US Patent 7783888 Watermarking in an audiovisual product

An audiovisual product (400) is recorded with a set of watermark characters (421, 701) as video or audio objects. A sequence of the watermark characters (421, 701) is selected and reproduced upon playback to uniquely identify a particular playback instance. Ideally, a user identity code is received upon playback amongst a predetermined set of user identity codes, and the sequence of watermark characters (421, 701) is selected and replayed according to the received user identity code. The sequence of watermark characters (421, 701) allows the user identity code to be traced should the audio and/or visual output of the audiovisual product (400) be recorded such as with a video cassette recorder (VCR).