US 5,953,417 A · Method and apparatus for digitally removing or defeating effects of copy protection signals from a video signal

Abstract

Video signals in today's environment exist in both the analog domain and the digital domain. In many instances it may be desirable to delete or reduce the effectiveness of a video signal containing analog copy protection signals while the signals are in the digital domain. The invention uses digital techniques for defeating the effects of the analog copy protected signal while the signal is in the digital domain. The types of copy protection signals includes pseudo sync pulses and AGC pulses. Additionally digital techniques may be used for reducing or eliminating the affects of a chroma copy protection process. A digital video copy protection eliminator allows removal of substantially all pseudo sync pulses and/or AGC pulses in the digital domain. The location of pseudo syncs and/or AGC pulses are determined, while the signal is in the digital domain. These known pixel locations of all or some of the pseudo syncs and/or AGC pulses are used to digitally modify the signal so as to effectively remove the pseudo sync pulses and/or AGC pulses. Digital methods can also be applied to effectively eliminate or correct the chroma (burst phase modulation) protection process and or enhanced video copy protection signals in the digital domain.

Claims19

Dependent claims

A method of removing the effects of pseudo sync and AGC pulse pair copy protection signals within a video signal while in the digital domain, the copy protection signals being for inhibiting the making of acceptable analog video recordings of the video signal after digital to analog conversion, the method comprising:

determining in which lines of the video signal said copy protection signals are present;
wherein the act of determining comprises, counting a predetermined number of lines in a vertical blanking area from vertical sync, which predetermined lines contain the copy protection signals, and outputting a control signal;
modifying the copy protection signals while in the digital domain in at least some of those lines whereby an acceptable video recording of the video signal after digital to analog conversion can be made;
wherein the act of modifying includes;
inputting a digital video signal to a first signal input of a multiplexer;
inputting a digital number into a second signal input of said multiplexer;
and
inputting said control signal into a control input of said multiplexer.

5 more elements

A method of digitally reducing the effects of pseudo sync and/or AGC pulse copy protection signals within a digital video signal having normal sync pulses, wherein the copy protection signals allow viewing said digital video signal while inhibiting the making of acceptable analog video recordings of said digital video signal after digital to analog conversion, the method comprising:

digitally generating a digital control signal indicative of selected lines of the video signal in which said copy protection signals are present;
providing a selected digital modification signal;
and
digitally modifying in response to said digital control signal, with said selected digital modification signal, said copy protection signals in less than all of said selected lines of said digital video signal in which the copy protection signals are present but a sufficient number of the selected lines to allow an acceptable video recording of said digital video signal to be made after the digital to analog conversion.

1 more element

An apparatus for digitally removing the effects of chroma copy protection signals of improper phase within a digital video signal, wherein the copy protection signals allow viewing said digital video signal while inhibiting the making of acceptable analog video recordings of said video signal after digital to analog conversion, comprising:

a digital line location circuit for digitally determining the location of chroma copy protection signals within selected lines of said digital video signal;
and
a digital signal modification circuit responsive to said digital line location circuit for modifying, with a chroma signal of proper phase, a selected portion of said chroma copy protection signals which is sufficient to allow an acceptable video recording of said video signal to be made after digital to analog conversion.

Dependencies are inferred from the claim text.

Method and apparatus for digitally removing or defeating effects of copy protection signals from a video signal

Life of this patent

Method and apparatus for digitally removing or defeating effects of copy protection signals from a video signal

Life of this patent

Abstract

Claims19