bool ParseSegmentHeader(BitReader br)
{
m_segment_hdr.UseSegment = br.GetNextBit() != 0;
if (m_segment_hdr.UseSegment)
{
m_segment_hdr.UpdateMap = br.GetNextBit() != 0;
if (0 != br.GetNextBit())
{ // update data
m_segment_hdr.AbsoluteDelta = br.GetNextBit() != 0;
for (int s = 0; s < NumMbSegments; ++s)
{
m_segment_hdr.Quantizer[s] = (byte)(br.GetNextBit() != 0 ? br.GetSignedValue (7) : 0);
}
for (int s = 0; s < NumMbSegments; ++s)
{
m_segment_hdr.FilterStrength[s] = (byte)(br.GetNextBit() != 0 ? br.GetSignedValue (6) : 0);
}
}
if (m_segment_hdr.UpdateMap)
{
for (int s = 0; s < TreeProbs; ++s)
{
m_proba.Segments[s] = (byte)(br.GetNextBit() != 0 ? br.GetBits (8) : 255);
}
}
}
else
{
m_segment_hdr.UpdateMap = false;
}
return !br.Eof;
}
void ParseQuant(BitReader br)
{
int base_q0 = br.GetBits (7);
int dqy1_dc = br.GetNextBit() != 0 ? br.GetSignedValue (4) : 0;
int dqy2_dc = br.GetNextBit() != 0 ? br.GetSignedValue (4) : 0;
int dqy2_ac = br.GetNextBit() != 0 ? br.GetSignedValue (4) : 0;
int dquv_dc = br.GetNextBit() != 0 ? br.GetSignedValue (4) : 0;
int dquv_ac = br.GetNextBit() != 0 ? br.GetSignedValue (4) : 0;
for (int i = 0; i < NumMbSegments; ++i)
{
int q;
if (m_segment_hdr.UseSegment)
{
q = m_segment_hdr.Quantizer[i];
if (!m_segment_hdr.AbsoluteDelta)
q += base_q0;
}
else if (i > 0)
{
m_dqm[i] = m_dqm[0];
continue;
}
else
{
q = base_q0;
}
var m = m_dqm[i];
m.y1_mat[0] = kDcTable[Clip (q + dqy1_dc, 127)];
m.y1_mat[1] = kAcTable[Clip (q + 0, 127)];
m.y2_mat[0] = kDcTable[Clip (q + dqy2_dc, 127)] * 2;
// For all x in [0..284], x*155/100 is bitwise equal to (x*101581) >> 16.
// The smallest precision for that is '(x*6349) >> 12' but 16 is a good
// word size.
m.y2_mat[1] = (kAcTable[Clip (q + dqy2_ac, 127)] * 101581) >> 16;
if (m.y2_mat[1] < 8) m.y2_mat[1] = 8;
m.uv_mat[0] = kDcTable[Clip (q + dquv_dc, 117)];
m.uv_mat[1] = kAcTable[Clip (q + dquv_ac, 127)];
m.uv_quant = q + dquv_ac; // for dithering strength evaluation
}
}
bool ParseFilterHeader(BitReader br)
{
m_filter_hdr.Simple = br.GetNextBit() != 0;
m_filter_hdr.Level = br.GetBits (6);
m_filter_hdr.Sharpness = br.GetBits (3);
m_filter_hdr.UseLfDelta = br.GetNextBit() != 0;
if (m_filter_hdr.UseLfDelta)
{
if (0 != br.GetNextBit())
{ // update lf-delta?
for (int i = 0; i < NumRefLfDeltas; ++i)
{
if (0 != br.GetNextBit())
m_filter_hdr.RefLfDelta[i] = br.GetSignedValue (6);
}
for (int i = 0; i < NumModeLfDeltas; ++i)
{
if (0 != br.GetNextBit())
m_filter_hdr.ModeLfDelta[i] = br.GetSignedValue (6);
}
}
}
m_filter_type = (0 == m_filter_hdr.Level) ? 0 : m_filter_hdr.Simple ? 1 : 2;
return !br.Eof;
}
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);
}
void GetHeaders()
{
int chunk_size = m_info.DataSize;
int bits = ReadInt24();
chunk_size -= 3;
m_frame_header.KeyFrame = 0 == (bits & 1);
m_frame_header.Profile = (bits >> 1) & 7;
m_frame_header.Show = 0 != (bits & (1u << 4));
m_frame_header.PartitionLength = bits >> 5;
if (m_frame_header.Profile > 3)
throw new InvalidFormatException ("Incorrect keyframe parameters.");
if (!m_frame_header.Show)
throw new InvalidFormatException ("Frame not displayable.");
if (m_frame_header.KeyFrame)
{
// Paragraph 9.2
if (!CheckSignature())
throw new InvalidFormatException ("Bad code word");
ushort w = m_input.ReadUInt16();
ushort h = m_input.ReadUInt16();
m_pic_hdr.Width = (ushort)(w & 0x3fff);
m_pic_hdr.XScale = (byte)(w >> 14); // ratio: 1, 5/4 5/3 or 2
m_pic_hdr.Height = (ushort)(h & 0x3fff);
m_pic_hdr.YScale = (byte)(h >> 14);
chunk_size -= 7;
mb_w_ = (m_pic_hdr.Width + 15) >> 4;
mb_h_ = (m_pic_hdr.Height + 15) >> 4;
// Setup default output area (can be later modified during m_io.setup())
m_io.width = m_pic_hdr.Width;
m_io.height = m_pic_hdr.Height;
m_io.mb_w = m_io.width;
m_io.mb_h = m_io.height;
m_proba.Reset();
m_segment_hdr.Reset();
}
if (m_frame_header.PartitionLength > chunk_size)
throw new InvalidFormatException ("bad partition length");
m_br = new BitReader (m_input, m_frame_header.PartitionLength);
chunk_size -= m_frame_header.PartitionLength;
if (m_frame_header.KeyFrame)
{
m_pic_hdr.Colorspace = (byte)m_br.GetNextBit();
m_pic_hdr.ClampType = (byte)m_br.GetNextBit();
}
if (!ParseSegmentHeader (m_br))
throw new InvalidFormatException ("Cannot parse segment header");
// Filter specs
if (!ParseFilterHeader (m_br))
throw new InvalidFormatException ("Cannot parse filter header");
if (!ParsePartitions (m_br, chunk_size))
throw new InvalidFormatException ("Cannot parse partitions");
for (int i = 0; i < m_dqm.Length; ++i)
m_dqm[i] = new QuantMatrix();
// quantizer change
ParseQuant (m_br);
// Frame buffer marking
if (!m_frame_header.KeyFrame)
throw new InvalidFormatException ("Not a key frame");
m_br.GetNextBit(); // ignore the value of update_proba_
ParseProba (m_br);
}