Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
1994-02-04
2001-04-03
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S155000, C348S700000
Reexamination Certificate
active
06211912
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method for automatically detecting scene changes in image sequences such as video programs, and more particularly to a method for detecting inter-shot scene changes resulting from camera operations such as panning, tilting, and zooming.
BACKGROUND
Video programs are generally formed from a compilation of different video segments which are known as “shots” in the film and video industry. Each shot consists of a sequence of consecutive frames (i.e., images) generated during a continuous (uninterrupted) operating interval from a single camera. For example, in motion pictures, a shot is a continuous series of frames recorded on film that is generated by a single camera from the time it begins recording until is stops.
In live television broadcasts a shot constitutes those images seen on the screen from the time a single camera is broadcast over the air until it is replaced by another camera.
Shots can be joined together either in an abrupt mode (i.e., butt-edit, or switch) in which the boundary between two consecutive shots (known as a “cut”) is well-defined, or through one of many other editing modes such as fade or dissolve which result in a gradual transition from one shot to the next. The particular transition mode that is employed is generally chosen by the director to provide clues about changes in time and place which help the viewer follow the progress of events.
There are known automatic video indexing methods which detect abrupt transitions between different shots. An example of such a method, which can detect abrupt as well as gradual transitions, has been disclosed in patent application Ser. No. 08/171,136, filed Dec. 21, 1993, entitled “Method and Apparatus for Detecting Abrupt and Gradual Scene Changes In Image Sequences”, the contents of which is hereby incorporated by reference. In the context of automatic video program indexing these abrupt transitions are often referred to as “scenes” and the detected boundaries (i.e., cuts) are referred to as “scene boundaries”. A “scene”, however, is commonly considered to be a sequence of frames with closely related contents conveying substantially similar information. If video programs consisted only of “still shots” (i.e., shots in which the camera is motionless), each shot would contain only a single scene. However, in general, video programs are composed not only of still shots but also “moving shots” (i.e., shots in which the camera undergoes operations such as pan, tilt and zoom). Consequently, because of camera motion the contents of a series of frames over an individual shot may change considerably, resulting in the existence of more than one scene in a given shot. Therefore, while boundaries between different shots are scene boundaries, such boundaries may be only a subset of all the scene boundaries that occur in a video program since camera motion may produce inter-shot scene changes.
Known scene change detection methods are deficient because they can only detect scene changes that occur at the boundary between shots, not scene changes that occur within an individual shot.
SUMMARY
In accordance with this invention, a method has been developed for determining camera-induced scene changes in a sequence of visual information-bearing frames which constitute a single shot. In one example of this method, camera-induced motion is determined between each of a plurality of pairs frames within a single camera shot. The camera-induced motion for each of the pairs of frames is decomposed into at least a first component. The values of the first component for each of the pairs of frames are summed to form a first cumulative signal. A scene change is indicated when the first cumulative signal meets a certain decision criterion.
In one particular example of the invention, the first component into which the camera motion is decomposed represents either image pan, image tilt, or image zoom. In another example of the invention, the camera motion is decomposed into all three of these components.
In another example of the invention, a signal is generated which represents camera-induced motion between each of a plurality of pairs of frames within a single camera shot. A plurality of the signals are summed for a plurality of pairs of frames to form a first cumulative signal. A scene change is indicated when the first cumulative signal meets a certain decision criterion.
In yet another example of the invention, the method of the invention works in conjunction with a known method such as block matching for detecting abrupt and gradual transitions between camera shots. The known method is used to find the beginning of each camera shot, which is designated as the beginning of a new scene. Any known method may be then employed to extract the image pan, image tilt, and image zoom that occurs between consecutive frames within the shot. For each of the camera operations of image pan, image tilt, and image zoom, the values computed between consecutive frames are used to generate two signals: 1) a continuous signal representing the cumulative value of the camera operation since the beginning of the new scene; and 2) a binary signal indicating continuous activation of the camera for the given operation. A scene change is indicated whenever: 1) the magnitude of the cumulative value for any of the operations exceeds a predetermined threshold; or 2) a continuous operation period for any of the operations (i.e., pan, tilt, or zoom) terminates (as indicated by the binary signal) and the corresponding cumulative value has a magnitude at least as large as another predetermined threshold.
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Co-pending U.S. patent application Ser. No. 08/171,136, filed Dec. 21, 1993, “Method and Apparatus for Detecting Abrupt and Gradual Scene Changes In Image Sequences”.
The Television Program: Its Direction and Production,Stasheff, E. and Bretz, R., pp. 53-56 (Chapter 1), 76-87 (Chapter 5) and 248-68 (Chapter 15) Fourth Edition, Hill and Wang Publishers, New York, 1968.
“Automatic Image Stabilizing System by Full Digital Signal Processing”, K. Umori et al.,IEEE Transactions on Consumer Electronics,vol. 36, No. 3, pp. 510-519, Aug. 1990.
“Video Indexing Using Motion Vectors”, A. Akutsu et al., Proc. SPIE Conf. Visual Communications and Image Processing (VCIP'92), vol. 1818, pp. 1522-1530.
Garber Wendy R.
Lucent Technologies - Inc.
Wilson Jacqueline
LandOfFree
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