Relating to watermarks
US6804374B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 20, 2000 |
| Grant date | Oct 12, 2004 |
| Priority date | — |
| Expiry date | Jul 20, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2201/327
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus detects the presence of a watermark in digital data. The digital data may represent picture or sound information and maybe in the form of a broadcast television signal or a signal that has been recorded on a recording medium such as a compact disc. The watermark includes coefficients which have been subject to an inverse local orthogonal transform before being embedded in the input data. In order to detect the presence of the watermark, the input watermarked data is first forward transformed and subtracted from the watermark coefficients so as to derive the data coefficients. The data coefficients are squared and formed into a local average to obtain a measure of the power in the local average. The watermark coefficients are divided by the local average so as to scale them and the scaled watermark coefficients are cross-correlated with the input data to detect whether the watermark is present. The cross-correlation is performed by means of a multiplier receiving the input data as a first input and the scaled watermark coefficients as a second input. The resulting output detection signal is subjected to a thresholding operation using a threshold set in depende…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.