 Image signal selector for television receiver combined with video cassette recorder |
| OF THE INVENTION Referring to the drawing, the invention shall be described in details. According ... |
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| Automatic sharpness control circuit for a television receiver |
| It is an object of the present invention to provide an automatic control of the degree of picture ... |
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| NTSC color television transmission without chroma crawl |
| In accordance with the present invention, the upward moving pattern at the edges of luminance is ... |
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| Color burst phase detection system for use in a video disk player system |
| The present invention is made to avoid the above mentioned problem, and an object of the present ... |
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| Engine idling speed sensing system |
| Accordingly, it is an object of this invention to provide an engine idling speed sensing system. It ... |
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| Method and system for interference suppression in a color television system |
| FIG. 1 collectively, illustrates the system which is known in accordance with the prior art. In FIG... |
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| Interface for a video display processor arranged to provide an overlay on a video display |
| The foregoing and additional objects are achieved in accordance with the present invention by an ... |
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Method and apparatus for scrambling and descrambling of video signal with edge fill
| Details |
Inventors: Ryan, John O.; Quan, Ronald; Holzgrafe, James R.; Wonfor, Peter J.;
Assignee: Macrovision Corporation (Sunnyvale, CA)
Primary Examiner: Barron, Jr.; Gilberto
Assistant Examiner:
Attorney, Agent or Firm: Brill; Gerow D.
A video-scrambling system induces a random wobble i.e., time shifting, in the location of active portion of the video frame, without affecting the horizontal sync signal and colorburst in each video line, thus providing both security and concealment. The security is enhanced by filling in the gap between the nominal beginning of active video and the actual beginning of active video with a synthesized video signal which replicates the adjacent active video using a digitally generated filling pattern. Also, a random noise overlay further conceals the location of the gap. Additional concealment is provided by wiggling in time the location of the horizontal sync signal using one or two frequencies and also by randomly altering the location of the vertical sync signal. The NTSC digital encoding in accordance with the invention is simplified by using only two channels, chrominance and luminance, and by a heterodyne circuit for chrominance stability. NTSC encoding is enhanced by providing detail normally lost, by use of the chroma channel. Additionally, a non-standard video signal may be provided with a portion of the colorburst on the front porch of the horizontal blanking, thus allowing use of a relatively simple decoder. |
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DETAILED DESCRIPTION OF THE INVENTION Scrambler Operation Throughout the description following, specified parameters ("eight-bit", "ten-bit", "0-909 counters" etc.
) refer to the preferred embodiment of the invention in the particular case of a 4-times subcarrier frequency sampled NTSC-standard unit.
The principles described herein are generally applicable to other standards (such as PAL), and other sampling rates by applying detail modifications in accordance with principles well known to those versed in the art.
FIG.
3 is a flowchart showing scrambling in accordance with the invention as performed in the scrambling device.
Beginning at step 42, the incoming analog video signal is digitized and written into a conventional random access memory.
In parallel, the conventional random-number generator generates a randomly varying number in step 44.
Then the randomly generated number is converted to an analog waveform and the waveform is used to make the wobbling time base for purposes of video encryption in step 46.
Step 46 generates an analog waveform in conjunction with the randomly frequency modulated sine wave which is used to generate a wobbling time base.
In an alternative embodiment, the wobbling time base can be generated digitally, identically to the process described for the digital descrambler (FIG.
16A).
The 1:1880 counter 588 referenced there provides precisely the desired address bus.
In step 48, for the digitized video previously written into memory, the luminance Y is separated from the chrominance C by an addition and subtraction process and both of the signals Y, C are read out of memory with the same randomly wobbling timing.
This provides both luminance and chrominance which are wobbling.
Since there is intrinsically a one line delay in this separation process of step 48, the vertical blanking interval video, which is not scrambled but needs to match time-wise with luminance and chrominance, is delayed by one line in step 50 so as to maintain its time alignment with the luminance and chrominance portion of the signals
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TV Signal 
