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A frequency domain approach for Intra-coding pictures Presenter: Andy C. Yu for Microsoft Research Cambridge 16 th May 2006

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Outline: Introduction - H.264/AVC Intra coding v. Motion JPEG-2000 coding. The proposed Fintra algorithm – based on frequency domain Simulation results – comparison with state-of-the-art algorithms Conclusions

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Introduction H.264/AVC is standardised by ITU-T and MPEG ISO/IEC in Dec. 2001 for commercial video coding. It represents a major step forward in the development of video standards*. It typically outperforms all existing standards by a factor of two. Another important fact is that H.264/AVC is a public and open standard*. * R. Schäfer, T. Wiegand and H. Schwarz, The emerging H.264/AVC standard, EBU Technical Review, Jan 2003

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Conventional Intra-coding structure Video Sequence 8 x 8 DCT … … Quantization Process (Lossy) Entropy Coding 8 Decomposition 8

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H.264/AVC Intra-coding structure Video Sequence Integer 4 x 4 DCT & Quantisation Process … … Entropy Coding Decomposition 4 4 Predicted block Original block Residue Data Mode Selection

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Intra-Prediction in H.264/AVC ABCDEFGHQ I J K L M N O P abcd efgh ijkl mnop A : Neighbouring sample that are already reconstructed at the encoder and decoder sides. a : Samples to be predicted.

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Picture from I. Richardson, H.264 and MPEG-4 Video Compression, Willey Publisher, 1 st edition, 2003.

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Lagrangian Evaluation Final mode decision is selected to minimise Lagrangian cost. Where D : measure of the distortion R : the number of bits. λ : Lagrange parameter. Qp : Quantisation factor.

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Lagrangian evaluation (cont.)

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H.264 Intra-coding v. Motion JPEG2000 coding Picture from J. Ostermann, J. Bormans et al., Video Coding with H.264/AVC: Tools, Performance, and Complexity, IEEE Circuits and Systems Magazine, first quarter, 2004

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The Proposed Fast Intra-coding Algorithm ( Fintra )

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H.264/AVC Intra-coding structure Video Sequence Integer 4 x 4 DCT & Quantisation Process … … Entropy Coding Decomposition 4 4 Predicted block Original block Residue Data Mode Selection

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H.264/AVC Intra-coding structure Video Sequence Integer 4 x 4 DCT & Quantisation Process … … Entropy Coding Decomposition 4 4 Predicted block Original block Residue Data Mode Selection

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The search strategy for the proposed Fintra algorithm The proposed algorithm selects fewer modes to undergo full Lagrangian cost evaluation. The entire selection process operates in the discrete cosine transform (DCT) domain. Generally, larger residue block energy is produced by intra-coding. It is observed that the modes that provide the least residue energy will result in minimum R and hence minimise the Lagrangian cost.

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Algorithm formulation The selection criterion can be measured from the SAD of residue block in Discrete Cosine Transform domain: The definition of 2D-DCT is:

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Thus, the selection is the least residue energy produced by the mode. We separate the low frequency spectrum, DC, from other AC frequencies.

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DC and low-frequency AC coefficients contain more energy than the high- frequency coefficients. Task: Develop efficient approach to calculate DC P|mode and AC P|mode ( i )

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17 x 1

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. 9 x 17

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17 x 1 9 x 17 9x19x1 =.

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17 x 1 9 x 17 9x19x1 =.

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Thus, the selection process, becomes

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Compared with 2D-DCT ? General practice: apply 1D-DCT twice, row-wise and column-wise ?

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General Practice: 0.1 X (B + D + J + L – F – H – N - P) + 0.2 X (C + K - G - O) 2 Multiplication + 11 Addition operators

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Features of conversion matrix Ω Uniquely existed at each position in frequency domain. Independent of the video sequences. Low computational demand. The coefficients can be calculated and stored in advance.

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We may select at least 2 modes to undergo the full Lagrangian process.

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Simulations and Results Comparison of the results with the two best performing algorithms detailed in the literatures. Simulation Settings –JM6.1e version in Microsoft Visual C++ –Various values of M are selected. Measurements: picture quality (dB), compression ratio (Kbits/sec) and entire encoding time (sec).

