Wyner-Ziv Coding of Motion Video

1
Wyner-Ziv Coding of Motion Video
2
Overview

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

3
Interframe Video Compression

• Current video standards
• Interframe predictive coding for compression
• Encoder is 5-10 times more complex than decoder

4
Intraframe Encoding Interframe Decoding

• Dual System
• Simpler encoder
• Possibly complex decoder

Wyner-Ziv Coding
Side Information
5
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

6
Wyner-Ziv Video Codec
Interframe Decoder
Intraframe Encoder
Slepian-Wolf Codec
Turbo Decoder
Turbo Encoder
Scalar Quantizer
Buffer
Request bits
previous
Interpolation
Odd frames
next

• Even frames are encoded independently
• Odd frames are known as side information at the
  decoder

7
RCPT-Based Slepian-Wolf Codec
Slepian-Wolf Codec
Decoded quantized symbols
Turbo Decoder
Turbo Encoder
Scalar Quantizer
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

8
Side Information
Y
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

9
Reconstruction Function
Decoded quantized symbols
Reconstruction
X
Y

• Limits the magnitude of the reconstruction
  distortion
• Need dithering to avoid contouring
• Pixels reconstructed independently

10
Simulation

• Quantizer
• 2, 4, 16 levels
• Slepian-Wolf codec
• Rate 4/5 Turbo code
• Embedded puncturing pattern with period 8
• Pelt10-3 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

11
Carphone Sequence
12
Foreman Sequence
13
Foreman sequence
After Wyner-Ziv Coding
Side information SMV Interpolation
16-level quantization (1 bpp)
14
Sample Frame
After Wyner-Ziv Coding
Side information SMV Interpolation
16-level quantization (1 bpp)
15
Sample Frame
After Wyner-Ziv Coding
Side information Average Interpolation
16-level quantization (1 bpp)
16
Carphone sequence
Wyner-Ziv Codec SMV Interpolation 384 kbps
H263 Intraframe Coding 410 kbps
17
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