A method for modulating mark (20) within content signal (18) that has frames, where each of the frames has content lines and one or more measurable parameters, where each of the content lines has pixels, and where each of the pixels has a value, the method comprising selecting framesets from among the frames of the content signal; modulating at least two of the framesets; and causing mark (20) to be present within content signal (18) by at least modulating at least two of the framesets.