Multiple reference frame motion re-estimation for H.264/AVC frame-skipping transcoding with zonal search

In this paper we propose an efficient multiple reference frame motion re-estimation for H.264/AVC frame-skipping transcoding. In the proposed algorithm, all information including reference frame number, motion vector etc. in original H.264/AVC-coded videos are reused when the original reference frame is not skipped; while an efficient multiple reference frame motion re-estimation is employed when the reference frame is dropped. The neighboring reference frames around the skipped reference frame are selected for motion re-estimation, and in addition a zonal search method is used for motion re-estimation. The experimental results reveal that average 87% of computation time (corresponding to a speed-up factor of 8) can be saved for the proposed H.264 frame-skipping transcoding algorithm, when compared with fully decoding/encoding procedure. The degradation in the rate-distortion performance is fairly small.