METHOD AND APPARATUS FOR COMPRESSION COMPATIBLE VIDEO FINGERPRINTING

Abstract: Fingerprinting and fingerprint detection techniques are described which, unlike typical fingerprint systems used to conceal video signals, are compatible with all conceivable forms of signal compression systems while still allowing viewing of the video signal. The fingerprint technique is based on the principle of applying very slight local spatial distortion to the pixels in a video image, and the like, by means of selected warp patterns. Thus the technique provides means for conveying, within the video signal, selected information in the form of the fingerprint which is detectable electronically but which is not noticeable to a critical viewer who is watching the video signal. That is, the resultant fingerprinted video signal will appear to be identical to the undistorted video signal. The fingerprint detection technique provides for the recovery of the conveyed information which may comprise an instruction to prevent the fingerprinted video image from being copied, messages which allow identifying the source and date of an unauthorized copy of the video image, etc.

Description: METHOD AND APPARATUS FOR COMPRESSION COMPATIBLE VIDEO FINGERPRINTING CROSS REFERENCE TO RELATED APPLICATIONS This application is related to copending patent application Serial No 08/473,047 ('047), filed 06/07/95 entitled Method and Apparatus for Copy Protection for Various Recording Media Using a Video Finger Print, by John O. Ryan and Gregory C Copeland, to U S Patent No. 5,513,260 ('260) issued 04/30/96 entitled Method and Apparatus for Copy Protection for Various Recording Media, by John O Ryan, and to copending application Serial No 08/294,983 ('983), filed 08/24/94 entitled A Video Finger Print Method and Apparatus, by Gregory C Copeland This application also is related to copending patent application Serial No , filed entitled Method and Apparatus for Compression Compatible Video Scrambling, by John O Ryan BACKGROUND OF THE INVENTION The present invention relates to the fingerprinting of video signals and the like, and more particularly, to a fingerprint technique which conveys selected information within a transmitted video signal while still permitting a viewer to watch the video signal There are two prior patent applications of mention above which discuss video fingerprint methods for video signals The '983 application by G C Copeland, incorporated herein by reference, discloses a video fingerprint method that inserts a low frequency low level signal within the video signal, such that is not observable to the viewer, but is readily detectable by a special detection circuit This low level signal operates over many fields in a manner that makes it possible to detect and identify the source of the signal The disadvantage of '983 prior art is that the fingerprint method may not be compatible with certain video compression systems The second application, the '047 application by J.O. Ryan and G.C. Copeland, incorporated herein by reference, uses the concepts of the '635 patent application for a scrambling system for various recording media There is a need for a secure video fingerprint method having the property that the fingerprinted video be compatible with the various video compression systems currently in use In particular, it should be compatible with compression systems based on for example the Discrete Cosine Transform (DCT), which may employ inter-field redundance coding Motion picture experts group (MPEG-1 and MPEG-2) are examples of such compression systems In anticipated applications, the video signal generally is subjected to the processes of fingerprinting, compression, decompression and fingeφrint detection - in that order The fingerprinted video therefore will be subjected to the processes of compression and decompression prior to fingerprint detection The fingerprint systems of previous mention may tend to disturb the inter-field redundancy in a television signal that the compression systems of previous mention depend upon for proper operation When the inter-field redundancy is disturbed, the bit rate requirements for the compression system rise, possibly to an unacceptable level, for the transmission path of the compressed video signal Therefore there is need for a fingerprint system that does not degrade the inter-field redundancy to a level that requires excessive bit rates to provide a given picture quality SUMMARY OF THE INVENTION The present invention provides a fingerprint method and apparatus which overcomes the compression system incompatibility of the prior art fingerprint systems of previous mention, while further meeting other various desirable requirements such as not being observable to a viewer while conveying information in the active video signal In addition, the present invention meets requirements such as the following Video standards The fingerprint method and apparatus of the invention is applicable to either analog (NTSC, PAL, SEC AM) or digital (CCIR-601) video signals Security The present fingerprint method and apparatus intrinsically provides a high level of resistance to hacking In other words, it is very difficult to remove the fingerprint from the video Invisibility The present fingerprint method and apparatus primarily is intended to convey information in entertainment applications such as video movies, television (TV) shows, and the like It is essential that the