Genesis-Plus-GX/core/cd_hw/cdd.c

/***************************************************************************************
 *  Genesis Plus
 *  CD drive processor & CD-DA fader
 *
 *  Copyright (C) 2012-2022  Eke-Eke (Genesis Plus GX)
 *
 *  Redistribution and use of this code or any derivative works are permitted
 *  provided that the following conditions are met:
 *
 *   - Redistributions may not be sold, nor may they be used in a commercial
 *     product or activity.
 *
 *   - Redistributions that are modified from the original source must include the
 *     complete source code, including the source code for all components used by a
 *     binary built from the modified sources. However, as a special exception, the
 *     source code distributed need not include anything that is normally distributed
 *     (in either source or binary form) with the major components (compiler, kernel,
 *     and so on) of the operating system on which the executable runs, unless that
 *     component itself accompanies the executable.
 *
 *   - Redistributions 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 OWNER 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.
 *
 ****************************************************************************************/
#include "shared.h"
#include "megasd.h"

#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
#define SUPPORTED_EXT 20
#else
#define SUPPORTED_EXT 10
#endif

/* CD blocks scanning speed */
#define CD_SCAN_SPEED 30

/* CD tracks type (CD-DA by default) */
#define TYPE_AUDIO 0x00
#define TYPE_MODE1 0x01
#define TYPE_MODE2 0x02

/* BCD conversion lookup tables */
static const uint8 lut_BCD_8[100] =
{
  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 
  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 
  0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 
  0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 
  0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 
  0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 
  0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 
  0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 
  0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 
  0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 
};

static const uint16 lut_BCD_16[100] =
{
  0x0000, 0x0001, 0x0002, 0x0003, 0x0004, 0x0005, 0x0006, 0x0007, 0x0008, 0x0009, 
  0x0100, 0x0101, 0x0102, 0x0103, 0x0104, 0x0105, 0x0106, 0x0107, 0x0108, 0x0109, 
  0x0200, 0x0201, 0x0202, 0x0203, 0x0204, 0x0205, 0x0206, 0x0207, 0x0208, 0x0209, 
  0x0300, 0x0301, 0x0302, 0x0303, 0x0304, 0x0305, 0x0306, 0x0307, 0x0308, 0x0309, 
  0x0400, 0x0401, 0x0402, 0x0403, 0x0404, 0x0405, 0x0406, 0x0407, 0x0408, 0x0409, 
  0x0500, 0x0501, 0x0502, 0x0503, 0x0504, 0x0505, 0x0506, 0x0507, 0x0508, 0x0509, 
  0x0600, 0x0601, 0x0602, 0x0603, 0x0604, 0x0605, 0x0606, 0x0607, 0x0608, 0x0609, 
  0x0700, 0x0701, 0x0702, 0x0703, 0x0704, 0x0705, 0x0706, 0x0707, 0x0708, 0x0709, 
  0x0800, 0x0801, 0x0802, 0x0803, 0x0804, 0x0805, 0x0806, 0x0807, 0x0808, 0x0809, 
  0x0900, 0x0901, 0x0902, 0x0903, 0x0904, 0x0905, 0x0906, 0x0907, 0x0908, 0x0909, 
};

/* pre-build TOC */
static const uint16 toc_snatcher[21] =
{
  56014,   495, 10120, 20555, 1580, 5417, 12502, 16090,  6553, 9681,
   8148, 20228,  8622,  6142, 5858, 1287,  7424,  3535, 31697, 2485,
  31380
};

static const uint16 toc_lunar[52] =
{
  5422, 1057, 7932, 5401, 6380, 6592, 5862,  5937, 5478, 5870,
  6673, 6613, 6429, 4996, 4977, 5657, 3720,  5892, 3140, 3263,
  6351, 5187, 3249, 1464, 1596, 1750, 1751,  6599, 4578, 5205,
  1550, 1827, 2328, 1346, 1569, 1613, 7199,  4928, 1656, 2549,
  1875, 3901, 1850, 2399, 2028, 1724, 4889, 14551, 1184, 2132,
  685, 3167
};

static const uint32 toc_shadow[15] =
{
  10226, 70054, 11100, 12532, 12444, 11923, 10059, 10167, 10138, 13792,
  11637,  2547,  2521,  3856, 900
};

static const uint32 toc_dungeon[13] =
{
  2250, 22950, 16350, 24900, 13875, 19950, 13800, 15375, 17400, 17100,
  3325,  6825, 25275
};

static const uint32 toc_ffight[26] =
{
  11994, 9742, 10136, 9685, 9553, 14588, 9430, 8721, 9975, 9764,
  9704, 12796, 585, 754, 951, 624, 9047, 1068, 817, 9191, 1024,
  14562, 10320, 8627, 3795, 3047
};

static const uint32 toc_ffightj[29] =
{
  11994, 9752, 10119, 9690, 9567, 14575, 9431, 8731, 9965, 9763,
  9716, 12791, 579, 751, 958, 630, 9050, 1052, 825, 9193, 1026,
  14553, 9834, 10542, 1699, 1792, 1781, 3783, 3052
};


/* supported audio file extensions */
static const char extensions[SUPPORTED_EXT][16] =
{
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
  "%02d.ogg",
  " %02d.ogg",
  "-%02d.ogg",
  "_%02d.ogg",
  " - %02d.ogg",
  "%d.ogg",
  " %d.ogg",
  "-%d.ogg",
  "_%d.ogg",
  " - %d.ogg",
#endif
  "%02d.wav",
  " %02d.wav",
  "-%02d.wav",
  "_%02d.wav",
  " - %02d.wav",
  "%d.wav",
  " %d.wav",
  "-%d.wav",
  "_%d.wav",
  " - %d.wav"
};

#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)

static int seek64_wrap(void *f,ogg_int64_t off,int whence){
  return cdStreamSeek(f,off,whence);
}

static ov_callbacks cb =
{ 
  (size_t (*)(void *, size_t, size_t, void *))  cdStreamRead,
  (int (*)(void *, ogg_int64_t, int))           seek64_wrap,
  (int (*)(void *))                             cdStreamClose,
  (long (*)(void *))                            cdStreamTell
};

#ifdef DISABLE_MANY_OGG_OPEN_FILES
static void ogg_free(int i)
{
  /* clear OGG file descriptor to prevent file from being closed */
  cdd.toc.tracks[i].vf.datasource = NULL;

  /* close VORBIS file structure */
  ov_clear(&cdd.toc.tracks[i].vf);

  /* indicates that the track is a seekable VORBIS file */
  cdd.toc.tracks[i].vf.seekable = 1;

  /* reset file reading position */
  cdStreamSeek(cdd.toc.tracks[i].fd, 0, SEEK_SET);
}
#endif

#endif

void cdd_init(int samplerate)
{
  /* CD-DA is running by default at 44100 Hz */
  /* Audio stream is resampled to desired rate using Blip Buffer */
  blip_set_rates(snd.blips[2], 44100, samplerate);
}

void cdd_reset(void)
{
  /* reset drive access latency */
  cdd.latency = 0;

  /* reset track index */
  cdd.index = 0;

  /* reset logical block address */
  cdd.lba = 0;

  /* reset status */
  cdd.status = cdd.loaded ? CD_TOC : NO_DISC;
  
  /* reset CD-DA fader (full volume) */
  cdd.fader[0] = cdd.fader[1] = 0x400;

  /* clear CD-DA output */
  cdd.audio[0] = cdd.audio[1] = 0;
}

int cdd_context_save(uint8 *state)
{
  int bufferptr = 0;
  unsigned int offset = 0;

  save_param(&cdd.cycles, sizeof(cdd.cycles));
  save_param(&cdd.latency, sizeof(cdd.latency));
  save_param(&cdd.index, sizeof(cdd.index));
  save_param(&cdd.lba, sizeof(cdd.lba));
  save_param(&cdd.scanOffset, sizeof(cdd.scanOffset));
  save_param(&cdd.fader, sizeof(cdd.fader));
  save_param(&cdd.status, sizeof(cdd.status));

  /* current track is an audio track ? */
  if (cdd.toc.tracks[cdd.index].type == TYPE_AUDIO)
  {
    /* get file read offset */
#if defined(USE_LIBCHDR)
    if (cdd.chd.file)
    {
      /* CHD file offset */
      offset = cdd.chd.hunkofs;
    }
    else
#endif
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
    if (cdd.toc.tracks[cdd.index].vf.seekable)
    {
      /* VORBIS file sample offset */
      offset = ov_pcm_tell(&cdd.toc.tracks[cdd.index].vf);
    }
    else
#endif 
    if (cdd.toc.tracks[cdd.index].fd)
    {
      /* PCM file offset */
      offset = cdStreamTell(cdd.toc.tracks[cdd.index].fd);
    }
  }

  save_param(&offset, sizeof(offset));
  save_param(&cdd.audio, sizeof(cdd.audio));

  return bufferptr;
}

int cdd_context_load(uint8 *state, char *version)
{
  unsigned int offset, lba, index;
  int bufferptr = 0;

  load_param(&cdd.cycles, sizeof(cdd.cycles));
  load_param(&cdd.latency, sizeof(cdd.latency));
  load_param(&index, sizeof(cdd.index));
  load_param(&lba, sizeof(cdd.lba));
  load_param(&cdd.scanOffset, sizeof(cdd.scanOffset));
  load_param(&cdd.fader, sizeof(cdd.fader));
  load_param(&cdd.status, sizeof(cdd.status));

  /* update current sector */
  cdd.lba = lba;

  /* support for previous state version (1.7.5) */
  if ((version[11] == 0x31) && (version[13] == 0x37) && (version[15] == 0x35))
  {
    /* current track is an audio track ? */
    if (cdd.toc.tracks[index].type == TYPE_AUDIO)
    {
      /* stay within track limits when seeking files */
      if (lba < cdd.toc.tracks[index].start)
      {
        lba = cdd.toc.tracks[index].start;
      }

      /* seek to current track sector */
      cdd_seek_audio(index, lba);
    }
  }
  else
  {
    load_param(&offset, sizeof(offset));
    load_param(&cdd.audio, sizeof(cdd.audio));

