Method and apparatus to determine the sampling frequency for decoding watermark information embedded in the received signal sampled at the original sampling frequency at encoder side, to use

摘要

Many watermarking systems make use of correlation for calculating a detection metric, which means that reference patterns are generated at encoder side and are embedded inside the audio or video signal, dependent on the message to be embedded. The same reference patterns are generated at decoder side. The embedded message is decoded by correlating the reference patterns with the watermarked signal. The watermark detector decides, depending on the size of the correlation result values, whether or not a given reference pattern was embedded. However, decoding watermarked audio or video signals is difficult if the link between the watermark encoder and the watermark decoder is not a digital one, for example an acoustic path. According to the invention, a re-sampler control unit controls the sampling frequency of a re-sampler, in connection with a watermark decoder that outputs, in addition to the watermark information bits, a corresponding confidence value that is derived from the correlation result and that is used for synchronising the re-sampler sampling frequency with the original sampling frequency of the watermarked signal. The synchronisation processing includes a search mode and a synchronised mode.