We have developed a system called Rosetta which creates from video content a series of video stills representing a sequence of video footage. A storyboard allows the writers and directors to plan the action to be shot and from what camera angle, and in essence provides a summary of the entire film. Normally, the storyboard is not available to a viewer as it is discarded after the movie is completed. If however, the storyboard for a piece of video, or a close approximation to it, could be generated from the video itself, then the viewer could be provided with an easy means of browsing and indexing an entire video sequence. The first two of these properties may be found by a process of transition detection and the third by representative frame choice.
Transitions are the links between successive shots in sequences.
The most frequently used type of transition is the cut , but effects such as fades , dissolves , and wipes are also used. Transitions are detected by comparing the amount and constancy of change between individual frames. Having identified the start and finish of each shot, an image must be produced that conveys the same meaning as the entire shot. In Rosetta, a single frame from the shot is chosen as being representative. The algorithm compares each frame in the shot to an 'average frame' generated by simply finding the mean colour of the corresponding pixels in each frame of the shot.