Intra 4x4 Prediction in H.264/AVC (1) Intra 4x4 prediction
Predicts each pixel in the block from the previously encoded and reconstructed pixels in the nearby blocks Each 4x4 luma block can select one of nine prediction modes To generate the predicted images the 13 boundary pixels from the reconstructed blocks are required for the prediction mode additional operations such as DCT, Q, IQ, IDCT should be performed for the reconstruction
Cannot be performed before the reconstruction of a previous 4x4 block cannot be pipelined!!
Proposed Intra Prediction (1) Pipelined intra 4x4 prediction The intra prediction process is pipelined by rearranging its encoding order
Proposed encoding order of 16 4×4 blocks in a macroblock. Blocks 1, 2, 9, 14 and 15 still have to wait for the reconstruction results of the previous blocks!!
Proposed Intra Prediction (3) Prediction mode scheduling Even though the encoding order is rearranged, some blocks cannot still be pipelined Nine intra 4×4 prediction modes are divided into three groups and the prediction order of the groups is scheduled based on the availability of the required pixels Group 1: Vertical (0) Group 2: Diagonal Down-Left (3), Vertical Left (7) Group 3: Horizontal (1), DC (2), Diagonal Down-Right (4), Horizontal Down (5), Vertical Right (6), Horizontal UP (8)
Proposed Intra Prediction (5) Prediction mode scheduling (cont’d)
Proposed pipelined process of 4×4 intra prediction with prediction mode scheduling. Total processing time (ttotal): t total = 16t p + 2t '+3t ' '+t r if t r > t p 3 if t r > t p1 t − t t − t t ' = r p1 t ' ' = r p3 otherwise otherwise 0 0
+ 10t r ' if t r > t p t − t tr ' = r p otherwise 0
1 2 7 t p1 = t p , t p 2 = t p , t p 3 = t p 3 3 9 10