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A New Fast Motion Estimation Algorithm Based on H.264

A New Fast Motion Estimation Algorithm Based on H.264. LI Hong-ye, LIU Ming- jun , ZHANG Zhi-qiang MINES 2009. Fast and Efficient Fractional Pixel Motion Estimation for H.264/AVC Video Coding. Humaira Nisar and Tae-Sun Choi, Senior Member, IEEE ICIP 2009. Outline . Introduction

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A New Fast Motion Estimation Algorithm Based on H.264

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  1. A New Fast Motion Estimation Algorithm Based on H.264 LI Hong-ye, LIU Ming-jun, ZHANG Zhi-qiang MINES 2009

  2. Fast and Efficient Fractional Pixel Motion Estimation for H.264/AVC Video Coding HumairaNisar and Tae-Sun Choi, Senior Member, IEEE ICIP 2009

  3. Outline • Introduction • Introduction to UMHexagonS • New Fast Motion Estimation Algorithm • Simulation • Introduction to Fractional Motion Estimation • Fractional Pixel Error Surface • Quadrant Based Directional Fractional Pixel ME Algorithm • Simulation • Conclusion

  4. Introduction • Motion estimation(ME) is time consuming. Many fast motion estimation algorithms which have been proposed still can’t satisfy the real-time application. • ME consists of two stages: • Integer pixel ME • Fractional pixel ME • Generally Integer pixel ME takes most of computational time of the whole ME. Due to the development of fast ME algorithm, computational cost of integer pixel has been greatly reduced. • Fractional ME has strong impact on PSNR, and has complex sub pel interpolation process.

  5. Block Matching Algorithm – Full Search • Integer-pixel • Search range = • Fractional-pixel • Search range = 16 3 16 3 =1089

  6. Introduction to UMHexagonS • Combine many strategies together and achieve both fast speed and high accuracy. • Performs well both in small motion sequences and large motion sequences. • Adaptively adopt different searching pattern according to SAD and have early termination strategy to reduce searching time. • Only 10% complexity compare with Full Search algorithm. • Adapted in H.264 reference software. [10] Zhibo Chen, JianfengXu, Yun He, and JunliZheng, “Fast integer-pel and fractional-pel motion estimation for H.264/AVC,”Journalof Visual Communication & Image Representation, April 2006, pp. 264-290.

  7. Introduction to UMHexagonS • Search process of UMHexagonS algorithm, search range = (0) (1) ` (2) (3) (4-1) Step1: Unsymmetrical-cross search Step2: Small rectangular full search Step3: Uneven multi-hexagon-grid search Step4: Extended hexagons-based search (4-2)

  8. New Fast Motion Estimation Algorithm • Ameliorates UMHexagonS algorithm to reduce search point on three aspects: replace

  9. New Square Pattern • 5x5 full search  3x3 • By studying the distribution of MV • 80% in 5x5 grid region • 70% in 3x3 grid region • Replace reason • 80%70% • 5x5=253x3=9 36%

  10. Multi-Octagon-Grid Search • Hexagon(6)  Octagon(8) • Replace reason • Octagon has more edges than hexagon and closing to circle • 16 points  8 points 50%

  11. Horizontal Hexagon and Vertical Hexagon • Add horizontal and vertical hexagons • Add reason • Orientation bias Uniform Horizontal Vertical

  12. Simulation

  13. Introduction to fractional motion estimation HFPS: 17 points CBFPS [2] Z. Chen, P. Zhou, Y. He and Y. Chen, “Fast Integer Pel and Fractional Pel Motion Estimation for JVT” ITU-T, Doc. #JVT-F-017, Dec. 2002.”

  14. Fractional Pixel Error Surface Error surface of fractional-pelmotion estimation (1/8-pel case) Error surface of integer-pelmotion estimation (search range = 32) Drop into local minimum • Unimodal error surface • Redundant to check opposite direction points

  15. Quadrant Based Directional Fractional-Pixel ME Algorithm

  16. Quadrant Based Directional Fractional-Pixel ME Algorithm • Half pel points: • Step1: Calculate the cost of the best integer-pel • position and 2 search points . • Step2: Use quadrant selection approach selects • quadrant, and selects additional ½ pel • points. • Case1: For quadrant I, only one • additional ½ pel point is • selected. • Case2: For quadrant II, two additional ½ • pelpoints are selected. • Case3: For quadrant III, three additional • ½ pel points are selected. • Case4: For quadrant IV, two additional • ½ pelpoints are selected. • Choose the best ½ pel point for search ¼ pel start point. III II IV I

  17. Quadrant Based Directional Fractional-Pixel ME Algorithm III II • Quarter pel points: • search procedure is the same as ½ pel points. • At most : 11 points IV I II I

  18. Simulation

  19. Simulation

  20. Simulation

  21. Conclusion • New fast motion estimation algorithm based on H.264 improves on the UMHexagonS in three aspects. Reduce 30%~40% computational complexity of UMHexagonS without accuracy loss. Efficient for real time video coding applications. • Fast fractional search motion estimation algorithm based on uni-modal error surface assumption divides search range into four quadrants and finds the minimum error points by searching only some points that lie in that quadrant. Reduce computation time and keep almost same performance as CBFPS algorithm.

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