unsafe void decode_residual(BitReader bitreader, FlacFrame frame, int ch)
{
// rice-encoded block
// coding method
frame.subframes[ch].best.rc.coding_method = (int)bitreader.readbits(2); // ????? == 0
if (frame.subframes[ch].best.rc.coding_method != 0 && frame.subframes[ch].best.rc.coding_method != 1)
throw new Exception("unsupported residual coding");
// partition order
frame.subframes[ch].best.rc.porder = (int)bitreader.readbits(4);
if (frame.subframes[ch].best.rc.porder > 8)
throw new Exception("invalid partition order");
int psize = frame.blocksize >> frame.subframes[ch].best.rc.porder;
int res_cnt = psize - frame.subframes[ch].best.order;
int rice_len = 4 + frame.subframes[ch].best.rc.coding_method;
// residual
int j = frame.subframes[ch].best.order;
int* r = frame.subframes[ch].best.residual + j;
for (int p = 0; p < (1 << frame.subframes[ch].best.rc.porder); p++)
{
if (p == 1) res_cnt = psize;
int n = Math.Min(res_cnt, frame.blocksize - j);
int k = frame.subframes[ch].best.rc.rparams[p] = (int)bitreader.readbits(rice_len);
if (k == (1 << rice_len) - 1)
{
k = frame.subframes[ch].best.rc.esc_bps[p] = (int)bitreader.readbits(5);
for (int i = n; i > 0; i--)
*(r++) = bitreader.readbits_signed((int)k);
}
else
{
bitreader.read_rice_block(n, (int)k, r);
r += n;
}
j += n;
}
}
