Optimal block-overlapping synthesis transforms for coding images and video at very low bitrates

In this paper we address the problem of coding images and video at very low bitrates using conventional hybrid differential pulse code modulation/discrete cosine transform (DPCM/DCT) coding schemes with reduced blocking artifacts. To this end, optimal block-overlapping synthesis filterbanks (block-overlapping inverse transform kernels) with minimum least-squares reconstruction error properties are derived which replace the conventional inverse DCT if only a few DCT coefficients are transmitted to the receiver. Results show that the proposed inverse block-overlapping transforms can significantly outperform the conventional inverse DCT both in terms of objective and subjective quality measures.