1. A watermark detector for detecting a watermark embedded in a content stream, the watermark having a watermark pattern and a payload encoded in the watermark pattern, a payload encoded in the watermark pattern in a first segment of the content stream being different from a payload encoded in the watermark pattern in a second segment of the content stream, the payload in the second segment of the content stream having a predetermined relationship with the payload in the first segment of the content stream, the watermark detector comprising: a splitter, for selecting a point in the content stream as an end of the first segment and a beginning of the second segment, a first sample accumulator, for obtaining a first set of samples of either one of the first segment and the second segment with respect to the selected point in the content stream, a first feature extractor, for extracting from the first set features in which the watermark for the payload is embedded, a watermark payload mapper, for transforming a detection pattern correlating with features in which the watermark for the payload is embedded of a second set of samples of another of the first segment and the second segment with respect to the selected point and different from the segment from which the first set is obtained, providing a transformed set of features by exploiting the relationship that exists between the different payloads in the first and second segments, and a detector, for detecting the watermark from features of the first set and features of the transformed set.