Coding of advanced TV for BISDN using multiple subbands

Abstract

The purpose of this paper is to describe a sub-band based coding scheme for the digital transmission of advanced television (ATV) signals within Broadband ISDN (BISDN). It is intended for the delivery of high quality video to the home or office at the CCITT recommended H4 rate of roughly 130 Mbps. The scheme uses intra-field processing only, resulting in relatively low complexity for hardware implementation, very desirable error propagation properties and, of course, the elimination of motion related &acts.The use of the shortest kemel (2-tap) quadrature mirror filter (QMF) pairs for signal decomposition and reconstruction minimizes quantization noise spread and further reduces complexity. Through successive QMF operations, the signal is decomposed into ski bands to achieve low noise coding not normally associated with the shortest kemel implementations. In effect, the coding scheme is identical to a Hadamard transform (HT) with non-constant block sizes. From the viewpoint of coding performance and system complexity, the shortest kemel filter outperforms most of the other longer filters. Compared with our previously investigated pyramid coding scheme, this scheme reduces the entropy by about 10% at similar reconstructed picture quality. In addition, the scheme permits a graceful adjustment of picture quality as a function of bit rate. When combined with entropy coding, this approach achieves the roughly 5.6:l compression desired while retaining very high image quality. In cqllaboration with others, work is under way to realize a custom VLSI based research prototype ATVDISDN codec which implements this compression algorithm.