An improved method for predetermining the blocks whose quantized DCT coefficients are completely zero is proposed.It is applied to eliminate redundant computations in the low bit rate video coding process and reduce the computational complexity of motion estimation algorithms.Experimental results show that 50% luminance blocks of the typical videophone sequence can be determined to be all-zero coefficients

and the average search times for motion estimation are reduced by＞30%.It is very useful for reducing the computational load in software coders and the power consumption in hardware coders.