Method and apparatus for copy-once watermark for video recording
US6374036B1 · kind B1 · utility
Assignees
Inventors
Key dates
| Filing date | Oct 1, 1998 |
| Grant date | Apr 16, 2002 |
| Priority date | — |
| Expiry date | Oct 1, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2005/91335
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Method and apparatus for “copy-once” of a digital video signal uses a watermark in the video signal. The embedded watermark has two versions: one indicates copy-never and a second indicates copy-once, the difference being a single watermark bit. The watermark carries additional bits representing a digitized attribute (image characteristic) of a particular video frame of the video signal, for instance an average value of the amplitude of a video field. The frame whose attribute is carried in the watermark has a field (or frame) marker, which is a special signal located in the overscan portion of the frame. A compliant video recorder verifies the watermark and the copy-once bit, extracts the associated attribute from the watermark, and compares it to the measured attribute of the marked video frame. Only if the extracted attribute value and the measured attribute value match is recording enabled. During the recording process, the frame markers are stripped, preventing second generation copies of the recorded video signal, and the copy-once bit is set to copy-never.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.