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US 4,907,093 AGranted
Method and apparatus for preventing the copying of a video program
AssigneeMacrovision Corporation
InventorJohn O. Ryan
Life of this patent
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AssigneeMacrovision Corporation
InventorJohn O. Ryan
Estimating the term…
A video signal is modified so that a television receiver will still provide a normal color picture but which a video tape recorder will detect and prohibit its being recorded. A plurality of ordered pairs of pseudo-sync and positive pulses are added to the video signal vertical blanking interval following the normal sync pulse. A disabiling circuit associated with a recorder detects the modified signal. This detection may be by comparing the voltage differential between the pseudo-sync pulse tip and the positive pulse relative to the normal voltage differential between the sync pulse tip and the back porch of the blanking interval. Alternatively, the modified signal can be detected by identifying the pulse frequency of the signal in the blanking interval. A high frequency is indicative of the presence of the modified signal. Detection is also shown by peak-detecting the video signal and sampling this peak-detected signal during the vertical blanking period. A control signal is produced, when the modified signal is present, which disables the recording device. If no modified signal is detected, the recording device is enabled.
A method for processing a video signal so as to prevent the making of video tape recordings therefrom, wherein the video signal has a blanking interval which includes a sync pulse and at least one pulse added to the video signal following the sync pulse to produce an added waveform in said blanking interval, said method comprising:
A tape recorder for prohibiting the recording of a modified video signal on a recording medium, which signal has a blanking interval which includes a sync pulse, comprising:
In a method for processing a video signal having a blanking interval that has a sync pulse and to which a waveform is added following such sync pulse having at least one pseudo-sync pulse followed by a positive pulse, comprising the step of detecting the amplitude differential between the tip of said pseudo-sync pulse and that of the associated positive pulse.
A method for processing a video signal having a vertical blanking interval that has a sync pulse and to which a waveform is added which includes a plurality of selected pulses following the sync pulse, comprising the step of detecting the presence of said added waveform by generating a signal representative of the frequency of the plurality of selected pulses.
A method for processing a video signal having a blanking interval that has a sync pulse and to which a wave form is added following such sync pulse having at least one positive pulse having an amplitude greater than the normal blanking reference level, comprising the steps of detecting the peak amplitude of the video signal and sampling the peak-detected signal during the blanking interval.
A tape recorder for processing video signals, each of which has a selected waveform added to a conventional video signal within its blanking interval, which added waveform includes at least one pseudo-sync pulse following the normal sync pulse of the blanking interval and a positive pulse following the pseudo-sync pulse, comprising detecting means for detecting the amplitude difference between the tip of each pseudo-sync pulse and that of the associated positive pulse.
A tape recorder for processing video signals having a selected waveform added to a conventional video signal within its blanking interval, which wave form includes at least a plurality of pseudo-sync pulses following the normal sync pulse of the blanking interval comprising means for detecting the frequency of the video signal caused by said plurality of pseudo-sync pulses.
A tape recorder for processing video signals having a selected waveform added to a conventional video signal within its blanking interval following a normal sync pulse, which waveform includes at least one positive pulse following said sync pulse, comprising means for detecting the peak amplitude of the video signal, and means for sampling the peak-detected signal during said blanking interval.
Dependencies are inferred from the claim text.