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Brief Overview of Wyner-Ziv CODEC and Research Plan

Brief Overview of Wyner-Ziv CODEC and Research Plan. Jin-soo KIM. Contents. Overview of Wyner-Ziv CODEC Application of Wyner-Ziv CODEC Basic Principle of WZ CODEC Generation of S.I. at the Decoder How to Encode WZ frames Research Plan Q&A. Application of WZ CODEC. 2010.

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Brief Overview of Wyner-Ziv CODEC and Research Plan

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  1. Brief Overview of Wyner-Ziv CODEC and Research Plan Jin-soo KIM

  2. Contents • Overview of Wyner-Ziv CODEC • Application of Wyner-Ziv CODEC • Basic Principle of WZ CODEC • Generation of S.I. at the Decoder • How to Encode WZ frames • Research Plan • Q&A

  3. Application of WZ CODEC

  4. 2010 Coding Efficiency Network awareness + implementation? 2005 HDTV SVC H.264 2003 Mobile TV MPEG4 1999 Hand PC Video Conferencing MPEG2 H.263 Mobile Phone 1994 1992 MPEG1 Year Video coding : history and trends H.265(?) mobile • Mobile : 3low1high • Low (battery, bandwidth, CPU) • High cost

  5. (Conventional) Interframe Video Coding PredictiveInterframe Encoder PredictiveInterframe Decoder X’ Side Information

  6. Low Complexity Encoder Wyner-ZivIntraframe Encoder Wyner-ZivInterframe Decoder X’ Side Information [Witsenhausen, Wyner, 1980] [Puri, Ramchandran, Allerton 2002] [Aaron, Zhang, Girod, Asilomar 2002] …

  7. Applications of WZ codec • Light encoder and light decoder B. Girod, A. Aaron, S. Rane, D. Rebollo-Monedero, “Distributed video coding,” Proceedings of the IEEE, Vol93, pp71-83, Jan. 2005.

  8. Applications of WZ codechttp://www.discoverdvc.org/deliverables/Discover-D4.pdf • Wireless low power video surveillance • Disposable video cameras • Sensor network • Multi-view image acquisition • Medical applications • Networked camcoders

  9. Applications of WZ codechttp://www.discoverdvc.org/deliverables/Discover-D4.pdf • SensorCamPillCamWearableCamDisposable cam.ScanCam

  10. Basic Principle of WZ CODEC

  11. Lossless Compression with Side Information R≥ H(X|Y) Encoder Decoder Statistically dependent Side Information Wyner-Ziv showed that the conditional rate-mean squared error distortion function for X is the same whether the side information Y is available only at the decoder, or both at the encoder and the decoder. R≥ H(X|Y) Encoder Decoder Statistically dependent [Slepian, Wolf, 1973] Side Information

  12. Shannon Theory with side info. • Example) x : dice number • H(X) = 6Σlog26 = 2.58 bits • Shannon coding theorem • No error, if H(X) < R(X) = 3 bits • If R(X) = 2, {00,01,10,11}{1,2,{3,4},{5,6}} • With side information Y=“even number” • H(X|Y) = 3Σlog23 = 1.58 < R(X|Y) = 2 Information loss X X R decoder encoder Y

  13. Wyner-Ziv coding (lossy) • A. Majumdar, R. Puri, P. Ishwar, K. Ramchandran, “Complexity/performance trade-offs for robust distributed video coding,” IEEE ICIP2005, Vol. 2,  pp678-81, 11-14 Sept. 2005 • WZ = quantization + Slepian-Wolf • Random coset partitioning operation, • 3bit-info can be represented by 2bit(LSB first  increase Δ) • X : original value U : quantized value • Y : side information in the decoder • given Y + sent 10U=101

  14. History of DVC • Slepian and Wolf : lossless DVC (1973) • “Noiseless coding of correlated information sources,” IEEE Tr. On Information Theory, 1973. • Wyner and Ziv : lossy DVC (1976) • “The rate-distortion function for source coding with side information at the decoder,” IEEE Tr. Information Theory, 1976. • Ramchandran in Berkeley : PRISM (2002) • Power-efficient, Robust, hIgh-compression, Syndrome-based Multimedia coding • Girod in Stanford : Good review (2005) • “Distributed video coding,” IEEE Proceedings, 2005. • EU : DISCOVER(~2006), www.discoverdvc.org • DIStributed COding for Video sERvices

  15. Towards Practical Slepian-Wolf Coding • Convolution coding for data compression [Blizard, 1969] • Convolutional source coding [Hellman, 1975] • Syndrome source coding [Ancheta, 1976] • Coset codes [Pradhan and Ramchandran, 1999] • Trellis codes [Wang and Orchard, 2001] • Turbo codes [García-Frías and Zhao, 2001] [Bajcsy and Mitran, 2001] [Aaron and Girod, 2002] • LDPC codes [Liveris, Xiong, and Georghiades, 2002] • . . . • . . .

