[picodrive.git] / pico / cd / cdd.c

/***************************************************************************************
 *  Genesis Plus
 *  CD drive processor & CD-DA fader
 *
 *  Copyright (C) 2012-2013  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 "../pico_int.h"
#include "genplus_macros.h"
#include "cd_parse.h"
#include "cdd.h"

#ifdef USE_LIBTREMOR
#define SUPPORTED_EXT 20
#else
#define SUPPORTED_EXT 10
#endif

cdd_t cdd;

#define is_audio(index) \
  (cdd.toc.tracks[index].type & CT_AUDIO)

/* 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
};

#if 0
/* supported WAVE file header (16-bit stereo samples @44.1kHz) */
static const unsigned char waveHeader[32] =
{
  0x57,0x41,0x56,0x45,0x66,0x6d,0x74,0x20,0x10,0x00,0x00,0x00,0x01,0x00,0x02,0x00,
  0x44,0xac,0x00,0x00,0x10,0xb1,0x02,0x00,0x04,0x00,0x10,0x00,0x64,0x61,0x74,0x61
};
#endif

#ifdef USE_LIBTREMOR
#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 */
  fseek(cdd.toc.tracks[i].fd, 0, SEEK_SET);
}
#endif
#endif

static off_t read_pos = -1;

void cdd_reset(void)
{
  /* stop audio streaming */
  Pico_mcd->cdda_stream = NULL;

  /* reset cycle counter */
  cdd.cycles = 0;
  
  /* reset drive access latency */
  cdd.latency = 0;
  
  /* reset track index */
  cdd.index = 0;
  
  /* reset logical block address */
  cdd.lba = 0;

  /* reset status */
  cdd.status = NO_DISC;

  /* reset CD-DA fader (full volume) */
  cdd.volume = 0x400;

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

  /* no audio track playing */
  Pico_mcd->s68k_regs[0x36+0] = 0x01;
  /* reset file read position */
  read_pos = -1;
}

/* FIXME: use cdd_read_audio() instead */
void cdd_play_audio(int index, int lba)
{
  int i, base, lba_offset, lb_len;

  for (i = index; i >= 0; i--)
    if (cdd.toc.tracks[i].fd != NULL)
      break;
  // prevent playing from file with binary track if MD+ (Doom Fusion)
  // TODO: this doesn't cover all tracks being in a single bin file properly:
  // in that case, fd should be duplicated to work properly with this MD+ shit.
  if (! is_audio(index) || (read_pos >= 0 && cdd.index == i && ! is_audio(i)))
    return;

  Pico_mcd->cdda_stream = cdd.toc.tracks[i].fd;
  Pico_mcd->cdda_type = cdd.toc.tracks[i].type;
  base = cdd.toc.tracks[index].offset;
  lba_offset = lba - cdd.toc.tracks[index].start;
  lb_len = cdd.toc.tracks[index].end - cdd.toc.tracks[index].start;

  elprintf(EL_CD, "play #%d lba %d base %d", index, lba, base);

  cdda_start_play(base, lba_offset, lb_len);
}

static void cdd_seek(int index, int lba)
{
#ifdef USE_LIBTREMOR
#ifdef DISABLE_MANY_OGG_OPEN_FILES
  /* close previous track VORBIS file structure to save memory */
  if (is_audio(cdd.index) && cdd.toc.tracks[cdd.index].vf.datasource)
  {
    ogg_free(cdd.index);
  }

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

  /* update current track index and LBA */
  cdd.index = (index < 0 ? 0 : index);
  cdd.lba = lba;
  if (index < 0) return;

