KR100489717B1 - Method and apparatus for compression compatible video scrambling - Google Patents

Abstract

Unlike many typical scrambling systems, scrambling and descrambling techniques are described that are compatible with all conceivable forms of signal compression systems. Scrambling techniques are based on the principle of applying fine local spatial distortion to pixels in a video image or the like to locally displace the pixels from their normal positions. Most compression systems rely on the condition that a good correlation exists in the image and that some small part of the image, i.e., the pixel is very similar to adjacent parts or pixels. Because the present technique does not reduce correlating the image and provides fine local spatial distortion that does not rearrange the pixels in the image, the pixels around other pixels before the application of the scrambling technique are the same after scrambling. It has a positional relationship. Complementary descrambling techniques restore locally displaced pixels to their normal positions to restore the video image to its original unscrambled state.

Description

Method and apparatus for compression compatible video scrambling

This application was filed on June 7, 1995 by John O. Ryan and Gregory C. Copenland, entitled "Method and Apparatus for Copy Protection for Various Storage Media Using Video Fingerprints." for pending application No. 08 / 473,047 ('047), entitled Copy Protection for Various Recording Media Using a Video Finger Print, published on 30 April 1996 by John O. Ryan. US Patent No. 5,513,260 ('260) entitled "Method and Apparatus for Copy Protection for Various Recording Media", entitled Gregory, on August 24, 1994 C. pending patent application No. 08 / 294,983 ('983), filed by Copenland, entitled "A Video Finger Print Method and Apparatus." In addition, this application, issued Nov. 12, 1996, by John O. Ryan, entitled "Apparatus and Method for Comprehensive Copy Protection for Video Platforms and Unprotected Source Material." for Comprehensive Copy Protection for Video Platforms and Unprotected Source Material, "US Patent No. 5,574,787 ('787).

The present invention relates to scrambling of video signals and the like, and more particularly, to an image scrambling method and apparatus compatible with all video recording, transmission and processing systems including signal compression processes.

There is a need for a stable video scrambling method in which the scrambled video is compatible with the various video compression systems currently in use. In particular, it should be compatible with compression systems based on Discrete Cosine Transform (DCT), which may use, for example, inter-field redundancy coding. Video expert groups (MPEG-1 and MPEG-2) are examples of such compression systems. In the foregoing applications, video signals are generally subjected to a sequence of scrambling, compression, decompression, and descrambling. Thus, the scrambled video undergoes compression and decompression processes prior to descrambling.

Scrambling systems in use tend to interfere with natural redundancy in the television signal that the aforementioned compression systems rely on to achieve maximum compression. If redundancy is hindered, the bit rate requirements for the compression system increase to an unacceptable level for the transmission path of the compressed video signal. Therefore, there is a need for a scrambling system that does not reduce natural redundancy to a level that requires excessive bit rates to provide a given picture quality.

For example, prior art scrambling systems that use line cut and rotation or line shuffling techniques greatly reduce the correlation of information in the DCT pixel matrix, and therefore, are inherently limited to DCT-based compression methods. Not compatible As mentioned above, the optimal operation of DCT systems is based on the presence of a high degree of interrelationship within each such matrix for performing efficient intra-field compression.

Moreover, pseudo-random field-by-field changes in the scrambling pattern that such scrambling systems often use to increase the stability can be achieved at a normal high level of inner-field redundancy of the video signal. The dependency makes it impossible to perform additional compression. For example, as disclosed by the trademark PhaseKrypt, as described in US Patents 5,058,157, Re 35,078, 5,438,620, 5,504,815, 5,608,789, 5,581,507 and 5,579,390, all filed as the same applicant. And scrambling systems based on the processes cited by reference herein are in fact also unsuitable for achieving the objects of the present invention, since the laws also reduce redundancy in this natural field.

There are various other scrambling methods that are fully compatible with DCT-based compression, such as sync suppression and video inversion. However, these methods cannot provide sufficient signal security and are therefore also unsuitable for achieving the objects of the present invention.

1 is a photograph of a scene where scrambling is not applied by the present invention.

2 is a photograph of a first simulation of an scrambled image in accordance with the present invention.

3 is a photograph of a second simulation of an scrambled image in accordance with the present invention.

4 is a photograph of a third simulation of an scrambled image in accordance with the present invention.

5 is a photograph of a fourth simulation of an scrambled image in accordance with the present invention.

6 is a block diagram illustrating one embodiment of a scrambling apparatus according to the present invention.