  16. Generation of S.I. at the Decoder

  17. Motion Compensation • Motion-compensated interpolation (MC-I)using the decoded Key frame at time t-1 & t+1

  18. Side Information

  19. Motion Compensation • Motion-compensated extrapolation (MC-E)estimate the motion between the Wyner-ziv frame at time t-2 and the Key frame at time t-1

  20. Side Information

  21. Motion Compensation

  22. How to Encode WZ frames

  23. Wyner-Ziv Residual Video Codec WZ frames X’ WZ Decoder WZ Encoder W X Xer Xer Y • Residual of a frame with respect to an encoder reference frame (Xer) is fed into a Wyner-Ziv encoder. To avoid drift, Xer should be replicable at the decoder. • Since the decoder takes into account motion, Y is expected to be a better estimate of frame X than Xer. The Wyner-Ziv decoder uses both Y and Xer to calculate the reconstruction X’. [Aaron, Zhang, Girod, Asilomar 2002]

  24. Pixel-Domain Wyner-Ziv Video Codec Interframe Decoder Intraframe Encoder Slepian-Wolf Codec WZ frames Reconstruction Turbo Decoder Turbo Encoder W’ Scalar Quantizer W Buffer Request bits Side information Y Interpolation/ Extrapolation Key frames Conventional Intraframe decoding Conventional Intraframe coding I I’ [Aaron, Zhang, Girod, Asilomar 2002]

  25. Pixel-Domain Wyner-Ziv Video Codec After Wyner-Ziv Decoding Decoder side informationgenerated by motion-compensated interpolationPSNR 24.8 dB 16-level quantization – 2.0 bpp0 pixels in errorPSNR 36.5 dB [Aaron, Zhang, Girod, Asilomar 2002]

  26. DCT-Domain Wyner-Ziv Video Codec Intraframe Encoder Interframe Decoder WZ frames Dk Dk’ Turbo Encoder Recon Scalar Quantizer Turbo Decoder W W’ DCT IDCT Buffer Request bits Side information Yk For each transform band k DCT Y Interpolation/ Extrapolation Key frames Conventional Intraframe coding I Conventional Intraframe decoding I’ [Aaron, Zhang, Girod, Asilomar 2003]

  27. Interframe 100% 3 dB 6 dB Rate-Distortion Performance - Salesman Encoder Runtime Pentium 1.73 GHz machine • Every 8th frame is a key frame • Salesman QCIF sequence at 10fps • 100 frames [Aaron, Zhang, Girod, Asilomar 2003]

  28. Salesman at 10 fps DCT-based Intracoding 149 kbps PSNRY=30.0 dB Wyner-Ziv DCT codec 152 kbps PSNRY=35.6 dB GOP=8 [Aaron, Zhang, Girod, Asilomar 2003]

  29. Conclusion • Increase efficiency of DVC • Reduce H(X) : simple ME/MC? • Increase H(Y) : better interpolation/extrapolation • Stronger correlation between X and Y. X X R encoder decoder Y X? Y? P(X/Y)

  30. Conclusion • Distributed coding is a fundamentally new paradigm for video compression • Slepian-Wolf encoding, is fundamentally harder for practical applications due to the general statistics of the correlation channel • The rate-distortion performance of Wyner-Ziv coding does not yet reach the performance of conventional interframe coder • It is unlikely that distributed video coding algorithm will ever beat conventional video coding schemes in R-D performance • Many authors believe that distributed coding techniques will soon complement conventional video coding to provide the best overall system performance and enable novel applications

  31. Research Plan (with M.S. Vidhya Murthy)

  32. Research Plan Plan ■ Planand achievements done Now

  33. Q&A Thank you

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