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Department of Electrical Engineering,Stanford University
Anne Aaron, Rui Zhang and Bernd Girod
Wyner-Ziv Coding of Motion Video
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Overview
Intraframe encoding with Interframe decoding
Wyner-Ziv Video Codec Simulation Results
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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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
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Intraframe Encoding – Interframe Decoding
Interframe Decoder
Intraframe EncoderXi
Xi-1’
Xi’
Proposed codecWyner-Ziv Coding
Side Information
• Dual SystemSimpler encoderPossibly complex
decoder
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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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]
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Wyner-Ziv Video Codec
Interframe Decoder
• Even frames are encoded independently• Odd frames are known as side information at the decoder
Scalar Quantizer
Turbo Encoder
Buffer
Even frameX
Intraframe Encoder
Turbo Decode
r
Request bits
Slepian-Wolf Codec
Interpolation
Reconstruction X’
Y
Odd frames
previous
next
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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RCPT-Based Slepian-Wolf Codec
Y2iScalar
QuantizerTurbo
EncoderBuffer Turbo
Decoder
Request bits
Slepian-Wolf Codec
• Uniform scalar quantizer – no coset grouping• RCPT Slepian-Wolf Codec
Flexibility for varying statisticsEmbedded puncturing patternBit rate controlled by decoder through feedback
Decoded quantizedsymbols
Y
Even frameX
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Side Information
• Interpolation Average same block from previous and next frameMotion-compensated interpolation with symmetric motion
vectors• Flexibility in design for decoder • Statistics between side information and current frame
Laplacian residual modelEstimate the Laplacian parameter at the decoder
Interpolation
Y
Odd frames
previous
next
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Reconstruction Function
•Limits the magnitude of the reconstruction distortion
•Need dithering to avoid contouring
•Pixels reconstructed independently
Reconstruction X’
Y
Decoded quantizedsymbols
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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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
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Carphone Sequence
6 dB
2 dB
8 dB
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Foreman Sequence
7 dB
4 dB
7 dB
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Foreman sequence
Side information SMV Interpolation
After Wyner-Ziv Coding16-level quantization (~1 bpp)
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Sample Frame
Side information SMV Interpolation
After Wyner-Ziv Coding16-level quantization (~1 bpp)
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Sample Frame
Side information Average Interpolation
After Wyner-Ziv Coding16-level quantization (~1 bpp)
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Carphone sequence
H263+ Intraframe Coding 410 kbps
Wyner-Ziv Codec SMV Interpolation
384 kbps
Aaron, Zhang, Girod: Wyner-Ziv Coding of Motion Video November 4, 2002
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Conclusion
• Use Wyner-Ziv coding for practical compression applicationUsed statistics of the source
• New video system Intraframe encoder – Interframe Decoder
• Compared to H263+2 to 7 dB better than Intraframe coding5 to 8 dB worse than Interframe coding with MC
• Further improvementsExploit spatial correlationAcceptable symbol error rate