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 ver y low bitrates using conventional hybrid differential pulse code modul ation/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 repla ce the conventional inverse DCT if only a few DCT coefficients are tra nsmitted to the receiver. Results show that the preposed inverse block -overlapping transforms can significantly outperform the conventional inverse DCT both in terms of objective and subjective quality measures .