Copy protection for analog video signals from computing devices
View Patent ↗A copy protection method and apparatus is provided to inhibit unauthorized viewing or copying of a video signal. A varying set of additional or invalid video pulses are generated onto a typical video signal. A pulse sequence identifier identifies the location of the invalid or additional pulses and is likewise generated onto the video signal prior to the occurrence of the identified pulses. The combined signal is received at an authorized display which then decodes or filters the additional or invalid portion of the video signal from the original signal according to a decode protocol stored in local memory. A resultant video output signal is guaranteed from only the original signal.
1. A method of processing a video signal from a computing device, the video signal including a first plurality of valid signal pulses, the method comprising the steps of:
generating a first plurality of invalid signal pulses onto the video signal; generating a
first pulse sequence identifier onto the video signal;
transmitting the video signal to a display device;
decoding the first pulse sequence identifier from the video signal to distinguish the first plurality of valid signal pulses and the first plurality of invalid signal pulses, and to determine the location of a second pulse sequence identifier embedded in the video signal; and
generating an output video signal from the video signal based on only the first plurality of valid signal pulses.
2. The method of claim 1 , further comprising the steps of:
generating a second plurality of invalid signal pulses onto the video signal;
generating the second pulse sequence identifier onto the video signal;
decoding the second pulse sequence identifier from the video signal to distinguish the second plurality of valid signal pulses from the second plurality of invalid signal pulses; and
generating an output video signal from the transmitted video signal using only the second plurality of valid signal pulses.
3. The method of claim 2 , wherein the first, second, and subsequent pluralities of invalid signal pulses and the first, second, and subsequent pulse sequence identifiers are successively generated onto the video signal.
4. The method of claim 1 , wherein the first plurality of invalid signal pulses and the first pulse sequence identifier are generated after generation of a predetermined number of subsequent pulse sequence identifiers.
5. The method of claim 1 , wherein the first plurality of invalid signal pulses and the first pulse sequence identifier are generated onto the video signal during a blanking period.
6. The method of claim 1 , further comprising the steps of:
polling the display device to determine if the display device includes a decode circuitry to perform the decoding step; and
enabling the decode circuitry to perform the decoding step if the display device includes the decode circuitry.
7. The method of claim 1 , further comprising:
polling a video source to determine if the video signal is unprotected; and
disabling the generation of invalid signals if the video signal is unprotected.
8. The method of claim 1 , wherein the valid signal pulses and the invalid signal pulses are horizontal sync pulses.
9. The method of claim 1 , wherein the valid signal pulses and the invalid signal pulses are vertical sync pulses.
10. The method of claim 1 , further comprising the steps:
polling the display device to determine if the display device is authorized to display the decoded video signal; and
disabling decoding if the display device is not authorized.