A storyboard allows 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. However, if 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 or collection of sequences. In order to reverse-engineer a storyboard from the finished video sequence, it is necessary to identify three properties of each shot in the 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. Additionally, since the resulting image is a composite of all the frames in the shot, it will generally be very different from any single frame. Although this may be unimportant for some applications, it is unacceptable in e.g. a professional video database application where assessment of the exact framing of the shot is needed.