Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1998-10-01
2002-04-16
Boccio, Vincent F. (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C380S203000, C382S233000
Reexamination Certificate
active
06374036
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to copy protection of video material by embedding robust identification codes (e.g., watermarks or fingerprints) in video signals, and use of these identification codes for a “copy-once” method and apparatus.
2. Description of the Related Art
Copy protection of video material, for instance movies on video tape, is a well-known problem. A solution for conventional analog video taped material is the well-known Macrovision anticopy process, which adds pulses to the vertical blanking interval of the video signal (see Ryan U.S. Pat. Nos. 4,631,603 and 4,695,901, incorporated herein by reference). These added pulses confuse the automatic gain control circuitry of a typical VCR (video cassette recorder) and thereby make any recording of the video signal unviewable, by disrupting the picture.
Copy protection is an even more important problem with digital video, because by its nature a digital recording of a video signal is an exact replica of the original, and unlike analog recording, suffers no degradation. Hence with digital video recording there is even more incentive for people to make unauthorized copies of copyrighted video material. This has been a major impediment to the introduction of prerecorded digital video media and to commercial introduction of digital video recorders.
One known solution to this problem is use of watermarks. Watermarks are digital codes embedded in a video signal which can be read by a reader (detector) present in a compliant video recorder or player, where the watermark itself does not visibly interfere with the video signal (i.e., there is no significant degradation). The watermark is read by the detector circuitry in the recorder or player which instructs the recorder or player to perform certain functions, such as do not copy, or allow only a single copy of the material, depending on the watermark. Use of watermarks requires special detector circuitry in a compliant recorder or player.
Watermarks are special signals that are built into the video, so they cannot be stripped out without substantially damaging the video signal; it is difficult to remove a watermark deliberately or accidentally. Watermarks are a so-called bilateral copy protection scheme that require a specially adapted (“compliant”) recorder/player which can detect and respond to the watermark. A conventional non-compliant recorder ignores the watermark and hence the watermark will have no effect. This to be contrasted with the above-described “unilateral” Macrovision anticopy process which however in general is not suitable for protecting a digital signal.
While such watermarks are useful and have already been introduced to a limited extent in commercial applications, they have significant drawbacks. The most important drawback is in the copy-once situation, typically encountered in the cable television industry with pay per view broadcasting, for instance of movies. The cable television industry has created an expectation amongst its subscribers that they are allowed to make their own personal recordings, using a VCR, of the cable transmission of for instance a movie. While this single recording by a user for his personal use has apparently generally been found acceptable by both copyright owners and the cable television industry, the copyright owners (e.g. movie studios) do not wish to allow any second generation recordings to be made. Hence it is desirable to allow a copy-once video transmission, for instance via cable television, while prohibiting any second generation copies of the first copy.
Prohibition of such second generation recordings is possible using conventional watermark technology. Typically, for this situation, there are two classes of watermarks: a “copy-never” watermark and a “copy-once” watermark. Both must be read by the compliant video recorder doing the copying, which changes the copy-once watermark to a copy-never watermark upon recording. A problem with this is the extra cost in the compliant recorder, since it must be able to detect both of the two different watermarks and also add (write) the copy-never watermark. Such a system, in addition to being relatively expensive to implement, is also easily subject to technical defeat, and hence is inadequate.
SUMMARY
There is a need for a copy-once method in the digital video recording field that offers improved economics and security over the existing art. There is also a need for a copy-once method that requires only one watermark and therefore only one watermark detector per compliant recorder (or player) apparatus. Such a method needs to have no watermark adders or modifiers in compliant recorders. (“Compliant” here means an otherwise conventional apparatus that has been modified by additions of special circuitry and/or software in accordance with the invention.) Manufacturers of video players and recorders will add the complying circuitry and software to their products if they wish to practice the invention, and suppliers of video material will similarly add the required signals to their programs.
Additionally such a system should be simple to execute, require no secrets to be maintained to ensure its security, and operate in both the analog and digital domains. A further requirement is that even if the first (permitted) recording is made on an existing conventional consumer VCR, whether VHS, S-VHS or 8 mm (which normally could not be expected to comply with a digital copy-once protocol), second generation copying by a compliant recording device is still prevented.
Therefore in accordance with the present invention, there is a single class of watermark, which has two versions: copy-never and copy-once, which are identical except for a single bit. In accordance with the invention there is no need to add a watermark to the video upon recording, because instead the copy-once watermark is converted, by a simple one bit change, to the copy-never watermark. (“Watermark” as used here means both watermarks and other types of digital “fingerprints.”) The present invention is applicable to both digital video and analog video (e.g. VHS, S-VHS or 8 mm video), as described below. The present watermark survives conversion from the analog to the digital domain or digital to analog domain, survives compression, and survives conversion between television standards i.e., PAL to NTSC or NTSC to PAL.
In accordance with the invention, a watermark, which is a digital signal, is conventionally embedded in a video image. A subset of the watermark bits carries a digital attribute (a number) which is a numeric characteristic of the video signal, for instance an average amplitude of the video signal over one video field or frame. The video attribute in accordance with this invention preferably is some unique characteristic of a video signal which changes maximally from frame to frame and which is not subject to the typical distortion present in the associated analog or digital transmission channel. The attribute is used only for the copy-once situation.
To prepare (encode) the video with the watermark, in addition to conventionally embedding the watermark, one also randomly (or pseudo-randomly) chooses one frame (or field), for instance one frame per every 10 seconds of video, and digitally calculates the attribute for that frame (or field) of the video signal. A “field marker” (“tag”) is also added to that frame to indicate that it is a selected frame. This field marker is a special signal located in the normally invisible portion of the video frame, for instance in the overscan portion.
The encoded video signal is conventionally transmitted e.g. via cable television or satellite, to the consumer who attempts to record it using his compliant digital video recorder. The compliant digital video recorder prior to recording examines the watermark, verifies it, detects the copy-once bit in the watermark, and extracts the associated attribute value from the watermark. The compliant recorder also detects the field marker on a particular marked field, measures the attribute of
Capitant Patrice
Davidson Clayton L.
Holzgrafe James
Kurowski Kordian J
Mellows Andrew
Boccio Vincent F.
Klivan Norman R.
Macrovsion Corporation
Okumoto Victor
LandOfFree
Method and apparatus for copy-once watermark for video... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for copy-once watermark for video..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for copy-once watermark for video... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2915343