2015/6/271 Intra-Prediction in H.264(JM82) Student : 林鴻志 Advisor : 杭學鳴 教授

2015/6/272 Outline Introduction Intra-Prediction Procedure in H.264 Analysis of Computational Complexity Fast Intra-Prediction Algorithm Result Reference

2015/6/273 Introduction Block diagram of Encoder part MB based

2015/6/274 Intra Prediction Procedure in H.264(1/6) Three components, Y, U, and V, all use intra-prediction For Y component, two encoding types, Intra4x4 and Intra16x16, are used. For U and V components, only Intra8x8 type is used since they is usually smooth than Y.

2015/6/275 Intra Prediction Procedure in H.264(2/6) Y component Intra4x4Intra16x16

2015/6/276 Intra Prediction Procedure in H.264(3/6) Intra4x4 Intra16x16

2015/6/277 Intra Prediction Procedure in H.264(4/6) UV component –4 prediction modes are very similar to the 16x16 luma prediction modes Intra8x8

2015/6/278 Intra Prediction Procedure in H.264(5/6) Intra Prediction Procedure (Y component) –1.Generate a 4×4 predicted block according to a mode I –2.Calculate sum of absolute difference (SAD i ) between the original 4x4 block and the predicted block –3.Compute COST 4x4,i =SAD i +4λ(Q P )R, where λ(Qp) is is an approximately exponential function of the quantization factor Q P, R equals 0 for the most probable mode, and 1 for other modes. –4.Repeat 1 to 3 for all the 9 modes, and choose the one that has the minimum cost. C A B

2015/6/279 Intra Prediction Procedure in H.264(6/6) Intra Prediction Procedure (Y component) –5.Generate the predicted MB according to a 16x16 prediction mode –6.For the residue MB, perform Hadamard transform for each 4x4 block –7.Extract all the DC from the 16 4x4 blocks to form another 4x4 block and perform Hadamard transform on it –8.Repeat 5 to 7 for all 4 modes and choose the one with minimum cost as the COST 16x16 –9.If Eqn.(*) is true, the 4x4 intra-prediction will be selected for the current MB, otherwise, the 16x16 intra-prediction is chosen We ignore the procedure of UV since it is similar with Y.

2015/6/2710 Analysis of Computational Complexity[1] H.264 video coding is based on the concept of rate distortion optimization (RDO) which means that the encoder has to encode the intra block using all the mode combinations and choose the one that gives the best RDO performance. In an MB, there are 4x(9x16+4)=592 [ M8x(M4x16+M16) ] different RDO calculations before the best RDO mode is determined. We need fast algorithm to speed up !!

2015/6/2711 Fast Intra-Prediction Algorithm(1/3)[2] The scaling factor, S, can be implemented by shift operator.

2015/6/2712 Fast Intra-Prediction Algorithm(2/3) CaseThe relationship between F v and F h Edge directionCBPMs 1|F v |=|F h |=0No obvious edge2 2|F h |=0 and |F v |>0Vertical edge0,2 3|F v |=0 and |F h |>0Horizontal edge1,2 4|F v |=|F h |>0 and F v /F h >0Diagonal down/left edge3,2 5|F v |=|F h |>0 and F v /F h <0Diagonal down/right edge4,2 6|F v |>|F h |>0Vertical-dominant edge0,5,7,3,4,2 7|F h |=|F v |>0Horizontal-dominant edge1,6,8,3,4,2

2015/6/2713 Fast Intra-Prediction Algorithm(3/3) Algorithm Description –1.Calculate F v and F h. The scaling factor S is a function of QP, thus F v and F h could be obtained by additions and shifts –2.Determine CBPMs for the current block according to F v and F h –3.Generate a 4x4 predicted block according to a mode from CBPMs –4.Compute the cost of the mode –5.Repeat 3. and 4. for all the modes in CBPMs, and choose the one with min. cost

2015/6/2714 Result(1/5) QpMethodTime (sec)Bit-ratePSNR (dB) 20 FS K43.14 FMS K43.03 Improved % FS K38.90 FMS K38.84 Improved % FS K36.39 FMS K36.30 Improved %-0.09 Foreman

2015/6/2715 Result(2/5) QpMethodTime (sec)Bit-ratePSNR (dB) 20 FS K FMS K Improved % FS K37.43 FMS K37.32 Improved % FS K33.82 FMS K33.70 Improved %-0.08 Mobile

2015/6/2716 Result(3/5) QpMethodTime (sec)Bit-ratePSNR (dB) 20 FS K43.51 FMS K43.4 Improved % FS K38.51 FMS K38.43 Improved % FS K35.12 FMS K35.02 Improved %-0.10 Stefan

2015/6/2717 Result(4/5) QpMethodTime (sec)Bit-ratePSNR (dB) 20 FS K45.09 FMS K44.99 Improved % FS K41.64 FMS K41.60 Improved % FS K39.07 FMS K39.02 Improved %-0.05 Akiyo

2015/6/2718 Result(5/5) QpMethodTime (sec)Bit-ratePSNR (dB) 20 FS K44.67 FMS K44.55 Improved % FS K40.86 FMS K40.79 Improved % FS K38.31 FMS K38.22 Improved %-0.09 Mother and daughter

2015/6/2719 Reference [1]FAST INTRA MODE DECISION ALGORITHM FOR H.264/AVC VIDEO CODING, F. Pan, X. Lin, S. Rahardja, K. P. Lim, Z. G. Li, D. Wu, S. Wu [2]Fast 4x4 intra-prediction mode selection for H.264 Zhang Yong-dong; Dai Feng; Lin Shou-xun; Multimedia and Expo, ICME ' IEEE International Conference on Volume 2, June 2004 Page(s): Vol.2 JVT Reference Software JM82,