fingerprint method not affect the entertainment value of the video image while being securely concealed within the image, but must be readily detectable by, for example, a detection circuit in a disk or tape recorder or other signal processing apparatus. General video system compatibility In addition to the foregoing requirements and attendant advantages, for maximum operational flexibility, the invention ensures that the fingerprinted video signal appears as a normal video signal to most if not all video processing methods and devices designed to operate with unfingerprinted video signals, and the like. In particular, the video signal fingerprinted in accordance with the invention is compatible with all video recording, transmitting and processing devices likely to exist in a production or editing environment Passage of the fingerprinted video through these devices does not cause the fingerprint to be removed or be made more difficult to detect. Further, the present fingerprint method and apparatus, or at least a particular embodiment thereof, is compatible with consumer video cassette recorders (VCRs). That is, the invention makes it possible to record the fingerprinted video signal on a consumer grade VCR, and replay it later for detection without any likelihood of it being removed during the record/replay process. More particularly, the invention provides a library of warp patterns, each of which is capable of imparting a selected degree of local spatial distortion to a video image. In response to an operator's selection, a pattern select code determines which stored warp pattern is supplied as a fingerprint signal to a warp engine. The warp engine in turn applies the selected warp pattern to the video image to correspondingly locally spatially distort the image. The slight distortion imparted by the selected warp pattern is not observable to a viewer, but is detectable by a circuit in a recording device to, for example, prevent the recording device from copying the video signal. Alternatively, the fingerprint also allows subsequently comparing the original unfingerprinted video signal and an unauthorized copy of the fingerprinted video signal, to determine the origin, date, etc., of the unauthorized copy. For example, in the event a fingerprinted video signal is illegally recorded onto a disk or tape, the spatial distortion imparted by the fingerprint technique remains with the recorded video image. Thus a subsequent comparison between the pixel positions of a fingerprinted signal (that is, an illegal copy) and the unfingerprinted original signal, can be used to identify the source of the illegal copy. BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a photograph of an image in which a fingerprint has not been applied by the invention, FIG 2 is a photograph of an image in which a fingeφrint has been applied in accordance with the invention, FIG 3 is a block diagram illustrating an embodiment of a fingerprint apparatus in accordance with the invention, and FIG 4 is a block diagram illustrating an embodiment of a fingeφrint detection apparatus in accordance with the invention DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method and apparatus for fingerprinting, via a signal fingerprinting technique, various program distribution media such as digital video disk (DVD) or digital video cassette recorder (DVCR), as well as broadcast and cable video distribution channels A compression system such as, for example, MPEG 1 and 2 of previous mention, relies on the condition that a high degree of redundancy exists in the image, both intra-field and inter-field redundancy The invention employs the same basic spatial image distortion concept as disclosed in the above-mentioned related application entitled Method and Apparatus for Compression Compatible Video Scrambling, by J O Ryan However, the present invention applies a much smaller distortion which can still be detected by a suitable circuit and which will not be noticeable to a viewer The explanation of the invention method and apparatus is facilitated by the following analogy Consider a scene viewed through a sheet of colorless transparent glass with a slightly bumpy surface By specifying very slight "bumpiness" parameters, the resultant image will appear to be identical to the undi storied image, although the positions of the specific pixels in the image are slightly shifted relative to their normal positions In effect, the applied fingerprint does not distort the image visibly, but the small distortion may still be readily detectable by a suitable detector circuit For example, a recorder having this fingerprint detector circuit could be prevented from copying the fingerprinted video signal Thus, in effect the fingerprint added to the video signal is a means for conveying a message or instruction which, in the above example, instructs the recorder to not copy the video signal Alternatively, in the event that an illegal copy of the fingerprinted video signal is found, the message conveyed can be used to identify the source of the illicit copy, the date of recording, or other information. Although the present invention conveys information within the video signal, the fingeφrint technique is compatible with all conceivable forms of compression systems because the application of the fingerprint does not materially increase the information content of the video signal The various pixels may be very slightly closer or