Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1988-11-01
1991-04-23
Peng, John K.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358 22, 358160, 358178, H04N 5262, H04N 974, H04N 514, H04N 553
Patent
active
050104071
DESCRIPTION:
BRIEF SUMMARY
This invention relates generally to video systems for the creation of a variety of special effects and, more particularly, to a video system in which separately calculated key signals are employed to adjust the gain of input video signals, recirculating video signals and output video signals presented to an output combiner so that a composite video signal can be formed therefrom.
BACKGROUND OF THE INVENTION
In the television industry there is an ongoing desire to combine video signals in a variety of ways to create various special effects For example, a common function of a digital video effects system is to compress a full field of video to a size smaller than the raster area occupied by a full size field of television signal. The smaller raster is then displayed at a predetermined location within the larger raster of video
Framestores recently have been developed for use in the video industry to store video information for the creation of special effects Such devices typically include a memory device capable of holding at least one complete raster of video information, i.e., either a field or a complete frame of video information. One such framestore system is described in U.S. Patent Application entitled "A Recirculating Special Effects Video Framestore" by David E. Trytko, filed Sept. 13, 1989 as U.S. patent application Ser. No. 07/407,722, which was a continuation of copending application Ser. No. 07/195,370 filed May 11, 1988, now abandoned, which was a continuation of copending application Ser. No. 06/943,282 filed Dec. 8, 1986, now abandoned, which was a continuation-in-part of copending application International Application No. PCT/US86/00733 filed Apr. 11, 1986, which was a continuation-in-part of copending application Ser. No. 06/722,532 filed Apr. 12, 1985, now abandoned and assigned to the same assignee as the present patent application the details of which are hereby incorporated by reference.
In creating special effects, digital video signals are typically combined through the use of key signals. Two unprocessed video signals cannot be directly combined because the combined signal gain would be the sum of the initial gains of each unprocessed video signal and could exceed the maximum gain resource of the system, i.e., the combined video signal can have a maximum gain no larger than the maximum gain of any of the component video signals. Thus, if all component video signals in the system are allowed to vary in gain anywhere from 0 to 1 volt, the maximum gain excursion of a composite video signal consisting of a combination of two or more component video signals can be no more than from 0 to 1 volt The key signals are used according to the teachings of the invention to cut the gain of component video signals according to calculations relating to the transparency factor of each signal, the maximum available gain for the composite signal and the priority of the various signals. By using separate key signals for each video signal, the key signals can be independently processed to control the gains of the component video signals in such a manner that the final composite video signal uses all the available gain resource without the injection of spurious noise. That is, prior to combining video signals, each individual video signal is gain adjusted by its respective key signal in such a manner that the composite video signal does not exceed an overall reference gain which is the maximum allowable gain resource available to any video signal in the system. A more complete understanding of key signals in video signal processing can be obtained from U.S Patent Application entitled "Apparatus and Method for Processing Video Signals With Key Signals in Accordance With Previous Processing of the Video Signals " by John F. Bloomfield, filed Sept. 1, 1989 as U.S. patent application Ser. No. 07/403,898, which was a continuation of copending application Ser. No. 07/191,778 filed May 2, 1988, now abandoned, which was a continuation of copending application Ser. No. 07/119,223 filed Nov. 3, 1987, now abandone
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Ampex Corporation
Bell John S.
Peng John K.
Roddy Richard J.
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