EE368b Project

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EE368b Project

• Evaluation of search strategies
• for block matching
• Marcus Isaksson
• Joakim Jalden

Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
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Block matching

• Main goals of a block matching scheme
• Find best match for any given block
• Minimize number of block comparisons
• Contradictory goals

Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
3
Presentation overview

• Distortion function
• Search strategies
• Test data
• Algorithm performance
• Conclusions

Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
4
Distortion measurement

• Mean square error

• Bilinear interpolation is used for non-integer
  values of i and j.

Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
5
Search strategies

• Full search
• 2D logarithmic search
• Jain J.R., Jain A.K., 1981
• Conjugate direction search
• Srinivasan R., Rao K.R., 1985

Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
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Conjugate direction search
Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
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Description of test data

• Suzie1
• Frames 47-52 from the suzie qcif sequence
• Limited motion in parts of the image, different
  directions
• Foreman
• Frames 308-313 from the foreman qcif sequence
• Panning camera, large motion over the whole image

Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
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Suzie1
Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
9
Foreman
Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
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Distortion function
Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
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Choosing a start point for the search

• Use motion vectors from adjacent blocks

Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
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Results
Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
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Results
Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson
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Conclusions

• Major speedups compared to full search
• Number of block comparisons reduced by a factor
  100 for integer pel
• 500 for quarter pel
• Conjugate direction with memory is the fastest
  strategy, but sensitive to selection of start
  point
• If time is not a problem choose full search

Evaluation of search strategies for block matching
Joakim Jald?n and Marcus Isaksson