mode is invoked when Intra4x4PredMode[ luma4x4BlkIdx ] is equal to 4. This mode shall be used only when the samples p[x,-1] with x=0..3 and pl -1, y ] with y = -1..3 are marked as "available for Intra_4x4 prediction". The values of the prediction samples pred4x41[x,y with X, y = 0..3, are derived as follows: If X is greater than y, (8-54) Otherwise if X is less than y, (8-55) Otherwise (x is equal to y), pred4x4L[x,y]=(p[0,-1]+2*p[-1,-1]+p[-1,0]+2)>>2 (8-56) 8.3.1.2.6 Specification of Intra_4x4_Vertical_Rightprediction mode This Intra_4x4 prediction mode is invoked when Intra4x4PredMode[ luma4x4BlkIdx ] is equal to 5. This mode shall be used only when the samples p[ x, -1] with X = 0..3 and p[ -1, y ] with y = - -1..3 are marked as "available for Intra_4x4 prediction". Let the variable zVR be set equal to 2* X -y. - The values of the prediction samples pred4x4L x, y ], with X, y = 0..3, are derived as follows: If zVR is equal to 0, 2, 4, or 6, (8-57) Otherwise, if zVR is equal to 1, 3, or 5, (8-58) Otherwise, if zVR is equal to -1, (8-59) Otherwise (zVR is equal to -2 or -3), pred4x4L[x,y]=(p[-1,y-1]+2*p[-1,y-2]+p[-1,y-3]+2)>>2 (8-60) 8.3.1.2.7 Specification of Intra_4x4_Horizontal_Down prediction mode This Intra_4x4 prediction mode is invoked when Intra4x4PredMode[ luma4x4BlkIdx ] is equal to 6. This mode shall be used only when the samples p[x,-1] with X = 0..3 and p[ -1, y ] with y = -1..3 are marked as "available for Intra_4x4 prediction". Let the variable zHD be set equal to 2 * y-x. The values of the prediction samples pred4x4L[ X, y ], with X, y = 0..3, are derived as follows: If zHD is equal to 0, 2, 4, or 6, Rec. ITU-T H.264 (01/2012) pred4x4L[x,y]=(p[-1,y-(x>>1)-1]+p[-1,y-(x>>1)]+1)>>1 (8-61) Otherwise, if zHD is equal to 1, 3, or 5, (8-62) Otherwise, if zHD is equal to -1, d4x4L[x,y]=(p[-1,0]+2*p[-1,-1]+p[0,-1]+2)>>2 (8-63) Otherwise (zHD is equal to -2 or -3), (8-64) 8.3.1.2.8 Specification of Intra_4x4_Vertical_Leftprediction mode This Intra_4x4 prediction mode is invoked when Intra4x4PredMode[luma4x