It embeds the watermark in a digital still image or in a video frame by producing alterations in the luminance of the pixels. For audio signals, alterations are p erformed on the amplitude of the signal. Alterations are of low energy and they are designed by taken into account the main characteristics of the human visual and auditory system. Since video and audio signals require large amounts of memory, data are input in WEAs and watermarked sequentially. For video watermarking, the motion vectors that calculated by a MPEG encoder-decoder should be used to increase the performance of the al gorithm.
Detection is the most crucial part in the watermarking framework.
WDAs should be trustworthy producing insignificant false alarm errors. Therefore, the result of the detector should be an indisputable indication about the ownership of a digital product. WDA s based on statistical hypothesis testing. They provide the certainty , which characterises a possible decision that accepts the existence of a particular watermark. Numerical experiments indicate that watermark detection is en ough reliable and suitable to prove copyright ownership.