ck prediction mode equal to Intra_4x4 followed by the transform decoding process and picture construction process prior to deblocking for each 4x4 luma block. Inputs to this process are: the index of a 4x4 luma block luma4x4BlkIdx, an (PicWidthInSamples)x(PicHeightInSamples) array CSL containing constructed luma samples prior to the deblocking filter process of neighbouring macroblocks. Output of this process are the prediction samples pred4x4L[ X, y ], with X, y = 0..3, for the 4x4 luma block with index luma4x4BlkIdx. The position of the upper-left sample of a 4x4 luma block with index luma4x4BlkIdx inside the current macroblock is derived by invoking the inverse 4x4 luma block scanning process in clause 6.4.3 with luma4x4BlkIdx as the input and the output being assigned to ( xO, yO). The 13 neighbouring samples p[x,y ] that are constructed luma samples prior to the deblocking filter process, with X = -1, y =-1..3 andx=0..7,y=-1,are derived as specified by the following ordered steps: 1. The luma location ( NN, yN ) is specified by xN=xO+x (8-42) yN = yO+y (8-43) The derivation process for neighbouring locations in clause 6.4.12 is invoked for luma locations with ( NN, yN ) as input and mbAddrN and xx, yW) as output. Each sample p[ X, y ] with X ==1, y = -1..3 and X = 0..7, y=-1 is derived as follows: If any of the following conditions are true, the sample p[ X, y ] is marked as "not available for Intra_4x4 prediction" mbAddrN is not available, the macroblock mbAddrN is coded in an Inter macroblock prediction mode and constrained_intra_pred_flag is equal to 1, the macroblock mbAddrN has mb_type equal to SI and constrained_intra_pred_flag is equal to 1 and the current macroblock does not have mb_type equal to SI, X is greater than 3 and luma4x4BlkIdx is equal to 3 or 11. Otherwise, the sample p[x,y] is marked as "available for Intra_4x4 prediction" and the value of the sample p[ X, y ] is derived as specified by the following ordered steps: The location of the upper-left luma sample of the macroblock mbAddrN is d