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

  /* seek to current block */
  if (!is_audio(cdd.index))
  {
    /* DATA track */
    read_pos = lba * cdd.sectorSize;
    pm_seek(cdd.toc.tracks[cdd.index].fd, read_pos, SEEK_SET);
  }
#ifdef USE_LIBTREMOR
  else if (cdd.toc.tracks[cdd.index].vf.seekable)
  {
    /* VORBIS AUDIO track */
    ov_pcm_seek(&cdd.toc.tracks[cdd.index].vf, (lba - cdd.toc.tracks[cdd.index].start) * 588 - cdd.toc.tracks[cdd.index].offset);
  }
#endif
#if 0
  else if (cdd.toc.tracks[cdd.index].fd)
  {
    /* PCM AUDIO track */
    fseek(cdd.toc.tracks[cdd.index].fd, (lba * 2352) - cdd.toc.tracks[cdd.index].offset, SEEK_SET);
  }
#else
  else
  {
    cdd_play_audio(cdd.index, lba);
  }
#endif
}

int cdd_context_save(uint8 *state)
{
  int bufferptr = 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.volume, sizeof(cdd.volume));
  save_param(&cdd.status, sizeof(cdd.status));

  return bufferptr;
}

int cdd_context_load(uint8 *state)
{
  int bufferptr = 0;

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

  /* seek to current track position */
  cdd_seek(cdd.index, cdd.lba);

  return bufferptr;
}

int cdd_context_load_old(uint8 *state)
{
  memcpy(&cdd.lba, state + 8, sizeof(cdd.lba));
  cdd_seek(cdd.index, cdd.lba);

  return 12 * 4;
}

int cdd_load(const char *filename, int type)
{
  char header[0x210];
  int ret;

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

  /* genplus parses cue here, in PD we use our own parser */
  ret = load_cd_image(filename, &type);
  if (ret != 0)
    return ret;

  if (type == CT_ISO) {
    /* ISO format (2048 bytes data blocks) */
    cdd.sectorSize = 2048;
  } else {
    /* audio or BIN format (2352 bytes data blocks) */
    cdd.sectorSize = 2352;
  }

  /* read first 16 bytes */
  pm_read(header, 0x10, cdd.toc.tracks[0].fd);

  /* look for valid CD image ID string */
  if (!Pico.romsize && memcmp("SEGADISCSYSTEM", header, 14))
  {
    /* if not found, read next 16 bytes */
    pm_read(header, 0x10, cdd.toc.tracks[0].fd);

    /* look again for valid CD image ID string */
    if (memcmp("SEGADISCSYSTEM", header, 14))
    {
      elprintf(EL_STATUS|EL_ANOMALY, "cd: bad cd image?");
      /* assume bin without security code */
    }
  }

  pm_sectorsize(cdd.sectorSize, cdd.toc.tracks[0].fd);

  /* Simulate audio tracks if none found */
  if (!Pico.romsize && cdd.toc.last == 1)
  {
    /* read CD image header + security code */
    pm_read(header + 0x10, 0x200, cdd.toc.tracks[0].fd);

    /* 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);
    }
#if 0
    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));
    }
#endif
  }

  /* Lead-out */
  cdd.toc.tracks[cdd.toc.last].start = cdd.toc.end;

  /* CD loaded */
  cdd.loaded = 1;

  /* disc not scanned yet */
  cdd.status = NO_DISC;

  return 0;
}

int cdd_unload(void)
{
  int was_loaded = cdd.loaded;

  if (cdd.loaded)
  {
    int i;

    /* stop audio streaming */
    if (Pico_mcd) Pico_mcd->cdda_stream = NULL;

    /* close CD tracks */
    if (cdd.toc.tracks[0].fd)
    {
      pm_close(cdd.toc.tracks[0].fd);
      cdd.toc.tracks[0].fd = NULL;
      if (cdd.toc.tracks[0].fname)
        free(cdd.toc.tracks[0].fname);
      cdd.toc.tracks[0].fname = NULL;
    }

    for (i = 1; i < cdd.toc.last; i++)
    {
#ifdef USE_LIBTREMOR
      if (cdd.toc.tracks[i].vf.datasource)
      {
        /* close VORBIS file (if still opened) */
        ov_clear(&cdd.toc.tracks[i].vf);
      }
      else
#endif
      if (cdd.toc.tracks[i].fd)
      {
        /* close file */
        if (cdd.toc.tracks[i].type == CT_MP3)
          fclose(cdd.toc.tracks[i].fd);
        else
          pm_close(cdd.toc.tracks[i].fd);
        cdd.toc.tracks[i].fd = NULL;
        if (cdd.toc.tracks[i].fname)
          free(cdd.toc.tracks[i].fname);
        cdd.toc.tracks[i].fname = NULL;

