Hierarchical coding of HDTV

Abstract

The Broadband Integrated Services Digital Network (BISDN) based on lightwave technology is supposed to become the all-purpose exchange area communication network of the future. All digital services are integrated with applications ranging from facsimile, videophone, teleconferencing to digital standard-resolution TV — sometimes referred to as Extended Quality TV (EQTV) — and High Definition TV (HDTV). In order to make efficient use of the available network bandwidth hierarchical coding schemes combine the necessary data compressions of the HDTV and EQTV signals such that the HDTV signal can be transmitted at 135 Mbit/s with the embedded EQTV signal coded in a sub-channel of approximately 35 Mbit/s. This paper investigates in detail three possible coding strategies for fixed bit-rate hierarchical coding schemes, namely distributed coding, error feedback coding and selective coding. With the aid of the rate distortionn theory it is determined under which conditions both EQTV and HDTV are encoded optimally for each of the three strategies. These conditions are verified with three introduced hierarchical subband coding schemes, namely the Distributed system, the Refinement system and the Selection system, which are direct implementations of the three coding strategies. It is concluded that if both EQTV and HDTV have to be encoded optimally, the error feedback coding strategy is the best suitable one because this strategy is able to cancel propagation of coding errors of the EQTV signal into the reconstructed HDTV signal.