ADPCM Functions

• • ADPCM FUNCTIONS **

---

 ad_reset();   [3.02+]

    Resets ADPCM hardware.

 ad_stop();    [3.21+]

    Stop playing adpcm.

 ad_stat();    [3.21+]

    Returns current adpcm status. Return FALSE(0) if adpcm

    playing isn't in progress else non zero value.

 ad_trans(int ovl_index, int sect_offset, char nb_sectors, int ad_addr); [3.21+]

    Transfer data from CDROM into adpcm buffer.

    Read it from the overlay segment specified by 'ovl_idx', with sector

    offset (ie. multiples of 2048 bytes) of 'sect_offset'.

    Read 'nb_sectors' sectors and store data into adpcm buffer starting

    from offset 'ad_addr'.

    Non-zero return values indicate errors.

 ad_read(int ad_addr, char mode, int buf, int bytes); [3.21+]

    Read data from the adpcm buffer.

    Read 'bytes' bytes starting at offset 'ad_addr' in adpcm buffer.

    The mode 'mode' determines the meaning of the 'buf' offset.

     Valid modes          Meaning of 'buf'

     -----------          ----------------

     0                  Offset in the mapped ram.

     2-6                Directly into memory mapped to MMR #'mode'

     0xFF               Offset in video ram.

    Non-zero return values indicate errors.

  ad_write(int ad_addr, char mode, int buf, int bytes); [3.21+]

    Write data into the adpcm buffer.

    Write 'bytes' bytes starting at offset 'ad_addr' in adpcm buffer.

    The mode 'mode' determines the meaning of the 'buf' offset.

     Valid modes          Meaning of 'buf'

     -----------          ----------------

     0                  Offset in the mapped ram.

     2-6                Directly into memory mapped to MMR #'mode'

     0xFF               Offset in video ram.

    Non-zero return values indicate errors.

   ad_play(int ad_addr, int bytes, char freq, char mode); [3.21+]

     Play adpcm sound from data loaded in the adpcm buffer.

     Start playing from 'ad_addr' offset in the adpcm buffer, for 'bytes' bytes.

     The frequency used for playback is computed from 'freq' using the

     following formula : real_frequency_in_khz = 32 / (16 - 'freq'). Valid range

     for 'freq' is 0-15.

     If bit 0 of 'mode' is on, values of 'ad_addr', 'bytes' and 'freq' from

     the previous ad_play call are reused.

     If bit 7 of 'mode' is on, playback loops instead of stopping at the end

     of the range.