| 摘要 |
An apparatus for detecting and recovering data embedded in information material e.g. watermarks, the data embedded in the material in a transform domain representation by using the data to modulate a predetermined data sequence to form modulated data and combining the modulated data with the material. The apparatus comprising a transform processor operable to transform the material into the transform domain representation, and a correlation processor 334 operable to correlate transform domain data symbols bearing the modulated data from the transform domain representation with a reproduced version of the predetermined data sequence to form a correlation output signal, and to recover the embedded data from the correlation output signal. The correlation processor 334 is operable to repeat the correlation for transform domain data symbols and data symbols of the predetermined data sequence for a plurality of start position (Figure 10) in transform domain, the start positions representing the transform domain data. If the shift of transform domain data represents a loss of transform domain symbols, corresponding symbols from the predetermined data sequence are omitted and the lost transform domain data symbols and corresponding symbols of the predetermined data sequence are not included in calculating the correlation output signal. |