7 is a block diagram illustrating an embodiment of a descrambling apparatus according to the present invention.

The present invention provides a scrambling method and apparatus that overcomes the incompatibility problems of the above-described prior art scrambling systems, while further providing additional compatibility and satisfying various desired needs.

In particular, the present invention provides compatibility to prevent unwanted interactions between the scrambling system and the compression system, in particular,

Enable the compression system to operate on scrambled video against unscrambled video without any increase in bit rate required to provide a given picture quality,

Ensure that system performance (noise, distortion, etc.) is not affected by the inclusion of the scrambling function.

In addition, the present invention satisfies the following requirements.

Video standards

The scrambling method and apparatus of the present invention can be applied to any one of analog (NTSC, PAL, SECAM) or digital (CCIR-601) video signals.

Security

The scrambling method of the present invention inherently provides a high level of resistance to hacking, providing a basis for a stable scrambling system. In other words, it is very difficult to descramble video simply by analyzing the scrambled video.

In addition, the scrambling method of the present invention allows a very large number of variations (scrambling patterns), referred to herein as "warp patterns," and is intended for attempts and error attacks by unauthorized persons. Ensure how to fight. Approved descrambling techniques and devices are provided with the correct variations through a designated secure data encryption method.

Image concealment

The scrambling method of the present invention is mainly for entertainment applications such as video movies, television (TV) shows and the like. Thus, it is not necessary for the scrambling method to perform full concealment of the image. However, sufficient image concealment or distortion is provided so that the entertainment value of the video is effectively removed.

General video system compatibility

In addition to the above requirements and the accompanying advantages, for maximum operational flexibility, the present invention provides, for most but not all video processing methods and apparatuses designed to operate with unscrambled video signals, etc. Ensure that the video signal appears as a normal video signal.

In particular, the scrambled video signal according to the present invention is compatible with all video recording, transmitting and processing devices present in the production or editing environment. Passage of scrambled video through these devices does not cause any signal degradation beyond that caused by the passage of unscrambled video through the same devices (after descrambling).

In addition, the scrambling method or at least a specific embodiment of the present invention is compatible with consumer video cassette recorders (VCRs). That is, the present invention makes it possible to record a scrambled video signal on a consumer grade VCR and to play it later to descramble without causing significant further signal degradation.

In particular, the present invention provides a library of warp patterns, each of which gives a selected degree of local spatial distortion to the video image. The pattern select code determines which stored warp pattern will be supplied to the warp engine. The warp engine in turn applies the selected warp pattern to the video image to correspondingly spatially distort the image. In a typical application, such a scrambled video image and a pattern selection code that identifies (appropriately encrypted) the pattern is transmitted via suitable networks, such as cables, satellites, etc., to reserved users, for example.

The present invention includes compatible descrambling of authorized users of the scrambled signal. To this end, a pattern selection code is used to detect a descrambling warp pattern that is detected in the transmitted scrambled video image and is a complement to the warp pattern used to scramble the original video image from the plurality of stored warp patterns. Used to select. The warp engine applies a complementing warp pattern to the scrambled image, restoring it to the original unscrambled video image, thus allowing an authorized user to access the image.

For example, compression systems such as MPEG 1 and 2 described above depend on the condition that there is a good correlation in the image. In other words, what points in the image are very similar to other nearby points. If the scrambling system mixes the points representing the image in the image, the image information disappears and it is no longer true that adjacent points at any given point in the image are very similar. In other words, the association of the scene disappears, and a substantial amount of high frequency details that did not exist before are added. Such scrambling systems greatly increase bandwidth requirements and are therefore incompatible with many compression systems.

The present invention can avoid the problem of incompatibility because it provides a scrambling technique that does not reduce the correlation of images. All pixels near other pixels before applying the scrambling process have the same relationship even after the scrambling process. The distances between the pixels can change some, but there is no rearrangement of the pixels in the image. As such, the frequency capacity is increased in some areas and reduced in other areas. This results in a small amount of high frequency information being lost due to low pass filtering in the associated video processing apparatus. However, this is acceptable to the extent that the present invention has the advantage of full compatibility with all conceivable compression systems.

The method and apparatus of the present invention are easily described by the following analogy. For example, consider a scene seen through a colorless, sunken glass plate, such as a transparent glass plate with a bumpy surface. By specifying "bumpiness" parameters, a glass plate can be designed that prevents recognition of the scene's face and details of important images, although the general features of the scene can still be identified. In short, because entertainment value has been eliminated, scenes and video signals generally no longer have commercial value.

