RU2195084C2 - " water-mark "method and single-copying device for video recording - Google Patents

Abstract

FIELD: copyprotecion of video materials by input of stable identification codes into video signals. SUBSTANCE: water mark is used in digital video signal in method and single-copying device. Built-in water-mark has two versions: one water-mark symbolizes total prohibition of copying and another water- mark denotes permission for single copying. They differ by one bit of water-mark. Water-mark includes additional bits presenting attribute ( image parameters ) of particular TV frame of video signal in digital form, for instance, mean value of amplitude of video signal field. Attribute frame of it is included in water-mark, has field or frame marker which is special signal located in invisible part of frame. Video tape recorder tests water-mark and bit ( 48, 54 ) of single copying, extracts proper attribute from water-mark ( 56 ) and compares it with measured attribute from marked video signal. Recording is allowed only if extracted value of attribute and measured value of attribute match. In process of recording frame marker is removed which prevents formation of second generation copies from recorded video signal and single copying bit is set in correspondence with total prohibition of copying. EFFECT: simplified approach to copyprotection of video materials. 45 cl, 11 dwg

Description

FIELD OF TECHNOLOGY
The invention relates to the protection of video material from copying by introducing strong identification codes (for example, so-called “watermarks” or “characteristic prints”) into the video signals and using these identification codes for a method and device that enables “one-time copying”.

BACKGROUND
The problem of protecting video material, such as films on a video tape, from copying is well known. For video material recorded on tape in the usual analogue way, the solution is the well-known Macrovision counter-copying process, in which pulses are added in the blanking interval of the vertical frame of the video signal (see U.S. Patents 4,631,603 and 4,695,901, issued to Ryan) and included here (by reference) These additional pulses interfere with the automatic gain control circuit of a conventional VCR (video cassette recorder) (VCR) and thus make it impossible to view any Recorded video signal, resulting in image disruption.

 For digital video, copy protection is an even more important problem, because by its nature, digital video recording is an exact copy of the original, and unlike analog recording, the image quality does not undergo any degradation. Consequently, in the case of digital video recording for people, there is even more incentive to make unlicensed copies of copyrighted video material. This is a major obstacle to the introduction of pre-recorded digital video media and the commercial introduction of digital video recorders.

 One known solution to this problem is the use of identification marks (“watermarks”). Watermarks are digital codes embedded in a video signal, which can be read out by a reader (detector), a video recorder according to the invention, or in a playback device (video player), and the watermark itself does not visually interfere with the video signal (i.e., there is no or a significant decrease in image quality). The “watermark” is read in the VCR or in the video player by means of a detector circuit, which, depending on the watermark, instructs the VCR or video player to perform certain functions, for example, not to copy or to allow only one-time copying of the material. To use watermarks, a special detector circuit must be present in the video recorder or video player of the invention.

 Watermarks are special signals that are embedded in the video signal in such a way that they cannot be deleted without significant damage to the video signal, and it is difficult to intentionally or accidentally delete a watermark. Watermarks are the so-called two-sided copy protection scheme, which requires a specially adapted ("according to the invention") VCR / video player that can detect and react to a watermark. The usual “non-inventive” VCR ignores the watermark, and therefore, the watermark will not have any effect. This is in contrast to the “one-way” Macrovision protection process described above for copy protection, which, however, is generally not suitable for protecting a digital signal.

 Despite the fact that such watermarks are convenient for use and have already been introduced to a limited extent for industrial use, they have significant drawbacks. The most important drawback arises in the situation when the opportunity is given for one-time copying, which usually occurs in the cable television industry when broadcasting pay-per-view, for example, movies. The cable television industry has created among its subscribers the expectation that they will be allowed to make their own personal recordings of cable TV shows, such as movies, using KVM. Despite the fact that the copyright owners and the cable television industry have come to the conclusion that it is generally acceptable for a user to record such a one-time recording for his personal use, the copyright holders (for example, a film studio) do not want to provide the possibility of making any repeated recordings (recordings of the second generation). Therefore, it is desirable to allow the transmission of a video signal, for example, on cable television with the possibility of only one-time copy while maintaining the ban on the creation of any copies of the second generation from the first copy.

