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Wyner-Ziv Coding of Motion Video

Wyner-Ziv Coding of Motion Video

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Wyner-Ziv Coding of Motion Video

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  1. Wyner-Ziv Coding of Motion Video

  2. Overview • Intraframe encoding with Interframe decoding • 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. Xi-1’ Interframe Decoder Intraframe Encoder Xi Xi’ Proposed codec Intraframe Encoding – Interframe Decoding • Dual System • Simpler encoder • Possibly complex decoder Wyner-Ziv Coding Side Information

  5. Slepian-Wolf and Wyner-Ziv Coding • Practical Codes • Coset encoding • [Pradhan and Ramchandran, 1999] • Trellis codes • [Wang and Orchard, 2001] • Turbo codes • [Garcia-Frias and Zhao, 2001], • [Bajcsy and Mitran, 2001] • [Aaron and Girod, 2002] • LDPC codes • [Liveris, Xiong, and Georghiades, 2002] • Practical Applications • [Pradhan and Ramchandran, 2001] • [Liveris, Xiong, and Georghiades, 2002] • [Jagmohan, Sehgal, and Ahuja, 2002]

  6. Even frame Reconstruction X’ X Y Wyner-Ziv Video Codec Interframe Decoder Intraframe Encoder Slepian-Wolf Codec Turbo Decoder Turbo Encoder Scalar Quantizer Buffer Request bits previous Interpolation Odd frames next • Even frames are encoded independently • Odd frames are known as side information at the decoder

  7. Even frame X RCPT-Based Slepian-Wolf Codec Slepian-Wolf Codec Decoded quantized symbols Turbo Decoder Turbo Encoder Scalar Quantizer Buffer Y2i Request bits Y • Uniform scalar quantizer – no coset grouping • RCPT Slepian-Wolf Codec • Flexibility for varying statistics • Embedded puncturing pattern • Bit rate controlled by decoder through feedback

  8. Side Information Y • Interpolation • Average same block from previous and next frame • Motion-compensated interpolation with symmetric motion vectors • Flexibility in design for decoder • Statistics between side information and current frame • Laplacian residual model • Estimate the Laplacian parameter at the decoder previous Interpolation Odd frames next

  9. Reconstruction Function Decoded quantized symbols Reconstruction X’ Y • Limits the magnitude of the reconstruction distortion • Need dithering to avoid contouring • Pixels reconstructed independently

  10. Simulation • Quantizer • 2, 4, 16 levels • Slepian-Wolf codec • Rate 4/5 Turbo code • Embedded puncturing pattern with period 8 • Pe<10-3 ~ 25 pixels per frame • Interpolation • Averaging • MC with symmetric motion vectors (SMV) • Rate-PSNR Comparison with H263+ • Intraframe coding • Interframe coding (B frames) with no motion compensation • Interframe coding (B frames) with motion compensation

  11. 8 dB 2 dB 6 dB Carphone Sequence

  12. 7 dB 4 dB 7 dB Foreman Sequence

  13. Foreman sequence After Wyner-Ziv Coding Side information SMV Interpolation 16-level quantization (~1 bpp)

  14. Sample Frame After Wyner-Ziv Coding Side information SMV Interpolation 16-level quantization (~1 bpp)

  15. Sample Frame After Wyner-Ziv Coding Side information Average Interpolation 16-level quantization (~1 bpp)

  16. Carphone sequence Wyner-Ziv Codec SMV Interpolation 384 kbps H263+ Intraframe Coding 410 kbps

  17. Conclusion • Use Wyner-Ziv coding for practical compression application • Used statistics of the source • New video system • Intraframe encoder – Interframe Decoder • Compared to H263+ • 2 to 7 dB better than Intraframe coding(i-i-i-i) • 5 to 8 dB worse than Interframe coding with MC(i-b-i-b) • Further improvements • Exploit spatial correlation • Acceptable symbol error rate