 prediction mode. For a macroblock coded with mb_type equal to PCM, the Intra macroblock prediction mode shall be inferred. A macroblock type that may be referred to as the SI macroblock type is specified in Table 7-12. The macroblock types for SI slices are specified in Tables 7-12 and 7-11. The mb _type value 0 is specified in Table 7-12 and the mb_type values 1 to 26 are specified in Table 7-11, indexed by subtracting 1 from the value of mb_type. Table 7-12 - Macroblock type with value 0 for SI slices Intra_4x4 Equation 7-35 Equation 7-35 The following semantics are assigned to the macroblock type in Table 7-12: The SI macroblock is coded as Intra_4x4 prediction macroblock. Macroblock types that may be collectively referred to as P macroblock types are specified in Table 7-13. The macroblock types for P and SP slices are specified in Tables 7-13 and 7-11. mb_type values 0 to 4 are specified in Table 7-13 and mb_type values 5 to 30 are specified in Table 7-11, indexed by subtracting 5 from the value of mb_type. Rec. ITU-T H.264 (01/2012) Table 7-13 - Macroblock type values 0 to 4 for P and SP slices P_L0_16x16 Pred_L0 P LO LO 16x8 Pred L0 Pred L0 P_LO_LO_8x16 Pred L0 Pred_L0 P_8x8 P_8x8ref0 inferred P_Skip Pred L0 The following semantics are assigned to the macroblock types in Table 7-13: P L0 16x16: the samples of the macroblock are predicted with one luma macroblock partition of size 16x16 luma samples and associated chroma samples. P_LO_LO_MxN, with MxN being replaced by 16x8 or 8x16: the samples of the macroblock are predicted using two luma partitions of size MxN equal to 16x8, or two luma partitions of size MxN equal to 8x16, and associated chroma samples, respectively. 8x8: for each sub-macroblock an additional syntax element (sub_mb_type[ mbPartIdx ] with mbPartIdx being the macroblock partition index for the corresponding sub-macroblock) is present in the bitstream that specifies the type of the corresponding sub-macroblock (see clause 7.4.5.2). P 8x8ref0: has the same semantics as P_8x8 but no syntax 