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  1. A Parallelism Encoding Framework for The Temporal Scalability of H.264/AVC Scalable ExtensionShu-Sian Yang, Sung-Wen Wang, Hong-Ming Chen, and Ja-Ling WuDepartment of Computer Science and Information EngineeringGraduate Institute of Networking and MultimediaNational Taiwan University, Taipei, TaiwanE-mail:{pigyoung, song, blacksmith, wjl}@cmlab.csie.ntu.edu.tw

  2. Outline • Problem Statement • Overview of H.264/AVC Scalable Extension • Temporal Scalability • Spatial Scalability • Complexity Reduction • Previous Parallel Encoding Scheme for Video Coding • MB-Level (Wave-front) Parallelism • Frame-Level Parallelism • Parallel Encoding Based on Hierarchical B-Picture Structure • Frame-Level Parallel Scheme • Conclusions and Future Work

  3. SVC Encoder Structure Overview • Combined scalability. • H.264 based, layered video coding.

  4. Higher Complexity • Base Layer (BL) is identical to the standard H.264 • Enhancement Layers (EL) have “inter-layer” predictions in additional: • BL Inter 16x16 w. residue pred. • BL Inter 8x16 w. residue pred. • BL Inter 16x8 w. residue pred. • BL Inter 8x8 w. residue pred.. • BL Inter 8x8 w. residue pred. • BL Inter 4x8 w. residue pred. • BL Inter 8x4 w. residue pred. • BL Inter 4x4 w. residue pred. • BL Intra 16x16 w. residue pred. • BL Intra 4x4 w. residue pred. • H.264: • Inter 16x16 • Inter 8x16 • Inter 16x8 • Inter 8x8 • Inter 8x8 • Inter 4x8 • Inter 8x4 • Inter 4x4 • Intra 16x16 (4 modes) • Intra 4x4 (9 modes) • SVC additional: • BL Inter 16x16 • BL Inter 8x16 • BL Inter 16x8 • BL Inter 8x8 • BL Inter 8x8 • BL Inter 4x8 • BL Inter 8x4 • BL Inter 4x4 • BL Intra 16x16 • BL Intra 4x4

  5. Scalabilities • Three kinds of scalabilities: • Quality (SNR) scalability • Fine-Grain-Scalability (FGS) • Bit-plane coding • Spatial scalability • Decimation • Wavelet transform • Temporal scalability • Hierarchical B-picture QCIF CIF 4CIF 30 fps 15 fps 7.5 fps

  6. Temporal Scalability • Hierarchical B-picture • H.264 allows B pictures may or may not be used as references. • Hierarchical prediction. • Temporal scalability can be achieved by hierarchical truncating B pictures. Group of Pictures (GOP size = 16) Key Picture Key Picture 16 16 Level 1 8 Level 2 4 12 Level 3 2 6 10 14 Level 4 1 3 5 7 9 11 13 15

  7. Temporal Scalability- Motion Characteristics of Different Temporal Levels • Higher temporal level, larger distance between current and reference frames. • Frames at higher temporal level are the references frames of subsequent lower temporal level frames. 8 pictures away 16 Level 1 4 pictures away 8 Level 2 4 12 8 pictures away Level 3 2 6 10 14 Level 4 1 3 5 7 9 11 13 15

  8. Temporal Scalability- Motion Characteristics of Different Temporal Levels • Statistical distribution of optimal MVs • Obtained from full search. • Total 7 test sequences. • MVs are scattered sparsely at higher temporal levels. 8 Level 1 Level 2 Level 3 Level 4 1 (%)

  9. Temporal Scalability- Motion Characteristics of Different Temporal Levels -16 -16 -16 -16 0 0 0 0 -16 -16 -16 -16 0 0 0 0 16 16 16 16 16 16 16 16

  10. Parallel Encoding Based on Hierarchical B-Picture Structure • Data-Level Parallelism • GOP, Slice, Picture, Macroblock • GOP: Extensive memory usage limits its scalability. • Picture: Difficult to identify independent pictures. • Slice: Coding efficiency degrades due to slice boundaries. • MB: Extensive requirement of synchronizations. • Applicable to all encoders • Function-Level Parallelism • Asymmetric workload • Depends on encoder implementations

  11. Parallel Encoding Based on Hierarchical B-Picture Structure • MB-Level (Wave-front) Parallelism: • Only MB-Level parallelism can be achieved in traditional codecs. • Extensive controls and synchronizations required. • Frame-Level Parallelism: • Using IBBPBBP pattern, set B pictures as non-reference pictures.

  12. Parallel Encoding Based on Hierarchical B-Picture Structure • Proposed Picture Decomposition Based on Hierarchical B-Picture: • Utilizing the hierarchical B-Picture structure, picture-level parallelism is allowed in SVC Level 1 Level 2 Level 3 Level 4

  13. Parallel Encoding Based on Hierarchical B-Picture Structure • Experimental results: execution time of motion estimation

  14. Parallel Encoding Based on Hierarchical B-Picture Structure • Experimental results: coding efficiency comparison

  15. Future Work • For parallel video encoding, modules like motion compensation and up-sampling are good candidates for data level parallel processing. Along with data level parallelism, the function level one can also be integrated into a hybrid scheme. • Platform dependent issues such as power consumption and load balancing on asymmetric architectures are also important research issues

  16. Thank for your attendance! Any Comment is Welcome

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