Digital watermark generator, digital watermark decoder, method to provide a digital watermark signal in dependence on binary message data, method to provide binary message data in dependence on a digital watermark signal and computer program that uses differential coding

摘要

Watermark generator (101; 2400) for supplying a watermark signal (101b; 2420) based on binary message data (101a, m; 2410), the watermark generator comprising: an information processor ( 303, 304, 305; 2430) configured to distribute the binarious message data a plurality of frequency bands or frequency subbands and to provide, based on information units of the binary message data, a first representation in the azitotemporal-frequency (b (ij); 2432) whose values represent binary message data for a plurality of frequency bands or sub-bands of frequencies and time blocks, where b (i, j) is the bit for the i -th frequency band or sub-frequency band and the jth time block; and a differential encoder (306; 2440) configured to derive a second representation in the field-time-frequency (306a, bdiff (i, j); 2442) of the first representation in the time-frequency field, so that the second representation in the temporal-frequency scope comprises a plurality of values, where a bdiff value (i, j) of the second representation in the temporal-frequency scope is a function of a bdiff value (i, j-1) of the second representation in the temporal-frequency field and of a value b (i, j) of the first representation in the temporal-frequency scope and where a difference between two values (bdiff (i, j), bdiff (i, j-1)) of the second representation in the scope temporal-frequency represents a corresponding value of the first representation in the temporal-frequency scope, to obtain a differential codification of the values of the first representation in the temporal-frequency field; and a watermark signal provider (307; 2450) configured to deliver the watermark signal based on the second representation in the time-frequency scope.