further from each other in any direction. Thus it follows that the high frequency content or detail is very slightly increased and decreased in various areas of the image, but there is no noticeable change in the bit rate of the compressed (or uncompressed) signal. Thus, the technique of the invention is based upon a "local spatial distortion" of the active video signal More particularly, the invention comprises a particular kind of optical image scrambling which when modeled in the video domain becomes the basis of a video fingerprint system having all of the desirable properties and requirements, and thus the attendant advantages, of previous mention. To this end, a video processing means for providing the fingeφrint method and apparatus of the invention, embodies a slight local spatial image distortion of a video signal which is not visually noticeable and which is electronically detectable Such a device is referred to herein as a spatial image distortion (SID) fingerprint inserter having the following properties- • displacement of each pixel of the original image by a slight amount unnoticeable to the eye (which may be zero) horizontally and/or vertically • maintaining a given pixel in the fingerprinted image with the same set of contiguous pixels that it had in the original image. An array of number pairs, one pair for each pixel, is needed to describe the fingerprint signal for each field The field fingeφrint signal, herein termed a "warp" pattern for ease of description, may be arranged to remain fixed for relativity long periods, to change slowly with time, or to change from field to field. By appropriate choice of warp patterns and by limitation of their range so as to be detectable electronically but not visually noticeable, it is possible to effect a fingerprint system having all of the properties and requirements specified above There are an infinite number of waφ patterns available each of which designates the amount of displacement horizontally and vertically of each pixel in the image The waφ pattern can be fixed for an entire movie or vary throughout the movie In one application of the invention the warp pattern remains unchanged throughout the entire movie or program, and that particular pattern may designate a particular copy, or the broadcast time and source, of the program for broadcast application If illicit copies of the program are discovered later, these copies may be compared with the original unwaφed program in a suitable correlating device which identifies the specific warp pattern used, to thereby identify the source of the illicit copy. For this application, the warp pattern can be "morphed" from one pattern to another, or can be faded to zero warp and back again, preferably gradually over a selected time interval such as a number of frames up to a longer time interval of a plurality of seconds. The puφose for applying changing warp patterns is to increase the level of security, that is, to make it even more difficult for unauthorized persons to discover the identify of the warp pattern and thus override the fingeφrint process In another application the teachings of the present invention may be used to convey instructions to a device such as, for example, a video recording device The presence of the warp pattern may be used to instruct the recording device to not copy that particular program carrying the warp pattern For this application, it is desirable that the warp pattern vary over time at a rate just enough to facilitate detection, but not so fast as to cause visible change in the picture when viewed by critical viewers Clearly, if the warp pattern is fixed in time it will be difficult or impossible to detect it without reference to the unwarped image because of its subtle nature and because normal geometrical distortions in the camera or picture origination device may generate "natural" warp patterns In this latter application the detector is designed to look for small changing geometrical distortions of the image which follow a pre-ordained pattern In the presence of rapidly changing scenes the detector would not be expected to work reliably. However, most programs contain periods of little scene change when reliable unambiguous detection becomes feasible For copy protection applications, for example, it would not matter if the detection process took several minutes to make an unambiguous decision that the program is not to be copied FIG 3 illustrates an embodiment of a fingerprint apparatus of the invention herein referred to as a fingerprint inserter 10 A digital video signal or the like is supplied to a field/frame store 14 via an input lead 12 The field/frame store 14 provides means to store a field or frame of video and to supply the video to a first input of a warp engine 16 In response to a user selection, a warp pattern select code generator 18 generates a warp pattern select code which, in turn, selects a desired warp pattern from a warp pattern library 20 which may include for example a look up table. The selected warp pattern is supplied as a fingerprint signal to a second input of the warp engine 16. The warp pattern is applied by the warp engine to distort accordingly the pixel positions in the appropriate lines of the field or frame of video from the field/frame store 14 The output of the waφ engine 16 consists of the fingerprinted video signal which is coupled via an output lead 24 to any downstream digital processing