A low-frequency, temporally asymmetric watermark carrier decreases in luminance
in a substantially monotonic manner more slowly than it increases in luminance
in a substantially monotonic manner. This allows the carrier to be embedded, e.g.,
in a video work, in a manner that renders the resultant watermark virtually invisible
to the human eye. Moreover, the resultant watermark is substantially resistant
to common pirating techniques in which high-frequency visual content (e.g., including
watermark data) tends to be filtered out by piracy processing.
