE *fd;
  int i;
  fd = fopen("dump.txt", "wb");
  if (fd == NULL) return;
  for (i = 0; i < 256; i++) {
    char *comma = "";
    if (i < 255) comma = ",";
    fprintf(fd, "{0x%07lX,0x%07lX,0x%02X,0x%02X,0x%02X,%d}%s\r\n", gmtimbres[i].modulator_E862, gmtimbres[i].carrier_E862, gmtimbres[i].modulator_40, gmtimbres[i].carrier_40, gmtimbres[i].feedconn, gmtimbres[i].finetune, comma);
  }
  fclose(fd);
}*/

int opl_loadbank(char *file) {
  char *instruments = NULL, *percussion = NULL;
  int i, res;
  instruments = strdup(file); /* duplicate the string so we can modify it */
  if (instruments == NULL) return(-64); /* out of mem */
  /* if a second file is provided, it's for percussion */
  for (i = 0; instruments[i] != 0; i++) {
    if (instruments[i] == ',') {
      instruments[i] = 0;
      percussion = instruments + i + 1;
      break;
    }
  }
  /* load the file(s) */
  res = opl_loadbank_internal(instruments, 0);
  if ((res == 0) && (percussion != NULL)) {
    res = opl_loadbank_internal(percussion, 128);
  }
  free(instruments);
  /*dump2file();*/ /* dump instruments to a 'dump.txt' file */
  return(res);
}

#endif /* #ifdef OPL */