Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Synchronizing
Reexamination Certificate
2000-08-26
2001-11-13
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Synchronizing
C348S194000
Reexamination Certificate
active
06316974
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of analog and digital signal processing, and more specifically to circuitry and systems for providing switching, scan conversion, scaling, and processing where the output frequency is different from the input frequency.
2. Background Art
Switchers are a means of connecting an input source to an output device or a system. Typically, a switcher allows a user to provide an output derived from a selection between more than one input signal source or connector type. Furthermore, various types of switchers have various components, capabilities, options and accessories.
2.1 Graphics Environment
For digital display technologies, a Graphics Switcher (GS) is a device that enables multiple analog and digital input signals to be selected and sent to various selected output devices, such as presentation displays.
FIG. 1
illustrates a typical graphics environment showing various pieces of digital display technology connected by a graphics switcher, in accordance with an embodiment of the present invention.
Hence, a graphics switcher
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allows source signals derived from inputs such as video cameras
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, VCRs
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, DVDs
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, TV video, audio/video systems, and computers
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,
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, and
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to be selected and viewed on a presentation display
120
one at a time. For example, when trying to display from two computer inputs
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and
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having separate presentations, a graphics switcher
100
can physically connect both of the computers to the display device and allow input selection from the two computers for display on the display device
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. Other examples of graphics switcher use are for generating special graphics and movie effects; in industrial settings or security applications for switching between video cameras inputs for displaying certain areas on monitors or systems of display devices.
Typical inputs to a graphics switcher comprise computers, TV video, composite video, red-green-blue (RGB) video, S-Video, D-1 (digital) video, computer input (e.g. VGA, SVGA and Mac video formats), video cameras, VCRs, and various other audio/video inputs as appropriate. Furthermore, inputs may originate from different physical locations. For instance, to form a presentation on a larger screen display, a switch may be used to choose between inputs received from a computer at one end of one room, a computer in another room, a video camera taking video of a performance, and a video conferencing system.
Similarly, a switcher provides output to various sources or presentation formats. Examples of outputs comprise LCD panels (including high-resolution LCD projectors), DLP displays (including high-resolution DLP projectors), high resolution plasma displays, TV displays, CRT display devices
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and
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(e.g. VGA, SVGA and Mac video formats), audio stereo systems, and various other audio/video outputs as appropriate. For instance digital projectors used for business presentation supply digitally addressed elements to LCD panels, DLP panels, digital light processing devices, and various others.
A TV signal has a set number of horizontal lines. In PAL and SECAM, it's 625; in NTSC, it's 525. However, not all of these lines are visible. In fact, only 576 lines in PAL and SECAM and 483 lines in NTSC are seen by the TV viewer; the remainder are called blanking lines, which contain no picture information and are hidden at the top and bottom of the screen.
By contrast, the number of horizontal lines on a computer display can range dramatically, from lower resolutions of 480 visible horizontal lines or less, up to very high resolutions with 1280 or more lines. Many computers contain video cards that allow the user to choose between several different display resolutions.
The higher the display resolution, the more crisp and clear small details and text become. For example, a computer screen composed of 768 horizontal lines is able to contain and display more detail than a computer picture composed of only 480 lines, or a TV picture composed of 576. The relatively small number of horizontal lines in a TV video picture limits the ability to display very small text or other intricate visual details.
TV video is defined by either the NTSC, PAL or SECAM standard, which dictates the number of lines in the picture, how the color information is defined and the speed with which the lines are painted on the screen from top to bottom (refresh rate). However, within PAL, NTSC, and SECAM, there are actually several signal formats that meet these standards. Composite video is the most commonly used format. In composite video, all the video information (e.g. information for red, green, blue (RGB) and sync) are all combined into a single signal. S-Video, which provides a superior picture quality, separates the chrominance (color) from the luminance and sync information. Other variations of PAL and NTSC include RGB at 15 kHz, component video and D-1 (digital) video.
While all of these formats differ in the way the video information is combined into a signal, they still have certain things in common. They are all interlaced, they have either 576 (PAL and SECAM) or 483 (NTSC) visible lines, and they have an established, unvarying refresh rate. For PAL, two interlaced fields, making up a single “frame,” are painted onto the screen 25 times each second (a rate of 25 Hz), and for NTSC, this occurs 30 times each second (30 Hz).
Unlike TV video, there is no single standard by which all computer video signals must abide. As discussed earlier, there is a wide range of commonly used display resolutions. There is an equally wide range of refresh rates, most falling between 60 and 85 Hz. And, while almost all computer displays are non-interlaced, some video display cards do offer an interlaced display option. However, what computer video signals do all have in common is the way in which they describe chrominance and luminance information to the monitor. All VGA, SVGA and Mac video formats transmit the red, green and blue information as separate signals. But, there is some variation between computers in the way sync information is combined with the color signals. By keeping red, green and blue separate from each other, computer monitors are able to display a wide range of colors with minimal distortion.
2.2 Types of Switchers
In order to support such a wide variety of analog and digital inputs and outputs, numerous types and “lines” of switchers have been developed. For example, there are audio/video (A/V) switchers; VGA, Mac and RGB switchers; system switchers; and matrix switchers. In addition, the numerous signal characteristics associated with switching mixtures of inputs to outputs has led to number of switch options and accessories.
For instance, a line of A/V switchers may accept NTSC/PAL/SECAM composite and S-video type video sources, as well as two channels of stereo audio from amongst six selectable inputs. Each model in the line is then differentiated by the type or combinations of video audio formats that it accepts.
Another line of switchers, VGA, Mac and RGB switchers, are used for simple routing applications. A model of this line can be dedicated to switching signals of only one specific computer type, such as VGA or Mac. Alternatively, another model may provide more input flexibility, by accepting both VGA and Mac video signals.
A more complex switcher type, the system switcher, may be compatible with all types of digitally controlled projectors and accept virtually all source signals. Thus, a system switcher can easily switch between computers, A/V components and audio sources. In addition, an accessory may allow a system switcher to communicate with a projector and be recognized by the projector as if the switcher were the same brand as the projector.
A special type of switcher, the matrix switcher, routes multiple inputs to multiple outputs. For example, input #1 (e.g. camera
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) can be routed to output #1 (e.g. preview monitor
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) or output #2 (e.g. program monitor
122
); input #2 (e.g
Taraci Brian Richard
Truong Duy Duc
Callahan Timothy P.
Nguyen Linh
RGB Systems, Inc.
The Hecker Law Group
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