H．263中的运动搜索和变换域编码是运算量很大的部分，也是影响系统实时性能的瓶颈，为了减少图像编码的运算量，在采用整数变换代替浮点DCT变换的基础上，提出了一种全局判决方法，即在运动搜索中和变换前进行全零块判决。该方法是根据整数变换和量化结果为零的特点，在运动搜索中，对差值块先进行全零块判决，如果找到全零块，就停止搜索，以省却以后的搜索运算和全零块的整数变换以及相应的量化运算，由于其可在基本保持H．263原有编码算法图像质量的同时，减少运算量和缩短码流，从而大幅度提高了编码器的编码效率。

The computation in video codec mainly concentrates on transformation and motion search,which are the bottlenecks of realization of real time video codec.In order to reduce the computation in the transformation and motion search of H.263 encoder, float-point DCT is replaced by integer transform,which make video encoder free of float-point operations, and an all-zero decision technology based on integer transform is proposed in this paper. The all-zero decision is made in inter frame coding by comparing sum of the absolute differences(SAD) to a value related with quantization parameter during motion search.If the all-zero block is found, later computiaon of motion search and integer transform are eliminated, which can avoid a large amount of computiaon when mtion search is very accurate. This technology can basically maintain the quality of image,and highly improve the efficiency of real time H.263 encoder by skiping all-zero block before integer transformaion and shortening the code stream at the same time.