Abstract: To improve the compression efficiency of the video, a self-adaptive diamond search
algorithm is put forward based on traditional diamond search algorithm. The algorithm is improved in
the prediction of the beginning search spot, diamond search mode and search suspended algorithm by
bringing in dynamic threshold. It realizes the self-adaptive search, which reduces the internal
redundant SAD operation and skips all the irrelevant blocks in the search area. The experiment result
shows that the self-adaptive diamond search algorithm suits all kinds of motional video sequence,
especially those sequences changing poignantly in movement. Comparing to the FS algorithm, the
improved algorithm decreases approximately 95% of the motion estimation time (MET) of all the
sequences under the condition that the PSNR and the code rate value are very close to FS algorithm.
The motion estimation time is greatly decreased.

Key words: video compression, H.264, motion estimation, diamond search, block matching