Patent US 3,941,925

A digital soft edge transition system for use in a video special effects generator utilizes digital circuitry responsive to a transition signal for switching either a first video input signal or a second video input signal into a composite video output signal. An analog video switch is utilized to provide a gradual transition between the video input signals. The gradient of the transition is determined by a counter and a variable speed clock, driving a digital-to-analog converter, or by a data selector interposed between the counter and the digital-to-analog converter. A "mirror image" circuit is utilized to generate symmetrical effects such as circles, diamonds and other effects requiring more than one transition between the video input signals. The "mirror image" circuit serves to store the location of the completion of the first transition and to begin the second transition at a location on the displayed image determined by the value of the stored location. In the preferred embodiment, the locations of the completion of the first transition and the beginning of the second transition are symmetrically disposed about a center line of the displayed image so that the desired effect is symmetrically displayed on the viewing screen.