 The prohibition of such repeated recordings is possible using conventional technology using watermarks. As a rule, in such a situation, watermarks of two types are used: the watermark of the "complete copy ban" and the watermark of the "one-time copy". Both of them must be read by the copying VCR corresponding to the invention, which after recording replaces the watermark of a single copy with a watermark of total prohibition of copying. Because of this, there is a problem associated with the additional cost of a VCR according to the invention, since it must be able to detect both of two different watermarks, as well as add (record) a watermark to completely prohibit copying. In addition to the fact that such a system is very expensive to implement, it is also possible to technically cancel its effect, and therefore it does not meet the requirements for it.

SUMMARY OF THE INVENTION
In the field of digital video recording, there is a need to create a one-time copying method that offers improvements in terms of cost-effectiveness and protection compared with the prior art. There is also a need to create a one-time copy method in which only one watermark is required and, therefore, only one watermark detector for each recording (or reproducing) device according to the invention. In this method, the video recorders of the invention do not have to add watermark devices or modifiers. (Here, the term "corresponding to the invention") refers to a device that differs from the usual one, which is modified by adding a special circuit and / or software in accordance with the invention). If the manufacturers of video players and VCRs wish to put the invention into practice, they will supplement their products with the circuit and software corresponding to the invention, and video suppliers will likewise add the required signals to their programs.

 In addition, such a system should be simple to implement, not require the need to preserve any secrets to ensure its protection, and to ensure functioning both in the field of analog signals and digital. Another requirement is that even if the first (authorized) recording is on an existing ordinary household KVM, having either a VHS (home video system), or S-VHS (advanced home video system), or 8 mm (for which it is not usually assumed Since it can comply with the digital single-copy protocol) has already been made, the prohibition on creating second-generation copies by means of a recording device according to the invention remains.

 Therefore, in accordance with the present invention, there is proposed a single type of watermark that has two options: a complete prohibition of copying and permission for single copying, which are identical except for one bit. According to the invention, there is no need to add a watermark to the video signal after recording, since instead a watermark of a single copy is converted to a watermark of total copy prohibition by simply replacing the bit. (As used herein, the term “watermark” refers to both watermarks and other types of digital “signature fingerprints”). As described below, the present invention can be used for both a digital video signal and an analog video signal (for example, for a VHS system, for an S-VHS system, or for an 8 mm video system). The watermark according to the present invention withstands the conversion from analog to digital or from digital to analog, can withstand compression and can withstand the conversion from one television standard to another, that is, from PAL to NTSC or NTSC to PAL.

 In accordance with the invention, a watermark, which is a digital signal, is usually introduced into the video image. A subset of the watermark bits has a digital attribute (number), which is a numerical characteristic of the video signal, for example, the average value of the amplitude of the video signal over one television field or frame. According to the present invention, in a preferred embodiment, the attribute of the video signal is a certain uniquely defined characteristic of the video signal, the change of which from frame to frame is the maximum, and which is not subject to the typical distortion existing in the corresponding channel of analog or digital transmission. The attribute is used only for a one-time copy option.

 To generate (encode) a watermarked video signal, in addition to the usual watermarking, a random (or pseudo-random) selection of one frame (or field), for example, one frame every 10 seconds of the video signal, is carried out and the attribute is digitally calculated for this frame (or fields) of the video signal. A “field marker" ("label") is also added to this frame to indicate that it is the selected frame. This field marker is a special signal located in the usually invisible part of the television frame, for example, in the inactive part of the screen.

 The transmission of the encoded video signal to a consumer who is trying to record it using his digital video recorder according to the invention is usually carried out, for example, by cable television or via satellite. Before recording, the digital video recorder corresponding to the invention looks at the watermark, checks it, registers for the presence of the single-copy bit in the watermark, and extracts the value of the corresponding attribute from the watermark. A VCR according to the invention also detects the presence of a field marker in a particular marked field, measures the attribute of that particular field, and compares the measured attribute with the extracted attribute value. If these two attribute values match, then the VCR is recording. If they do not match, then write (copy) is prohibited.

