Abstract

Apparatus for producing a video display on a television receiver or equivalent from two channels of audio. The audio channels are fed through two banks of audio filters to separate the audio into descrete frequency bands. In the preferred embodiment, sixty-four filters per bank are used. Each set of frequency bands is mixed electrically to produce a third set of signals which are a function of the difference in phase or amplitude of the original two. These three sets of audio signals are then rectified to produce dc levels and are used sequentially, as red, green and blue inputs to produce a color display. The sequence is determined by a digital apparatus which provides that, in the basic configuration the horizontal position of each dot on the raster corresponds to a particular frequency, the color and intensity of each dot being a function of input audio amplitude and the relative phase or amplitude of the input audio channels. The vertical position of a display is a function of time so that linear bars of color are produced in response to the audio input. Additional digital circuits are provided to transform the basic display into numerous positional variations including repetitive images and mirror images in the vertical and horizontal planes, diagonal displays and circular displays.