    /* current track is an audio track ? */
    if (cdd.toc.tracks[index].type == TYPE_AUDIO)
    {
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
#ifdef DISABLE_MANY_OGG_OPEN_FILES
      /* check if track index has changed */
      if (index != cdd.index)
      {
        /* close previous track VORBIS file structure to save memory */
        if (cdd.toc.tracks[cdd.index].vf.datasource)
        {
          ogg_free(cdd.index);
        }

        /* open current track VORBIS file */
        if (cdd.toc.tracks[index].vf.seekable)
        {
          ov_open_callbacks(cdd.toc.tracks[index].fd,&cdd.toc.tracks[index].vf,0,0,cb);
        }
      }
#endif
#endif
      /* seek to current file read offset */
#if defined(USE_LIBCHDR)
      if (cdd.chd.file)
      {
        /* CHD file offset */
        cdd.chd.hunkofs = offset;
      }
      else
#endif
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
      if (cdd.toc.tracks[index].vf.seekable)
      {
        /* VORBIS file sample offset */
        ov_pcm_seek(&cdd.toc.tracks[index].vf, offset);
      }
      else
#endif 
      if (cdd.toc.tracks[index].fd)
      {
        /* PCM file offset */
        cdStreamSeek(cdd.toc.tracks[index].fd, offset, SEEK_SET);
      }
    }
  }

  /* seek to current subcode position */
  if (cdd.toc.sub)
  {
    /* 96 bytes per sector */
    cdStreamSeek(cdd.toc.sub, lba * 96, SEEK_SET);
  }

  /* update current track index */
  cdd.index = index;

  return bufferptr;
}

int cdd_load(char *filename, char *header)
{
  char fname[256+10];
  char line[128];
  char *ptr, *lptr;
  cdStream *fd;
  
  /* assume normal CD image file by default */
  int isCDfile = 1;
  int isMSDfile = 0;

  /* first unmount any loaded disc */
  cdd_unload();

  /* open file */
  fd = cdStreamOpen(filename);
  if (!fd)
  {
    /* do not return an error as this could be a ROM loaded in memory */
    /* which should be handled by load_archive function */
    return (0);
  }

#if defined(USE_LIBCHDR)
  if (!memcmp("chd", &filename[strlen(filename) - 3], 3) || !memcmp("CHD", &filename[strlen(filename) - 3], 3))
  {
    int sectors = 0;
    char metadata[256];
    const chd_header *head;

    /* open CHD file */
    if (chd_open_file(fd, CHD_OPEN_READ, NULL, &cdd.chd.file) != CHDERR_NONE)
    {
      chd_close(cdd.chd.file);
      cdStreamClose(fd);
      return -1;
    }

    /* retrieve CHD header */
    head = chd_get_header(cdd.chd.file);

    /* detect invalid hunk size */
    if ((head->hunkbytes == 0) || (head->hunkbytes % CD_FRAME_SIZE))
    {
      chd_close(cdd.chd.file);
      cdStreamClose(fd);
      return -1;
    }

    /* allocate hunk buffer */
    cdd.chd.hunk = (uint8 *)malloc(head->hunkbytes);
    if (!cdd.chd.hunk)
    {
      chd_close(cdd.chd.file);
      cdStreamClose(fd);
      return -1;
    }

    /* initialize hunk size (usually fixed to 8 sectors) */
    cdd.chd.hunkbytes = head->hunkbytes;

    /* initialize buffered hunk index */
    cdd.chd.hunknum = -1;

    /* retrieve tracks informations */
    for (cdd.toc.last = 0; cdd.toc.last < 99; cdd.toc.last++)
    {
      int tracknum = 0, frames = 0, pregap = 0, postgap = 0;
      char type[16], subtype[16], pgtype[16], pgsub[16];
      type[0] = subtype[0] = pgtype[0] = pgsub[0] = 0;

      /* attempt fetch either complete or partial metadata for current track */
      if (chd_get_metadata(cdd.chd.file, CDROM_TRACK_METADATA2_TAG, cdd.toc.last, metadata, 256, 0, 0, 0) == CHDERR_NONE)
      {
        if (sscanf(metadata, CDROM_TRACK_METADATA2_FORMAT, &tracknum, &type[0], &subtype[0], &frames, &pregap, &pgtype[0], &pgsub[0], &postgap) != 8)
          break;
      }
      else if (chd_get_metadata(cdd.chd.file, CDROM_TRACK_METADATA_TAG, cdd.toc.last, metadata, 256, 0, 0, 0) == CHDERR_NONE)
      {
        if (sscanf(metadata, CDROM_TRACK_METADATA_FORMAT, &tracknum, &type[0], &subtype[0], &frames) != 4)
          break;
      }

      /* no more track */
      else break;

      /* detect out of order track number or invalid parameter */
      if ((tracknum != (cdd.toc.last + 1)) || (frames < 0) || (pregap < 0) || (postgap < 0))
        break;

      /* detect track type  */
      if (cdd.toc.last)
      {
        /* CD-ROM track supported only for first track */
        if (strcmp(type, "AUDIO"))
          break;

        /* Audio track start LBA (adjusted with pregap length) */
        cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end + pregap;
      }
      else
      {
        if (!strcmp(type, "MODE1_RAW"))
        {
          /* Mode 1 RAW format (2352 bytes data blocks) */
          cdd.sectorSize = 2352;
          cdd.toc.tracks[0].type = TYPE_MODE1;
        }
        else if (!strcmp(type, "MODE1"))
        {
          /* Mode 1 COOKED format (2048 bytes data blocks) */
          cdd.sectorSize = 2048;
          cdd.toc.tracks[0].type = TYPE_MODE1;
        }
        else if (!strcmp(type, "MODE2_RAW"))
        {
          /* Mode 2 RAW format (2352 bytes data blocks) */
          cdd.sectorSize = 2352;
          cdd.toc.tracks[0].type = TYPE_MODE2;
        }
        else if (strcmp(type, "AUDIO"))
        {
          /* unsupported track format */
          break;
        }

        /* First track start LBA (2s pause assumed by default) */
        cdd.toc.tracks[0].start = 0;
      }

      /* detect pregap type */
      if (pgtype[0] != 'V')
      {
        /* clear pause length for further calculations (not included in CHD file) */
        pregap = 0;
      }

      /* track end LBA (remove included pause from CHD track length) */
      cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + frames - pregap;
   
      /* CHD file offset for current track */
      cdd.toc.tracks[cdd.toc.last].offset = (sectors + pregap - cdd.toc.tracks[cdd.toc.last].start) * CD_FRAME_SIZE;

      /* update TOC end with postgap length */
      cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end + postgap;

      /* update CHD file sector count (adjusted with end of the track padding) */
      sectors += (((frames + CD_TRACK_PADDING - 1) / CD_TRACK_PADDING) * CD_TRACK_PADDING);

      /* indicate valid track file */
      cdd.toc.tracks[cdd.toc.last].fd = fd;
    }

    /* valid CD-ROM image file ? */
    if (cdd.sectorSize)
    {
      /* read first chunk of data */
      cdd.chd.hunknum = cdd.toc.tracks[0].offset / cdd.chd.hunkbytes;
      chd_read(cdd.chd.file, cdd.chd.hunknum, cdd.chd.hunk);

      /* copy CD image header + security code (skip RAW sector 16-byte header) */
      memcpy(header, cdd.chd.hunk + (cdd.toc.tracks[0].offset % cdd.chd.hunkbytes) + ((cdd.sectorSize == 2048) ? 0 : 16), 0x210);
    }

    /* valid CD image ? */
    if (cdd.toc.last && (cdd.toc.end < (100*60*75)))
    {
      /* Lead-out */
      cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;

      /* CD mounted */
      cdd.loaded = HW_ADDON_MEGACD;
      return 1;
    }

    /* invalid CHD file */
    chd_close(cdd.chd.file);
    cdStreamClose(fd);
    return -1;
  }
#endif

  /* save a copy of base filename (max. 255 characters) */
  strncpy(fname, filename, 255);
  fname[256] = 0;

  /* check loaded file extension */
  if (memcmp("cue", &filename[strlen(filename) - 3], 3) && memcmp("CUE", &filename[strlen(filename) - 3], 3))
  {
    int len;

    static const uint8 sync[12] = {0x00,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x00};

    /* read first 16 bytes */
    cdStreamRead(header, 0x10, 1, fd);

    /* auto-detect valid Sega CD image */
    if (!memcmp("SEGADISCSYSTEM", header, 14))
    {
      /* COOKED CD-ROM image (2048 bytes data blocks) */
      cdd.sectorSize = 2048;

      /* CD-ROM Mode 1 by default */
      cdd.toc.tracks[0].type = TYPE_MODE1;
    }

    /* auto-detect CD-ROM synchro pattern */
    else if (!memcmp(sync, header, 12))
    {
      /* RAW CD-ROM image (2352 bytes data blocks) */
      cdd.sectorSize = 2352;

      /* auto-detect CD-ROM mode from block header (byte 15) */
      cdd.toc.tracks[0].type = header[15];

      /* read next 16 bytes (start of user data) */
      cdStreamRead(header, 0x10, 1, fd);
    }

    /* supported CD-ROM image file ? */
    if ((cdd.toc.tracks[0].type == TYPE_MODE1) || (cdd.toc.tracks[0].type == TYPE_MODE2))
    {
      /* read Sega CD image header + security code */
      cdStreamRead(header + 0x10, 0x200, 1, fd);

      /* initialize first track file descriptor */
      cdd.toc.tracks[0].fd = fd;

      /* DATA track end LBA (based on DATA file length) */
      cdStreamSeek(fd, 0, SEEK_END);
      cdd.toc.tracks[0].end = cdStreamTell(fd) / cdd.sectorSize;

      /* DATA track length should be at least 2s (BIOS requirement) */
      if (cdd.toc.tracks[0].end < 150)
      {
        cdd.toc.tracks[0].end = 150;
      }
        
      /* DATA track start LBA (logical block 0) */
      cdStreamSeek(fd, 0, SEEK_SET);
      cdd.toc.tracks[0].start = 0;

