Motion-compensated priority discrete cosine transform coding of image sequences

In this paper a new motion compensated (MC) predictive coding method for image sequences is presented. This method utilizes a prediction of the displacement vector field (DVF) in order to produce a MC prediction error which is coded and transmitted using the Discrete Cosine Transform (DCT) and the Partition Priority Coding (PPC) approach. Assuming that 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. This way there is no need to transmit the DVF. Using the predicted DVF, the MC prediction error is obtained. It is then transformed and the irrelevancy reduction is carried out using the PPC method. According to this method, the transform coefficients are ordered based on their magnitude and, therefore, magnitude and location information is transmitted. Due to the properties of the MC prediction error, PPC proves to be very suitable. The proposed algorithm was experimentally tested on standard video-conferencing image sequences. Significantly improved results were obtained compared to previously reported DCT and Priority DCT based methods without MC in terms of reduced bit-rate and quality of the reconstructed image sequence.