
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 ...











