A computer-based video editing system provides software controlled wipes between scenes. These wipes may be the conventional horizontal, vertical, or clock type wipes used in video to transition from one scene to the next. Instead of being generated by conventional digital wave form generators, the wipes are generated as a bit map in computer memory, thus allowing the editor to design his own wipes as desired. The wipes are generated by comparators which have as their inputs line-by-line video data and computer controlled threshold data so as to control a video switcher to select between scenes as determined by the wipe pattern.