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 *
 * 0: header size in shorts (8 = 16 bytes) (OGI says this is in bytes)
 * 2: version (1)
 * 4: chans
 * 6: rate (srate = 4000000/rate)
 * 8: samples (int) -- seems to be off by 2 -- are they counting ints here?
 * 12: data format (0 = big-endian)
 * 16: data start
*/ 

static int read_adc_header(const char *filename, int fd)
{
  bool little;
  little = (mus_char_to_uninterpreted_int((unsigned char *)(hdrbuf + 12)) != 0); /* 0 = big endian */
  data_location = 16;
  if (little) data_format = MUS_LSHORT; else data_format = MUS_BSHORT;
  chans = big_or_little_endian_short((unsigned char *)(hdrbuf + 4), little);
  srate = 4000000 / big_or_little_endian_short((unsigned char *)(hdrbuf + 6), little);
  data_size = 2 * big_or_little_endian_int((unsigned char *)(hdrbuf + 8), little);
  comment_start = 0;
  comment_end = 0;
  true_file_length = SEEK_FILE_LENGTH(fd);
  if (data_size > true_file_length)
    {
      data_size = true_file_length - data_location;
      if (data_size < 0) return(mus_error(MUS_HEADER_READ_FAILED, "%s: data_size = " OFF_TD "?", filename, data_size));
    }
  data_size = mus_bytes_to_samples(data_format, data_size);
  return(MUS_NO_ERROR);
}



/* ------------------------------------ AVR -------------------------------------- 
 *
 *   0: "2BIT"
 *   4: sample name (null padded ASCII)
 *  12: chans (short) (0 = mono, -1 = stereo)
 *  14: sample size (8 or 16 bit) (short) (value is 8, 12, or 16)
 *  16: sample format (signed or unsigned) (short) (0 = unsigned, -1 = signed)
 *  18: loop (on/off), 20: midi (-1 = no MIDI)
 *  22: srate 
 *      avr.txt has:
 *      22: Replay speed 0 = 5.485 Khz, 1 = 8.084 Khz, 2 = 10.971 Khz, 3 = 16.168 Khz, 4 = 21.942 Khz, 5 = 32.336 Khz, 6 = 43.885 Khz, 7 = 47.261 Khz
 *      23: sample rate	in Hertz (as a 3 byte quantity??)
 *  26: length in samples
 *  30: loop beg, 34: loop end, 38: midi (keyboard split), 40: compression, 42: nada ("reserved"), 44: name
 *  64: comment (limited to 64 bytes)
 * 128: data start
 *
 * the Atari .avr files appear to be 8000 Hz, mono, 8-bit linear unsigned data with an unknown header of 128 words
 * apparently there was a change in format sometime in the 90's.
 * 
 * The actual avr files I've found on the net are either garbled, or
 * something is wrong with this definition (taken from CMJ and www.wotsit.org's avr.txt). 
 * SGI dmconvert assumes big-endian here -- this is an Atari format, so it's probably safe to assume big-endian.
 */

static int read_avr_header(const char *filename, int fd)
{
  int dsize, dsigned, i;
  chans = mus_char_to_bshort((unsigned char *)(hdrbuf + 12));
  if (chans == 0) chans = 1; else if (chans == -1) chans = 2; else return(mus_error(MUS_HEADER_READ_FAILED, "%s chans: %d", filename, chans));
  data_location = 128;
  data_size = mus_char_to_bint((unsigned char *)(hdrbuf + 26));
  srate = mus_char_to_ubshort((unsigned char *)(hdrbuf + 24));
  dsize = mus_char_to_bshort((unsigned char *)(hdrbuf + 14));
  dsigned = mus_char_to_bshort((unsigned char *)(hdrbuf + 16));
  if (dsize == 16) 
    {
      if (dsigned == 0)
	data_format = MUS_UBSHORT;
      else data_format = MUS_BSHORT;
    }
  else 
    {
      if (dsize == 8)
	{
	  if (dsigned == 0) 
	    data_format = MUS_UBYTE;
	  else data_format = MUS_BYTE;
	}
      else return(mus_error(MUS_HEADER_READ_FAILED, "%s: unknown data format", filename));
    }
  if (seek_and_read(fd, (unsigned char *)hdrbuf, 64, 64) <= 0)
    return(mus_error(MUS_HEADER_READ_FAILED, "%s avr header: ran off end of file", filename));
  comment_start = 64;
  i = 0;
  while ((i < 64) && (hdrbuf[i] != 0)) i++;
  comment_end = 64 + (i - 1);
  true_file_length = SEEK_FILE_LENGTH(fd);
  if (data_size > true_file_length)
    {
      data_size = true_file_length - data_location;
      if (data_size < 0) return(mus_error(MUS_HEADER_READ_FAILED, "%s: data_size = " OFF_TD "?", filename, data_size));
    }
  data_size = mus_bytes_to_samples(data_format, data_size);
  return(MUS_NO_ERROR);
}




/* ------------------------------------ SNDT -------------------------------------
 *
 * this taken from sndrtool.c (sox-10): (modified 6-Feb-98)
 *   0: "SOUND" (or off by two throughout if not "0x1a"?)
 *   5: 0x1a
 *   6-7: 0
 *   8-11: nsamps (at 12)
 *  12-15: 0
 *  16-19: nsamps
 *  20-21: srate (little endian short) (at 22)
 *  22-23: 0 
 *  24-25: 10
 *  26-27: 4
 *  28-> : <filename> "- File created by Sound Exchange"
 *  .->95: 0 ?
 */

/* similar is Sounder format: 
 * 0: 0
 * 2: short srate (little endian)
 * 4: 10
 * 6: 4
 * then data
 * but this format can't be distinguished from a raw sound file
 */

static int read_sndt_header(const char *filename, int fd)
{
  if (hdrbuf[4] != 'D') return(mus_error(MUS_HEADER_READ_FAILED, "%s: SNDT[4] != 'D'", filename));
  data_format = MUS_UBYTE;
  chans = 1;
  srate = mus_char_to_ulshort((unsigned char *)(hdrbuf + 20));
  data_location = 126;
  data_size = mus_char_to_lint((unsigned char *)(hdrbuf + 8));
  if (data_size < 0) data_size = mus_char_to_lint((unsigned char *)(hdrbuf + 10));
  if (srate <= 1) srate = mus_char_to_ulshort((unsigned char *)(hdrbuf + 22));