      /* initialize TOC */
      cdd.toc.end = cdd.toc.tracks[0].end;
      cdd.toc.last = 1;
    }
    else
    {
      /* this is not a supported CD-ROM image file */
      isCDfile = 0;

      /* close file */
      cdStreamClose(fd);
    }

    /* automatically try to mount CD associated CUE file */
    len = strlen(fname);
    while ((len && (fname[len] != '.')) || (len > 251)) len--;
    strcpy(&fname[len], ".cue");
    fd = cdStreamOpen(fname);
  }

  /* parse CUE file */
  if (fd)
  {
    int mm, ss, bb, pregap = 0;
    int index = 0;

    /* DATA track already loaded ? */
    if (cdd.toc.last)
    {
      /* skip first track */
      while (cdStreamGets(line, 128, fd))
      {
        if (strstr(line, "INDEX 01") && !strstr(line, "INDEX 1"))
          break;
      }
    }

    /* read lines until end of file */
    while (cdStreamGets(line, 128, fd))
    {
      /* skip any SPACE characters */
      lptr = line;
      while (*lptr == 0x20) lptr++;

      /* decode FILE commands */
      if (!(memcmp(lptr, "FILE", 4)))
      {
        /* retrieve current path */
        ptr = fname + strlen(fname) - 1;
        while ((ptr - fname) && (*ptr != '/') && (*ptr != '\\')) ptr--;
        if (ptr - fname) ptr++;

        /* skip "FILE" attribute */
        lptr += 4;

        /* skip SPACE characters */
        while (*lptr == 0x20) lptr++;

        /* retrieve full filename */
        if (*lptr == '\"')
        {
          /* skip first DOUBLE QUOTE character */
          lptr++;
          while ((*lptr != '\"') && (lptr <= (line + 128)) && (ptr < (fname + 255)))
            *ptr++ = *lptr++;
        }
        else
        {
          /* no DOUBLE QUOTE used */
          while ((*lptr != 0x20) && (lptr <= (line + 128)) && (ptr < (fname + 255)))
            *ptr++ = *lptr++;
        }
        *ptr = 0;

        /* open current track file descriptor */
        cdd.toc.tracks[cdd.toc.last].fd = cdStreamOpen(fname);
        if (!cdd.toc.tracks[cdd.toc.last].fd)
        {
          /* error opening file */
          break;
        }

        /* reset current file PREGAP length */
        pregap = 0;

        /* reset current track file read offset */
        cdd.toc.tracks[cdd.toc.last].offset = 0;

        /* check supported audio file types */
        if (!strstr(lptr,"BINARY") && !strstr(lptr,"MOTOROLA"))
        {
          /* read file header */
          unsigned char head[12];
          cdStreamRead(head, 12, 1, cdd.toc.tracks[cdd.toc.last].fd);
          cdStreamSeek(cdd.toc.tracks[cdd.toc.last].fd, 0, SEEK_SET);

          /* autodetect WAVE file */
          if (!memcmp(head, "RIFF", 4) && !memcmp(head + 8, "WAVE", 4))
          {
            /* look for 'data' chunk */
            int chunkSize, dataOffset = 0;
            cdStreamSeek(cdd.toc.tracks[cdd.toc.last].fd, 12, SEEK_SET);
            while (cdStreamRead(head, 8, 1, cdd.toc.tracks[cdd.toc.last].fd))
            {
              if (!memcmp(head, "data", 4))
              {
                dataOffset = cdStreamTell(cdd.toc.tracks[cdd.toc.last].fd);
                cdStreamSeek(cdd.toc.tracks[cdd.toc.last].fd, 0, SEEK_SET);
                break;
              }
              chunkSize = head[4] + (head[5] << 8) + (head[6] << 16) + (head[7] << 24);
              cdStreamSeek(cdd.toc.tracks[cdd.toc.last].fd, chunkSize, SEEK_CUR);
            }

            /* check if 'data' chunk has not been found */
            if (!dataOffset)
            {
              /* invalid WAVE file */
              cdStreamClose(cdd.toc.tracks[cdd.toc.last].fd);
              cdd.toc.tracks[cdd.toc.last].fd = 0;
              break;
            }

            /* adjust current track file read offset with WAVE header length */
            cdd.toc.tracks[cdd.toc.last].offset -= dataOffset;
          }
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
          else if (!ov_open_callbacks(cdd.toc.tracks[cdd.toc.last].fd,&cdd.toc.tracks[cdd.toc.last].vf,0,0,cb))
          {
            /* retrieve stream infos */
            vorbis_info *info = ov_info(&cdd.toc.tracks[cdd.toc.last].vf,-1);
            if (!info || (info->rate != 44100) || (info->channels != 2))
            {
              /* unsupported VORBIS file format (stereo @44.1kHz only) */
              ov_clear(&cdd.toc.tracks[cdd.toc.last].vf);
              cdd.toc.tracks[cdd.toc.last].fd = 0;
              break;
            }
          }
#endif
          else
          {
            /* unsupported audio file */
            cdStreamClose(cdd.toc.tracks[cdd.toc.last].fd);
            cdd.toc.tracks[cdd.toc.last].fd = 0;
            break;
          }
        }
      }

      /* decode TRACK commands */
      else if ((sscanf(lptr, "TRACK %02d %*s", &bb)) || (sscanf(lptr, "TRACK %d %*s", &bb)))
      {
        /* autodetect DATA track type (first track only) */
        if (!cdd.toc.last)
        {
          if (strstr(lptr,"MODE1/2048"))
          {
            /* Mode 1 COOKED format (2048 bytes / block) */
            cdd.sectorSize = 2048;
            cdd.toc.tracks[0].type = TYPE_MODE1;
          }
          else if (strstr(lptr,"MODE1/2352"))
          {
            /* Mode 1 RAW format (2352 bytes / block) */
            cdd.sectorSize = 2352;
            cdd.toc.tracks[0].type = TYPE_MODE1;
          }
          else if (strstr(lptr,"MODE2/2352"))
          {
            /* Mode 2 RAW format (2352 bytes / block) */
            cdd.sectorSize = 2352;
            cdd.toc.tracks[0].type = TYPE_MODE2;
          }

          if (cdd.sectorSize)
          {
            if (cdd.sectorSize == 2352)
            {
              /* skip 16-byte header */
              cdStreamSeek(cdd.toc.tracks[0].fd, 0x10, SEEK_SET);
            }

            /* read CD image header + security code */
            cdStreamRead(header, 0x210, 1, cdd.toc.tracks[0].fd);
            cdStreamSeek(cdd.toc.tracks[0].fd, 0, SEEK_SET);
          }
        }
        else
        {
          /* check if same file is used for consecutive tracks */
          if (!cdd.toc.tracks[cdd.toc.last].fd)
          {
            /* clear previous track end time */
            cdd.toc.tracks[cdd.toc.last - 1].end = 0;
          }
        }

        /* save current track index */
        index = cdd.toc.last;
      }

      /* decode REM LOOP xxx command (MegaSD specific command) */
      else if (sscanf(lptr, "REM LOOP %d", &bb) == 1)
      {
        cdd.toc.tracks[index].loopEnabled = 1;
        cdd.toc.tracks[index].loopOffset = bb;
        isMSDfile = 1;
      }

      /* decode REM LOOP command (MegaSD specific command) */
      else if (strstr(lptr,"REM LOOP"))
      {
        cdd.toc.tracks[index].loopEnabled = 1;
        isMSDfile = 1;
      }

      /* decode REM NOLOOP command (MegaSD specific command) */
      else if (strstr(lptr,"REM NOLOOP"))
      {
        cdd.toc.tracks[index].loopEnabled = -1;
        isMSDfile = 1;
      }

      /* decode PREGAP commands */
      else if (sscanf(lptr, "PREGAP %02d:%02d:%02d", &mm, &ss, &bb) == 3)
      {
        /* increment current file PREGAP length */
        pregap += bb + ss*75 + mm*60*75;
      }

      /* decode INDEX commands */
      else if ((sscanf(lptr, "INDEX 00 %02d:%02d:%02d", &mm, &ss, &bb) == 3) ||
               (sscanf(lptr, "INDEX 0 %02d:%02d:%02d", &mm, &ss, &bb) == 3))
      {
        /* check if previous track end time needs to be set */
        if (cdd.toc.last && !cdd.toc.tracks[cdd.toc.last - 1].end)
        {
          /* set previous track end time (current file absolute time + PREGAP length) */
          cdd.toc.tracks[cdd.toc.last - 1].end = bb + ss*75 + mm*60*75 + pregap;
        }
      }
      else if ((sscanf(lptr, "INDEX 01 %02d:%02d:%02d", &mm, &ss, &bb) == 3) ||
               (sscanf(lptr, "INDEX 1 %02d:%02d:%02d", &mm, &ss, &bb) == 3))
      {
        /* adjust current track file read offset with current file PREGAP length (only used for AUDIO track) */
        cdd.toc.tracks[cdd.toc.last].offset += pregap * 2352;

        /* check if a single file is used for consecutive tracks */
        if (!cdd.toc.tracks[cdd.toc.last].fd && cdd.toc.last)
        {
          /* use common file descriptor */
          cdd.toc.tracks[cdd.toc.last].fd = cdd.toc.tracks[cdd.toc.last - 1].fd;

          /* current track start time (based on current file absolute time + PREGAP length) */
          cdd.toc.tracks[cdd.toc.last].start = bb + ss*75 + mm*60*75 + pregap;

          /* check if previous track end time needs to be set */
          if (!cdd.toc.tracks[cdd.toc.last - 1].end)
          {
            /* set previous track end time (based on current track start time, ignoring any "PREGAP"-type pause if no INDEX00) */
            cdd.toc.tracks[cdd.toc.last - 1].end = cdd.toc.tracks[cdd.toc.last].start;
          }
        }
        else
        {
          /* current file start time (based on previous track end time + PREGAP length) */
          cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end + pregap;

          /* adjust current track file read offset with previous track end time (only used for AUDIO track) */
          cdd.toc.tracks[cdd.toc.last].offset += cdd.toc.end * 2352;

#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
          if (cdd.toc.tracks[cdd.toc.last].vf.datasource)
          { 
            /* convert read offset to PCM sample offset */
            cdd.toc.tracks[cdd.toc.last].offset = cdd.toc.tracks[cdd.toc.last].offset / 4;

