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Adaptive Block Transforms for H.26L

Adaptive Block Transforms for H.26L. Mathias Wien Lehrstuhl und Institut für Nachrichtentechnik RWTH Aachen University of Technology, Germany Tel.: ++49-241-80-7681 E-mail: wien@ient.rwth-aachen.de. Introduction. H.26L: New Video Coding Standard

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Adaptive Block Transforms for H.26L

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  1. Adaptive Block Transforms for H.26L Mathias Wien Lehrstuhl und Institut für Nachrichtentechnik RWTH Aachen University of Technology, Germany Tel.: ++49-241-80-7681 E-mail: wien@ient.rwth-aachen.de

  2. Introduction H.26L: New Video Coding Standard ITU-T Q6/SG16 VCEG Video Coding Experts Group Main Features • Hybrid Coding Scheme • Intra : 9 Prediction Modes • Inter : 7 Macroblock Modes • Encoding • Base-Line: Universal Variable Length Code • Higher Profiles: Context-Based Adaptive Binary Arithmetic Coding (CABAC) Adaptive Block Transforms for H.26L

  3. Introduction (cont.) Main Features (cont.) • I-, P-, B-frames • In-loop deblocking filter • Long-term motion prediction • Sub-pel motion resolution • Integer DCT approximation • Rate/Distortion optimized coding Status H.26L Test Model Long-Term TML-8 Determination by November 2002 Adaptive Block Transforms for H.26L

  4. Comparison H.26L vs. H.263 M. Horowitz, document VCEG-M08 Adaptive Block Transforms for H.26L

  5. Outline • Introduction • Intra Frame Prediction in H.26L • Inter Frame Prediction in H.26L • Deblocking Filter • Transform Coding • Fixed Block Transform and Adaptive Block Transforms • Integer Transforms • Scan and Quantization • Simulation Results • Conclusions Adaptive Block Transforms for H.26L

  6. 2 1 3 I A B C D E a b c d F e f g h G i j k l H m n o p 4 4  4 Block 5 Prediction modes Intra Frame Prediction • 6 Modes for intra prediktion of 4  4 blocks • DC Prediction (Mode 0) • 5 directional predictions • 16  16 Intra Mode ( 'flat' regions ) • 4 Modes: Vertical, horizontal, DC, Plane Adaptive Block Transforms for H.26L

  7. 1 2 3 4 5 6 7 Inter Prediction in H.26L Macroblock Modes Motion Prediction • Macroblocks of 1616 pixel, 7 Modes • Multiframe prediction (5 reference frames) • Motion vectors in 1/4- or 1/8-pel resolution • Sub-pel motion estimation: • Hadamard transform of the prediction error • Sum of Absolute Transformed Differences (SATD)  Rate/Distortion criterion on sub-pel positions Adaptive Block Transforms for H.26L

  8. TML Deblocking Filter Normative in-loop deblocking filter • INTER blocks: filtering based on 4  4 blocks • INTRA blocks: filtering on macroblock basis • Filter strength is determined by • Mode of the current 4  4 Block (INTRA / INTER) • Non-zero transform coefficients in the block • Orientation of motion vectors in neigbouring blocks • Aktivity of the neigbouring blocks Adaptive Block Transforms for H.26L

  9. 1 2 3 4 5 6 7 Transform Coding Test Model Fixed Block Transform • Single 44 transform • Smallest block size used for motion compensation (MC) Proposal Adaptive Block Transforms • Transform block size connected to MC block size • No additional side information • Exploit signal length Adaptive Block Transforms for H.26L

  10. Separable transform of a block with nm elements Th, Tv : horizontal and vertical transform matrices Adaptive Block Transforms (ABT) • Desirable Properties • Integer approximation of the DCT • Small coefficients, small norm • High symmetry • Transforms • 44 transform used in the H.26L test model • New 88 and 1616 transform matrices • Similar complexity as fast DCT Adaptive Block Transforms for H.26L

  11. 4x4 4x8 8x8 Scan and Quantization • Zigzag-scan for quadratic and directional blocks • Quantization • Normalization of the transform coefficients • Scalar quantization • 1 quantization table for TML • 5 quantization tables for full ABT Adaptive Block Transforms for H.26L

  12. Simulation Conditions • Comparison on basis of H.26L Test Model Longterm 4 (TML-4 ) • No deblocking filter, no RD optimization • Quantization parameter qp = [13,16,19,22,25,28] • Rate estimation for transform coefficients • 2D (Level,Run) symbols for blocks < 88 • 3D (Last,Level,Run) symbols for blocks  88 • Statistics of the symbols for each macroblock mode for the whole sequence • 1st order entropy calculation for each macroblock mode Adaptive Block Transforms for H.26L

  13. Simulation Conditions • Motion estimation • SATD transform block size corresponds to block size used for transform coding • Comparison of three transform settings • Use only 44 transform (TML) 44 • 44, 48, 84, and 88 transform blocks ABT 88 • All applicable block sizes ABT 1616(44,48,84,88, 816,168,1616) Adaptive Block Transforms for H.26L

  14. Rate Distortion Results Adaptive Block Transforms for H.26L

  15. Rate Distortion Results Adaptive Block Transforms for H.26L

  16. Rate Distortion Results Adaptive Block Transforms for H.26L

  17. 44 ABT 1616 Subjective Results • Paris CIF 15Hz, Frame 120, QP=25 Adaptive Block Transforms for H.26L

  18. Conclusions • H.26L Test Model • Improved compression performance • Adaptive Block Transforms • Connect transform block size to block size used for motion compensation • No additional side information • Good Rate/Distortion performance for ABT 8x8 • Best subjective quality for ABT 16x16 Adaptive Block Transforms for H.26L

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