An efficient motion estimation algorithm for real-time MPEG-4 video encoding on multimedia processors

This paper describes an efficient motion estimation algorithm, the predictive line search (PLS), for real-time implementations of MPEG-4 encoder on multimedia processors. The motion vector predictor position is used as the starting point in the search process because the correlation between neighboring motion vectors is strong. The line search pattern is used in the proposed algorithm to reduce the memory access as well as to exploit the special multimedia processor instructions for SAD calculations. Experimental results show that the performance of the predictive line search is very close to the full search algorithm with a speed up of 10. Compared with the well-known diamond search, the predictive line search shows better performance and robustness especially for high motion sequences. prototype MPEG-4 encoding system is implemented on a 216 MHz multimedia processor with VLIW (very long instruction word) architecture to verify the effectiveness of the predictive line search. Real-time encoding of MPEG-4 Simple Profile Level 3 (CIF, 30 fps) can be achieved with only 63% of the processor load.