Method and apparatus to defeat certain copy protection pulses wi

Details Method and apparatus to defeat certain copy protection pulses wi Method and apparatus to defeat certain copy protection pulses wi

1995-05-02

1997-04-29

Barron, Jr., Gilberto

Cryptography

Cryptanalysis

380 15, 358500, H04N 716, H04N 980

Patent

active

056256914

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: 4024575 (1977-05-01), Harney et al.
patent: 4688097 (1987-08-01), Lin
patent: 4695901 (1987-09-01), Ryan
patent: 4928309 (1990-05-01), White
patent: 4951315 (1990-08-01), Switsen
patent: 5194965 (1993-03-01), Quan et al.
Graf et al, "Universal Descrambler", Radio-Electronics May 1990, pp. 37-43.

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