Copy protection for video signal added pulses
View Patent ↗Enhancements to a video anticopying process that causes an abnormally low amplitude video signal to be recorded on an illegal copy. In one version, positive going pulses are added to the video signal. 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.
1. Apparatus for providing a copy protected video signal, comprising:
a blanker for blanking a portion of the active video of the video signal at a location prior to a synchronization signal in the overscan portion of the video signal;
a pulse generator for generating a predetermined waveform having an amplitude less than that of a horizontal synchronization signal and insufficient to cause an erroneous synchronization or retrace;
circuitry for generating pairs of positive going and negative going pulses to be added to a vertical blanking interval of the video signal, the added pairs of pulses causing a reduced amplitude video signal on a recorded copy of the video signal; and
an adder for adding the generated waveform to the blanked portion of the video signal, wherein the added waveform increases the picture degradation in a copied video signal upon playback.
2. Apparatus for providing a copy protected video signal, comprising:
control circuitry for determining a portion of the active video of the copy protected video signal at a location prior to a synchronization signal in an overscan portion of the video signal;
a pulse generator for generating a predetermined waveform having an amplitude less than that of a horizontal synchronization signal and insufficient to cause an erroneous synchronization or retrace;
circuitry for generating pairs of positive going and negative going pulses to be added to a vertical blanking interval of the video signal, the added pairs of pulses causing a reduced amplitude video signal on a recorded copy of the video signal; and
a switch for switching the predetermined waveform into the determined portion of the active video, wherein the waveform increases picture degradation of the copied signal.
3. The apparatus of claim 1 , wherein the waveform defines a checker pattern.
4. The apparatus of claim 2 , wherein the predetermined waveform defines a checker pattern.
5. The apparatus of claim 1 , wherein the amplitude of the waveform is no more than about 20 IRE.
6. The method apparatus of claim 2 , wherein the amplitude of the waveform is no more than about 20 IRE.
7. Apparatus for providing a video copy protection signal with a high frequency level shifting signal, comprising:
an input terminal for receiving a video signal from a source of the video signal;
a circuit coupled to the input terminal and which adds a high frequency signal in the range of 100 KHz to 5 MHz in an overscan portion of the video signal, whereby the high frequency signal causes a level shifting effect on a portion of a basic copy protection signal in the video signal, wherein the basic copy protection signal includes one or more positive going pulses inserted or added to cause a gain reduction in an AGC amplifier of a video recorder; and
an output terminal coupled to the circuit to output the video signal with the level shifting effect.