However, even if the scene is obscured, the scrambling technique of the present invention is compatible with all conceivable forms of compression systems. This is because the application of scrambling techniques does not reduce the interrelation of the images. That is, pixels adjacent to each other before the application of the scrambling process remain correspondingly adjacent even after the image is scrambled. The various pixels may be slightly closer or further away in some direction, but they are not shifted from their original order to each other.

Thus, the technique of the present invention is based on "local spatial distortion" of the actual video signal. More specifically, the present invention includes a particular kind of optical image scrambling which is the basis of a video scrambling system with all the desired features and requirements and thus the following advantages described above when modeled within the video domain.

Because of this, the video processing means for providing the scrambling method and apparatus of the present invention performs local spatial image distortion of the video signal similar to what happens in the scene seen through the rugged glass. Such a device is referred to herein as a spatial image distortion (SID) scrambler and has the following characteristics.

Displacement of each pixel of the original image by a certain amount (may be zero) in the horizontal and / or vertical direction

A given pixel in the scrambled image maintains the same set of adjacent pixels that it originally had in the image

Pixels along the edge of the image are not displaced out of bounds to prevent loss of parts of the image

In order to describe the scrambling pattern for each field, an array of pairs of numbers corresponding to one pair for each pixel is needed. For technical accuracy and ease of description, the field scrambling pattern, referred to herein as "warp", is arranged to remain fixed over relatively long periods, or may change slowly over time or frame-by-frame. to-frame). By appropriately selecting the warp pattern, it is possible to achieve a scrambling system with all the characteristics and requirements described above.

As used herein, the term "warp pattern" is used to select localized variations or localities of the degree of scrambling that do not reduce the interrelationships of the present invention represented by the bumpy obscuring glass exemplified in the preceding discussion. It is to be understood that this represents scrambling patterns. There are a number of available warp patterns that specify the magnitude of each pixel's displacement in the up, down, left, and right directions. The warp pattern may be fixed or stable over the entire movie, or the pattern may be progressively transformed from one pattern to another at intervals ranging from a selected time interval, such as the number of frames, to a longer time of several seconds. have. The purpose of changing warp patterns is to increase the level of security. That is, to make it more difficult for unauthorized persons to identify warp patterns and invalidate the scrambling process.

6 shows one embodiment of the scrambling apparatus of the present invention, referred to herein as scrambler 10. A digital video signal or the like is supplied to the field / frame storage device 14 via the input lead 12. Field / frame storage 14 provides a means for storing a field or frame of video and for supplying the video to a first input of warp engine 16. The warp pattern selection code generator 18 generates a warp pattern selection code that sequentially selects a desired warp pattern from a warp pattern library 20 including a lookup table, for example. The selected warp pattern is supplied to the second input of the warp engine 16. The warp pattern is applied by the warp engine to distort the pixel positions of the appropriate lines of the field or frame of video from the field / frame storage 14 accordingly.

1 to 5 each show an original image or image that is not distorted and warp patterns of four possible distortions. As can be seen in the figure, each warp pattern causes a different degree of distortion to the image.

Further, the warp pattern selection code from the code generator 18 is connected to the warp pattern selection code inserter 22. The warp pattern selection code is added to the scrambled video signal from the warp engine 16 to provide information for the descrambling process. Warp pattern codes can be inserted in a variety of ways and are generally encrypted. The output of the warp pattern selection code inserter 22 consists of a warp pattern selection code appropriately inserted into the scrambled video signal and is connected to the transmission network or compression engine, for example, via the output lead 24.

An embodiment of the descrambler 30 is shown in FIG. 7, and like elements are denoted by like reference numerals in FIGS. 6 and 7. For example, the scrambled digital video signal along with the warp pattern selection code corresponding to the signal of the output lead 24 of FIG. 6 is supplied to the warp pattern selection code detector 32. The warp pattern selection code supplied through the code generator 18 of FIG. 6 is detected and supplied to the warp pattern library 38. Warp pattern library 38 includes complements of warp patterns in warp pattern library 20 in scrambler 10 of FIG. 6. The scrambled digital video signal is supplied to a field / frame storage device 34 that supplies a field or frame of scrambled digital video to the warp engine 36. Field / frame storage 34 and warp engine 36 are generally similar to storage 14 and engine 16 of FIG. 6. The warp pattern selection code signal from the detector 32 instructs the warp pattern library 38 to send the correct complementary warp pattern to the second input of the warp engine 36. Because the warp pattern connected to the warp engine is the complement of the warp pattern used to scrambling the signal, warp engine 36 restores the distorted pixel to proper original positions in the scrambling process. As such, the output of warp engine 36 includes a descrambled video signal supplied to output lead 40.

