Wyner-Ziv Coding of Motion Video

Overview Intraframe encoding with Interframe decoding Wyner-Ziv Video Codec Simulation Results

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

Intraframe Encoding – Interframe Decoding Dual System Simpler encoder Possibly complex decoder Interframe Decoder Intraframe Encoder Xi Xi-1’ Xi’ Proposed codec Wyner-Ziv Coding Side Information

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] [Jagmohan, Sehgal, and Ahuja, 2002]

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

RCPT-Based Slepian-Wolf Codec Even frame X Decoded quantized symbols Scalar Quantizer Turbo Encoder Turbo Decoder 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

Side Information Y Interpolation previous Interpolation Odd frames next 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

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

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

Carphone Sequence 6 dB 2 dB 8 dB

Foreman Sequence 7 dB 4 dB

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

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

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

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

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 5 to 8 dB worse than Interframe coding with MC Further improvements Exploit spatial correlation Acceptable symbol error rate