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Simulation 1: Compared with C. Kim, H. Shih, and C. Kuo, Fast H.264 Intra- prediction mode selection using joint spatial and transform domain features, Journal of Visual Communication and Image Representation, vol. 17, pp. 291-310, 2006. by selecting M=3

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Foreman QCIF 30Hz 300 frames All Intra-coding

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Perception sensitivity area Foreman QCIF 30Hz 300 frames All Intra-coding

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JM6.1e Proposed Result in [6]

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Δ 1 0.1dB Δ 2 0.3dB Foreman QCIF 30Hz 300 frames All Intra-coding JM6.1e Proposed Result in [6]

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Simulation 2: F. Pan, X. Lin, et al., Efficient prediction mode selection 4x4 blocks in H.264,JVT-013, ISO/IEC JTC1/SC29/ WG11 and ITU-T SG16 Q.6, Mar. 2003, Pattaya, Thailand. F. Pan, X. Lin, et al., Fast mode decision algorithm for Intraprediction in H.264/AVC video coding, IEEE transaction on Circuits and Systems for Video Technology, pp. 813-823, Jul. 2005. by selecting M=2

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Sequences PSNR differenceBit rate differenceSpeed up c.f. JM6.1e Pan et alProposedPan et alProposedPan et alProposed Bus (CIF)-0.22 dB-0.12 dB3.85 %1.46 %58.12 %75.22 % Coastguard-0.11 dB-0.06 dB2.36 %1.68 %55.03 %72.48 % Container-0.23 dB-0.10 dB3.70 %0.77 %56.36 %71.86 % Foreman-0.29 dB-0.07 dB4.44 %1.97 %65.38 %72.47 % News-0.29 dB-0.09 dB3.90 %1.18 %55.39 %73.13 % Paris (CIF)-0.23 dB-0.09 dB3.21 %1.47 %57.78 %73.43 % Silent-0.18 dB-0.05 dB3.54 %2.00 %65.17 %71.86 %

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Conclusions A fast algorithm using matrix formulae in the DCT domain is presented. The proposed Fintra algorithm does not need any a priori knowledge or magic number. The simulation results verify that the proposed algorithm outperforms two other algorithms in terms of all measurements. The rate-distortion curves show that the proposed algorithm achieves the same coding performance, yet reduces the computation requirement by up to 75%.

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Future Work The proposed Finter algorithm has been developed to achieve speed up for encoding P- and B- frames. The Finter algorithm produces competitive results to other algorithms recorded in the literatures. An integration for both proposed F intra and Finter algorithms has been done to attain a time of saving up to 86% without sacrificing both picture quality and bit rate efficiency.

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References [1] Andy C. Yu, Ngan King Ngi, and Graham Martin, Efficient Intra- and Inter-mode Selection Algorithms for H.264/AVC, in Journal of Visual Communication and Image Representation – Special Issue on Emerging H.264/AVC Video Coding Standard, vol. 17, issue 2, pp. 322-343, Elsevier Press, Apr 2006. [2]Andy C. Yu, Graham Martin, and Heechan Park, Improved Schemes for Inter-frame Coding in the H.264/AVC Standard, in Proc. of 12th IEEE Conference on Image Processing (ICIP) 05, vol. 2., pp. 902- 905, Genoa, Italy, Sep. 2005. [3]Andy C. Yu, Graham Martin, and Heechan Park, A Frequency Domain Approach to Intra Mode Selection in H.264/AVC, in Proc. of 13th European Signal Processing Conference (EUSIPCO) 05, 4pp., Antalya, Turkey, Sep. 2005 [4]Andy C. Yu and Graham Martin, Advanced Block Size Selection Algorithm for INTER frame Coding in H.264/AVC, in Proc. of 11th IEEE International Conference on Image Processing (ICIP) 04, vol. 1, pp.95- 98, Singapore, Oct 2004. [5]Andy C. Yu, Efficient Block Size Selection Algorithm for INTER frame Coding in H.264/AVC, in Proc. of 29th IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) 04, vol. 3, pp. 169-172, Montreal, Canada, May 2004. [6]F. Pan, X. Lin, et al., Fast mode decision algorithm for Intraprediction in H.264/AVC video coding, IEEE transaction on Circuits and Systems for Video Technology, pp. 813-823, Jul. 2005. [7]C. Kim, H. Shih, and C. Kuo, Fast H.264 Intra-prediction mode selection using joint spatial and transform domain features, Journal of Visual Communication and Image Representation, vol. 17, pp. 291-310, 2006. [8]__, Information technology – coding of audio visual objects – Part 10: advance video coding, ISO/IEC 14496-10:2003, Dec. 2003. [9]JVT reference software, JM6.1e, downloaded from http://bs.hhi.de/~suehring/http://bs.hhi.de/~suehring/

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