Two-source decomposition and discrete-cosine- transform-Hadamard-transform coding of low-correlation interframe differences

International standards such as ITU-T H.263 (H.261) and ISO MPEG use a hybrid coding scheme based on the discrete cosine trans- form (DCT). Although the DCT is an established technique for encoding interframe differences, it is not an optimal transform for low-correlation interframe differences, since its energy compaction performance largely depends on the correlation of the data. In this paper an effective tech- nique for encoding interframe difference is proposed and verified on an MPEG2 software encoder. The technique decomposes the interframe difference into two sources in order to exploit their improved statistical properties. The two-source interframe difference is encoded with a com- bined transform, which consists of the DCT and the Hadamard transform (HT). Two-source decomposition increases the correlation of the decom- posed prediction error, and the DCT-HT scheme is shown to efficiently encode the decomposed interframe difference with increased perfor- mance. Analytic and experimental comparison shows that the proposed DCT-HT scheme gives significant objective and subjective gains over the conventional DCT-based video encoding method. © 2001 Society of