APPARATUS FOR CONVERTING AN RGB SIGNAL INTO A COMPOSITE VIDEO SIGNAL AND ITS USE IN PROVIDING COMPUTER GENERATED VIDEO OVERLAYS

摘要

A circuit for converting RGB to composite video. The circuit is particularly useful in a video overlay application. Notch filters are used both in the video path and keying path. The notch filters are centered at frequencies equal to the dot clock frequency of the RGB divided by integers where the result of this division falls within the chroma subcarrier spectrum.