            /* current track end time */
            cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + ov_pcm_total(&cdd.toc.tracks[cdd.toc.last].vf,-1)/588;
            if (cdd.toc.tracks[cdd.toc.last].end <= cdd.toc.tracks[cdd.toc.last].start)
            {
              /* invalid length */
              ov_clear(&cdd.toc.tracks[cdd.toc.last].vf);
              cdd.toc.tracks[cdd.toc.last].fd = 0;
              cdd.toc.tracks[cdd.toc.last].end = 0;
              cdd.toc.tracks[cdd.toc.last].start = 0;
              cdd.toc.tracks[cdd.toc.last].offset = 0;
              break;
            }

#ifdef DISABLE_MANY_OGG_OPEN_FILES
            /* close VORBIS file structure to save memory */
            ogg_free(cdd.toc.last);
#endif
          }
          else
#endif
          {
            /* current track end time */
            cdStreamSeek(cdd.toc.tracks[cdd.toc.last].fd, 0, SEEK_END);
            if (cdd.toc.tracks[cdd.toc.last].type)
            {
              /* DATA track length */
              cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + (cdStreamTell(cdd.toc.tracks[cdd.toc.last].fd) / cdd.sectorSize);
            }
            else
            {
              /* AUDIO track length */
              cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + (cdStreamTell(cdd.toc.tracks[cdd.toc.last].fd) / 2352);
            }
            cdStreamSeek(cdd.toc.tracks[cdd.toc.last].fd, 0, SEEK_SET);
          }

          /* adjust track start time (based on current file start time + index absolute time) */
          cdd.toc.tracks[cdd.toc.last].start += (bb + ss*75 + mm*60*75);

          /* update TOC end */
          cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;
        }

        /* increment track number */
        cdd.toc.last++;
        
        /* max. 99 tracks */
        if (cdd.toc.last == 99) break;
      }
    }

    /* check if last track end time needs to be set */
    if (cdd.toc.last && !cdd.toc.tracks[cdd.toc.last - 1].end)
    {
      /* adjust TOC end with current file PREGAP length */
      cdd.toc.end += pregap;

      /* last track end time */
      cdd.toc.tracks[cdd.toc.last - 1].end = cdd.toc.end;
    }

    /* close any incomplete track file */
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
    if (cdd.toc.tracks[cdd.toc.last].vf.datasource)
    {
      ov_clear(&cdd.toc.tracks[cdd.toc.last].vf);
    }
    else
#endif
    if (cdd.toc.tracks[cdd.toc.last].fd)
    {
      cdStreamClose(cdd.toc.tracks[cdd.toc.last].fd);
    }

    /* close CUE file */
    cdStreamClose(fd);
  }
  else if (cdd.toc.last)
  {
    int i, offset = 1;

    /* set pointer at the end of filename */
    ptr = fname + strlen(fname) - 4; 

    /* autodetect audio track file extensions */
    for (i=0; i<SUPPORTED_EXT; i++)
    {
      /* auto-detect wrong initial track index */
      sprintf(ptr, extensions[i], cdd.toc.last);
      fd = cdStreamOpen(fname);
      if (fd)
      {
        offset = 0;
        break;
      }

      sprintf(ptr, extensions[i], cdd.toc.last + 1);
      fd = cdStreamOpen(fname);
      if (fd) break;
    }

    /* repeat until no more valid track files can be found */
    while (fd)
    {
      /* read file header */
      unsigned char head[12];
      cdStreamRead(head, 12, 1, fd);
      cdStreamSeek(fd, 0, SEEK_SET);

      /* autodetect WAVE file */
      if (!memcmp(head, "RIFF", 4) && !memcmp(head + 8, "WAVE", 4))
      {
        /* look for 'data' chunk */
        int chunkSize, dataOffset = 0;
        cdStreamSeek(fd, 12, SEEK_SET);
        while (cdStreamRead(head, 8, 1, fd))
        {
          if (!memcmp(head, "data", 4))
          {
            dataOffset = cdStreamTell(fd);
            cdStreamSeek(fd, 0, SEEK_SET);
            break;
          }
          chunkSize = head[4] + (head[5] << 8) + (head[6] << 16) + (head[7] << 24);
          cdStreamSeek(fd, chunkSize, SEEK_CUR);
        }

        /* check if 'data' chunk has not been found */
        if (!dataOffset)
        {
          /* invalid WAVE file */
          cdStreamClose(fd);
          break;
        }

        /* initialize current track file descriptor */
        cdd.toc.tracks[cdd.toc.last].fd = fd;

        /* initialize current track start time (based on previous track end time) */
        cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;

        /* add default 2s PAUSE between tracks */
        cdd.toc.tracks[cdd.toc.last].start += 150;

        /* current track end time */
        cdStreamSeek(fd, 0, SEEK_END);
        cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + ((cdStreamTell(fd) - dataOffset + 2351) / 2352);

        /* initialize file read offset for current track */
        cdd.toc.tracks[cdd.toc.last].offset = cdd.toc.tracks[cdd.toc.last].start * 2352;

        /* auto-detect PAUSE within audio files */
        cdStreamSeek(fd, 100 * 2352, SEEK_SET);
        cdStreamRead(head, 4, 1, fd);
        cdStreamSeek(fd, 0, SEEK_SET);
        if (*(int32 *)head == 0)
        {
          /* assume 2s PAUSE is included at the beginning of the file */
          cdd.toc.tracks[cdd.toc.last].offset -= 150 * 2352;
          cdd.toc.tracks[cdd.toc.last].end -= 150;
        }

        /* update TOC end */
        cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;

        /* adjust file read offset for current track with WAVE header length */
        cdd.toc.tracks[cdd.toc.last].offset -= dataOffset;

        /* increment track number */
        cdd.toc.last++;
      }
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
      else if (!ov_open_callbacks(fd,&cdd.toc.tracks[cdd.toc.last].vf,0,0,cb))
      {
        /* retrieve stream infos */
        vorbis_info *info = ov_info(&cdd.toc.tracks[cdd.toc.last].vf,-1);
        if (!info || (info->rate != 44100) || (info->channels != 2))
        {
          /* unsupported OGG file */
          ov_clear(&cdd.toc.tracks[cdd.toc.last].vf);
          break;
        }

        /* initialize current track file descriptor */
        cdd.toc.tracks[cdd.toc.last].fd = fd;

        /* initialize current track start time (based on previous track end time) */
        cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;

        /* add default 2s PAUSE between tracks */
        cdd.toc.tracks[cdd.toc.last].start += 150;

        /* current track end time */
        cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + ((ov_pcm_total(&cdd.toc.tracks[cdd.toc.last].vf,-1) + 587) / 588);
        if (cdd.toc.tracks[cdd.toc.last].end <= cdd.toc.tracks[cdd.toc.last].start)
        {
          /* invalid file length */
          ov_clear(&cdd.toc.tracks[cdd.toc.last].vf);
          cdd.toc.tracks[cdd.toc.last].fd = 0;
          cdd.toc.tracks[cdd.toc.last].end = 0;
          cdd.toc.tracks[cdd.toc.last].start = 0;
          break;
        }

        /* initialize file read offset for current track */
        cdd.toc.tracks[cdd.toc.last].offset = cdd.toc.tracks[cdd.toc.last].start * 588;

        /* auto-detect PAUSE within audio files */
        ov_pcm_seek(&cdd.toc.tracks[cdd.toc.last].vf, 100 * 588);
#if defined(USE_LIBVORBIS)
        ov_read(&cdd.toc.tracks[cdd.toc.last].vf, (char *)head, 32, 0, 2, 1, 0);
#else
        ov_read(&cdd.toc.tracks[cdd.toc.last].vf, (char *)head, 32, 0);
#endif
        ov_pcm_seek(&cdd.toc.tracks[cdd.toc.last].vf, 0);
        if (*(int32 *)head == 0)
        {
          /* assume 2s PAUSE is included at the beginning of the file */
          cdd.toc.tracks[cdd.toc.last].offset -= 150 * 588;
          cdd.toc.tracks[cdd.toc.last].end -= 150;
        }

#ifdef DISABLE_MANY_OGG_OPEN_FILES
        /* close VORBIS file structure to save memory */
        ogg_free(cdd.toc.last);
#endif

        /* update TOC end */
        cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;

        /* increment track number */
        cdd.toc.last++;
      }
#endif
      else
      {
        /* unsupported audio file format */
        cdStreamClose(fd);
        break;
      }

      /* max. 99 tracks */
      if (cdd.toc.last == 99)  break;

      /* try to open next audio track file */
      sprintf(ptr, extensions[i], cdd.toc.last + offset);
      fd = cdStreamOpen(fname);
    }

