song_drv.c

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return 0;
}


/*F**************************************************************************
* NAME: song_init
*----------------------------------------------------------------------------
* PARAMS:
*
* return:
*   header status:  SONG_NO_ERR:    header ok
*                   SONG_LAYER_ERR: not a layer 3 file
*                   SONG_BR_ERR:    bit rate not supported
*                   SONG_FS_ERR:    bad frequency sampling
*                   SONG_SYNC_ERR:  no header found
*----------------------------------------------------------------------------
* PURPOSE: 
*   Search frame header and initialize song playing according to this header
*----------------------------------------------------------------------------
* EXAMPLE:
*----------------------------------------------------------------------------
* NOTE:
*   Header search is stopped when errors number exceeds 
*----------------------------------------------------------------------------
* REQUIREMENTS:
*****************************************************************************/
Byte song_init (void)
{
Byte    b, c;
Byte    head_status;                        /* return error byte */
Byte    err_count;                          /* error counter */
bit     err_set;                            /* error flag */
Byte    bit_rate;                           /* Bit Rate  */
Byte    song_fs;                            /* Frequency sample */
Byte    song_version;                       /* Song verison : MPEG1 or MPEG2 */
Uint16  song_one_frame_size;                /* Size of one frame */


  head_status = SONG_NO_ERR;
  err_count = SONG_MAX_ERR;
  while (!Feof())
  {
    if (err_count != 0)
    { /* continue searching synchro */
      if (Fgetc() == MP3_SYNC_H)
      { /* high order sync found */
        b = Fgetc();
        if ((b & MP3_MSK_SYNC) == MP3_SYNC_L)
        { /* low order sync found */
          if ((b & MP3_MSK_LAYER) != MP3_LAYER_III)
          {
            Fseek( (Int16) -1 );
            head_status |= SONG_LAYER_ERR;  /* bad layer */
            err_count--;
          }
          else
          {
            c = Fgetc();
            if (c & 0x02)
              song_one_frame_size = 1;
            else
              song_one_frame_size = 0;
            b = (b & MP3_MSK_VER) >> 1;       /* keep MPEG Version B3 -> B2 */

            if (b)
            {
              song_version = 0;   /* Version MPEG1 */
            }
            else
            {
              song_version = 1;   /* Version MPEG2 */
            }
            bit_rate = c >> 4;
            song_fs = (c & MP3_MSK_FS) >> 2;
            switch (song_fs)
            {
              case 0x00 :   /* 44100 Hz / 22050 Hz */
                song_one_frame_size += song_tab_frame_size_00[song_version][bit_rate];
                break;
              case 0x01 :   /* 48000 Hz / 24000 Hz */
                song_one_frame_size += song_tab_frame_size_01[song_version][bit_rate];
                break;
              case 0x10 :   /* 32000 Hz / 16000 Hz */
                song_one_frame_size += song_tab_frame_size_10[song_version][bit_rate];
                break;
            }
            song_frame_size = (song_tab_seek[song_version][bit_rate]) >> 3;
            b |= (c & MP3_MSK_FS) >> 2;       /* read FS B3:2 -> B1:0 */
            c &= MP3_MSK_BR;

            
			err_set = FALSE;

