What is watermarking? What is a digital watermark?
A digital watermark is an imperceptible signal hidden in an audio clip, or an image, or any other object of value. The hidden signal is intended to communicate information about the marked object. There are many applications of watermarking. In the context of SDMI, the application is screening and piracy prevention: an audio clip with a watermark is recognized as copyrighted, warning a portable device that it should not be recorded (or possibly even played) except under specific conditions. Watermarking is apparently one of the central technologies behind SDMI’s music protection system.
