element for the reference index (ref_idx_10[ mbPartIdx ] with mbPartIdx = 0..3) is present in the bitstream and ref_idx_10[ mbPartIdx ] shall be inferred to be equal to 0 for all sub-macroblocks of the macroblock (with indices mbPartIdx = 0..3). P_Skip: no further data is present for the macroblock in the bitstream. The following semantics are assigned to the macroblock prediction modes (for macroblocks that are not partitioned) and macroblock partition prediction modes (for macroblocks that are partitioned) specified by MbPartPredMode() in Table 7-13: Pred L0: specifies that the Inter prediction process is invoked using list 0 prediction. Pred L0 is an Inter macroblock prediction mode (for macroblocks that are not partitioned) and an Inter macroblock partition prediction mode (for macroblocks that are partitioned). When mb_type is equal to any of the values specified in Table 7-13, the macroblock is coded in an Inter macroblock prediction mode. Macroblock types that may be collectively referred to as B macroblock types are specified in Table 7-14. The macroblock types for B slices are specified in Tables 7-14 and 7-11. The mb_type values 0 to 22 are specified in Table 7-14 and the mb_type values 23 to 48 are specified in Table 7-11, indexed by subtracting 23 from the value of mb_type. Rec. ITU-T H.264 (01/2012) Table 7-14 - Macroblock type values 0 to 22 for B slices B_Direct_16x16 Direct B_L0_16x16 Pred L0 B_L1_16x16 Pred_L1 B_Bi_16x16 BiPred B_L0_L0_16x8 Pred_L0 Pred L0 B_L0_L0_8x16 Pred_L0 Pred I B_L1_L1_16x8 Pred_L1 Pred_L1 B_L1_L1_8x16 Pred_L1 Pred_L1 B_L0_L1_16x8 Pred_L0 Pred_L1 B_L0_L1_8x16 Pred L0 Pred_L1 B_L1_L0_16x8 Pred L1 Pred_L0 B_L1_L0_8x16 Pred_L1 Pred_L0 B_L0_Bi_16x8 Pred_L0 BiPred B_L0_Bi_8x16 Pred_L0 BiPred Pred_L1 BiPred B_L1_Bi_8x16 Pred_L1 BiPred B_Bi_L0_16x8 BiPred Pred_L0 B_Bi_L0_8x16 BiPred Pred_L0 B Bi L1 16x8 BiPred Pred_L1 B_Bi_L1_8x16 BiPred Pred_L1 B_Bi_Bi_16x8 BiPred BiPred B_Bi_Bi_8x16 BiPred BiPred B_8x8 inferred B_Skip Direct The following semantics are assigned to the macroblock