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Short-term CV Motion Prediction and its use in long term motion compensation

Short-term CV Motion Prediction and its use in long term motion compensation. Stanford University EE398 Final Project Zhengyun Zhang, Dileep George Winter 2005. Overview. Problem Formulation Short-term Constant Velocity Predictor Results Conclusions. Problem Formulation.

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Short-term CV Motion Prediction and its use in long term motion compensation

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  1. Short-term CV Motion Predictionand its use in long term motion compensation Stanford University EE398 Final Project Zhengyun Zhang, Dileep George Winter 2005

  2. Overview • Problem Formulation • Short-term Constant Velocity Predictor • Results • Conclusions

  3. Problem Formulation • New codecs (e.g. H.264/AVC) can use long-term motion compensation to increase coding gain • Computationally expensive, O(NxM2xD) • N macro-blocks • ~M length of average motion vector • D frames to search • Can we find a more efficient algorithm?

  4. Short-term Constant Velocity Model • Objects in motion tend to not change in velocity drastically • Short term velocity approximately constant • Predictor can follow this model

  5. Short-term CV: First Step Predictor t-2 Desired predictor from past t-1 t x-1 x x+1

  6. Short-term CV: Second Step Predictor t-N t-N+1 Predictor: b t-N+2 c=2b-a c a ... t x-1 x x+1

  7. Short-term CV:Motion Search • Search fixed window centered on predictor (x,y) • Same as brute-force search, except brute-force search always predicts (0,0) • Short term CV also keeps track of best predictor for each frame in the backbuffer while searching

  8. Results:Foreman (frames 1-399)

  9. Results:Mobile (frames 1-299)

  10. Conclusions • Works comparatively well for small search ranges, but not for larger ones • Good predictor, since it’s closer to optimal for very small search ranges • Combining with a better per-frame search algorithm should get better gain • e.g. steepest descent • Combining with decision-tree structure can reduce errors with large search ranges

  11. References • H. Chung, A. Ortega, A. A. Sawchuk, "Low complexity motion estimation for long term memory motion compensation," Proc. Visual Communications and Image Processing, VCIP 2002, San Jose, CA, January 2002. • A. M. Tourapis, “Enhanced predictive zonal search for single and multiple frame motion estimation”, VCIP 2002, pp.1069-1079 • T. Wiegand, G. J. Sullivan, G. Bjontegaard, A. Luthra, “Overview of the H.264/AVC Video Coding Standard,” IEEE Trans. CSVT, Vol. 13, No. 7, pp.560-576, July, 2003

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