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Video Coding Concept

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  1. Video Coding Concept Kai-Chao Yang

  2. Video Sequence and Picture • Video sequence • Large amount of temporal redundancy • Intra Picture/VOP/Slice (I-Picture) (p.295) • Encoded without referencing others • All MBs are intra coded • Inter Picture/VOP/Slice (P-Picture, B-Picture) (p.295) • Encoded by referencing other pictures • Some MBs are intra coded, and some are inter coded Intra 0 Inter 1 Inter 2 Inter 3 Inter 4 Inter 5

  3. Group of Pictures GOP GOP GOP … • Group of Pictures (GOP) (p.295, p.455-457) • GOP in H.264/AVC • Multiple reference frames • B-pictures can be referenced • Variable number of B-pictures • GOP in Scalable Video Coding (SVC) of H.264/AVC • Hierarchical prediction structure I B B P B B P … B B I B B P … Video stream Frame order: 0 1 2 3 4 5 6 Encoding order: 0 2 3 1 5 6 4

  4. Picture, Slice, MacroBlock, and Block 8 8 • H.264/AVC • Variable MB size • 4x4 transform block block 8 MB 8 Slice Picture

  5. Flow Chart of Video Coding • (p.293-295) Low frequency High frequency (lossy compression) (lossless compression) (spatial  frequency) MB Transform Quantization Entropy Coding - Decoder Motion Compensation Quantization-1 (removing temporal redundancy) Inverse Transform + Motion Estimation (frame reconstruction) Current frame Reference frame (estimating similar blocks)

  6. Coding of I-Slice • Example DCT Original block Transformed block Quantization matrix Bit-stream 15 0 -2 -1 -1 -1 0 … Entropy coding Zig-zag scan

  7. Coding of P-Slice • Example Motion Compensation - = Original current frame Residual = Motion Vectors + Motion Estimation Frame buffer Reconstructed reference frame

  8. Structure of H.264/AVC Encoder Representation of video content Formats of VCL representation

  9. H.264/AVC Flow Chart Input Video Signal Split into Macroblocks 16x16 pixels Coder Control Control Data Transform/Scal./Quant. Quant.Transf. coeffs - Decoder Scaling & Inv. Transform Entropy Coding De-blocking Filter Intra-frame Prediction Output Video Signal Motion- Compensation Intra/Inter Motion Data Motion Estimation

  10. New Features of H.264/AVC Multiple reference frames Variable block size 1/4 and 1/8 motion vector precision Weighted prediction 4x4 transform block Intra prediction De-blocking filter CABAC & CAVLC 16x16 8x8 16x8 8x16 0 MB 0 1 0 0 1 Types 2 3 1 4x8 8x8 8x4 4x4 0 1 0 8x8 0 1 0 Types 2 3 1 Various block sizes and shapes

  11. FMO and ASO Examples of Flexible MB Order (FMO) Arbitrary Slice Order (ASO) sending and receiving the slices of the picture in any order relative to each other Slice #0 Slice Group #0 Slice Group #0 Slice Group #1 Slice #1 Slice Group #1 Slice Group #2 Slice #2

  12. H.264/AVC Profiles

  13. H.264/AVC FRExt Amendment Completed in July 2004 For coding of high-fidelity video material Professional film production, video post production, or high-definition TV/DVD Higher quality, higher rates Professional extensionsFidelity Range extensions (FRExt) http://plusd.itmedia.co.jp/lifestyle/articles/0407/09/news074.html

  14. Profiles of H.264/AVC FRExt High profiles High profile (HP) Supporting 8-bit with 4:2:0 sampling High 10 profile (Hi10P) Supporting 10-bit with 4:2:0 sampling High 4:2:2 profile (H422P) Supporting 10-bit with 4:2:2 sampling High 4:4:4 profile (H444P) Supporting 12-bit with 4:4:4 sampling, and efficient lossless coding and an integer residual color transform for coding RGB video

  15. References • T. Wiegand, G.J. Sullivan, G. Bjntegaard, and A. Luthra, “Overview of the H. 264/AVC video coding standard,” in IEEE Transaction on Circuits and Systems for Video Technology, 2003. • Iain E. G. Richardson, H.264 and MPEG-4 Video Compression: Video Coding for Next-generation Multimedia, Wiley, 2003. • G. J. Sullivan, P. Topiwala, and A. Luthra, “The H.264/AVC Advanced Video Coding Standard: Overview and Introduction to the Fidelity Range Extensions,” in SPIE Conference on Applications of Digital Image Processing, 2004.