private IMacroblockType GetMacroBlockType()
{
//Table 7-10,7-11,..
switch (_sliceState.SliceType)
{
case SliceType.I:
uint mbTypeI = _reader.GetExpGolombCoded(25);
return(MacroblockType.GetMbTypeI(mbTypeI));
case SliceType.Si:
uint mbTypeSi = _reader.GetExpGolombCoded(26);
return(MacroblockType.GetMbTypeSi(mbTypeSi));
case SliceType.P:
case SliceType.Sp:
uint mbTypeP = _reader.GetExpGolombCoded(30);
return(MacroblockType.GetMbTypeP(mbTypeP));
case SliceType.B:
uint mbTypeB = _reader.GetExpGolombCoded(48);
return(MacroblockType.GetMbTypeB(mbTypeB));
}
throw new InvalidOperationException("Current type not set");
}
private IMacroblockType GetMbTypeP()
{
// Note: The 'MbTypeNotZero' flag is not used in P-slices!
// Table 9-37 – Binarization for macroblock types in P, SP, and B slices
const uint ctxOffsetPrefix = 14;
if (_arithmeticDecoder.DecodeDecision(ctxOffsetPrefix) == 0)
{
// 9.3.3.1.2 Assignment process of ctxIdxInc using prior decoded bin values
uint b1 = _arithmeticDecoder.DecodeDecision(ctxOffsetPrefix + 1);
uint b2 = _arithmeticDecoder.DecodeDecision(ctxOffsetPrefix + (b1 + 2));
return(MacroblockType.GetMbTypeP((b1 << 1) ^ (3 * b2)));
}
const uint ctxOffsetSuffix = 17;
if (_arithmeticDecoder.DecodeDecision(ctxOffsetSuffix) == 0)
{
return(MacroblockType.GetMbTypeI(0));
}
return(GetMbTypeIntra(ctxOffsetSuffix, MbTypeIntraCtxIdxIncInterSlice));
}