circuits and/or devices used in the associated video processing application FIGs. 1 and 2 illustrate an original picture or video image without a fingeφrint and a video image with the addition of a fingerprint, respectively, in accordance with the present invention As may be seen in FIG 2, the application of a warp pattern does not cause a visually noticeable distortion in the image In this embodiment, the fact that the video has undergone varying spatial image distortion according to some pre-arranged pattern and/or timetable can be used to instruct a video recorder not to copy this video, for example A special detector circuit in a video recorder makes a determination that the video has been fingerprinted according to the pre¬ arranged pattern and generates a "don't copy" command. For example, a particular SID pattern may be used which generates a slight vertical nonlinearity in the scene, such that while the center of the image is held fixed, the top and bottom regions are caused to meander vertically about their proper locations at a predetermined rate The amount of the displacement may be a fraction of a percent of picture height so as to be invisible, and the reate of change may be, say, one cycle per second. A suitable detector may be constructed as shown in Figure 4. Firstly, in order to minimize the effect of normal scene movements, a motion detector examines the edges and the center region of the image for movement and applies a compensating correction to the video fed to the SID detector In the event that large changes are detected, the measurement process is temporarily halted. This makes it easier for the SID detector to detect the SED pattern in the presence of normal scene motion The motion-compensated video is then subjected to motion detection in only those regions affected by the SID pattern, in this case regions near the top and bottom of the image The resulting motion vectors are examined for correspondence both in magnitude and time with the vectors expected for the particular SID pattern used, and if a correspondence is found the "fingerprint " has been detected In this embodiment, the fact that the video has undergone spatial image distortion according to some pre-arranged pattern and/or timetable is used to indicate the source of an illicit copy The various sources or prints of the original video are subjected to different SID patterns which uniquely identify the source or the print At a later time, if an illicict copy of the program surfaces, it will be possible to identify the source or print from which this copy was made To do this, the original video (from an archive) is compared with the illicit copy The two video signals are first frame-synchronized and the signal levels are adjusted to be equal Any horizontal or vertical offsets between the two images are also corrected for using simple subtraction techniques to show up difference In one embodiment of the invention, the SID may be applied only to specific segments of the video program In another embodiment, a specific SID pattern may be faded in and out according to a specific timetable Or both embodiments may be combined to increase the possible permutations In an example of the latter, a particular SID pattern may be used which generates a slight horizontal non-linearity in the scene, such that while both sided of the image remain fixed, the center meanders to the left and right of its proper location at a predetermined rate Furthermore, only certain time segments of the program are subjected to this distortion An operator viewing the subtracted images on a monitor can easily see this SID pattern, note the time segments when it occurs and its rate of change, and thereby identify the source of the illicit copy Although the invention has been described herein relative to specific embodiments, various additional features and advantages will be apparent from the description and drawings For example, the invention techniques may be applied to a medium other than video signals, such as, for example, photographs, computer generated images, etc By way of example, the local spatial distortion technique can be used to identify the origin of illegal copies of proprietary photographs To this end, as described above, a negative of a photograph may be electronically reproduced several times using a slightly different warp pattern each time by altering the scanning beam very slightly Each resulting new negative thus contains a different fixed spatial distortion which can be detected subsequently in accordance with the invention as described above to identify the photograph and thus the source of any illegal copies thereof. Thus the scope of the invention is defined by the following claims and their equivalents

