DPCM

This is a set of DPCM codecs used in AUD and VMD.

Old DPCM

Decoding of DPCM is very simple: read nibble, get corresponding delta value from table and update current sample value.

Delta table:

 { 0,  1,  2,  3,  6, 10, 15, 21,
 -21,-15,-10, -6, -3, -2, -1, -0}

New DPCM

New scheme differs from old one by delta table (note the order of its second part):

 { 0,  1,  2,  3,  6,  10,  15,  21,
  -0, -1, -2, -3, -6, -10, -15, -21}