| 摘要 |
A detector (100) detects the presence of a watermark in an information signal. The information signal is correlated with an expected watermark (Wi) for each of a plurality of relative positions of the information signal with respect to the watermark to derive a set of correlation results (64). Part of the correlation results (64) are cross-correlated (82) with information (81) about an expected shape of a correlation peak in the results. This can improve the sensitivity of the detector (100). The cross-correlation result (84) is compared with a threshold at peak detection unit (85). The threshold used in this comparison (85) is set in an adaptive manner according to the expected shape. The information (81) about an expected shape of the correlation peak can be based on knowledge of processing operations that the information signal has undergone or expected to have undergone or from the shape of previous correlation results.
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