k mbAddrN is equal to 0), condTermFlagN is set equal to 1. The variable ctxIdxInc is derived by: ctxIdxInc = condTermFlagA + condTermFlagB (9-7) 9.3.3.1.1.2 Derivation process of ctxIdxInc for the syntax element mb_field_decoding_flag Output of this process is ctxIdxInc. Rec. ITU-T H.264 (01/2012) The derivation process for neighbouring macroblock addresses and their availability in MBAFF frames as specified in clause 6.4.10 is invoked and the output is assigned to mbAddrA and mbAddrB. When both macroblocks mbAddrN and mbAddrN + 1 have mb_type equal to P_Skip or B_Skip, the inference rule for the syntax element nb_field_decoding_fla as specified in clause 7.4.4 is applied for the macroblock mbAddrN. Let the variable condTermFlagN (with N being either A or B) be derived as follows: If any of the following conditions are true, condTermFlagN is set equal to 0: mbAddrN is not available, the macroblock mbAddrN is a frame macroblock. Otherwise, condTermFlagN is set equal to 1. The variable ctxIdxInc is derived by ctxIdxInc = condTermFlagA + condTermFlagB (9-8) 9.3.3.1.1.3 Derivation process of ctxIdxInc for the syntax element mb_type Input to this process is ctxIdxOffset. Output of this process is ctxIdxInc. The derivation process for neighbouring macroblocks specified in clause 6.4.11.1 is invoked and the output is assigned to mbAddrA and mbAddrB. Let the variable condTermFlagN (with N being either A or B) be derived as follows: If any of the following conditions are true, condTermFlagN is set equal to 0: mbAddrN is not available, ctxIdxOffset is equal to 0 and mb_type for the macroblock mbAddrN is equal to SI, ctxIdxOffset is equal to 3 and mb_type for the macroblock mbAddrN is equal to NxN, ctxIdxOffset is equal to 27 and mb_type for the macroblock mbAddrN is equal to B_Skip or B_Direct_16x16. Otherwise, condTermFlagN is set equal to 1. The variable ctxIdxInc is derived as ctxIdxInc = condTermFlagA + condTermFlagB (9-9) 9.3.3.1.1.4 Derivation process of ctxIdxInc for the syntax element coded_block_pattern Inputs to 