            switch (b)
            {
              case MP3_FS_44:
              case MP3_FS_48:
              case MP3_FS_32:
              case MP3_FS_22:
              case MP3_FS_24:
              case MP3_FS_16:
              {
                if (c == MP3_BR_FREE)
                {
                  head_status |= SONG_BR_ERR; /* bad bit-rate */
                  err_count--;
                  err_set = TRUE;
                }
                break;
              }
              default:
              {
                head_status |= SONG_FS_ERR;   /* bad sampling frequency */
                err_count--;
                err_set = TRUE;
                break;
              }
            }
            if (!err_set)
            {
              Fseek((Int16)(song_one_frame_size) - 3);
              if (Fgetc() == MP3_SYNC_H)                        /* first header byte */
              { /* high order sync found */
                b = Fgetc();                                    /* second header byte */  
                if ((b & MP3_MSK_SYNC) == MP3_SYNC_L)
                { /* low order sync found */
                  if ((b & MP3_MSK_LAYER) != MP3_LAYER_III)
                  {
                    head_status |= SONG_LAYER_ERR;  /* bad layer */
                    err_count--;
                    Fseek(-(Int16)(song_one_frame_size) - 1 );
                  }
                  else
                  {
                    c = Fgetc();                                /* third header byte */
                    if ( song_fs == ((c & MP3_MSK_FS) >> 2) )
                    {
                      b = (b & MP3_MSK_VER) >> 1;       /* keep MPEG Version B3 -> B2 */
                      b |= (c & MP3_MSK_FS) >> 2;       /* read FS B3:2 -> B1:0 */ 
                      c &= MP3_MSK_BR;
                      song_audio_init();                /* init audio interface */
                      clock_song_init(b);               /* program the song clocks */
                      Fseek(-(Int16)(song_one_frame_size) - 3);
                      return SONG_NO_ERR;
                    }
                    else    
                    { /* Frequency sample does not match */
                      Fseek(-(Int16)(song_one_frame_size) - 2);
                    }
                  }
                }
                else
                { /* no low order synchro found */
                  Fseek(-(Int16)(song_one_frame_size) - 1);
                }
              }
              else
              { /* No high order synchro found */
                Fseek(-(Int16)(song_one_frame_size));
              }
              
            }
			else
			{ /* bad bit-rate or bad sampling frequency */
	            Fseek( (Int16) -2 );
			}
          }
        }
		else
		{ /* No low order sync found */
            Fseek( (Int16) -1 );
		}

      }
    }
    else
    { /* too much error */
      return head_status;
    }
  }
  return (head_status | SONG_SYNC_ERR);
}


/*F**************************************************************************
* NAME: song_audio_init
*----------------------------------------------------------------------------
* PARAMS:
*
* return:
*----------------------------------------------------------------------------
* PURPOSE: 
*   Audio interface initialization in song mode
*----------------------------------------------------------------------------
* EXAMPLE:
*----------------------------------------------------------------------------
* NOTE:
*   DAC_NB_BIT defined in config.h
*----------------------------------------------------------------------------
* REQUIREMENTS:
*****************************************************************************/
void song_audio_init (void)
{
  Aud_set_pcm_32(DAC_NB_BIT);
  Aud_set_song();
  Aud_enable();
  Aud_disable_int();                        /* disable audio interrupt */
}


/*F**************************************************************************
* NAME: song_start
*----------------------------------------------------------------------------
* PARAMS:
*
* return:
*----------------------------------------------------------------------------
* PURPOSE: 
*   Start song playing
*----------------------------------------------------------------------------
* EXAMPLE:
*----------------------------------------------------------------------------
* NOTE:
*----------------------------------------------------------------------------
* REQUIREMENTS:
*****************************************************************************/
void song_start (void)
{
  Dac_unmute();                             /* maestro please! */
  Aud_song_play();                          /* start sample request */
  mp3_init();                               /* enable mp3 decoder */
}


/*F**************************************************************************
* NAME: song_pause
*----------------------------------------------------------------------------
* PARAMS:
*
* return:
*----------------------------------------------------------------------------
* PURPOSE: 
*   Stop song playing
*----------------------------------------------------------------------------
* EXAMPLE:
*----------------------------------------------------------------------------
* NOTE:
*   clocks are not disabled by this functions
*----------------------------------------------------------------------------
* REQUIREMENTS:
*****************************************************************************/
void song_pause (void)
{
  Aud_song_pause();                         /* disable audio */
  mp3_stop();                               /* disable mp3 macrocell */
}


/*F**************************************************************************
* NAME: song_stop
*----------------------------------------------------------------------------
* PARAMS:
*
* return:
*----------------------------------------------------------------------------
* PURPOSE: 
*   Stop song playing
*----------------------------------------------------------------------------
* EXAMPLE:
*----------------------------------------------------------------------------
* NOTE:
*----------------------------------------------------------------------------
* REQUIREMENTS:
*****************************************************************************/
void song_stop (void)
{
  Dac_mute();                               /* silence please! */
  aud_stop();                               /* disable audio */
  mp3_stop();                               /* disable mp3 macrocell */
  clock_disable();                          /* disable clocks */
}