Claims: What is claimed is. 1. A method of fingerprinting a video image and the like, comprising the steps of providing a predetermined warp pattern commensurate with a selected very slight local spatial distortion to be applied to the video image; and applying the selected very slight local spatial distortion to the video image to locally displace individual portions of the image with respect to their normal locations, in response to the warp pattern. 2 The method of claim 1 wherein the local spatial distortion produced by the associated predetermined warp pattern represents conveyed information such as a notice that the video image is not to be copied, the originating source and/or the date of the image 3 The method of claim 1 including the step of storing a multiplicity of predetermined warp patterns commensurate with selected different patterns of local spatial distortions to be applied to a video field corresponding to the video image. 4 The method of claim 3 wherein the warp patterns are such that the very slight local spatial distortion applied to the portions of the video image renders the fingerprinted image watchable while being electronically detectable 5. The method of claim 4 including the step of: retaining information which identifies the predetermined warp pattern used, to allow subsequent identification of a copy of the fingerprinted video image. 6 The method of claim 2 including supplying the original video image in the form of a two-dimensional array of pixels, and wherein the step of applying includes locally spatially displacing very slightly the pixels within the array while retaining inter-pixel relationships, in response to the predetermined warp pattern, to provide a fingerprinted video image 7 The method of claim 6 wherein the step of applying further includes the steps of displacing each pixel of the video image by a selected slight amount, beginning with zero amount, horizontally and/or vertically; and maintaining a given pixel in the displaced pixels with the same set of contiguous pixels that it had in the original video image 8 The method of claim 7 wherein the pixels are displaced a selected fraction of a pixel 9 The method of claim 6 wherein the fingerprinted video image is delivered via a delivery networks, including the steps of detecting the pixel spatial displacements between the original video image and an illicit copy of the delivered fingerprinted video image, and wherein the displacements correspond to the fingerprint and comprise the information conveyed with the video image 10 The method of claim 9 including the step of comparing the pixel spatial displacements with a multiplicity of predetermined warp patterns to determine the warp pattern corresponding to the fingerprint contained in the illicit copy, to identify the illicit copy 1 1 The method of claim 6 wherein the fingerprinted video image is delivered as a succession of video fields, including the steps of detecting the fingerprint in the video image by detecting the pixel displacements m the field of video, and preventing the delivered fingerprinted video image from being copied in response to the step of detecting the fingerprint 12 The method of claim 3 wherein there are a successive plurality of changing video images over a period of time, wherein a fixed warp pattern is applied to the plurality of images over the period of time 13 The method of claim 3 wherein there are a successive plurality of changing video images over a period of time, wherein changing warp patterns are applied to the plurality of images over the period of time 14 The method of claim 13 wherein the warp patterns change slowly over a time period of from a field to several seconds of time 15 The method of claim 3 including the steps of applying a different warp pattern to each print of a video image to provide fingerprinted prints, detecting the different fingeφrints in each of the respective fingeφrinted prints, and comparing the different detected fingerprints of respective fingerprinted prints of the video image with the unfingerprinted video image to identify an illicit copy of a video image print 16 Apparatus for fingerprinting video data and the like, comprising means for generating a warp pattern select code commensurate with a selected very slight local spatial distortion to be applied to the video data, and means responsive to the warp pattern select code for applying a corresponding selected warp pattern to the video data to effect the selected very slight local spatial distortion as very slight local displacements of portions of the video data from their normal locations 17 The apparatus of claim 16 wherein the data comprises a field of video, and the means for applying includes means for storing the selected warp pattern, and wherein the selected warp pattern provides a very slight distortion which is un- noticeable in the scrambled video data while being detectable electronically 18 The apparatus of claim 17 wherein the very slight local spatial distortion applied by the warp pattern comprises a fingerprint which represents information conveyed within the video data itself 19 The apparatus of claim 18 wherein the fingerprint video data is selectively delivered to a receiving facility, including means receiving the fingerprinted video data for preventing the copying of the video data in response to the fingerprint in the video data 20 The apparatus of claim 18 including a field/frame store for storing and providing fields or frames of the video data, wherein a field or frame comprises a two-dimensional array of pixels 21 The apparatus of claim 20 including memory means comprising a warp pattern library for storing a multiplicity of warp patterns each of which imparts a different pattern of distortion to said array of pixels, and said generating means supplies to said applying means a selected warp pattern, commensurate with a respective fingerprint, from the multiplicity of warp patterns stored in the warp pattern library 22 The apparatus of claim 21 wherein said generating means supplies to the applying means a selected succession of changing warp patterns over a predetermined