 At the same time, the VCR, when recording, removes the field marker from the video signal to prevent any re-copying of the resulting record. The absence of field markers does not allow any re-recording of a particular video signal by means of a video recorder according to the invention.

 Therefore, a video recorder according to the invention includes a watermark reader (detector and verifier), an attribute measurement circuit, a field marker removal device (removal device), and corresponding computing means (software) in a microprocessor, which is usually located in such a video recorder, for performing necessary calculations and logical functions, including a comparison of attributes.

 In a preferred embodiment, the field marker is a signal that cannot be detected and reproduced by conventional analog VCRs, since the type of field markers is chosen so that the color signal filtering circuitry commonly found in such analog VCRs removes them. Therefore, if the original transmitted video signal was recorded using such a conventional analog video recorder, then the field markers are not saved during the analog recording, which prevents the creation of a duplicate copy on any digital video recorder according to the invention.

 The field marker is usually introduced into the invisible part of the active video signal, that is, into the non-working area of the screen of television receivers. In an alternative embodiment, the field markers are placed in the blanking intervals of a frame or line scan. In a preferred embodiment, the field marker is a signal that is automatically removed as described above by means of a conventional recording device, but this is not a necessary condition.

 Although a typical application of the present watermarking process is the above-described cable television systems or satellite distribution of television programs, this is not a limiting feature. Of course, for pre-recorded, for example, on tape or on a DVD (Universal Digital Video Disc (DVD)) video material, this process is usually not carried out, since such material is usually not subject to single copying, but is a material with "complete prohibition of copying". However, the actual watermarking process that allows for one-time copying can also be used for pre-recorded video material.

BRIEF DESCRIPTION OF THE DRAWINGS
In FIG. 1 shows a block diagram of an encoding device according to the invention.

 Figure 2 shows a block diagram of a VCR for a watermark / playback control circuit in accordance with the invention.

 Figure 3 is a table of characteristics for a system with two watermarks.

 Figure 4 shows a method of undoing the operation of the single copy process.

 Figure 5 shows the device cancel the action of Figure 4.

 The drawings of FIG. 6A to FIG. 6G illustrate the use of a particular video marker according to the invention.

DETAILED DESCRIPTION
MAIN PROCESS
In accordance with the invention, a watermark is introduced into the video signal (encoded with it) with a “payload”, for example, equal to 8 bits. (The payload is the number of bits to change). Bits 1 and 2 of the eight payload bits are ordinary (digital video) bits of the copy generation management system (CGMS), and bits 3 and 4 are bits of an analog protection system (ACPS) (APS). In reality, the analog protection system is, for example, the well-known Macrovision process of counteracting video copying. Therefore, these four bits are usually used to indicate a one-time copy / complete prohibition of copying / prohibition of further copying and to enable or disable the analog protection system. (Macrovision or other analog anti-copying processes are applicable for digital recording, since digital video recorders usually have the ability to input analog video). According to the invention, the remaining four payload bits define an image attribute of a selected frame of the main video signal, examples of which are described below.

 For a program (video signal) with a “complete prohibition of copying”, the values of bits 1 and 2 of the eight bits of the payload are, by general agreement, set equal to (1,1). In this case, the state of bits 5 through 8 is “irrelevant”. When the configuration of bits (1,1) is detected, the recording apparatus according to the invention refuses to record any material.

 For the “one-time copy” program, again, by general agreement, the values of bits 1 and 2 are set equal to (1.0), and bits 5 through 8 now serve as a 4-bit display of the program attribute. Here, the term “attribute” means a numerical expression of some characteristic of the video material. In a preferred embodiment, the change of attribute from frame to frame is the maximum subject to a change in image. In a preferred embodiment, the attribute does not change if there are expected distortions of the video signal caused by distortions in the analog or digital transmission channel through which the video signal is transmitted, for example, by noise, non-linearity or frequency response.

