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Transform-domain Wyner-Ziv Codec for Video

Transform-domain Wyner-Ziv Codec for Video. Overview. Low-complexity video encoding Transform-domain Wyner-Ziv video codec Simulation results. Current video standards Interframe predictive coding for compression Encoder is 5-10 times more complex than decoder. Interframe Encoder.

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Transform-domain Wyner-Ziv Codec for Video

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  1. Transform-domain Wyner-Ziv Codec for Video

  2. Overview • Low-complexity video encoding • Transform-domain Wyner-Ziv video codec • Simulation results

  3. Current video standards Interframe predictive coding for compression Encoder is 5-10 times more complex than decoder Interframe Encoder Interframe Decoder Xi Xi’ Standard codec X’i-1 Interframe Video Compression

  4. Low-complexity encoding, possibly more complex decoding Applications: video sensors for surveillance, wireless PC cameras, mobile camera phones Xi-1’ Interframe Decoder Intraframe Encoder Xi Xi’ Proposed codec Low-complexity Video Coding Wyner-Ziv Coding Lossy source coding with decoder side information Side Information Similar work: [Puri and Ramachandran, Allerton 2002, ICASSP 2003, ICIP 2003]

  5. Slepian-Wolf Theorem Encoder Statistically dependent Decoder Encoder Statistically dependent Distributed Source Coding Wyner-Ziv Theorem Encoder Decoder

  6. Wyner-Ziv Pixel Video Codec Interframe Decoder Intraframe Encoder WZ frames Slepian-Wolf Codec Reconstruction Turbo Decoder Turbo Encoder Scalar Quantizer W W’ Buffer Request bits Side information Y Interpolation/ Extrapolation Key frames Conventional Intraframe decoding Conventional Intraframe coding K K’ [Aaron, Zhang, and Girod, Asilomar 2002] [Aaron, Rane, Zhang, and Girod, DCC 2003] [Aaron, Setton and Girod, ICIP 2003]

  7. DCT DCT bit-plane 2 bit-plane 1 Turbo Encoder Turbo Encoder level Quantizer level Quantizer Extract bit-planes Extract bit-planes Turbo Decoder Turbo Decoder Buffer Buffer Wyner-Ziv DCT Video Codec WZ frames Decoded WZ frames W’ W Intraframe Encoder Interframe Decoder IDCT Xk Xk’ qk qk’ Reconstruction … Request bits bit-plane Mk Side information Yk For each transform band k DCT Y Interpolation/ Extrapolation Interpolation/ Extrapolation Key frames Conventional Intraframe decoding Conventional Intraframe coding K K’

  8. 32 64 32 16 8 32 8 16 4 8 16 1 1 4 8 1 32 8 16 8 8 4 1 16 1 4 8 1 4 4 1 1 4 1 16 8 8 1 4 1 4 1 4 1 4 1 1 1 4 8 1 1 1 1 4 4 1 1 1 4 1 1 1 1 Quantizers • Each coefficient band is quantized using a scalar quantizer with levels. WZ frame W Mk = number of bit planes for kth coefficient band 4x4 DCT Xk For each transform band k • Combination of quantizers determines the bit allocation across bands. level Quantizer qk Sample quantizers: Values represent number quantization levels for coefficient band DC band Highest freq AC band

  9. bit-plane 1 bit-plane 2 RCPT-based Slepian-Wolf Codec Turbo Encoder Extract bit-planes Turbo Decoder qk qk’ Buffer … Request bits bit-plane Mk Yk • Bit planes of coefficients are encoded independently but decoded successively • Rate-compatible punctured turbo code (RCPT) • Flexibility for varying statistics • Bit rate controlled by decoder through feedback • Turbo decoder can perform joint-source channel decoding

  10. Flexible Side Information • To generate side information • Interpolation or extrapolation • With or without motion-compensation (MC) • Flexibility in design for decoder • Laplacian residual model between transform coefficients of side information and of current frame. Different Laplacian parameter for each coefficient band. Side information Y Interpolation/ Extrapolation Decoded frames

  11. 2 dB 11 dB Compression Performance • Mother and Daughter QCIF sequence • Alternating key frames and Wyner-Ziv frames (K-W-K-W) • Slepian-Wolf codec: Rate 4/5 Turbo code • Side information – • MC-Interpolation • MC-Extrapolation

  12. 3 dB 8 dB Compression Performance • Foreman QCIF sequence • Alternating key frames and Wyner-Ziv frames (K-W-K-W) • Slepian-Wolf codec: Rate 4/5 Turbo code • Side information – • MC-Interpolation • MC-Extrapolation

  13. Low-Complexity Side Information • To decrease complexity in generating side information • Average Interpolation • Previous frame copy • For low-motion sequences, minimal performance degradation • Transform-domain codec

  14. Low-Complexity Side Information

  15. Low-Complexity Side Information Side information Average Interpolation After Wyner-Ziv Coding 370 kbps

  16. H263+Intra vs WZ Codec H263+ Intraframe Coding 330 kbps, 32.9 dB Wyner-Ziv Codec 274 kbps, 39.0 dB WZ codec: Transfor-domain, side information using MC-Interpolation. Only WZ-frames shown

  17. H263+Inter vs WZ Codec H263+ I-B-I-B 145 kbps, 40.4 dB Wyner-Ziv Codec 156 kbps, 37.5 dB WZ codec: Transfor-domain, side information using MC-Interpolation. Only WZ-frames shown

  18. Conclusion • A new video compression system with intraframe encoding but interframe decoding • Low-complexity encoding for applications such as mobile camera phones and video surveillance networks, wireless PC cameras • Transform-domain codec performs up to 2 dB better than pixel-domain scheme • Compared to H.263+ • Up to 11 dB better than Intraframe coding • Performance gap from H.263+ interframe coding

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