根据基于对象的MPEG－4视频标准[1]，以对象宏块的运动矢量作类似的多边形匹配，利用相邻帧中运动矢量和图象像素的相关性，提出了一种“准菱形”搜索运动估计方法，该方法在图象运动复杂的情况下，不仅能根据方向选择来扩大搜索范围，而且能有效地降低搜索点数和搜索次数，该算法利用C语言编程，结合Matlab数学工具来处理典型图象序列，其结果表明，该方法与菱形搜索，六角形搜索相比，具有既能够有效地保持图象质量又能降低计算的复杂度等优点。

Considering the object based video standard MPEG 4 , this paper proposes a new motion estimation method--pseudo diamond searching algorithm(PDS), which uses motion vector as referent variable to execute a polygon matching procedure. The motion vectors in near blocks and points in same blocks between sequent frames are correlated. Considering these characteristics, pseudo diamond searching method uses a direction selective strategy to reduce the average searching points and enlarge the searching region. This strategy is efficient under the conditions where movement is complex and vehement. Using C programming and using matlab kits to test an image sequence, this paper shows that such method, compared with the diamond search method(DS) and Hexagon based Search Method (HS), keeps the image quality efficiently as well as reducing the computation complexity.