Method and apparatus for watermarking an audio or video signal with watermark data using a spread spectrum

摘要

Watermark information (denoted WM) consists of several symbols which are embedded continuously in an audio or a video signal using spread-spectrum. At decoder site the WM is regained using correlation of the received signal with an m-sequence. According to the invention, not only is the watermark made audio or video signal level dependent (PAS), but also the spreading sequence used for the watermark is made audio or video signal level dependent. This means that the same WM symbol is encoded by several different spreading sequences (NSS). The encoder tests (DEC), which one of these WM symbols or sequences can be retrieved best in a decoder, and embeds that selected spreading sequence WM in the audio or video signal to be watermarked. At decoder side all candidate WM spreading sequences are correlated with the received signal and the spreading sequence with the best match is chosen as the correct one.