04577216 is referenced by 53 patents and cites 9 patents.

A method and apparatus which modifies a color video signal in such a manner that a conventional television receiver produces a normal color picture from the modified signal, whereas a videotape recording made from the modified signal exhibits annoying color interference. This is achieved by phase modulating the color burst component of the video signal with a noise signal. A videotape recorder interprets the phase variation as a velocity error and alters the chrominance signal, giving rise to color noise in the videotape recording. The characteristics of the noise signal are chosen to preclude interfering with the receiver's subcarrier regenerator.

Title
Method and apparatus for modifying the color burst to prohibit videotape recording
Application Number
6/551696
Publication Number
4577216
Application Date
November 14, 1983
Publication Date
March 18, 1986
Inventor
John O Ryan
Cupertino
CA, US
Agent
Cushman Darby & Cushman
Assignee
Macrovision
CA, US
IPC
H04N 5/78
H04N 7/167
H04N 9/80
H04N 9/45
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