Although the present invention has been described herein in connection with specific embodiments, various additional features and advantages will be apparent from the specification and drawings. Therefore, the scope of the present invention is defined by the following claims and their equivalents.

Claims (33)

In the method of scrambling a video image or the like, Providing a predetermined warp pattern suitable for fine local spatial distortion to be applied to individual portions of the video image; Applying the fine local spatial distortion to the individual portion of the video image such that individual portions of the image are locally finely displaced relative to their normal positions, as provided by the predetermined warp pattern; , Whereby the scrambled video image is compatible with signal compression processes. The method of claim 1, The warp pattern is sufficient to cause the fine local spatial distortion applied to portions of the video image to render the scrambled image invisible. The method of claim 2, Supplying the original video image in the form of a two-dimensional array of pixels, And said applying step comprises locally and spatially displacing pixels in said array in response to said predetermined warp pattern, while maintaining relationships between pixels. The method of claim 3, wherein The applying step, Starting with an amount of zero, displacing each pixel of the video image horizontally and / or vertically by a selected amount; And maintaining a given pixel in the displaced pixels as the same set of adjacent pixels that it had in the original video image. The method of claim 1, Storing a plurality of predetermined warp patterns suitable for selected different patterns of fine local spatial distortions to be applied to the video image. The method of claim 5, Retaining information identifying the predetermined warp pattern used to allow subsequent descrambling of the scrambled video image, when approved. The method of claim 6, The scrambled video image is transmitted over delivery networks, The holding step, Generating a pattern selection code indicative of a predetermined warp pattern to be applied to the video image; Inserting the pattern selection code into a scrambled video image that is transmitted for transmission with the pattern selection code. The method of claim 7, wherein Supplying the scrambled video image as an array of pixels; Providing a descrambling warp pattern that is complementary to the predetermined warp pattern; Applying the complementary warp pattern to the scrambled video image to restore the pixels of the array to their normal positions in the original video image prior to scrambling, wherein the scrambled video image is subsequently descrambled. The method of scrambling, such as a video image. The method of claim 8, Providing the descrambling warp pattern, Detecting a pattern selection code sent with the scrambled video image to identify the predetermined warp pattern; In response to the detected pattern selection code, providing the complementary descrambling warp pattern. The method of claim 5, And a fixed warp pattern is applied to the plurality of images over the period of time, wherein the plurality of changing video images are continuous over a period of time. The method of claim 5, And a plurality of varying warp patterns are applied to the plurality of images over the period of time, wherein the plurality of varying video images are continuous over a period of time. The method of claim 11, And the warp patterns change slowly over a period of time from a frame to a few seconds. In the apparatus for scrambling video data, etc., Means for generating a scrambling pattern selection code suitable for fine local spatial distortion to be applied to the individual portions of the video data; In response to the scrambling pattern selection code, applying a corresponding selected scrambling pattern to the individual portions of the video data to perform the fine local spatial distortion of the individual portions from normal positions of the individual portions of the video data. Means for Whereby the scrambled video data is compatible with signal compression processes. The method of claim 13, The applying means comprises means for storing the selected scrambling pattern; The selected scrambling pattern provides the micro local spatial distortion with sufficient distortion to render the scrambled video data invisible. The method of claim 14, A first field / frame storage device for storing and providing fields or frames of said video data, The field or frame comprises a two dimensional array of pixels. The method of claim 15, The storage means comprises a first memory means comprising a warp pattern library for storing a plurality of warp patterns each giving a different pattern of distortion to the array of pixels, And said generating means supplies to said applying means a warp pattern selected from said plurality of warp patterns stored in said warp pattern library. The method of claim 16, The application means, Receiving the array of pixels and responsive to the selected warp pattern to displace the pixels of the array by selected amounts, while maintaining a given pixel in the displaced pixels with the same set of pixels originally adjacent to it. A scrambling device, such as video data, comprising a warp engine. The method of claim 15, Responsive to said generating means, means for inserting said scrambling pattern selection code into said scrambled video data for transmission therewith. The method of claim 18, The insertion means, When approved, receive an array of pixels of a field or frame of video data to allow subsequent descrambling of the scrambled video data, and send the pattern selection code from the generating means to a field or frame of scrambled video data. A scrambling apparatus such as video data, comprising