method for copy-protecting a digital video signal; method of reproducing a protected video signal; digital video recorder adapted for a once copy protocol for a video signal; coding apparatus for protecting a video signal; method for enabling copying of a protected video signal; apparatus for enabling copying of a protected video signal and method of processing an original video signal to limit its copying.

摘要

Method and apparatus for "copy-once" of a digital video signal uses a watermark in the video signal. The embedded watermark has two versions: one indicates copy-never and a second indicates copy-once, the difference being a single watermark bit. The watermark carries additional bits representing a digitized attribute (image characteristic) of a particular video frame of the video signal, for instance an average value of the amplitude of a video field. The frame whose attribute is carried in the watermark has a field (or frame) marker, which is a special signal located in the overscan portion of the frame. A compliant video recorder verifies the watermark and the copy-once bit, extracts the associated attribute from the watermark, and compares it to the measured attribute of the marked video frame. Only if the extracted attribute value and the measured attribute value match is recording enabled. During the recording process, the frame markers are stripped, preventing second generation copies of the recorded video signal, and the copy-once bit is set to copy-never.