a4x4PredMode[ luma4x4BlkIdx ] is equal to 2. The values of the prediction samples pred4x4L X, y ], with X, y=0..3, are derived as follows: If all samples p[ X, -1], with X = 0..3, and pl [-1,y], with y = 0..3, are marked as "available for Intra_4x4 prediction", the values of the prediction samples pred4x4L[ X, y ], with X, y = 0..3, are derived by (8-48) Otherwise, if any samples p[ X, -1], with X = 0..3, are marked as "not available for Intra_4x4 prediction" and all samples p[-1,y], with y = 0..3, are marked as "available for Intra_4x4 prediction", the values of the prediction samples pred4x4[ X, y ], with X, y = 0..3, are derived by pred4x4L[x,y]=(p[-1,0]+p[-1,1]+p[-1,2]+p[-1,3]+2)>>2 (8-49) Otherwise, if any samples p[ -1, ], with y = 0..3, are marked as "not available for Intra_4x4 prediction" and all samples p[ X, -1] with x=0.. 3, are marked as "available for Intra_4x4 prediction", the values of the prediction samples pred4x4 X, y ], with X, y=0. 3, are derived by (8-50) Otherwise (some samples p[ -1], with X = 0..3, and some samples p[ -1, y ], with y = 0..3, are marked as "not available for Intra_4x4 prediction"), the values of the prediction samples pred4x4L[ X, y ], with X, y = 0..3, are derived by pred4x4L[x,y]=(1<<(BitDepthy-1)) = (8-51) NOTE - A 4x4 luma block can always be predicted using this mode. 8.3.1.2.4 Specification of Intra_4x4_Diagonal_Down_Left prediction mode This Intra_4x4 prediction mode is invoked when Intra4x4PredMode[ luma4x4BlkIdx ] is equal to 3. This mode shall be used only when the samples p[x,-1] with X = 0..7 are marked as "available for Intra_4x4 prediction". The values of the prediction samples pred4x4L X, ], with X, y = 0..3, are derived as follows: Rec. ITU-T H.264 (01/2012) If X is equal to 3 and y is equal to 3, pred4x4L[x,y]=(p[6,-1]+3*p[7,-1]+2)>>2 (8-52) Otherwise (x is not equal to 3 or y is not equal to 3), pred4x4L[x,y]=(p[x+y,-1]+2*p[x+y+1,-1]+p[x+y+2,-1]+2)>>2 (8-53) 8.3.1.2.5 Specification of Intra_4x4_Diagonal_Down_Rightprediction mode This Intra_4x4 prediction 