    /* Valid CD-ROM Mode 1 track found ? */
    if (cdd.toc.tracks[0].type == TYPE_MODE1)
    {
      /* simulate audio tracks if none found */
      if (cdd.toc.last == 1)
      {
        /* some games require exact TOC infos */
        if (strstr(header + 0x180,"T-95035") != NULL)
        {
          /* Snatcher */
          cdd.toc.last = cdd.toc.end = 0;
          do
          {
            cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;
            cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + toc_snatcher[cdd.toc.last];
            cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;
            cdd.toc.last++;
          }
          while (cdd.toc.last < 21);
        }
        else if (strstr(header + 0x180,"T-127015") != NULL)
        {
          /* Lunar - The Silver Star */
          cdd.toc.last = cdd.toc.end = 0;
          do
          {
            cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;
            cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + toc_lunar[cdd.toc.last];
            cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;
            cdd.toc.last++;
          }
          while (cdd.toc.last < 52);
        }
        else if (strstr(header + 0x180,"T-113045") != NULL)
        {
          /* Shadow of the Beast II */
          cdd.toc.last = cdd.toc.end = 0;
          do
          {
            cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;
            cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + toc_shadow[cdd.toc.last];
            cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;
            cdd.toc.last++;
          }
          while (cdd.toc.last < 15);
        }
        else if (strstr(header + 0x180,"T-143025") != NULL)
        {
          /* Dungeon Explorer */
          cdd.toc.last = cdd.toc.end = 0;
          do
          {
            cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;
            cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + toc_dungeon[cdd.toc.last];
            cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;
            cdd.toc.last++;
          }
          while (cdd.toc.last < 13);
        }
        else if (strstr(header + 0x180,"MK-4410") != NULL)
        {
          /* Final Fight CD (USA, Europe) */
          cdd.toc.last = cdd.toc.end = 0;
          do
          {
            cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;
            cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + toc_ffight[cdd.toc.last];
            cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;
            cdd.toc.last++;
          }
          while (cdd.toc.last < 26);
        }
        else if (strstr(header + 0x180,"G-6013") != NULL)
        {
          /* Final Fight CD (Japan) */
          cdd.toc.last = cdd.toc.end = 0;
          do
          {
            cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;
            cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + toc_ffightj[cdd.toc.last];
            cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;
            cdd.toc.last++;
          }
          while (cdd.toc.last < 29);
        }
        else if (strstr(header + 0x180,"T-06201-01") != NULL)
        {
          /* Sewer Shark (USA) (REV1) */
          /* no audio track */
        }
        else
        {
          /* default TOC (99 tracks & 2s per audio tracks) */
          do
          {
            cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end + 2*75;
            cdd.toc.tracks[cdd.toc.last].end = cdd.toc.tracks[cdd.toc.last].start + 2*75;
            cdd.toc.end = cdd.toc.tracks[cdd.toc.last].end;
            cdd.toc.last++;
          }
          while ((cdd.toc.last < 99) && (cdd.toc.end < 56*60*75));
        }
      }
    }

  }

  /* CD tracks found ? */
  if (cdd.toc.last)
  {
    /* Lead-out */
    cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;

    /* CD mounted */
    cdd.loaded = isMSDfile ? HW_ADDON_MEGASD : HW_ADDON_MEGACD;

    /* Automatically try to open associated subcode data file */
    memcpy(&fname[strlen(fname) - 4], ".sub", 4);
    cdd.toc.sub = cdStreamOpen(fname);

    /* return 1 if loaded file is CD image file */
    return (isCDfile);
  }

  /* no CD image file loaded */
  return 0;
}

void cdd_unload(void)
{
  if (cdd.loaded)
  {
    int i;

#if defined(USE_LIBCHDR)
    chd_close(cdd.chd.file);
    if (cdd.chd.hunk)
      free(cdd.chd.hunk);
#endif

    /* close CD tracks */
    for (i=0; i<cdd.toc.last; i++)
    {
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
      if (cdd.toc.tracks[i].vf.datasource)
      {
        /* close any opened VORBIS file */
        ov_clear(&cdd.toc.tracks[i].vf);
      }
      else
#endif
      if (cdd.toc.tracks[i].fd)
      {
        /* check if single file is used for consecutive tracks */
        if ((i > 0) && (cdd.toc.tracks[i].fd == cdd.toc.tracks[i-1].fd))
        {
          /* skip track */
          i++;
        }
        else
        {
          /* close file */
          cdStreamClose(cdd.toc.tracks[i].fd);
        }
      }
    }

    /* close any opened subcode file */
    if (cdd.toc.sub)
      cdStreamClose(cdd.toc.sub);

    /* CD unloaded */
    cdd.loaded = 0;
  }

  /* reset TOC */
  memset(&cdd.toc, 0x00, sizeof(cdd.toc));

#if defined(USE_LIBCHDR)
  /* reset CHD data */
  memset(&cdd.chd, 0x00, sizeof(cdd.chd));
#endif

  /* no CD-ROM track */
  cdd.sectorSize = 0;
}

void cdd_read_data(uint8 *dst, uint8 *subheader)
{
  /* only allow reading (first) CD-ROM track sectors */
  if (cdd.toc.tracks[cdd.index].type && (cdd.lba >= 0))
  {
#if defined(USE_LIBCHDR)
    if (cdd.chd.file)
    {
      /* CHD file offset */
      int offset = cdd.toc.tracks[0].offset + (cdd.lba * CD_FRAME_SIZE);

      /* CHD hunk index */
      int hunknum = offset / cdd.chd.hunkbytes;

      /* update CHD hunk cache if necessary */
      if (hunknum != cdd.chd.hunknum)
      {
        chd_read(cdd.chd.file, hunknum, cdd.chd.hunk);
        cdd.chd.hunknum = hunknum;
      }

      /* check sector size */
      if (cdd.sectorSize == 2048)
      {
        /* read Mode 1 user data (2048 bytes) */
        memcpy(dst, cdd.chd.hunk + (offset % cdd.chd.hunkbytes), 2048);
      }
      else
      {
        /* check if sub-header is required (Mode 2 sector only) */
        if (!subheader)
        {
          /* read Mode 1 user data (2048 bytes), skipping block sync pattern (12 bytes) + block header (4 bytes)*/
          memcpy(dst, cdd.chd.hunk + (offset % cdd.chd.hunkbytes) + 12 + 4, 2048);
        }
        else
        {
          /* read Mode 2 sub-header (first 4 bytes), skipping block sync pattern (12 bytes) + block header (4 bytes)*/
          memcpy(subheader, cdd.chd.hunk + (offset % cdd.chd.hunkbytes) + 12 + 4, 4);

          /* read Mode 2 user data (max 2328 bytes), skipping Mode 2 sub-header (8 bytes) */
          memcpy(dst, cdd.chd.hunk + (offset % cdd.chd.hunkbytes) + 12 + 4 + 8, 2328);
        }
      }

      return;
    }
#endif

    /* check sector size */
    if (cdd.sectorSize == 2048)
    {
      /* read Mode 1 user data (2048 bytes) */
      cdStreamSeek(cdd.toc.tracks[0].fd, cdd.lba * 2048, SEEK_SET);
      cdStreamRead(dst, 2048, 1, cdd.toc.tracks[0].fd);
    }
    else
    {
      /* check if sub-header is required (Mode 2 sector only) */
      if (!subheader)
      {
        /* skip block sync pattern (12 bytes) + block header (4 bytes) then read Mode 1 user data (2048 bytes) */
        cdStreamSeek(cdd.toc.tracks[0].fd, (cdd.lba * 2352) + 12 + 4, SEEK_SET);
        cdStreamRead(dst, 2048, 1, cdd.toc.tracks[0].fd);
      }
      else
      {
        /* skip block sync pattern (12 bytes) + block header (4 bytes) + Mode 2 sub-header (first 4 bytes) then read Mode 2 sub-header (last 4 bytes) */
        cdStreamSeek(cdd.toc.tracks[0].fd, (cdd.lba * 2352) + 12 + 4 + 4, SEEK_SET);
        cdStreamRead(subheader, 4, 1, cdd.toc.tracks[0].fd);

        /* read Mode 2 user data (max 2328 bytes) */
        cdStreamRead(dst, 2328, 1, cdd.toc.tracks[0].fd);
      }
    }
  }
}

void cdd_seek_audio(int index, int lba)
{
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
#ifdef DISABLE_MANY_OGG_OPEN_FILES
  /* check if track index has changed */
  if (index != cdd.index)
  {
    /* close previous track VORBIS file structure to save memory */
    if (cdd.toc.tracks[cdd.index].vf.datasource)
    {
      ogg_free(cdd.index);
    }

    /* open current track VORBIS file */
    if (cdd.toc.tracks[index].vf.seekable)
    {
      ov_open_callbacks(cdd.toc.tracks[index].fd,&cdd.toc.tracks[index].vf,0,0,cb);
    }
  }
#endif
#endif

  /* seek to track position */
#if defined(USE_LIBCHDR)
  if (cdd.chd.file)
  {
    /* CHD file offset */
    cdd.chd.hunkofs = cdd.toc.tracks[index].offset + (lba * CD_FRAME_SIZE);
  }
  else
#endif
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
  if (cdd.toc.tracks[index].vf.seekable)
  {
    /* VORBIS AUDIO track */
    ov_pcm_seek(&cdd.toc.tracks[index].vf, (lba * 588) - cdd.toc.tracks[index].offset);
  }
  else
#endif 
  if (cdd.toc.tracks[index].fd)
  {
    /* PCM AUDIO track */
    cdStreamSeek(cdd.toc.tracks[index].fd, (lba * 2352) - cdd.toc.tracks[index].offset, SEEK_SET);
  }
}

void cdd_read_audio(unsigned int samples)
{
  /* previous audio outputs */
  int prev_l = cdd.audio[0];
  int prev_r = cdd.audio[1];

  /* audio track playing ? */
  if (!scd.regs[0x36>>1].byte.h && cdd.toc.tracks[cdd.index].fd)
  {
    int i, mul, l, r;

    /* current CD-DA fader volume */
    int curVol = cdd.fader[0];

    /* CD-DA fader volume setup (0-1024) */
    int endVol = cdd.fader[1];

    /* read samples from current block */
#if defined(USE_LIBCHDR)
    if (cdd.chd.file)
    {
#ifndef LSB_FIRST
      int16 *ptr = (int16 *) (cdd.chd.hunk + (cdd.chd.hunkofs % cdd.chd.hunkbytes));
#else
      uint8 *ptr = cdd.chd.hunk + (cdd.chd.hunkofs % cdd.chd.hunkbytes);
#endif

      /* process 16-bit (big-endian) stereo samples */
      for (i=0; i<samples; i++)
      {
        /* CHD hunk index */
        int hunknum = cdd.chd.hunkofs / cdd.chd.hunkbytes;

        /* update CHD hunk cache if necessary */
        if (hunknum != cdd.chd.hunknum)
        {
          chd_read(cdd.chd.file, hunknum, cdd.chd.hunk);
          cdd.chd.hunknum = hunknum;
        }

        /* CD-DA fader multiplier (cf. LC7883 datasheet) */
        /* (MIN) 0,1,2,3,4,8,12,16,20...,1020,1024 (MAX) */
        mul = (curVol & 0x7fc) ? (curVol & 0x7fc) : (curVol & 0x03);

