| US 7,492,896 B2 | ||
| Copy protection for video signal using added negative amplitude pulse | ||
| Ronald Quan, Cupertino, Calif. (US) | ||
| Assigned to Macrovision Corporation, Santa Clara, Calif. (US) | ||
| Filed on May 07, 2007, as Appl. No. 11/800,905. | ||
| Application 11/800905 is a division of application No. 11/206093, filed on Aug. 16, 2005, granted, now 7,352,863. | ||
| Application 11/206093 is a continuation of application No. 09/965345, filed on Sep. 26, 2001, granted, now 7,085,380. | ||
| Application 09/965345 is a continuation of application No. 09/733659, filed on Dec. 07, 2000, granted, now 6,501,842. | ||
| Application 09/733659 is a continuation of application No. 09/070958, filed on May 01, 1998, granted, now 6,285,765. | ||
| Application 09/070958 is a continuation of application No. 08/753970, filed on Dec. 04, 1996, granted, now 5,748,733. | ||
| Application 08/753970 is a continuation of application No. 08/062866, filed on May 17, 1993, granted, now 5,583,936. | ||
| Prior Publication US 2007/0211898 A1, Sep. 13, 2007 | ||
| This patent is subject to a terminal disclaimer. | ||
| Int. Cl. H04N 7/167 (2006.01) | ||
| U.S. Cl. 380—221 [380/204; 380/224; 380/226] | 6 Claims |
| 1. Apparatus for providing a copy protected video signal, comprising:
an input terminal which receives a video signal;
processing circuitry which is coupled to the input terminal and modifies the video signal to include therein selected copy
protection signals, which cause a reduced amplitude in a recording of the copy protected video signal; and
circuitry which adds a pulse having a selected negative amplitude to a selected position in a back porch region following
a horizontal sync pulse, wherein the copy protection of the video signal is enhanced by the added negative pulse.
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