DCT/DST ALTERNATE-TRANSFORM IMAGE CODING.

An image coding method for low bit rates is proposed. It is based on alternate use of the discrete cosine transform (DCT) and discrete sine transform (DST) on image blocks. This procedure achieves the removal of redundancies in the correlation between neighboring blocks, as well as the preservation of continuity across the block boundaries. The motivation behind the method is explained assuming a certain first-order Gauss-Markov model. The resulting theoretical coding method is then adapted to nonstationary real images by locally adapting the model parameters and improving the block classification technique. Finally, simulation results are shown and compared with the performance of previous related methods, namely, adaptive-DCT and fast Karhunen-Loeve transform (FKLT).