        /* left & right channels */
#ifndef LSB_FIRST
        l = ((ptr[0] * mul) / 1024);
        r = ((ptr[1] * mul) / 1024);
        ptr+=2;
#else
        l = (((int16)((ptr[1] + ptr[0]*256)) * mul) / 1024);
        r = (((int16)((ptr[3] + ptr[2]*256)) * mul) / 1024);
        ptr+=4;
#endif

        /* CD-DA output mixing volume (0-100%) */
        l = (l * config.cdda_volume) / 100;
        r = (r * config.cdda_volume) / 100;

        /* update blip buffer */
        blip_add_delta_fast(snd.blips[2], i, l-prev_l, r-prev_r);
        prev_l = l;
        prev_r = r;

        /* update CHD file offset */
        cdd.chd.hunkofs += 4;

        /* detect end of sector data (2352 bytes) */
        if ((cdd.chd.hunkofs % CD_FRAME_SIZE) == CD_MAX_SECTOR_DATA)
        {
          /* skip subcode data (96 bytes) */
          cdd.chd.hunkofs += CD_MAX_SUBCODE_DATA;

          /* reinitialize hunk cache pointer */
#ifndef LSB_FIRST
          ptr = (int16 *) (cdd.chd.hunk + (cdd.chd.hunkofs % cdd.chd.hunkbytes));
#else
          ptr = cdd.chd.hunk + (cdd.chd.hunkofs % cdd.chd.hunkbytes);
#endif
        }

        /* update CD-DA fader volume (one step/sample) */
        if (curVol < endVol)
        {
          /* fade-in */
          curVol++;
        }
        else if (curVol > endVol)
        {
          /* fade-out */
          curVol--;
        }
        else if (!curVol)
        {
          /* audio will remain muted until next setup */
          break;
        }
      }
    }
    else
#endif
#if defined(USE_LIBTREMOR) || defined(USE_LIBVORBIS)
    if (cdd.toc.tracks[cdd.index].vf.datasource)
    {
      int len, done = 0;
      int16 *ptr = (int16 *) (cdc.ram);
      samples = samples * 4;
      while (done < samples)
      {
#ifdef USE_LIBVORBIS
        len = ov_read(&cdd.toc.tracks[cdd.index].vf, (char *)(cdc.ram + done), samples - done, 0, 2, 1, 0);
#else
        len = ov_read(&cdd.toc.tracks[cdd.index].vf, (char *)(cdc.ram + done), samples - done, 0);
#endif
        if (len <= 0) 
        {
          done = samples;
          break;
        }
        done += len;
      }
      samples = done / 4;

      /* process 16-bit (host-endian) stereo samples */
      for (i=0; i<samples; i++)
      {
        /* CD-DA fader multiplier (cf. LC7883 datasheet) */
        /* (MIN) 0,1,2,3,4,8,12,16,20...,1020,1024 (MAX) */
        mul = (curVol & 0x7fc) ? (curVol & 0x7fc) : (curVol & 0x03);

        /* left & right channels */
        l = ((ptr[0] * mul) / 1024);
        r = ((ptr[1] * mul) / 1024);

        /* CD-DA output mixing volume (0-100%) */
        l = (l * config.cdda_volume) / 100;
        r = (r * config.cdda_volume) / 100;

        /* update blip buffer */
        blip_add_delta_fast(snd.blips[2], i, l-prev_l, r-prev_r);
        prev_l = l;
        prev_r = r;
        ptr+=2;

        /* update CD-DA fader volume (one step/sample) */
        if (curVol < endVol)
        {
          /* fade-in */
          curVol++;
        }
        else if (curVol > endVol)
        {
          /* fade-out */
          curVol--;
        }
        else if (!curVol)
        {
          /* audio will remain muted until next setup */
          break;
        }
      }
    }
    else
#endif
    {
#ifdef LSB_FIRST
      int16 *ptr = (int16 *) (cdc.ram);
#else
      uint8 *ptr = cdc.ram;
#endif
      cdStreamRead(cdc.ram, 1, samples * 4, cdd.toc.tracks[cdd.index].fd);

      /* process 16-bit (little-endian) stereo samples */
      for (i=0; i<samples; i++)
      {
        /* CD-DA fader multiplier (cf. LC7883 datasheet) */
        /* (MIN) 0,1,2,3,4,8,12,16,20...,1020,1024 (MAX) */
        mul = (curVol & 0x7fc) ? (curVol & 0x7fc) : (curVol & 0x03);

        /* left & right channels */
#ifdef LSB_FIRST
        l = ((ptr[0] * mul) / 1024);
        r = ((ptr[1] * mul) / 1024);
        ptr+=2;
#else
        l = (((int16)((ptr[0] + ptr[1]*256)) * mul) / 1024);
        r = (((int16)((ptr[2] + ptr[3]*256)) * mul) / 1024);
        ptr+=4;
#endif

        /* CD-DA output mixing volume (0-100%) */
        l = (l * config.cdda_volume) / 100;
        r = (r * config.cdda_volume) / 100;

        /* update blip buffer */
        blip_add_delta_fast(snd.blips[2], i, l-prev_l, r-prev_r);
        prev_l = l;
        prev_r = r;

        /* update CD-DA fader volume (one step/sample) */
        if (curVol < endVol)
        {
          /* fade-in */
          curVol++;
        }
        else if (curVol > endVol)
        {
          /* fade-out */
          curVol--;
        }
        else if (!curVol)
        {
          /* audio will remain muted until next setup */
          break;
        }
      }
    }

    /* save current CD-DA fader volume */
    cdd.fader[0] = curVol;

    /* save last audio output for next frame */
    cdd.audio[0] = prev_l;
    cdd.audio[1] = prev_r;
  }
  else
  {
    /* no audio output */
    if (prev_l | prev_r)
    {
      /* update blip buffer */
      blip_add_delta_fast(snd.blips[2], 0, -prev_l, -prev_r);

      /* save audio output for next frame */
      cdd.audio[0] = 0;
      cdd.audio[1] = 0;
    }
  }

  /* end of blip buffer timeframe */
  blip_end_frame(snd.blips[2], samples);
}

void cdd_update_audio(unsigned int samples)
{
  /* get number of internal clocks (CD-DA samples) needed */
  samples = blip_clocks_needed(snd.blips[2], samples);

  if (cart.special & HW_MEGASD)
  {
    /* MegaSD add-on specific CD-DA processing */
    megasd_update_cdda(samples);
  }
  else
  {
    /* read needed CD-DA samples */
    cdd_read_audio(samples);
  }
}

static void cdd_read_subcode(void)
{
  uint8 subc[96];
  int i,j,index;

  /* update subcode buffer pointer address */
  scd.regs[0x68>>1].byte.l = (scd.regs[0x68>>1].byte.l + 98) & 0x7e;
  
  /* 16-bit register index */
  index = (scd.regs[0x68>>1].byte.l + 0x100) >> 1;

  /* read interleaved subcode data from .sub file (12 x 8-bit of P subchannel first, then Q subchannel, etc) */
  cdStreamRead(subc, 1, 96, cdd.toc.sub);

  /* convert back to raw subcode format (96 bytes with 8 x P-W subchannel bits per byte) */
  for (i=0; i<96; i+=2)
  {
    int code = 0;
    for (j=0; j<8; j++)
    {
      int bits = (subc[(j*12)+(i/8)] >> (6 - (i & 6))) & 3;
      code |= ((bits & 1) << (7 - j));
      code |= ((bits >> 1) << (15 - j));
    }

    /* subcode buffer is accessed as 16-bit words */
    scd.regs[index].w = code;

    /* subcode buffer is limited to 64 x 16-bit words */
    index = (index + 1) & 0xbf;
  }

  /* level 6 interrupt enabled ? */
  if (scd.regs[0x32>>1].byte.l & 0x40)
  {
    /* trigger level 6 interrupt */
    scd.pending |= (1 << 6);

    /* update IRQ level */
    s68k_update_irq((scd.pending & scd.regs[0x32>>1].byte.l) >> 1);
  }
}

void cdd_update(void)
{  
#ifdef LOG_CDD
  error("LBA = %d (track %d)(latency=%d)\n", cdd.lba, cdd.index, cdd.latency);
#endif

  /* drive latency */
  if (cdd.latency > 0)
  {
    cdd.latency--;
    return;
  }

  /* reading disc */
  if (cdd.status == CD_PLAY)
  {
    /* end of disc detection */
    if (cdd.index >= cdd.toc.last)
    {
      cdd.status = CD_END;
      return;
    }

    /* subcode data processing */
    if (cdd.toc.sub)
    {
      cdd_read_subcode();
    }

    /* track type */
    if (cdd.toc.tracks[cdd.index].type)
    {
      /* CD-ROM sector header */
      uint8 header[4];
      uint32 msf = cdd.lba + 150;
      header[0] = lut_BCD_8[(msf / 75) / 60];
      header[1] = lut_BCD_8[(msf / 75) % 60];
      header[2] = lut_BCD_8[(msf % 75)];
      header[3] = cdd.toc.tracks[cdd.index].type;

      /* decode CD-ROM track sector */
      cdc_decoder_update(*(uint32 *)(header));
    }
    else
    {
      /* check against audio track start index */
      if (cdd.lba >= cdd.toc.tracks[cdd.index].start)
      {
        /* audio track playing */
        scd.regs[0x36>>1].byte.h = 0x00;
      }

      /* audio blocks are still sent to CDC as well as CD DAC/Fader */
      cdc_decoder_update(0);
    }

    /* read next sector */
    cdd.lba++;

    /* check end of current track */
    if (cdd.lba >= cdd.toc.tracks[cdd.index].end)
    {
      /* seek to next track start (assuming it can only be an audio track) */
      cdd_seek_audio(cdd.index + 1, cdd.toc.tracks[cdd.index + 1].start);

      /* increment current track index */
      cdd.index++;

      /* PAUSE between tracks */
      scd.regs[0x36>>1].byte.h = 0x01;
    }
  }

  /* scanning disc */
  else if (cdd.status == CD_SCAN)
  {
    /* current track index */
    int index = cdd.index;

    /* fast-forward or fast-rewind */
    cdd.lba += cdd.scanOffset;

    /* check current track limits */
    if (cdd.lba >= cdd.toc.tracks[index].end)
    {
      /* next track */
      index++;