multiplexing means for embedding. The method of claim 18, Further provides descrambling of the scrambled video data, Means for receiving the combined scrambled video data and scrambling pattern selection code and detecting the pattern selection code; Second memory means for supplying a selected descrambling pattern that is complementary to the selected scrambling pattern, in response to the pattern selection code; In response to the selected descrambling pattern, means for descrambling the scrambled video data to restore portions of the video data to their regular positions. The method of claim 20, A second field / frame storage device for providing said descrambling means with fields or frames of said scrambled video data, A scrambling apparatus such as video data, in which a field or frame is formed of a two-dimensional array of pixels. The method of claim 21, And the second memory means comprises a warp pattern library for storing a plurality of descrambling warp patterns that are complements of respective scrambling patterns in the first memory means. The method of claim 21, The descrambling means, A warp engine for receiving the array of pixels and responsive to a selected descrambling warp pattern to restore the pixels of the array to their normal positions in the original two-dimensional array. . In the apparatus for scrambling video data, etc., Means for providing a selected amount of video data; Means for generating a scrambling pattern selection code; Memory means for supplying a selected scrambling pattern for responsive to the scrambling pattern selection code, for locally displacing individual portions of the video data from their normal positions; Means for, in response to the selected scrambling pattern, locally displacing individual portions of the video data by an amount sufficient to render the video data invisible; Means for retaining the scrambling pattern selection code to allow identification of the selected scrambling pattern. The method of claim 24, The providing means comprises a field / frame storage device for providing a field / frame of video data; The memory means comprises a lookup table of a plurality of warp patterns; The displacement means comprises a warp engine for locally displacing individual portions of the field / frame according to a selected warp pattern. The method of claim 25, Further comprising descrambling of the scrambled video data, Means for detecting the scrambling pattern selection code in response to the holding means; Second memory means for supplying a descrambling warp pattern complementary to a pattern of each of the plurality of warp patterns, in response to the detected pattern selection code; And a second warp engine, and means for restoring individual portions of the locally displaced field / frame to regular positions in response to the complementary warp pattern. In the method of scrambling video data, Supplying a field or frame of video data; Storing a plurality of selected warp patterns that locally finely displace selected portions of the video data from their normal positions; Selecting a warp pattern from the stored plurality of warp patterns; In response to the selected warp pattern, locally displacing the field or frame of the video data sufficiently to render the video data invisible, Whereby the scrambled video data is compatible with signal compression processes. The method of claim 27, Adding a pattern selection code identifying the selected warp pattern to the locally displaced video data; Transmitting the scrambled video data including the pattern selection code to an associated video data processing system. The method of claim 28, Further provides descrambling of the scrambled video data, Detecting the pattern selection code in the scrambled video data; In response to the detected pattern selection code, selecting a descrambling warp pattern that is complementary to the scrambling warp pattern; Responsive to the complementary warp pattern, restoring locally displaced selected portions of the video data to their normal positions. In the method of scrambling digital video data, Supplying a field or frame of video data to a first input of a warp engine; Storing the selected warp patterns in a warp pattern library; Generating a pattern selection code indicative of a warp pattern to be applied to the video data; In response to the pattern selection code, selecting a warp pattern from the stored plurality of patterns; Responsive to the selected warp pattern, selecting the selected warp pattern to locally displace individual portions of the field or frame in a small amount horizontally and / or vertically by an amount sufficient to render the resulting scrambled video data invisible. And supplying to the second input of the warp engine. The method of claim 30, Adding a warp pattern selection code representing the selected warp pattern to the scrambled digital video data; Transmitting the scrambled digital video data comprising the warp pattern selection code to an associated video data processing system. The method of claim 31, wherein Further provides descrambling of the scrambled digital video data, Receiving the scrambled digital video data at a warp pattern selection code detector to detect the warp pattern selection code; Supplying a field or frame of scrambled digital video data to an input of a warp engine; In response to the detected warp pattern selection code, selecting a descrambling warp pattern that is complementary to the scrambling warp pattern; Supplying the complementary warp pattern to a second input of the warp engine; Responsive to the complementary warp pattern, recovering the locally displaced portions of the field or frame of digital video data to their normal positions to provide the unscrambled digital video data. Scrambling method. And applying spatial distortion to the image.