Transcript Mobile, Multimedia and Beyond

Wyner-Ziv Coding for Video:
Applications to Compression and
Error Resilience
Anne Aaron, Shantanu Rane,
Rui Zhang and Bernd Girod
Department of Electrical Engineering,
Stanford University
1
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, 2003
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Distributed Source Coding
Encoder
X
Statistically
dependent
Decoder
Encoder
Y
Slepian-Wolf Theorem
RX
X , Y 
Encoder
Statistically
dependent
RX  H ( X | Y )
RY  H (Y | X )
RY
RWZ
X |Y (d )
X
RX  RY  H ( X , Y )
Decoder
X
Wyner-Ziv Theorem
RWZ
X |Y (d )  RX |Y (d )
Y
Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience
March 25, 2003
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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, 2003
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Wyner-Ziv Video Codec
Wyner-Ziv Encoder
Wyner-Ziv Decoder
Slepian-Wolf Codec
X
Scalar
Quantizer
Turbo
Encoder
Turbo
Decoder
Reconstruction
X’
Y
Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience
March 25, 2003
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Wyner-Ziv Coding for Compression
• Compression for mobile
video cameras
 Simple encoder
 Possibly complex
decoder
Xi
Intraframe
Encoder
Interframe
Decoder
Xi’
Xi-1’
Wyner-Ziv Coding
Side Information
Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience
March 25, 2003
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Intraframe Encoder - Interframe Decoder
Interframe Decoder
Intraframe Encoder
Slepian-Wolf Codec
Even
frame
Scalar
Quantizer
Buffer
Turbo
Decoder
Reconstruction
Request
bits
X
Turbo
Encoder
Y
previous
Odd
frames
•
•
•
•
X’
Interpolation
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, 2003
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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
7 dB
4 dB
7 dB
Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience
March 25, 2003
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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
8 dB
2 dB
6 dB
Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience
March 25, 2003
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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, 2003
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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, 2003
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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, 2003
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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, 2003
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S
MPEG Encoder
Scalar
Quantizer
Turbo
Encoder
Wyner-Ziv Encoder
Error-Prone channel
Systematic Lossy Forward Error Protection
MPEG Decoder with
Error Concealment
S’
Turbo
Decoder
S*
Reconstruction
Wyner-Ziv Decoder
• 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
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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
Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience
March 25, 2003
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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, 2003
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Embedded Wyner-Ziv Codec
MPEG Decoder with
Error Concealment
MPEG Encoder
Wyner-Ziv
Encoder A
Error-Prone channel
S
Wyner-Ziv
Encoder B
S’
Wyner-Ziv
Decoder A
S*
Wyner-Ziv
Decoder B
S**
• Graceful degradation
• Does not require layered representation
Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience
March 25, 2003
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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
Wyner-Ziv Coding for Video: Applications to Compression and Error Resilience
March 25, 2003
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