Method and apparatus for copy-once watermark for video recording

A method of playing a protected video signal, the protected video signal including in at least one frame marker and having an associated signal including a numeric representation of an image attribute of the frame having the marker, the method comprising the steps of:

• detecting the marker to identify a particular frame;
• detecting the signal associated with the frame;
• measuring the image attribute of the identified frame;
• comparing the measured attribute to the numeric representation of the attribute for the identified frame;
• and
• enabling recording of the video signal only if the comparing step indicates a match.

A digital video recorder adapted for a copy-once protocol for a video signal, the recorder including:

• video recording circuitry;
• an input terminal for receiving the video signal;
• a marker detector which detects a mark in a frame of the received video signal;
• a detector which detects a signal associated with the frame;
• attribute measuring circuitry which measures an image attribute of the frame;
• and
• a comparator which compares the measured attribute to a numeric representation of the attribute in the signal and enables operation of the video recording circuitry only if there is a match.

An encoding apparatus for protecting a video signal, comprising:

• a terminal for receiving the video signal;
• a marker circuit which places a marker on selected frames of the received video signal;
• a measurement circuit which measures an image attribute of each of the selected frames;
• and
• a circuit which marks the video signal with a signal that includes a numeric representation of the measured attribute of each frame having a marker.

A method for enabling copying of a protected video signal including in at least one frame a marker and having an associated signal including a numeric representation of an image attribute of at least one frame, the method comprising the steps of:

• detecting frames carrying the marker;
• tagging one of the detected frames with a predetermined signal;
• storing data indicative of a timing of each of the detected frames;
• recording the video;
• replaying the recorder video;
• while replaying the video, detecting the tagged frame;
• and
• inserting in the tagged frame and in selected subsequent frames a marker resembling the marker included in the protected video, the inserting being in accordance with the stored data.

An apparatus for enabling copying of a protected video signal including in at least one frame a marker and having an associated signal including a numeric representation of an image attribute of the frame, comprising:

• an input terminal for receiving the protected video signal;
• a first detector coupled to the input terminal and which detects the frame markers;
• a circuit coupled to the detector which writes a predetermined signal in at least one of the marked frames;
• a memory coupled to the first detector which stores data indicative of a timing of each of the detected marked frames;
• a second detector which detects the predetermined signal;
• and
• a circuit for inserting a frame marker into the video signal which is similar to the markers present in the protected video signal, the inserting being in accordance with the stored data.

A method of processing an original video signal to limit copying thereof, the original video signal having a watermark therein conveying data related to copy restriction, the method comprising:

• inserting a video marker in the original video signal, the video marker having an attribute corresponding, in a predetermined manner, to characteristics of the original video signal, wherein the correspondence indicates that the video signal is the original video signal;
• in response to a request to output the video signal for copying, detecting the watermark and checking that the video signal is the original video signal, the checking including checking the video marker's predetermined correspondence to the video signal, and only if the video signal is thereby confirmed to be the original video signal then:
• processing the original video signal to produce a copy thereof, the copy being non-identical to the original video signal so that the video marker no longer corresponds, in said predetermined manner, thereto;
• wherein subsequent checking of the copied video signal indicates that the video signal is not the original signal, whereby further copying can be restricted.