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Enhancing H.264/AVC Scalability: A Parallelism Encoding Framework for Temporal Efficiency

This paper presents a novel parallelism encoding framework to enhance the temporal scalability of H.264/AVC's scalable extension. It explores the challenges of existing encoding schemes and introduces methods like macroblock-level and frame-level parallelism, capitalizing on hierarchical B-picture structures. The study highlights the significance of spatial and temporal scalability while detailing complexities in encoding. Experimental results show improved efficiency and execution time in motion estimation, paving the way for future research in hybrid parallel processing methodologies for video coding systems.

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Enhancing H.264/AVC Scalability: A Parallelism Encoding Framework for Temporal Efficiency

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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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