Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1986-11-12
1988-08-16
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358182, H04N 5272
Patent
active
047648090
DESCRIPTION:
BRIEF SUMMARY
This invention relates generally to the selective formation of an output video signal from at least two input video signals. This invention further relates to switching between video signals using a switching technique called a wipe, and more particularly to transition boundary of a wipe, called a border.
BACKGROUND OF THE INVENTION
A finished video presentation is rarely one continuous scene shot from one camera. More commonly, video presentations are a series of short scenes assembled together through an edit process to form the final presentation. Unlike motion picture film which is edited by physically cutting and splicing film segments together, video material is edited by electronically cutting and splicing together segments of video signals.
A video switcher is an electronic device used by the video industry to execute a form of editing wherein video material from a variety of sources are assembled into a finished video presentation. Video material is provided to the video switcher in the form of input video signals from a variety of video sources, such as video tape recorders, optical disk plays, and video cameras. The video switcher typically selects for presentation as an output video signal one or more of the input video signals from the available video sources. This selection is accomplished by switching from one input video signal to another signal, with the time of occurrence of the switch operator. This output video signal is utilized in a variety of ways, such as recording by a video tape recorder, displaying on a video monitor, or broadcasting to viewers.
This switch between input video sources can take many forms and often involves several different switching techniques. The most straight forward of the switching techniques is the simple switch between different video signal sources. In such switchers, the output of the switcher is instantaneously switched between the input video signals and only one of the input video signals is present at any one instant at the output of the switcher. To a viewer of the output signal displayed on a monitor or television receiver, the display changes instantaneously from one input video signal to the other different input video signal.
Another technique of effecting a switch between video sources is called a dissolve. A dissolve is a gradual transition between different video signals, with the different video signals appearing simultaneously in the output provided for display during part of the transition interval. The gradual transition is accomplished through adjustable video signal gain controllers, commonly variable attenuators, and a signal combiner, which additively combine and present to an output the gain adjusted video signals provided by the gain controllers. Usually, a dissolve begins with the output video signal being entirely composed of a first input video signal. At a rate determined by the operator, the gain on the first input video signal is reduced to zero, while the gain on a second input video signal is raised from zero to the level originally set for the first signal. To a viewer of the output signal displayed on a monitor, the picture based on the first input signal appears to dim, while the picture based on the second input video source appears very dim at first and then appears to brighten until only the picture based on the second input video source is visible. At the midpoint of the switch, both signals are at an equal gain of one half and the pictures resulting from the displays of the signals are both visible simultaneously on the monitor, each at one-half its normal brightness.
Yet another technique of effecting a switch between video sources is called a wipe. A wipe is created by the generating a control signal which is used by a video mixer to switch between input video signals on a line by line basis, such that a line of output video may be composed of parts of both input video signals. This control signal is usually based on the output of ramp generators which are processed by a ramp combiner, which manipulates the ram
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Fundamentals of Interactive Computer Graphics, Foley, Van Dan, Chap. 7, pp. 245-249.
Flora Jay L.
Haycock David A.
Almeida George B.
Ampex Corporation
Faris E. Anne
Groody James J.
Lange Richard P.
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