Multiplying Video Mixer

Video mixing circuit places transparent overlay image on all or portion of normal image on television screen. Overlay computer-generated graphics, text, or another image. Background video brightness signal fed into one input terminal of circuit, while overlay brightness signal fed into other input terminal. Amplitude of background brightness signal modulated by overlay brightness signal, resulting in video image in which background image appears as though viewed through overlay. Multiplying video mixer, combined with additional circuitry, places transparent or opaque overlay images on normal (background) video images.