Robust motion vector prediction algorithms with application to very lowbit rate image sequence coding,

摘要

Abstract: In this paper a new motion compensated (MC) predictive coding method for image sequences at very low bit rates is presented. This method utilizes a prediction of the displacement vector field (DVF) in order to produce an MC prediction error which is coded and transmitted. Assuming that the two previous frames are available both at the transmitter and the receiver the DVF corresponding to the previous frame is estimated. Then, based on this estimate a temporal prediction of the DVF at the current frame is obtained. Using the assumption that the motion is constant along its trajectory, an auto-regressive (AR) model based method for performing such a prediction is proposed. According to the proposed scheme there is no need to transmit the DVF. Since the transmission of the DVF represents a sizeable overhead in very low bit rate coding of video signals, this method constitutes a major contribution to bit rate reduction and quality improvement. Using the predicted DVF, the MC prediction error is obtained, which is then transform and entropy coded. The proposed algorithm is experimentally tested on standard video-conferencing image sequences and compared to previously reported methods which transmit the motion vectors. Significantly improved results are obtained compared to the methods that transmit the motion vectors in terms of reduced bit- rate and improved quality of the reconstructed image sequence. !24