void ParseIntraMode(BitReader br, int mb_x)
{
int top = 4 * mb_x; // within intra_t
int left = 0; // within intra_l
var block = m_mb_data[mb_x];
// Note: we don't save segment map (yet), as we don't expect
// to decode more than 1 keyframe.
if (m_segment_hdr.UpdateMap)
{
// Hardcoded tree parsing
block.segment_ = 0 == br.GetBit (m_proba.Segments[0])
? (byte)br.GetBit (m_proba.Segments[1])
: (byte)(2 + br.GetBit (m_proba.Segments[2]));
}
else
{
block.segment_ = 0; // default for intra
}
if (m_use_skip_proba)
block.skip_ = br.GetBit (m_skip_p) != 0;
block.is_i4x4_ = 0 == br.GetBit (145); // decide for B_PRED first
if (!block.is_i4x4_)
{
// Hardcoded 16x16 intra-mode decision tree.
int ymode =
0 != br.GetBit (156) ? (0 != br.GetBit (128) ? TM_PRED : H_PRED)
: (0 != br.GetBit (163) ? V_PRED : DC_PRED);
block.imodes_[0] = (byte)ymode;
for (int i = 0; i < 4; ++i)
{
m_intra_t[top+i] = (byte)ymode;
m_intra_l[left+i] = (byte)ymode;
}
}
else
{
int modes = 0; // within block.imodes_;
for (int y = 0; y < 4; ++y)
{
int ymode = m_intra_l[left + y];
for (int x = 0; x < 4; ++x)
{
int prob = m_intra_t[top + x];
int i = kYModesIntra4[br.GetBit (kBModesProba[prob,ymode,0])];
while (i > 0)
i = kYModesIntra4[2 * i + br.GetBit (kBModesProba[prob,ymode,i])];
ymode = -i;
m_intra_t[top + x] = (byte)ymode;
}
Buffer.BlockCopy (m_intra_t, top, block.imodes_, modes, 4);
modes += 4;
m_intra_l[left + y] = (byte)ymode;
}
}
// Hardcoded UVMode decision tree
block.uvmode_ = 0 == br.GetBit (142) ? DC_PRED
: 0 == br.GetBit (114) ? V_PRED
: 0 != br.GetBit (183) ? TM_PRED : H_PRED;
}
void ParseProba(BitReader br)
{
for (int t = 0; t < NumTypes; ++t)
{
for (int b = 0; b < NumBands; ++b)
for (int c = 0; c < NumCtx; ++c)
for (int p = 0; p < NumProbas; ++p)
{
int v = br.GetBit (CoeffsUpdateProba[t,b,c,p]) != 0 ?
br.GetBits (8) : CoeffsProba0[t,b,c,p];
m_proba.Bands[t,b].Probas[c][p] = (byte)v;
}
for (int b = 0; b < 16 + 1; ++b)
{
m_proba.BandsPtr[t][b] = m_proba.Bands[t,kBands[b]];
}
}
m_use_skip_proba = br.GetNextBit() != 0;
if (m_use_skip_proba)
m_skip_p = br.GetBits (8);
}
int GetCoeffs(BitReader br, BandProbas[] prob, int ctx, int[] dq, int n, short[] out_ptr, int dst)
{
var p = prob[n].Probas[ctx];
for (; n < 16; ++n)
{
if (0 == br.GetBit (p[0]))
return n; // previous coeff was last non-zero coeff
while (0 == br.GetBit (p[1])) // sequence of zero coeffs
{
p = prob[++n].Probas[0];
if (16 == n) return 16;
}
// non zero coeff
var p_ctx = prob[n + 1].Probas;
int v;
if (0 == br.GetBit (p[2]))
{
v = 1;
p = p_ctx[1];
}
else
{
v = br.GetLargeValue (p);
p = p_ctx[2];
}
out_ptr[dst+kZigzag[n]] = (short)(br.GetSigned (v) * dq[n > 0 ? 1 : 0]);
}
return 16;
}
