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EE368b Project

This project evaluates various search strategies for block matching in image processing, aimed at optimizing the match-finding process while minimizing block comparisons. It discusses the main goals, including the use of distortion functions, mean square error, and bilinear interpolation for non-integer values. The presentation covers the effectiveness of full search, 2D logarithmic search, and conjugate direction search strategies, using test data from the Suzie and Foreman sequences. Key findings highlight significant speed improvements with reduced block comparisons, emphasizing practical applications in real-time encoding.

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EE368b Project

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  1. 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

  2. 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

  6. Conjugate direction search Evaluation of search strategies for block matching Joakim Jald₫n and Marcus Isaksson

  7. 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

  8. 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

  10. Distortion function Evaluation of search strategies for block matching Joakim Jald₫n and Marcus Isaksson

  11. 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

  12. Results Evaluation of search strategies for block matching Joakim Jald₫n and Marcus Isaksson

  13. Results Evaluation of search strategies for block matching Joakim Jald₫n and Marcus Isaksson

  14. 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

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