研究生：何銘哲 指導教授：蔣依吾博士 中山大學資訊工程學系

1. H.264/AVC基於影像複雜度與提早結束之快速階層運動估計方法Content-Based Hierarchical Fast Motion Estimation with Early Termination in H.264/AVC 研究生：何銘哲 指導教授：蔣依吾博士 中山大學資訊工程學系

2. Terms • FME = Fast Motion Estimation • MB = Macroblock • MVCOST = Motion Vector Cost • PSNR = Peak Signal-to-Noise Ratio • RDO = Rate Distortion Optimization

3. Video Compression Intro.

4. Video Compression Intro. (cont.) • ITU-T • H.26x • ISO • Mpeg-x

5. Video Compression Indicator • PSNR (dB) • Bit Rate (kbit/s) • Time (msec, sec) Quality Compression ratio Encoding time

6. H.264 vs previous standards • Variable block size Level One 16x16 16x8 8x16 8x8 Level Two 8x8 8x4 4x8 4x4

7. H.264 vs previous standards • Quarter-pel motion compensation

8. H.264 vs previous standards • Multiple reference picture motion compensation

9. H.264 vs previous standards • Directional spatial prediction for intra coding • INTRA_4x4 • INTRA_16x16

11. H.264 vs previous standards • In-the-loop deblocking filtering

12. Visual Comparison(MPEG-4 Simple Profile VS JVT/H.264)

13. H.264 Encoder Dataflow

14. Motion Estimation

15. Block-based Matching Algorithms • Full Search (Exhaustive Search) • Exhaustively searching each pixel in the search range. Search range Minimum MSE Current Block

16. Block-based FME in H.264 • Why FME? • Spatial and Temporal analysis • Spatial Homogeneity and Temporal Stationarity [Pan, 2005] • Motion Vector Merging [Chen, 2005]

17. Block-based FME in H.264 (cont.) • Early Termination • Predicted Vector Block [Yang, 2005]

18. Block-based FME in H.264 (cont.) • Adaptive Search Pattern • Adaptive Search Window [Bailo, 2004] • UMHS(Uneven Multi-Hexagon Search) & CBDS(Center-Biased Diamond Search) [Chen, 2002][Tham, 1998]

19. Proposed Algorithm • Fast Hierarchical Motion Search (FHMS) • Early Termination Encode one MB Mode Decision Motion Estimation FHMS RDO

20. Hierarchical Motion Search (HMS) • Sub-sampling

21. Pre-processing • We apply our sub-sampling algorithm to only four larger block types to prevent imprecision.

22. Pre-processing (cont.) Start FHMS Satisfy Yes No ? 16x16 16x8 8x16 8x8 Fast Sub-sampling Search Fast Integer-pel Search

23. Proposed Algorithm (cont.) • Step 1: Utilize spatial median prediction schemes for initial search point prediction b c a Current MB

24. Step 2-1: After the initial search point is found, two local search patterns, namely, diamond and cross search, are initiated.

25. Step 2-2: After local search is finished, we come across a complex search condition which indicates that if current MVCOST is below some empirical threshold T, the search process is terminated immediately. complex_offset[blocktype] = {0, 0, 1, 1, 2, 3, 3, 1}

26. Step 3: If the complex search condition is satisfied, continue other search patterns as in the data flow diagram below.

27. Start : Check Predictors Multi big Hexagon Search Small Local Search Hexagon search Cross Search Yes Satisfy Complex Search Condition Small Local Search Need Refinement? No No Yes STOP Refinement Search

28. Step 4: After all search patterns are performed, if the current block type belongs to fast sub-sampling search, a further refinement stage proceeds. Otherwise, the motion search is terminated.

29. Proposed Search Patterns

30. Test Parameters (JM10.2)

31. Experimental Results • PSNR

32. Experimental Results (cont.) • Motion Estimation Time

33. Experimental Results (cont.) • Bit Rate

34. Diagram of Stefan

37. Conclusion • Our proposed algorithm makes H.264/AVC feasible for real-time applications. • Adaptively choosing the proper block type to further improve the bit rate and ME time will be the focus of the following research efforts.