Method of and system for detecting a watermark in MPEG-2 encoded video
data during high-speed copying of the video data. A bus spy (120) selects
independently coded frames, such as I-frames, from the video data and
feeds the selected frames to a watermark detector (130) for detecting a
watermark therein. By only supplying some of the frames to the watermark
detector (130), the average input data rate for the watermark detector
(130) is much lower than the data rate during the high-speed copying.
Various embodiments present various ways to efficiently supply the
contents of the selected frames to the watermark detector (130).