When a video signal having electronic watermark information embedded therein is recorded on a recording medium, a reference signal is inserted in the video signal at a position different from a position of embedment of the electronic watermark information. The electronic watermark information is embedded...http://www.google.com/patents/US6519351?utm_source=gb-gplus-sharePatent US6519351 - Method and apparatus for recording and reproducing electronic watermark information, and recording medium