      /* check disc limits */
      if (index < cdd.toc.last)
      {
        /* skip directly to next track start position */
        cdd.lba = cdd.toc.tracks[index].start;
      }
      else
      {
        /* end of disc */
        cdd.lba = cdd.toc.end;
        cdd.index = cdd.toc.last;
        cdd.status = CD_END;

        /* no audio track playing */
        scd.regs[0x36>>1].byte.h = 0x01;
        return;
      }
    }
    else if (cdd.lba < cdd.toc.tracks[index].start)
    {
      /* check disc limits */
      if (index > 0)
      {
        /* previous track */
        index--;

        /* skip directly to previous track end position */
        cdd.lba = cdd.toc.tracks[index].end;
      }
      else
      {
        /* start of first track */
        cdd.lba = 0;
      }
    }

    /* seek to current subcode position */
    if (cdd.toc.sub)
    {
      cdStreamSeek(cdd.toc.sub, cdd.lba * 96, SEEK_SET);
    }

    /* current track is an audio track ? */
    if (cdd.toc.tracks[index].type == TYPE_AUDIO)
    {
      /* seek to current track sector */
      cdd_seek_audio(index, cdd.lba);

      /* audio track playing */
      scd.regs[0x36>>1].byte.h = 0x00;
    }
    else
    {
      /* no audio track playing */
      scd.regs[0x36>>1].byte.h = 0x01;
    }

    /* udpate current track index */
    cdd.index = index;
  }
}

void cdd_process(void)
{
  /* Process CDD command */
  switch (scd.regs[0x42>>1].byte.h & 0x0f)
  {
    case 0x00:  /* Get Drive Status */
    {
      /* RS0-RS1 are normally unchanged unless reported drive status needs to be updated (i.e previous drive command has been processed) */
      /* Note: this function is called one 75hz frame ahead of CDD update so latency counter is always one step ahead of upcoming status */
      /* Radical Rex and Annet Futatabi both need at least respectively 2 and 3 interrupts with 'playing' status returned before sectors start getting incremented */
      if (cdd.latency <= 3)
      {
        /* update reported drive status */
        scd.regs[0x38>>1].byte.h = cdd.status;

        /* check if RS1 indicated invalid track infos (during seeking) */
        if (scd.regs[0x38>>1].byte.l == 0x0f)
        {
          /* seeking has ended so we return valid track infos, e.g current absolute time by default (fixes Lunar - The Silver Star) */
          int lba = cdd.lba + 150;
          scd.regs[0x38>>1].byte.l = 0x00;
          scd.regs[0x3a>>1].w = lut_BCD_16[(lba/75)/60];
          scd.regs[0x3c>>1].w = lut_BCD_16[(lba/75)%60];
          scd.regs[0x3e>>1].w = lut_BCD_16[(lba%75)];
          scd.regs[0x40>>1].byte.h = cdd.toc.tracks[cdd.index].type ? 0x04 : 0x00; /* Current block flags in RS8 (bit0 = mute status, bit1: pre-emphasis status, bit2: track type) */
        }

        /* otherwise, check if RS2-RS8 need to be updated */
        else if (scd.regs[0x38>>1].byte.l == 0x00)
        {
          /* current absolute time */
          int lba = cdd.lba + 150;
          scd.regs[0x3a>>1].w = lut_BCD_16[(lba/75)/60];
          scd.regs[0x3c>>1].w = lut_BCD_16[(lba/75)%60];
          scd.regs[0x3e>>1].w = lut_BCD_16[(lba%75)];
          scd.regs[0x40>>1].byte.h = cdd.toc.tracks[cdd.index].type ? 0x04 : 0x00; /* Current block flags in RS8 (bit0 = mute status, bit1: pre-emphasis status, bit2: track type) */
        }
        else if (scd.regs[0x38>>1].byte.l == 0x01)
        {
          /* current track relative time */
          int lba = abs(cdd.lba - cdd.toc.tracks[cdd.index].start);
          scd.regs[0x3a>>1].w = lut_BCD_16[(lba/75)/60];
          scd.regs[0x3c>>1].w = lut_BCD_16[(lba/75)%60];
          scd.regs[0x3e>>1].w = lut_BCD_16[(lba%75)];
          scd.regs[0x40>>1].byte.h = cdd.toc.tracks[cdd.index].type ? 0x04 : 0x00; /* Current block flags in RS8 (bit0 = mute status, bit1: pre-emphasis status, bit2: track type) */
        }
        else if (scd.regs[0x38>>1].byte.l == 0x02)
        {
          /* current track number */
          scd.regs[0x3a>>1].w = (cdd.index < cdd.toc.last) ? lut_BCD_16[cdd.index + 1] : 0x0A0A;
        }
      }
      break;
    }

    case 0x01:  /* Stop Drive */
    {
      /* update status */
      cdd.status = cdd.loaded ? CD_TOC : NO_DISC;

      /* no audio track playing */
      scd.regs[0x36>>1].byte.h = 0x01;

      /* RS1-RS8 ignored, expects 0x0 (CD_STOP) in RS0 once */
      scd.regs[0x38>>1].w = CD_STOP << 8;
      scd.regs[0x3a>>1].w = 0x0000;
      scd.regs[0x3c>>1].w = 0x0000;
      scd.regs[0x3e>>1].w = 0x0000;
      scd.regs[0x40>>1].w = ~CD_STOP & 0x0f;
      return;
    }

    case 0x02:  /* Report TOC infos */
    {
      /* Infos automatically retrieved by CDD processor from Q-Channel */
      /* commands 0x00-0x02 (current block) and 0x03-0x05 (Lead-In) */
      switch (scd.regs[0x44>>1].byte.l)
      {
        case 0x00:  /* Current Absolute Time (MM:SS:FF) */
        {
          int lba = cdd.lba + 150;
          scd.regs[0x38>>1].w = cdd.status << 8;
          scd.regs[0x3a>>1].w = lut_BCD_16[(lba/75)/60];
          scd.regs[0x3c>>1].w = lut_BCD_16[(lba/75)%60];
          scd.regs[0x3e>>1].w = lut_BCD_16[(lba%75)];
          scd.regs[0x40>>1].byte.h = cdd.toc.tracks[cdd.index].type ? 0x04 : 0x00; /* Current block flags in RS8 (bit0 = mute status, bit1: pre-emphasis status, bit2: track type) */
          break;
        }

        case 0x01:  /* Current Track Relative Time (MM:SS:FF) */
        {
          int lba = abs(cdd.lba - cdd.toc.tracks[cdd.index].start);
          scd.regs[0x38>>1].w = (cdd.status << 8) | 0x01;
          scd.regs[0x3a>>1].w = lut_BCD_16[(lba/75)/60];
          scd.regs[0x3c>>1].w = lut_BCD_16[(lba/75)%60];
          scd.regs[0x3e>>1].w = lut_BCD_16[(lba%75)];
          scd.regs[0x40>>1].byte.h = cdd.toc.tracks[cdd.index].type ? 0x04 : 0x00; /* Current block flags in RS8 (bit0 = mute status, bit1: pre-emphasis status, bit2: track type) */
          break;
        }

        case 0x02:  /* Current Track Number */
        {
          scd.regs[0x38>>1].w = (cdd.status << 8) | 0x02;
          scd.regs[0x3a>>1].w = (cdd.index < cdd.toc.last) ? lut_BCD_16[cdd.index + 1] : 0x0A0A;
          scd.regs[0x3c>>1].w = 0x0000;
          scd.regs[0x3e>>1].w = 0x0000; /* Disk Control Code (?) in RS6 */
          scd.regs[0x40>>1].byte.h = 0x00;
          break;
        }

        case 0x03:  /* Total length (MM:SS:FF) */
        {
          int lba = cdd.toc.end + 150;
          scd.regs[0x38>>1].w = (cdd.status << 8) | 0x03;
          scd.regs[0x3a>>1].w = lut_BCD_16[(lba/75)/60];
          scd.regs[0x3c>>1].w = lut_BCD_16[(lba/75)%60];
          scd.regs[0x3e>>1].w = lut_BCD_16[(lba%75)];
          scd.regs[0x40>>1].byte.h = 0x00;
          break;
        }

        case 0x04:  /* First & Last Track Numbers */
        {
          scd.regs[0x38>>1].w = (cdd.status << 8) | 0x04;
          scd.regs[0x3a>>1].w = 0x0001;
          scd.regs[0x3c>>1].w = lut_BCD_16[cdd.toc.last];
          scd.regs[0x3e>>1].w = 0x0000; /* Drive Version (?) in RS6-RS7 */
          scd.regs[0x40>>1].byte.h = 0x00;  /* Lead-In flags in RS8 (bit0 = mute status, bit1: pre-emphasis status, bit2: track type) */
          break;
        }

        case 0x05:  /* Track Start Time (MM:SS:FF) */
        {
          int track = scd.regs[0x46>>1].byte.h * 10 + scd.regs[0x46>>1].byte.l;
          int lba = cdd.toc.tracks[track-1].start + 150;
          scd.regs[0x38>>1].w = (cdd.status << 8) | 0x05;
          scd.regs[0x3a>>1].w = lut_BCD_16[(lba/75)/60];
          scd.regs[0x3c>>1].w = lut_BCD_16[(lba/75)%60];
          scd.regs[0x3e>>1].w = lut_BCD_16[(lba%75)];
          scd.regs[0x3e>>1].byte.h |= cdd.toc.tracks[track-1].type ? 0x08 : 0x00; /* RS6 bit 3 is set for CD-ROM track */
          scd.regs[0x40>>1].byte.h = track % 10;  /* Track Number (low digit) */
          break;
        }

        case 0x06:  /* Latest Error Information */
        {
          scd.regs[0x38>>1].w = (cdd.status << 8) | 0x06;
          scd.regs[0x3a>>1].w = 0x0000; /* no error */
          scd.regs[0x3c>>1].w = 0x0000;
          scd.regs[0x3e>>1].w = 0x0000;
          scd.regs[0x40>>1].byte.h = 0x00;
          break;
        }

        default:
        {
#ifdef LOG_ERROR
          error("Invalid CDD request code %02X (%X)\n", scd.regs[0x44>>1].byte.l, s68k.pc);
#endif
          return;
        }
      }
      break;
    }

    case 0x03:  /* Play */
    {
      /* reset track index */
      int index = 0;

