| 摘要 |
In order to enable a data signal, such as an audio or video signal, to be marked with multiple watermarks a set of different codes or keys is used within a given application field. The set of codes/keys is known to a watermark embedder ( 20 ) and a watermark detector ( 22 ). In each watermark embedding step, whether it is a first embedding step or a subsequent embedding step, a different key is used. The embedder ( 22 ) includes a data extractor ( 24 ) for determining which key or keys has or have been used previously. A data generator ( 26 ) then selects a new key from the set of known keys.
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