period of time 23 The apparatus of claim 21 wherein the applying means includes a warp engine receiving said array of pixels and responsive to said selected warp pattern for displacing the pixels of the array by selected very slight amounts while maintaining each pixel in the displaced pixels with the same set of pixels originally contiguous therewith 24. The apparatus of claim 20 wherein the fingerprinted video data is selectively delivered to a receiving facility, including: means for detecting the spatial displacements of the pixels in the original video data and the corresponding pixels in an illicit copy of the fingerprinted video data; and means for comparing the pixel displacements with a plurality of warp patterns to determine the identity of the corresponding fingerprint and thus of the illicit copy 25 Apparatus for fingeφrinting video data and the like, comprising: means for providing a field of the video data; means for generating a warp pattern select code; memory means for supplying a selected warp pattern corresponding to a respective fingerprint in response to the warp pattern select code, means for fingerprinting the field of the video data by locally slightly displacing individual portions thereof from their normal locations in response to the selected warp pattern, wherein the fingerprint is not noticeable to a viewer but is detectable electronically; and means for delivering the fingerprinted video data to a receiving facility, said fingerprint conveying to the receiving facility selected information pertinent to the video data. 26 The apparatus of claim 24 wherein the providing means includes a field/frame store for providing the field of video data; the memory means includes a lookup table of a multiplicity of warp patterns; and the fingerprinting means includes a warp engine for locally displacing the individual portions in accordance with the selected warp pattern 27. The apparatus of claim 25, including: means responsive to the delivering means for detecting the fingerprint in the field of video data; and means responsive to the detecting means for preventing copying of the fingerprinted video data 28 The apparatus of claim 25, including means for detecting the local slight spatial displacements in the individual portions of the original field of video data and an illicit copy of the fingeφrinted field; and means responsive to the detecting means for comparing the local spatial displacements with a multiplicity of warp patterns to identify the warp pattern used and thus identify the illicit copy 29 A method of fingerprinting digital video data, comprising the steps of supplying a field or frame of said video data, storing a selected plurality of warp patterns commensurate with different very slight local spatial distortions representative of a respective plurality of fingerprints, selecting a warp pattern from said stored plurality of warp patterns, and locally spatially displacing individual portions of said field or frame of said video data from their normal locations in response to said selected warp pattern to embed the corresponding fingerprint information within the video data without degrading the watchability of the video data 30 The method of claim 28 wherein the fingerprinted video data is selectively delivered to a receiving facility, including the steps of detecting the fingerprint information, and preventing the copying of the fingerprinted video data in response to the detected fingerprint information embedded within the video data 31 The method of claim 28 wherein the fingerprinted video data is selectively delivered to a receiving facility, including the steps of detecting a spatial displacement in the field or frame of the original video data and the corresponding field or frame of an illicit copy of the fingerprinted video data, and comparing the spatial displacement with the plurality of warp patterns to determine the identity of the corresponding fingerprint information and thus of the illicit copy 32 A method of fingerprinting digital video data, comprising the steps of: supplying a field or frame of said video data to a first input of a warp engine; storing a selected plurality of warp patterns, commensurate with a respective plurality of fingeφrints, in a warp pattern library; generating a pattern select code indicative of a warp pattern to be applied to the video data; selecting a warp pattern from said stored plurality of patterns in response to the pattern select code; and supplying said selected warp pattern to a second input of said warp engine to locally very slightly spatially displace selected portions of said field or frame an amount which is insufficient to be noticeable to a viewer, in response to said selected warp pattern, wherein said fingeφrint conveys selected information within the video data which is electronically detectable although not noticeable to the viewer. 33 The method of claim 31 including the steps of: delivering the fingerprinted video data to a receiving facility; detecting the fingerprint and the corresponding selected information; and applying the detected selected information to prevent copying of the fingerprinted video data or to identify a source of an unauthorized copy of the video data.

Inventors: RYAN JOHN O, RYAN, JOHN, O.
Applicants: MACROVISION CORP, RYAN JOHN O, MACROVISION CORPORATION, RYAN, JOHN, O.
Application year: 1997
Main classification: H04N5
IPC codes: G06T3, H04N5, H04N7