In digital video compression, motion estimation is most commonly used in reducing temporal redundancy. The motion information generated by motion estimation is usually coded in the compressed stream. In many situations, the compressed video needs to be post- processed, for example, filtered to generate an out-of-focus effect. The filtered video then requires another motion estimation to be coded in bit stream. We propose an algorithm to reuse the existing motion information in the original video to avoid or aid the motion estimation in the recompression. Since this technique significantly reduces post-processing time for compressed video when the output is required in compressed form, it is highly desirable in digital video broadcasting systems.