A circuit which receives RGB and composite video and provides both RGB and composite merged outputs. Merging of RGB signals occur where the input composite signal is converted to RGB; and also, merging occurs of composite signals where the input RGB is converted to a composite signal. 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.