1 Department of Electrical Engineering, Stanford University Anne Aaron, Shantanu Rane, Rui Zhang and Bernd Girod Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Overview  Distributed Source Coding  Intraframe Encoding with Interframe Decoding  Systematic Lossy Forward Error Protection

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Distributed Source Coding Encoder Decoder Statistically dependent Slepian-Wolf Theorem Encoder Decoder Wyner-Ziv Theorem Statistically dependent

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, 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]

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Wyner-Ziv Video Codec Wyner-Ziv Decoder Scalar Quantizer X Wyner-Ziv Encoder Reconstruction X’ Y Turbo Encoder Turbo Decoder Slepian-Wolf Codec

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Wyner-Ziv Coding for Compression Interframe Decoder Intraframe Encoder XiXi X i-1 ’Xi’Xi’ Wyner-Ziv Coding Side Information Compression for mobile video cameras  Simple encoder  Possibly complex decoder

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Intraframe Encoder - Interframe Decoder Reconstruction X’ Y Interframe Decoder Scalar Quantizer Turbo Encoder Buffer Even frame X Intraframe Encoder Turbo Decoder Request bits Slepian-Wolf Codec Interpolation Odd frames previous next 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

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Rate-PSNR Plots compared to H dB 4 dB 7 dB Foreman QCIF sequence Uniform {2, 4, 16} level quantizers Slepian-Wolf codec  Rate 4/5 Turbo code  P e <10 -3 ~ 25 pixels per frame Interpolation – MC with symmetric motion vectors

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Rate-PSNR Plots compared to H.263+ Carphone QCIF sequence Uniform {2, 4, 16} level quantizers Slepian-Wolf codec  Rate 4/5 Turbo code  P e <10 -3 ~ 25 pixels per frame Interpolation – MC with symmetric motion vectors 6 dB 2 dB 8 dB

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Foreman sequence Side information After Wyner-Ziv Coding 16-level quantization (~1 bpp)

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Sample Frame (Foreman) Side information After Wyner-Ziv Coding 16-level quantization (~1 bpp)

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Carphone Sequence H263+ Intraframe Coding 410 kbps Wyner-Ziv Codec 384 kbps

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, 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

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Systematic Lossy Forward Error Protection MPEG Encoder MPEG Decoder with Error Concealment Error-Prone channel S S’ Wyner-Ziv Decoder Scalar Quantizer Wyner-Ziv Encoder Reconstruction Turbo Encoder Turbo Decoder S*S* Protects the original video waveform “Lossy” protection For graceful degradation, does not require layered representation of video

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, 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 P e <10 -3 ~ 100 pixels per frame

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Carphone Sequence No Error Protection 1% macroblock loss 33 dB With forward error protection of 1.5 bpp 1% macroblock loss 38 dB

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Embedded Wyner-Ziv Codec MPEG Encoder MPEG Decoder with Error Concealment Error-Prone channel S S’ Wyner-Ziv Decoder A S*S* Wyner-Ziv Encoder A Wyner-Ziv Decoder B S ** Wyner-Ziv Encoder B Graceful degradation Does not require layered representation

Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience March 25, Conclusions Wyner-Ziv coding for two video applications Intraframe encoder-Interframe decoder  Very simple encoder  Performs up to 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