Joint Compression Scheme

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Joint Compression Scheme

• Vijay Chandrasekhar
• Louis Chen
• Gabriel Takacs
• Stanford University
• EE398A Final Project
• 13 March 2007

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Outline

• Motivation and Problem Statement
• System Overview
• Codebook
• Encoder
• Decoder
• Results
• Summary

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Packard Exterior
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Problem Statement

• Find a scheme to exploit inter-image redundancy
  to achieve better compression
• Scheme should be random-access

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Packard Lab
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Midtown
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System Overview
Image Set
Codebook Generator
Encoder
File System
Decoder
Joint Compression Scheme (JCS)
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Codebook Generator
For each block
For each code-block
MSE
Image Set
yes
lt thresh
Codes Left?
no
yes
no
Add Block
Codebook
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Sample Codebooks
Packard Exterior
Midtown
Packard Lab
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Encoder
Image
For each block
Intra
Residual
Shift Block
Best Match (MSE)
R-D Switch
Coded Block
Predict
Copy
Codebook
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The Rate-Distortion Switch

• Rate for All Modes
• Mode (run-length coding)
• Codebook storage (lossless coding)
• Predict-Mode Rate
• X offset, Y offset
• Codeword
• DCT coefficients of residual
• Intra-Mode Rate
• DCT coefficients
• Copy-Mode Rate
• X offset, Y offset
• Codeword

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Decoder
Decoded Block
Intra
Predict
Mode Switch

Coded Block
Copy
Shift Block
Codebook
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Packard Exterior Results
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Asymptotic Overhead
0.3 Bits/Pixel
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Packard Lab Results
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Midtown Results
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JCS vs. JPEG Example
JCS 3.4623 bpp
JPEG 3.3070 bpp
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JCS vs. JPEG Example
JCS 3.4623 bpp
JPEG 3.3070 bpp
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JCS vs. JPEG Example
JCS 3.4623 bpp
JPEG 3.3070 bpp
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JCS vs. JPEG Example
JCS 2.6419 bpp
JPEG 2.7209 bpp
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JCS vs. JPEG Example
JCS 1.9961 bpp
JPEG 2.0276 bpp
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JCS vs. JPEG Example
JCS 1.2215 bpp
JPEG 1.2107 bpp
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JCS vs. JPEG Example
JCS 0.5289 bpp
JPEG 0.5334 bpp
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JCS vs. JPEG Example
JCS 0.2348 bpp
JPEG 0.2360 bpp
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JCS vs. JPEG Example
JCS 0.2348 bpp
JPEG 0.2360 bpp
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JCS vs. JPEG Example
JCS 0.2348 bpp
JPEG 0.2360 bpp
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JCS vs. JPEG Example
JCS 0.18295 bpp
JPEG 0.1818 bpp
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JCS vs. JPEG Example
JCS 0.14009 bpp
JPEG 0.1318 bpp
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JCS vs. JPEG Example
JCS 0.14009 bpp
JPEG 0.1318 bpp
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JCS vs. JPEG Example
JCS 0.14009 bpp
JPEG 0.1318 bpp
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Block Size Trade-Off
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Codebook Size Trade-Off
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Explanation of Slope
Copy block Non-copy block
Packard Exterior
Expending 1 bit reduces distortion by equivalent
of 1/p bits!
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JPEG-2000 Comparison
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Video Coder Comparison
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Summary

• Exploit redundancy across images
• R-D switch is vital to achieve gains
• At high rates up to 20 gain over intra-coding
• Block-size sweet-spot at 16x16
• Larger gains at high rate for larger codebook
• Low rates suffer from overhead
• No significant gain from pel or sub-pel offsets

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Thank You
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Entropy vs. Run-length
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Offset Trade-Off