Abstract: To improve the compression efficiency of the video, based on diamond search algorithm and
cross diamond search algorithm, combined with the feature that motion vector was mainly focused on
horizontal direction vector in actual motion images, the thesis put forward an improved search
algorithm which combined partial to horizontal cross template search with biased toward double
diamond template search. Comparative experiments were conducted to test the effect of improved
algorithm. The result of the performance contrast experiment shows that the thesiss improved
algorithm suits all kinds of motional video sequences, especially those sequences changing poignantly
in movement. Under the condition that the PSNR and the BR value are very close to the optimal level,
compared to the FS algorithm, the improved algorithm decreases approximately 95% of the motion
estimation time of the QCIF pictures, and decreases about 94% of the motion estimation time of the CIF
pictures, thus decreases greatly the motion estimation time.

Key words: video compression, H.264, motion estimation, diamond search algorithm, cross diamond
search algorithm