Brief Overview of WynerZiv CODEC and Research Plan

1
Brief Overview of Wyner-Ziv CODEC and Research
Plan
Jin-soo KIM
2
Contents

• Overview of Wyner-Ziv CODEC
• Application of Wyner-Ziv CODEC
• Basic Principle of WZ CODEC
• Generation of S.I. at the Decoder
• How to Encode WZ frames
• Research Plan
• QA

3

• Application of WZ CODEC

4
Video coding history and trends
H.265(?)
mobile

• Mobile 3low1high
• Low (battery, bandwidth, CPU)
• High cost

5
(Conventional) Interframe Video Coding
PredictiveInterframe Encoder
PredictiveInterframe Decoder
X
Side Information
6
Low Complexity Encoder
Wyner-ZivIntraframe Encoder
Wyner-ZivInterframe Decoder
X
Side Information
Witsenhausen, Wyner, 1980 Puri, Ramchandran,
Allerton 2002 Aaron, Zhang, Girod, Asilomar
2002
7
Applications of WZ codec

• Light encoder and light decoder
• B. Girod, A. Aaron, S. Rane, D.
  Rebollo-Monedero, Distributed video coding,
  Proceedings of the IEEE, Vol93, pp71-83, Jan.
  2005.

8
Applications of WZ codechttp//www.discoverdvc.or
g/deliverables/Discover-D4.pdf

• Wireless low power video surveillance
• Disposable video cameras
• Sensor network
• Multi-view image acquisition
• Medical applications
• Networked camcoders

9
Applications of WZ codechttp//www.discoverdvc.or
g/deliverables/Discover-D4.pdf

• SensorCam?PillCam?WearableCam?Disposable
  cam.?ScanCam

10

• Basic Principle of WZ CODEC

11
Lossless Compression with Side Information
Wyner-Ziv showed that the conditional
rate-mean squared error distortion function for X
is the same whether the side information Y is
available only at the decoder, or both at the
encoder and the decoder.
12
Shannon Theory with side info.

• Example) x dice number
• H(X) 6Slog26 2.58 bits
• Shannon coding theorem
• No error, if H(X) lt R(X) 3 bits
• If R(X) 2, 00,01,10,11?1,2,3,4,5,6
• With side information Yeven number
• H(XY) 3Slog23 1.58 lt R(XY) 2

Information loss
13
Wyner-Ziv coding (lossy)

• A. Majumdar, R. Puri, P. Ishwar, K. Ramchandran,
  Complexity/performance trade-offs for robust
  distributed video coding, IEEE ICIP2005, Vol.
  2,  pp678-81, 11-14 Sept. 2005
• WZ quantization Slepian-Wolf
• Random coset partitioning operation,
• 3bit-info can be represented by 2bit (LSB first ?
  increase ?)
• X original value U quantized value
• Y side information in the decoder
• given Y sent 10?U101

14
History of DVC

• Slepian and Wolf lossless DVC (1973)
• Noiseless coding of correlated information
  sources, IEEE Tr. On Information Theory, 1973.
• Wyner and Ziv lossy DVC (1976)
• The rate-distortion function for source coding
  with side information at the decoder, IEEE Tr.
  Information Theory, 1976.
• Ramchandran in Berkeley PRISM (2002)
• Power-efficient, Robust, hIgh-compression,
  Syndrome-based Multimedia coding
• Girod in Stanford Good review (2005)
• Distributed video coding, IEEE Proceedings,
  2005.
• EU DISCOVER(2006), www.discoverdvc.org
• DIStributed COding for Video sERvices

15
Towards Practical Slepian-Wolf Coding

• Convolution coding for data compression Blizard,
  1969
• Convolutional source coding Hellman, 1975
• Syndrome source coding Ancheta, 1976
• Coset codes Pradhan and Ramchandran, 1999
• Trellis codes Wang and Orchard, 2001
• Turbo codes
• García-Frías and Zhao, 2001
• Bajcsy and Mitran, 2001
• Aaron and Girod, 2002
• LDPC codes Liveris, Xiong, and Georghiades,
  2002
• . . .
• . . .

