Digital watermark embedding and detection

摘要

A digital watermark detecting apparatus characterized by comprising:
a processing unit (41) which processes a detecting target by using a filter with a coefficient which is determined by a periodic number sequence;
a first cross-correlation calculator (43) which calculates a first cross-correlation between the processing result and the detecting target;
an auto-correlation calculator (35) which calculates an auto-correlation of the first cross-correlation;
a scaling rate calculator (72) which calculates a scaling rate based on a peak position of the auto-correlation and a period of the periodic number sequence;
a scaling unit (72) which scales one of the first cross-correlation and the periodic number sequence;
a second cross-correlation calculator (73) which calculates a second cross-correlation between the first cross-correlation scaled and the periodic number sequence not scaled or between the first cross-correlation not scaled and the periodic number sequence scaled; and
a detector (74) which detects whether a digital watermark is embedded in the detecting target based on the second cross-correlation.