      /* new LBA position */
      int lba = ((scd.regs[0x44>>1].byte.h * 10 + scd.regs[0x44>>1].byte.l) * 60 + 
                 (scd.regs[0x46>>1].byte.h * 10 + scd.regs[0x46>>1].byte.l)) * 75 +
                 (scd.regs[0x48>>1].byte.h * 10 + scd.regs[0x48>>1].byte.l) - 150;

      /* CD drive latency */
      if (!cdd.latency)
      {
        /* Fixes a few games hanging because they expect data to be read with some delay */
        /* Wolf Team games (Annet Futatabi, Aisle Lord, Cobra Command, Earnest Evans, Road Avenger & Time Gal) need at least 11 interrupts delay  */
        /* Space Adventure Cobra (2nd morgue scene) needs at least 13 interrupts delay (incl. seek time, so 11 is OK) */
        /* By default, at least one interrupt latency is required by current emulation model (BIOS hangs otherwise) */
        cdd.latency = 1 + 10*config.cd_latency;
      }

      /* CD drive seek time */
      /* max. seek time = 1.5 s = 1.5 x 75 = 112.5 CDD interrupts (rounded to 120) for 270000 sectors max on disc. */
      /* Note: This is only a rough approximation since, on real hardware, seek time is much likely not linear and */
      /* latency much larger than above value, but this model works fine for Sonic CD (track 26 playback needs to  */
      /* be enough delayed to start in sync with intro sequence, as compared with real hardware recording).        */
      if (lba > cdd.lba)
      {
        cdd.latency += (((lba - cdd.lba) * 120 * config.cd_latency) / 270000);
      }
      else 
      {
        cdd.latency += (((cdd.lba - lba) * 120 * config.cd_latency) / 270000);
      }

      /* update current LBA */
      cdd.lba = lba;

      /* get track index */
      while ((cdd.toc.tracks[index].end <= lba) && (index < cdd.toc.last)) index++;

      /* audio track ? */
      if (cdd.toc.tracks[index].type == TYPE_AUDIO)
      {
        /* stay within track limits when seeking files */
        if (lba < cdd.toc.tracks[index].start) 
        {
          lba = cdd.toc.tracks[index].start;
        }

        /* seek to current track sector */
        cdd_seek_audio(index, lba);
      }

      /* update current track index */
      cdd.index = index;

      /* seek to current subcode position */
      if (cdd.toc.sub)
      {
        cdStreamSeek(cdd.toc.sub, lba * 96, SEEK_SET);
      }

      /* no audio track playing (yet) */
      scd.regs[0x36>>1].byte.h = 0x01;

      /* update status (reported to host once seeking has ended) */
      cdd.status = CD_PLAY;

      /* RS0 should indicates seeking until drive is ready (fixes audio delay in Bari Arm) */
      /* RS1=0xf to invalidate track infos in RS2-RS8 until drive is ready (fixes Snatcher Act 2 start cutscene) */
      scd.regs[0x38>>1].w = (CD_SEEK << 8) | 0x0f;
      scd.regs[0x3a>>1].w = 0x0000;
      scd.regs[0x3c>>1].w = 0x0000;
      scd.regs[0x3e>>1].w = 0x0000;
      scd.regs[0x40>>1].w = ~(CD_SEEK + 0xf) & 0x0f;
      return;
    }

    case 0x04:  /* Seek */
    {
      /* reset track index */
      int index = 0;

      /* new LBA position */
      int lba = ((scd.regs[0x44>>1].byte.h * 10 + scd.regs[0x44>>1].byte.l) * 60 + 
                 (scd.regs[0x46>>1].byte.h * 10 + scd.regs[0x46>>1].byte.l)) * 75 +
                 (scd.regs[0x48>>1].byte.h * 10 + scd.regs[0x48>>1].byte.l) - 150;

      /* CD drive seek time  */
      /* We are using similar linear model as above, although still not exactly accurate, */
      /* it works fine for Switch/Panic! intro (Switch needs at least 30 interrupts while */
      /* seeking from 00:05:63 to 24:03:19, Panic! when seeking from 00:05:60 to 24:06:07) */
      if (lba > cdd.lba)
      {
        cdd.latency = ((lba - cdd.lba) * 120 * config.cd_latency) / 270000;
      }
      else
      {
        cdd.latency = ((cdd.lba - lba) * 120 * config.cd_latency) / 270000;
      }

      /* update current LBA */
      cdd.lba = lba;

      /* get current track index */
      while ((cdd.toc.tracks[index].end <= lba) && (index < cdd.toc.last)) index++;

      /* audio track ? */
      if (cdd.toc.tracks[index].type == TYPE_AUDIO)
      {
        /* stay within track limits when seeking files */
        if (lba < cdd.toc.tracks[index].start) 
        {
          lba = cdd.toc.tracks[index].start;
        }

        /* seek to current track sector */
        cdd_seek_audio(index, lba);
      }

      /* update current track index */
      cdd.index = index;

      /* seek to current subcode position */
      if (cdd.toc.sub)
      {
        cdStreamSeek(cdd.toc.sub, lba * 96, SEEK_SET);
      }

      /* no audio track playing */
      scd.regs[0x36>>1].byte.h = 0x01;

      /* update status (reported to host once seeking has ended) */
      cdd.status = CD_PAUSE;

      /* RS1=0xf to invalidate track infos in RS2-RS8 while seeking (fixes Final Fight CD intro when seek time is emulated) */
      scd.regs[0x38>>1].w = (CD_SEEK << 8) | 0x0f;
      scd.regs[0x3a>>1].w = 0x0000;
      scd.regs[0x3c>>1].w = 0x0000;
      scd.regs[0x3e>>1].w = 0x0000;
      scd.regs[0x40>>1].w = ~(CD_SEEK + 0xf) & 0x0f;
      return;
    }

    case 0x06:  /* Pause */
    {
      /* no audio track playing */
      scd.regs[0x36>>1].byte.h = 0x01;

      /* update status (RS1-RS8 unchanged) */
      cdd.status = scd.regs[0x38>>1].byte.h = CD_PAUSE;
      break;
    }

    case 0x07:  /* Resume */
    {
      /* update status (RS1-RS8 unchanged) */
      cdd.status = scd.regs[0x38>>1].byte.h = CD_PLAY;
      break;
    }

    case 0x08:  /* Forward Scan */
    {
      /* reset scanning direction / speed */
      cdd.scanOffset = CD_SCAN_SPEED;

      /* update status (RS1-RS8 unchanged) */
      cdd.status = scd.regs[0x38>>1].byte.h = CD_SCAN;
      break;
    }

    case 0x09:  /* Rewind Scan */
    {
      /* reset scanning direction / speed */
      cdd.scanOffset = -CD_SCAN_SPEED;

      /* update status (RS1-RS8 unchanged) */
      cdd.status = scd.regs[0x38>>1].byte.h = CD_SCAN;
      break;
    }

    case 0x0a:  /* N-Track Jump Control ? (usually sent before CD_SEEK or CD_PLAY commands) */
    {
      /* TC3 corresponds to seek direction (00=forward, FF=reverse) */
      /* TC4-TC7 are related to seek length (4x4 bits i.e parameter values are between -65535 and +65535) */
      /* Maybe related to number of auto-sequenced track jumps/moves for CD DSP (cf. CXD2500BQ datasheet) */
      /* also see US Patent nr. 5222054 for a detailled description of seeking operation using Track Jump */

      /* no audio track playing */
      scd.regs[0x36>>1].byte.h = 0x01;

      /* update status (RS1-RS8 unchanged) */
      cdd.status = scd.regs[0x38>>1].byte.h = CD_PAUSE;
      break;
    }

    case 0x0c:  /* Close Tray */
    {
      /* no audio track playing */
      scd.regs[0x36>>1].byte.h = 0x01;

      /* update status */
      cdd.status = cdd.loaded ? CD_TOC : NO_DISC;

      /* RS1-RS8 ignored, expects CD_STOP in RS0 once */
      scd.regs[0x38>>1].w = CD_STOP << 8;
      scd.regs[0x3a>>1].w = 0x0000;
      scd.regs[0x3c>>1].w = 0x0000;
      scd.regs[0x3e>>1].w = 0x0000;
      scd.regs[0x40>>1].w = ~CD_STOP & 0x0f;

#ifdef CD_TRAY_CALLBACK
      CD_TRAY_CALLBACK
#endif
      return;
    }

    case 0x0d:  /* Open Tray */
    {
      /* no audio track playing */
      scd.regs[0x36>>1].byte.h = 0x01;

      /* update status (RS1-RS8 ignored) */
      cdd.status = CD_OPEN;
      scd.regs[0x38>>1].w = CD_OPEN << 8;
      scd.regs[0x3a>>1].w = 0x0000;
      scd.regs[0x3c>>1].w = 0x0000;
      scd.regs[0x3e>>1].w = 0x0000;
      scd.regs[0x40>>1].w = ~CD_OPEN & 0x0f;

#ifdef CD_TRAY_CALLBACK
      CD_TRAY_CALLBACK
#endif
      return;
    }

    default:  /* Unknown command */
#ifdef LOG_ERROR
      error("Unsupported CDD command %02X (%X)\n", scd.regs[0x42>>1].byte.h & 0x0f, s68k.pc);
#endif
      scd.regs[0x38>>1].byte.h = cdd.status;
      break;
  }

  /* only compute checksum when necessary */
  scd.regs[0x40>>1].byte.l = ~(scd.regs[0x38>>1].byte.h + scd.regs[0x38>>1].byte.l +
                               scd.regs[0x3a>>1].byte.h + scd.regs[0x3a>>1].byte.l +
                               scd.regs[0x3c>>1].byte.h + scd.regs[0x3c>>1].byte.l +
                               scd.regs[0x3e>>1].byte.h + scd.regs[0x3e>>1].byte.l +
                               scd.regs[0x40>>1].byte.h) & 0x0f;
}