Abstract: A digital soft edge transition system for use in conjunction with 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 controlled by an analog ramp generator is utilized to provide a gradual transition between the video input signals. The gradient of the transition is determined by the time constant of the charging circuit in the ramp generator which is controlled by a digital border size control circuit. The digital border size control circuit includes circuitry responsive to the distance between the border and the edge of the viewing screen for gradually reducing the width of the border as the transition approaches the edge of the screen to prevent the abrupt disappearance of the border that usually occurs in digital soft edge generators when the transition approaches the edge of the screen.

Abstract: 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.