Synthetic Highs — An Experimental TV Bandwidth Reduction System

Abstract

A complete system is described which codes a standard video signal to match a narrower band channel and subsequently decodes the received signal for display on a standard TV monitor. The system transmits the low-frequency, or macro-contrast signal, in analog form. The location and amplitude of the edges are transmitted by a digital code. At the receiver the edge information is used to synthesize the highs content of the video, which is then added to the lows to reconstruct the original video signal. Bandwidth reduction is achieved by exploiting both statistical correlations and psychophysical phenomena. — Apparatus for the separation of low frequencies, detection of edges, quantization and binary digital coding of edge amplitude and synthetic reconstruction of highs is described. The digital coder for edge locations has been described elsewhere. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> Picture-tube photographs of the resulting pictures are shown. Factors affecting the degree of bandwidth reduction and the effect of variation of system parameters such as separation frequency and quantization levels are discussed.