Video copy protection process enhancement to introduce horizonta

Details Video copy protection process enhancement to introduce horizonta Video copy protection process enhancement to introduce horizonta

1995-05-05

1997-05-27

Barron, Jr., Gilberto

Cryptography

Cryptanalysis

380 15, 360 60, 386 1, G11B 15087, H04N 7167

Patent

active

056339275

ABSTRACT:
Enhancements to a video anticopying process that causes an abnormally low amplitude video signal to be recorded on an illegal copy. The enhancements in one version introduce into the overscan portion of the television picture, just prior to the horizontal or vertical sync signals but in active video, a negative going waveform that appears to the television receiver or videotape recorder to be a sync signal, thereby causing an early horizontal or vertical retrace. One version provides (in the right overscan portion of the picture), a checker pattern of alternating gray and black areas which causes the TV set on which the illegal copy is played to horizontally retrace earlier than normal in selected lines with a consequential horizontal shift of the picture information on those lines. This substantially degrades picture viewability. In another version a gray pattern at the bottom overscan portion of the picture causes vertical picture instability. In another version selected horizontal sync signals are narrowed, causing irregular vertical retraces. Also provided is apparatus for removing or attenuating these enhancements from the video signal, to allow copying.

REFERENCES:
patent: 4631603 (1986-12-01), Ryan
patent: 4695901 (1987-09-01), Ryan
patent: 4951315 (1990-08-01), Switsen
patent: 5194965 (1993-03-01), Quan et al.
"Macrovision Decoder/Blanker" Elektor Electronics, London, Gr. Britian Oct. 1988, No. 160. pp. 44-47.

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