Television – Studio equipment
Reexamination Certificate
1998-08-31
2001-11-13
Kostak, Victor R. (Department: 2611)
Television
Studio equipment
C348S521000, C348S036000, C348S218100, C348S262000
Reexamination Certificate
active
06317166
ABSTRACT:
BACKGROUND—FIELD OF THE INVENTION
This invention relates to the field of signal synchronization methods and panoramic television devices.
DESCRIPTION OF THE PRIOR ART
In audio-visual recording systems, it is often necessary to synchronize several streams of audio or visual images. Multiple cameras are often used for recording a scene simultaneously from several points of view, while at the same time one or more audio devices record the sound.
All of these streams of information must be synchronized to each other in the playback process. For multiple-camera systems, one or more of three synchronization methods are commonly used:
1. A visual cue simultaneously recorded on several media. One example of this is a clapboard, which gives simultaneous marking of a visual cue (the camera seeing the clapper coming together) and an audio cue (the sound of the clap being recorded on an audio track). This would work for multiple-camera shoots only if all of the cameras could clearly and simultaneously see the clapboard coming together. This same principle is embodied in a more convenient form for multiple-camera shoots by a device which flashes a bright light (for the camera) while emitting a sharp sound (for the audio). If any camera cannot clearly record the visual cue, then it cannot be synchronized with the others.
2. A separate synchronization signal is recorded simultaneously on all media. One example of this is SMPTE time code, which can be recorded on multiple film, video or audio devices, and which provides a common time reference for the numbering of individual frames. By making use of this information, all of the frames or audio recorded at a given time can be aligned to one another. This requires separate devices for reading and interpreting the synchronization signal information.
3. Physically marking visual cues on the media itself after recording is completed. For example, multiple strips of motion picture film are often used in the process of editing and when producing multi-layer effects. Audio recordings are also present in the form of mag track recordings with the same perforations as film. In a multi-gang synchronizer on an editing bench, these strips of film can be placed next to each other on linked spoked wheels, and markings made, either with grease pencil, permanent marker or by punching holes in the middle of the frame, to mark key synchronization frames common to all. By lining up these marked frames, synchronization can be achieved. Physical marking requires extra steps in the postproduction process, and is impractical for electronic media such as video where changes in the video image typically require a recopying process and the risk of loss of visual image quality.
Other approaches in the patent literature have relied upon variations in these approaches. For example, U.S. Pat. No. 4363055 “Control System for Audio Visual Projector” describes a separate control signal representing frame numbers. U.S. Pat. No. 5481307 “Method and Apparatus for Compression and Decompression Sequences of Digital Video Images Using Synchronization Frames” involves arbitrary marking of selected frames after recording for special handling in a compression process. A similar process is found in Motion Picture Experts Group Level 2 (MPEG-2) compression, where Intra (I) frames are identified and used for comparison to measure the changes in a moving video image.
The synchronization of multiple cameras usually involves making sure that all share the same frame rate. Otherwise, they will drift apart over time. Another step is to make sure that all frames begin and end together. Otherwise, if one frame ends during the exposure time for another, there is the possibility for a sync marker at a given moment in time extending over one frame on one track, and two frames on another track. For enforcing a common frame rate for film-based systems, a synchronization pulse controlling the camera motors is often used. For setting a frame rate for multiple video cameras, a single “genlock” signal is fed into all of the cameras, such as a “video black” signal.
OBJECTS AND ADVANTAGES OF THE INVENTION
The present invention comprises an improvement in marking synchronization points as part of a recording and playback apparatus for multi-channel imaging systems. This improvement generates an easily visible synchronization frame simultaneously for all channels, and can be applied to either video or motion-picture film-based systems. It does not rely upon any external objects or markers being simultaneously present in the field of view of any camera in the multi-camera system. It also does not rely upon a separate synchonization signal being recorded simultaneously along with the video images, or upon any marking or post-processing of the recorded image or the image media.
REFERENCES:
patent: 4231063 (1980-10-01), Ito et al.
patent: 4467365 (1984-08-01), Murayama et al.
patent: 4994916 (1991-02-01), Pshtissky et al.
patent: 5019905 (1991-05-01), Pshtissky et al.
patent: 5142367 (1992-08-01), Houg
patent: 5347322 (1994-09-01), Levine et al.
patent: 5495293 (1996-02-01), Ishida
Immersive Media Company
Kostak Victor R.
LandOfFree
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