s of the macroblock above the current macroblock and its availability status, - luma4x4BlkIdxB: the index of the 4x4 luma block above the 4x4 block with index luma4x4BlkIdx and its availability status. mbAddrN and luma4x4BlkIdxN (with N being A or B) are derived as specified by the following ordered steps: 1. The difference of luma location (xD, yD ) is set according to Table 6-2. 2. The inverse 4x4 luma block scanning process as specified in clause 6.4.3 is invoked with luma4x4BlkIdx as the input and (x,y) as the output. 3. The luma location ( xN, yN) is specified by: xN = x x x D (6-25) yN=y+yD (6-26) 4. The derivation process for neighbouring locations as specified in clause 6.4.12 is invoked for luma locations with xN, yN as the input and the output is assigned to mbAddrN and xW, yW). 5. The variable luma4x4BlkIdxN is derived as follows: If mbAddrN is not available, luma4x4BlkIdxN is marked as not available. Otherwise (mbAddrN is available), the derivation process for 4x4 luma block indices as specified in clause 6.4.13.1 is invoked with the luma location ( xW, yW) as the input and the output is assigned to luma4x4BlkIdxN. 6.4.11.5 Derivation process for neighbouring 4x4 chroma blocks This clause is only invoked when ChromaArrayType is equal to 1 or 2. Input to this process is a 4x4 chroma block index chroma4x4BlkIdx. Outputs of this process are: mbAddrA (either equal to CurrMbAddr or the address of the macroblock to the left of the current macroblock) and its availability status, - chroma4x4BlkIdxA (the index of the 4x4 chroma block to the left of the 4x4 chroma block with index chroma4x4BlkIdx) and its availability status, mbAddrB (either equal to CurrMbAddr or the address of the macroblock above the current macroblock) and its availability status, chroma4x4BlkIdxB (the index of the 4x4 chroma block above the 4x4 chroma block with index chroma4x4BlkIdx) and its availability status. mbAddrN and chroma4x4BlkIdxN (with N being A or B) are derived as specified by the following ordered steps: 1. The difference o