System and method for detecting modifications of video signals designed to prevent copying by traditional video tape recorders

1. In a digital recording system having a video receiver interface, a method for identifying whether a video signal has been modified by a video-tape-recorder-design based anti-copying process, said method comprising the steps of:

identifying frames in the video signal based upon a broadcasting standard, and identifying a proper portion of the video signal based upon the broadcasting standard and the video-tape-recorder-design based anti-copying process;

filtering noise from the proper portion of the video signal by calculating a moving average over a time frame that is selected based upon an expected time dimension of potential artifacts;

recognizing potential artifacts in the proper portion of the video signal by determining whether a segment of the proper portion of the video signal has crossed a predefined threshold;

counting the potential artifacts; and

cross-correlating results from said counting step with a predefined expectation derived from the anti-copying process.

2. The method of claim 1 , the method further comprising the steps of:

obtaining a discrete sample of the video signal prior to said identifying step; and

eliminating a majority of data elements from the discrete sample prior to said recognizing step.

3. The method of claim 1 , wherein the proper portion comprises scan lines, which may contain potential artifacts, within at least two of the frames, said scan lines having numerical positions within the frames.

4. The method of claim 3 , wherein said cross-correlating step further comprises the steps of:

finding a plurality of potentially modified lines comprising at least two of the scan lines, which each contain at least two potential artifacts; and

establishing that a potential artifact count for each of the plurality of potentially modified lines, the potential artifact count determined by said counting step, has the format of an equal number of the potential artifacts for each scan line, of equal position within the frames, included within the plurality of potentially modified lines across each of the at least two of the frames.

5. A computer program product on a computer readable medium for identifying whether a video signal has been modified by a video-tape-recorder-design based anti-copying process, said computer program product comprising:

instructions for identifying frames in the video signal based upon a broadcasting standard;

instructions for identifying a proper portion of the video signal based upon the broadcasting standard and the video-tape-recorder-design based anti-copying process;

instructions for recognizing potential artifacts in the proper portion of the video signal;

instructions for filtering, noise from the proper portion of the video signal, comprising instructions for calculating a moving average over a time frame that is selected based upon an expected time dimension of the potential artifacts;

instructions for counting the potential artifacts; and

instructions for cross-correlating results from said instructions for counting with a predefined expectation derived from the anti-copying process.

6. The computer program product of claim 5 , further comprising:

instructions for obtaining a discrete sample of the video signal; and

instructions for eliminating a majority of data elements from the discrete sample.

7. The computer program product of claim 5 , wherein said instructions for recognizing further comprise instructions for determining that a segment of the proper portion of the video signal has crossed a threshold, which is derived from the video-tape-recorder-design based anti-copying process.

8. The computer program product of claim 5 , wherein the proper portion comprises a predefined set of scan lines having numerical positions within the frames.

9. The computer program product of claim 8 , wherein said instructions for recognizing further comprise instructions for determining whether an element of the predefined set of scan lines has crossed a threshold.

10. The computer program product of claim 9 , wherein said instructions for cross-correlating further comprise:

instructions for finding a plurality of potentially modified lines comprising at least two elements from the predefined set of scan lines, wherein the at least two elements each contain at least two potential artifacts; and

instructions for establishing that a potential artifact count for each of the plurality of potentially modified lines, the potential artifact count being determined by said instructions for counting, has the format of an equal number of the potential artifacts for each scan line of equal position within the frames.

11. A digital video recording system comprising:

a video receiver interface for receiving a video signal;

a central processing unit coupled with said video receiver interface; and

a detector, which counts potential anti-copying artifacts in a proper portion of the video signal spanning multiple frames, filters noise from the proper portion by computing a modified moving average, and determines if the video signal is protected by a video-tape-recorder-design based anti-copying process by cross-correlating a count of said potential anti-copying artifacts with a predefined expectation derived from the video-tape-recorder-design based anti-copying process and a broadcasting standard.