Patent attributes
Methods, apparatus and articles of manufacture (e.g., computer readable media) to detect watermark modifications are disclosed. Example apparatus disclosed herein are to encode a first watermark in a first media signal to obtain a second media signal, the first watermark associated with a first watermark layer. Disclosed example apparatus are also to determine, from the second media signal, a first metric corresponding to the first watermark. Disclosed example apparatus are further to determine, from the second media signal, a second metric corresponding to a second watermark encoded in the second media signal, the second watermark associated with a second watermark layer different from the first watermark layer. Disclosed example apparatus are also to output, based on the first metric and the second metric, an indication of whether the second watermark has been modified.
