James C Redding

US Patent:

39898881, Nov 2, 1976

Filed:

Aug 14, 1975

Appl. No.:

5/604621

Inventors:

Albert E. Busch - Bloomington IN
John R. Hotsenpiller - Bloomington IN
James V. Redding - Nashville IN

Assignee:

Sarkes Tarzian, Inc. - Bloomington IN

International Classification:

H04N 522

US Classification:

178 68

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.