16

• Generation of S.I. at the Decoder

17
Motion Compensation

• Motion-compensated interpolation (MC-I)using the
  decoded Key frame at time t-1 t1

18
Side Information
19
Motion Compensation

• Motion-compensated extrapolation (MC-E)estimate
  the motion between the Wyner-ziv frame at time
  t-2 and the Key frame at time t-1

20
Side Information
21
Motion Compensation
22

• How to Encode WZ frames

23
Wyner-Ziv Residual Video Codec
WZ frames
X
WZ Encoder
WZ Decoder
W
X
Xer
Xer
Y

• Residual of a frame with respect to an encoder
  reference frame (Xer) is fed into a Wyner-Ziv
  encoder. To avoid drift, Xer should be
  replicable at the decoder.
• Since the decoder takes into account motion, Y is
  expected to be a better estimate of frame X than
  Xer. The Wyner-Ziv decoder uses both Y and Xer
  to calculate the reconstruction X.

Aaron, Zhang, Girod, Asilomar 2002
24
Pixel-Domain Wyner-Ziv Video Codec
Interframe Decoder
Intraframe Encoder
Slepian-Wolf Codec
WZ frames
Reconstruction
Turbo Encoder
Turbo Decoder
Scalar Quantizer
W
W
Buffer
Request bits
Side information
Y
Interpolation/ Extrapolation
Key frames
Conventional Intraframe decoding
Conventional Intraframe coding
I
I
Aaron, Zhang, Girod, Asilomar 2002
25
Pixel-Domain Wyner-Ziv Video Codec
After Wyner-Ziv Decoding
Decoder side informationgenerated by
motion-compensated interpolationPSNR 24.8 dB
16-level quantization 2.0 bpp0 pixels in
errorPSNR 36.5 dB
Aaron, Zhang, Girod, Asilomar 2002
26
DCT-Domain Wyner-Ziv Video Codec
Interframe Decoder
Intraframe Encoder
WZ frames
Dk
Dk
Recon
Scalar Quantizer
Turbo Encoder
Turbo Decoder
W
W
IDCT
DCT
Buffer
Request bits
Side information
Yk
For each transform band k
DCT
Y
Interpolation/ Extrapolation
Key frames
Conventional Intraframe coding
I
Conventional Intraframe decoding
I
Aaron, Zhang, Girod, Asilomar 2003
27
Rate-Distortion Performance - Salesman
Encoder Runtime
Pentium 1.73 GHz machine

• Every 8th frame is a key frame
• Salesman QCIF sequence at 10fps
• 100 frames

Aaron, Zhang, Girod, Asilomar 2003
28
Salesman at 10 fps
DCT-based Intracoding 149 kbps PSNRY30.0 dB
Wyner-Ziv DCT codec 152 kbps PSNRY35.6 dB
GOP8
Aaron, Zhang, Girod, Asilomar 2003
29
Conclusion

• Increase efficiency of DVC
• Reduce H(X) simple ME/MC?
• Increase H(Y) better interpolation/extrapolation
  
• Stronger correlation between X and Y.

30
Conclusion

• Distributed coding is a fundamentally new
  paradigm for video compression
• Slepian-Wolf encoding, is fundamentally harder
  for practical applications due to the general
  statistics of the correlation channel
• The rate-distortion performance of Wyner-Ziv
  coding does not yet reach the performance of
  conventional interframe coder
• It is unlikely that distributed video coding
  algorithm will ever beat conventional video
  coding schemes in R-D performance
• Many authors believe that distributed coding
  techniques will soon complement conventional
  video coding to provide the best overall system
  performance and enable novel applications

31

• Research Plan (with M.S. Vidhya Murthy)

32
Research Plan
Plan
Plan and achievements
done
Now
33

• QA
• Thank you