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Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience. Overview. Distributed Source Coding Intraframe Encoding with Interframe Decoding Systematic Lossy Forward Error Protection. Slepian-Wolf Theorem. Encoder. Statistically dependent. Decoder. Encoder.

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Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience

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  1. Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience

  2. Overview • Distributed Source Coding • Intraframe Encoding with Interframe Decoding • Systematic Lossy Forward Error Protection

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

  4. Practical Distributed Source 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] • Applications • Image and Video [Pradhan and Ramchandran, 2001] [Liveris, Xiong, and Georghiades, 2002] [Jagmohan, Sehgal, and Ahuja, 2002] [Puri and Ramchandran, 2002] [Aaron, Zhang and Girod, 2002] • Sensor Networks [Chou, Petrovic and Ramchandran, 2002]

  5. Slepian-Wolf Codec Turbo Encoder Turbo Decoder Wyner-Ziv Video Codec Wyner-Ziv Decoder Wyner-Ziv Encoder Reconstruction X Scalar Quantizer X’ Y

  6. Xi-1’ Xi Xi’ Wyner-Ziv Coding for Compression • Compression for mobile video cameras • Simple encoder • Possibly complex decoder Intraframe Encoder Interframe Decoder Wyner-Ziv Coding Side Information

  7. Interframe Decoder Intraframe Encoder Slepian-Wolf Codec Even frame Reconstruction Turbo Decoder Turbo Encoder Scalar Quantizer Buffer X’ X Request bits Y previous Interpolation Odd frames next Intraframe Encoder - Interframe Decoder • Limits reconstruction distortion based on quantizer coarseness • Very simple encoder • Turbo code can perform joint source-channel decoding • Decoder controls rate and generates side information

  8. 7 dB 4 dB 7 dB Rate-PSNR Plots compared to H.263+ • Foreman QCIF sequence • Uniform {2, 4, 16} level quantizers • Slepian-Wolf codec • Rate 4/5 Turbo code • Pe<10-3 ~ 25 pixels per frame • Interpolation – MC with symmetric motion vectors

  9. 8 dB 2 dB 6 dB Rate-PSNR Plots compared to H.263+ • Carphone QCIF sequence • Uniform {2, 4, 16} level quantizers • Slepian-Wolf codec • Rate 4/5 Turbo code • Pe<10-3 ~ 25 pixels per frame • Interpolation – MC with symmetric motion vectors

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

  11. Sample Frame (Foreman) After Wyner-Ziv Coding Side information 16-level quantization (~1 bpp)

  12. Carphone Sequence Wyner-Ziv Codec 384 kbps H263+ Intraframe Coding 410 kbps

  13. Wyner-Ziv Coding for Error Resilience • Conventional Forward Error Correction (FEC) • Protects the bit stream representing the video signal • “Lossless” correction • For graceful degradation, needs layered representation of video • Systematic Lossy Forward Error Protection

  14. Reconstruction Turbo Encoder Turbo Decoder Scalar Quantizer S* Wyner-Ziv Encoder Wyner-Ziv Decoder Systematic Lossy Forward Error Protection • Protects the original video waveform • “Lossy” protection • For graceful degradation, does not require layered representation of video MPEG Encoder MPEG Decoder with Error Concealment S S’ Error-Prone channel

  15. Results Carphone CIF Sequence H.26L encoding at 1 Mbps 1% macroblock loss Error-free Wyner-Ziv bits 4 and 16 level quantization Rate 4/5 turbo code Pe<10-3 ~ 100 pixels per frame

  16. Carphone Sequence With forward error protection of 1.5 bpp 1% macroblock loss 38 dB No Error Protection 1% macroblock loss 33 dB

  17. Wyner-Ziv Decoder A Wyner-Ziv Encoder A S* Wyner-Ziv Decoder B Wyner-Ziv Encoder B S** Embedded Wyner-Ziv Codec MPEG Encoder MPEG Decoder with Error Concealment • Graceful degradation • Does not require layered representation S S’ Error-Prone channel

  18. Conclusions • Wyner-Ziv coding for two video applications • Intraframe encoder-Interframe decoder • Very simple encoder • Performs up to 2 - 7 dB better than H.263+ intraframe coding • Systematic Lossy Forward Error Protection • Protects the video waveform • Backward compatible • Can achieve graceful degradation without layered representation

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