        /* detect single file images */
        if (cdd.toc.tracks[i+1].fd == cdd.toc.tracks[i].fd)
        {
          /* exit loop */
          i = cdd.toc.last;
        }
      }
    }

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

    if (cdd.status != CD_OPEN)
      cdd.status = NO_DISC;
  }

  /* reset TOC */
  memset(&cdd.toc, 0x00, sizeof(cdd.toc));
    
  /* unknown CD image file format */
  cdd.sectorSize = 0;

  return was_loaded;
}

void cdd_read_data(uint8 *dst)
{
  /* only read DATA track sectors */
  if (!is_audio(cdd.index) && (cdd.lba >= cdd.toc.tracks[cdd.index].start) &&
                              (cdd.lba < cdd.toc.tracks[cdd.index].end))
  {
    off_t pos;

    /* BIN format ? */
    if (cdd.sectorSize == 2352)
    {
      /* skip 16-byte header */
      pos = cdd.lba * 2352 + 16;
    }
    else
    {
      pos = cdd.lba * cdd.sectorSize;
    }

    if (pos != read_pos) {
      pm_seek(cdd.toc.tracks[cdd.index].fd, pos, SEEK_SET);
      read_pos = pos;
    }

    /* read sector data (Mode 1 = 2048 bytes) */
    read_pos += pm_read(dst, 2048, cdd.toc.tracks[cdd.index].fd);
  }
}

#if 0
void cdd_read_audio(unsigned int samples)
{
  /* previous audio outputs */
  int16 l = cdd.audio[0];
  int16 r = cdd.audio[1];

  /* get number of internal clocks (samples) needed */
  samples = blip_clocks_needed(blip[0], samples);

  /* audio track playing ? */
  if (!Pico_mcd->s68k_regs[0x36+0] && cdd.toc.tracks[cdd.index].fd)
  {
    int i, mul, delta;

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

    /* CD-DA fader volume setup (0-1024) */
    int endVol = Pico_mcd->regs[0x34>>1].w >> 4;

    /* read samples from current block */
#ifdef USE_LIBTREMOR
    if (cdd.toc.tracks[cdd.index].vf.datasource)
    {
      int len, done = 0;
      int16 *ptr = (int16 *) (cdc.ram);
      samples = samples * 4;
      while (done < samples)
      {
        len = ov_read(&cdd.toc.tracks[cdd.index].vf, (char *)(cdc.ram + done), samples - done, 0);
        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 channel */
        delta = ((ptr[0] * mul) / 1024) - l;
        ptr++;
        l += delta;
        blip_add_delta_fast(blip[0], i, delta);

        /* right channel */
        delta = ((ptr[0] * mul) / 1024) - r;
        ptr++;
        r += delta;
        blip_add_delta_fast(blip[1], i, delta);

        /* 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
      fread(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 channel */
  #ifdef LSB_FIRST
        delta = ((ptr[0] * mul) / 1024) - l;
        ptr++;
  #else
        delta = (((int16)((ptr[0] + ptr[1]*256)) * mul) / 1024) - l;
        ptr += 2;
  #endif
        l += delta;
        blip_add_delta_fast(blip[0], i, delta);

        /* right channel */
  #ifdef LSB_FIRST
        delta = ((ptr[0] * mul) / 1024) - r;
        ptr++;
  #else
        delta = (((int16)((ptr[0] + ptr[1]*256)) * mul) / 1024) - r;
        ptr += 2;
  #endif
        r += delta;
        blip_add_delta_fast(blip[1], i, delta);

        /* 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.volume = curVol;

    /* save last audio output for next frame */
    cdd.audio[0] = l;
    cdd.audio[1] = r;
  }
  else
  {
    /* no audio output */
    if (l) blip_add_delta_fast(blip[0], 0, -l);
    if (r) blip_add_delta_fast(blip[1], 0, -r);

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

  /* end of Blip Buffer timeframe */
  blip_end_frame(blip[0], samples);
  blip_end_frame(blip[1], samples);
}
#endif


void cdd_update(void)
{
#ifdef LOG_CDD