Method and apparatus for modifying the envelope of a RF carrier

Details Method and apparatus for modifying the envelope of a RF carrier Method and apparatus for modifying the envelope of a RF carrier

1997-02-04

2000-05-02

Swann, Tod R.

Cryptography

Video cryptography

Copy protection or prevention

380221, H04N 7167

Patent

active

060581913

ABSTRACT:
A method and apparatus is disclosed for disabling the effect of copy protection signals embedded in video signals, wherein the detection and modification of the copy protection signals is accomplished in the RF domain rather than in the baseband video domain as typically accomplished at the present time. To this end, various embodiments are disclosed for deriving a timing control signal from the modulated RF carrier signal, which timing control signal is indicative of the television lines which contain the copy protection signals. Several techniques in the RF domain responsive to the timing control signal are disclosed for replacing, attenuating, suppressing, pulse narrowing or otherwise modifying the modulated RF carrier signal during the interval of the copy protection signals to disable the affects thereof, to allow the making of acceptable recordings during demodulation subsequently by, for example, a record VCR. Also disclosed are means for adding copy protection signals to an RF carrier signal modulated with a video signal by modulating, for example, the protection signals onto the RF carrier signal in the RF domain.

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