An Adaptive Dual-Mode Coder/Decoder for Television Signals

An adaptive dual-mode coding system for television signals is described. Its main features are a low bit rate (1.5 bits per sample), the high quality of the reproduced picture, and its moderate hardware. The system is based on the statistical properties of video signals. Specifically, it makes use of the nonuniform spectrum of video signals in the form of a differential scheme containing linear prediction. Furthermore, areas of small amplitude changes between consecutive samples whose probability of occurrence is high are encoded with a reduced coding alphabet. Transients representing sharp edges in the picture are encoded and reproduced with little slope overload and busyness. A method for the buffering of the asynchronous data stream produced by the coder to match a synchronous channel is given.