Interactive video distribution systems – Video distribution system with upstream communication – Remote testing of cable system
Reexamination Certificate
1997-07-14
2001-07-31
Faile, Andrew (Department: 2611)
Interactive video distribution systems
Video distribution system with upstream communication
Remote testing of cable system
C348S180000, C348S192000
Reexamination Certificate
active
06269482
ABSTRACT:
BACKGROUND
The present invention is in the field of computer video systems. More particularly, the present invention relates to various methods of visually testing video systems for degradation of video signals that pass through video systems, as well as methods of compensating for this degradation.
Video systems may include a variety of video sources, including but not limited to computers, video cassette recorders, video cameras, and a variety of display devices, including but not limited to CRT monitors, CRT projectors, LCD projectors, DLP projectors, or other video display devices. The video sources can generate video signals of many types, including but not limited to NTSC, PAL, SECAM, as well as the types produced by computers, such as composite, monochrome analog, RGB, RGBS, RGBHV, RGsB, RsGsB, and any additional video standards developed by IBM for personal computer compatible technology, including but not limited to CGA, EGA, VGA, and SVGA type signals and any other standards developed by industry associations like VESA.
Regardless of the specific types of video signals produced, video signals frequently require processing and manipulation before they reach video display devices. To this end, video switchers, video distribution amplifiers and other equipment, as well as various types of interconnecting cables, are frequently installed between video signal sources and video display devices.
Those ordinarily skilled in the pertinent arts will recognize that after video signals pass through such video system and reach video display devices, the quality of the video signals frequently degrade. The degree and type of degradation of a video signal depends upon the characteristics of components of the circuits through which the video signal is passing. The number of components and the individual characteristics of these components, as well as the characteristics and length of interconnecting cables used to connect said devices together determine the video signal degradation level.
In order to determine the extent to which a particular circuit degrades a video signal, as well as to determine how to compensate for the degradation, it is necessary to compare the original video signal generated by the source, with the video signal received by a video display device after the video signal has passed through such circuit.
Conventionally, this is done by connecting a video display device to a video signal source and observing the original image generated by the original video signal on the screen of the video display device. The video display device can then be connected at the output of the video system and the degraded image generated by the video signal after passing through the video system can be compared to the original image before passing through the video system. A troublesome shortcoming of this method is that a person comparing these two images has to remember what the original image looked like because only one image is viewed at a time, and the original image is not displayed while the degraded image is observed.
It is also possible to use two monitors, one connected to the original video signal and displaying the original image and one connected at the output of the video system and displaying the degraded image. However, those skilled in the pertinent arts will recognize that this method requires close proximity between video signal sources and video display devices, which in many cases is not possible. In addition, different display characteristics of each monitor may provide inaccurate results. Alternatively, one can employ network analyzers which test video systems by measuring various bandwidth characteristics. However, those skilled in the pertinent arts will recognize that network analyzers, aside from being expensive, also require close proximity between video signal sources and video display devices, which in many cases is not possible. In addition, specially trained personnel are required to operate complex network analyzers, who are often in short supply, and expensive.
Accordingly, a clear need exists for an inexpensive and simple method of testing video systems for degradation of video signals that pass through video systems, as well as compensating for the degradation of the video systems in order to provide the highest quality image possible.
OBJECT AND SUMMARY OF THE INVENTION
The present invention is directed to methods of testing video systems and compensating for the degradation of those video signals after passing through the video systems, in which the methods meet the needs discussed above.
An additional object of the present invention is to provide a novel enhanced means of testing for degradation of signals and ameliorating same, which overcomes the drawbacks of the prior art.
A first improved method, which is the subject matter of this invention, comprises the steps of applying a first test video signal to an input of a video system (where computers, video cassette recorders, video cameras, or any other video signal sources are connected to the video system) in a way that images generated by a first test video signal are displayed only on a portion of a screen of a display device. This can be accomplished by a generator or any other means capable of generating signals which produce images only on portions of the screen, as opposed to images occupying the entire screen. The first test video signal is then passed through the video system and the image generated by the first test video signal, which has been subject to degradation, is displayed only on a portion of the screen of the video display device.
A second test video signal, acting as a reference signal, is generated substantially identical to the first test video signal. The second test video signal is designed so that the image it produces will be displayed on a portion of the screen not occupied by the signal from the first generator. The second test signal, along with the first test signal are synchronized and combined by a special circuit and connected to the video display device. Those ordinarily skilled in the pertinent arts will recognize that in order for the second test video signal to be substantially identical to the first test video signal, same can be, for example, calibrated to the first test video signal.
The image generated by the second test video signal, which has not passed through the circuitry that the first test signal has, therefore functions as a reference signal. The image of the second test video signal is then displayed only on a portion of the screen of the display device, other than that portion of the display device on which said degraded image is displayed. It is most convenient, but not necessary, to display the degraded image and the reference image side by side on the screen of the video display device. For example, the reference image can occupy the left side of the screen, and the degraded image can occupy the right side of the screen of the video display device. (Alternatively, the degraded image and the reference image can be displayed on top and bottom of the video display device.) By visually comparing the two images simultaneously displayed on different portions of the screen of the video display device, it is easy and convenient to determine the extent to which the video signal degraded after passing through the video system. It should be apparent to those skilled in the pertinent arts that both generators of test video signals used for this type of testing can have the ability of adjusting positions and sizes of images used for comparison.
According to a further feature of the present invention, there is provided an additional step of correcting the degradation of video signals by adjusting the degraded image while the reference image is simultaneously displayed on the screen of the video display device until the degraded image appears as close to the reference image as possible within the limitations of a particular video system, the limitations of a particular means of adjustment, and limitations of the particular video display device. Those o
Altinex, Inc.
Brown Reuben M.
Faile Andrew
Khiterer Vladimir
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