Audio Video coding Standard of AVS China Submitted by Swaminathan Sridhar EE 5359 Multimedia Processing Project Video coding standards 5 Video coding standards 4 5 MPEG 2 DVD MPEG 2 DVD SDTV HDTV More than 10 years old Compression efficiency 4 7GB DVD 2 hours movie 5 3Mbps 18GB 2 hours high definition movie 20Mbps MPEG 4 AVC H 264 Multimedia applications Advanced coding techniques Multiple reference frame prediction Context based adaptive binary arithmetic coding CABAC High compression efficiency 1 5 2Mbps for SD 6 8Mbps for HD Save storage space channel bandwidth and frequency spectrum Development stages of AVS 3 December 2003 In the 7th AVS meeting AVS video part 2 and AVS system part 1 was finalized December 2004 In the 11th AVS meeting AVS M part 7 was finalized March 2005 Authentication of AVS101 high definition decoding chip May 2005 AVS Industry Alliance was set up June 2005 Joint AVS ISMA workshop on IPTV standard and industry forum February 2006 AVS part 2 was announced as a national standard Parts of AVS 3 Applications of the commonly used parts of AVS China 3 AVS Part 2 HD SD video Jizhun Profile Zengqiang Profile HD broadcasting High density storage media Video surveillances Video on demand AVS Part 7 Mobile video Jiben Profile Record and local playback on mobile devices Multimedia Message Service MMS Streaming and broadcasting Real time video conversation Major and Minor coding tools used in AVS part 2 1 Major tools Interlace handling Picture level adaptive frame field coding PAFF Macroblock level adaptive frame field coding MBAFF Intra prediction 5 modes for luma and 4 modes for chroma Motion compensation 16x16 16x8 8x16 8x8 block size Resolution of MV 1 4 pel 4 tap interpolation filter Transform 16bit implemented 8x8 integer cosine transform Quantization and scaling scaling only in encoder Entropy coding 2D VLC and Arithmetic Coding In loop deblocking filter Minor tools Motion vector prediction Adaptive scan AVS encoder structure 1 Different picture types 2 Three types of picture are defined by AVS namely Intra pictures I Predicted pictures P At most two reference frames P or I Interpolated pictures B two reference frames I or P or both MB level Adaptive frame coding 2 MB level adaptive frame field coding MBAFF The frame field encoding decision is made independently for each vertical pair of macro blocks in a frame A frame consisting of both moving and non moving regions is coded more efficiently by frame mode for the non moving regions field mode for the moving regions MBAFF is much more complicated than PAFF zig zag scanning motion vector prediction intra prediction deblocking context modeling in entropy coding The advantage compared with the MBAFF in H 264 A field coded MB belonging to the bottom field CAN use the top field of the same frame as a reference for motion prediction Intra Prediction 2 Five different modes for luma Luma Intra Prediction difference between AVS and H 264 6 AVS Block size 8x8 5 modes Reference pixels low pass filtered Advantages low complexity with less modes H 264 Block size 4x4 or 16x16 9 modes for 4x4 8x8 4 modes for 16x16 Advantage better prediction Disadvantage more complex Intra prediction modes for Chroma 2 4 Prediction modes for Chroma Inter Prediction and Motion Compensation 1 At most 2 frames can be stored as reference for motion prediction Block size of motion prediction and compensation 16x16 16x8 8x16 and 8x8 In each MB the number of MV pairs can be 1 2 or 4 depending on the block size of MC MVD the difference between the predicted MV and the real MV is coded Resolution of MV 1 4 pixel for luma 1 8 pixel for chroma Motion prediction modes Forward Backward only applicable for B frame Bi directional only applicable for B frame Skip Direct Symmetric Reference Frame 1 At most 2 reference frames are used PAFF or MBAFF is used if the current MB is frame coded 2 frames can be used as reference for motion prediction if the current MB is field coded 4 fields can be used Reference index should be coded with every MC block to indicate which reference picture is used Reference Index 1 Motion Vector Prediction 3 Motion Vector Prediction 3 Use A B C D s MV MVA MVB MVC and MVD to predict E s MV PredMVE Reason reduce the bits for coding MV Method Geometrical median of MVA MVB MVC VAB Dist MVA MVB VBC Dist MVB MVC VCA Dist MVC MVA FMV Median VAB VBC VCA where Dist MV1 MV2 x1 x2 y1 y2 Determine PredMVE If FMV equals VAB PredMVE MVC If FMV equals VBC PredMVE MVA If FMV equals VCA PredMVE MVB Interpolation for Luma 3 Resolution Quarter pixel Filter Half pixel Blue 1 5 5 1 Quarter pixel White 1 7 7 1 Red bilinear Interpolation for Luma 3 Interpolation for Chroma 3 PredMatrix x y 8 dx 8 dy A dx 8 dy B 8 dx dy C dx dy D 64 Forward and Backward Prediction 1 Forward prediction MV pointing only to the previous frame Get reference block only from the previous frame Backward prediction MV pointing only to the next frame Get reference block only from the next frame Forward and Backward Prediction 1 Bi directional Prediction 1 Skip mode Block size of MC 16x16 No transform coefficient is coded since they all equal zeros No MV is coded since they can be calculated Direct mode Block size of MC 16x16 or 8x8 Transform coefficients are not all zeros so they have to be coded No MV is coded since they can be calculated the same way for skip mode Symmetric mode Block size of MC 16x16 16x8 8x16 8x8 Transform coefficients are not all zeros so they have to be coded Only forward MV is coded and the backward MV can be calculated by using the forward one MV Derivation for Skip and Direct Mode 1 MV Derivation for Symmetric Mode 1 Pre scale Transform 3 AVS 8 8 ICT Matrix 3 Context based Adaptive 2D Variable Length Coding CA 2D VLC 1 level run pair mapping to CodeNum using VLC tables level 0 CodeNum is the number in VLC tables directly level 0 CodeNum is number 1 in VLC tables Example level 2 run 1 CodeNum 11 level 2 run 1 CodeNum 12 CodeNum mapping to bit string using Exp Colomb coding Context based Adaptive 2D Variable Length Coding CA 2D VLC 1 Deblocking Filter 3 8x8 block Three steps Choose boundary strength BS according to Prediction modes MV Decide whether to filter according to Quantization Parameter QP BS Apply filter to the boundary Deblocking Filter 3 AVS Part 2 vs H 264 AVC 4 6 AVS Part 2 vs H 264 AVC 4 6 BS Boundary strength AVS Part 2 performance 1 A Container qcif sequence A Decoded frame A Claire qcif sequence A Decoded frame A News qcif sequence A
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