Algorithm 2 Decoder of ADPCM [19].

Require:p // an ADPCM value. Ensure: P // a unit of data to be compressed.   $w\leftarrow$ W_INIT   $P_{prev}\leftarrow$ P_INIT   $C\left[\right]\leftarrow [c_0,c_1,...,c_{2^{M-1}}]$   $f_{prev}\leftarrow w$   $step\leftarrow (w\times 2)/2^{M-1}$   if $p<2^{M-1}$ then     $d\leftarrow step\times (p\times 2+1)/2$   else     $d\leftarrow -step\times ((p-2^{M-1})\times 2+1)/2$   end if    $P\leftarrow P_{prev}+d$    $f_{prev}\leftarrow f_{prev}\times C[p\&((1\ll M)-1)]/64$    $w\leftarrow f_{prev}$