| 摘要 |
A method and an apparatus for implementing an identification code together with the data of a data stream, and to actively introduce a disturbance signal into the data stream, obscuring the presence of the identification code. In a preferred embodiment the disturbance signal is true random noise at a level below the cognitive threshold of a viewer or listener of the material that is represented by the data stream. Since the noise has true random behaviour, subtraction of one copy from another will not lead to any decrease in noise level. Hence, such a comparison will not lead to the unconvering of the indentity codes. The inventive apparatus and method is preferably used for recording audio or video material on digital recording media, including optical means such as DVD and CD as well as magnetic tape recording media, but is also useable for analog recordings. The invention is particularly suitable for marking video data streams transmitted to a video-on-demand user. |