 A video recorder according to the invention, upon detection of a bit configuration (1.0) that causes a one-time copy, calculates the same attribute of the corresponding frame of the video signal and compares it with the value that the payload bits 5 through 8 carry. If they match, then allow continued copying. If they do not match, then copying (recording) is stopped. In other words, the one-time copy command, which produces a mismatching attribute, stops the recording process carried out by the recording apparatus of the invention. Ultimately, when performing authorized recording of the first generation, the recorded video signal is changed into recordings so that subsequent recording devices of the invention cannot check the validity of the attribute value contained in the watermark, thereby prohibiting subsequent copying.

OPTION FOR CARRYING OUT
The following more detailed description of one embodiment of this method takes into account the possibility that, in the presence of noise or after compression, the watermark reader circuit may require, for example, 10 seconds or more to uniquely detect and decode the watermark. The indicated time intervals are given as an example only.

 ENCODING OPERATION.

 1. Coding refers to the process of protecting the video material "at the entrance." After each period of time equal to, for example, 20 seconds, the encoding device randomly selects one field (or frame) of the video signal from the program within the first five seconds, which allows reliable measurement of the attribute even after the video signal has been subjected to various distortions described above, existing in analog or digital transmission systems. The encoding device measures the attribute value for the selected field or frame.

 2. After waiting for a randomly selected period of time (for example, from zero to 5 seconds to improve protection), the encoding device encodes the measured attribute value of the selected field in the form of a 4-bit digital watermark word, usually different from generally accepted. (In a preferred embodiment, a watermark is continuously added to the video signal, and these 4 bits are set equal to some forbidden value, for example, F (in hexadecimal notation) until the command is given to enter the attribute value).

 3. The encoding device marks the field selected in step 1 so that the recording devices of the invention can reliably determine its location. The following describes an example of the method of introducing markers: they extinguish approximately the first microsecond of the first line of horizontal scanning for each field of the video frame and increase the amplitude only by adding 25 units of IRI (Institute of Radio Engineers, USA) during this period of time equal to one microsecond ( pulse). A more universal way of introducing markers is described below.

 In FIG. 1 shows an example of an encoding device located, for example, at the input of a cable television system. Before the video program is transmitted via cable to the subscribers, it is fed to input 10. Since it is a digital video signal, input 10 is usually a multi-wire (bus) connector. As described above, the frame selection device 12 randomly or pseudo-randomly selects specific fields or frames for encoding and provides a pointer to each selected field or frame on the control bus 14. In response, the field marker circuit 16 marks each video frame thus indicated. The control bus 14 is also connected to an attribute measurement circuit 18, which also receives an input video signal and calculates (measures) the attribute of the selected fields or frames. The measured value of the digital attribute is inputted via the bus (s) 26 into the watermark modifier circuit 32. Block 32 receives an ordinary watermark from the ordinary watermark generator 28 and modifies it with a 4-bit attribute value. A watermark modified in this way is introduced into the watermark insertion circuit 38 into a frame that records the modified watermark in each of the fields or frames having a field marker that is supplied via the bus 22. Then, the video signal with the watermark is supplied to the output 40 going to cable (or other) network distribution programs. It should be understood that some of the blocks in FIG. 1 (as well as in FIG. 2) have a circuit solution, and the rest are circuits or functions performed, for example, in a programmable microprocessor.

READING OPERATION IN ACCORDANCE TO THE INVENTION VIDEO RECORDER
1. During the recording process, upon detection of a marker of a field of the type described above in a received video program, a video recorder / video player according to the invention measures and stores an attribute of this field or frame.

 2. The VCR / video player compares the measured attribute with the attribute value that is decoded (extracted) from the watermark. The comparison is made only when the watermark detector in the VCR / video player first decides with a high degree of certainty that it correctly performed the decoding (verification) of the watermark.

 3. If these two attribute values coincide, then they are allowed to continue recording. For coincidence, it is not required that the values are identical, but some measurement errors, i.e. the presence of a certain tolerance, can be taken into account. If these two attribute values do not match, or if the program intended for one-time copying does not have periodic field markers, then recording is prohibited.

 4. The VCR during the recording process deletes all field markers. Alternatively, a “false” field marker is entered into the field whose attribute is noticeably different from the attribute whose carrier is a watermark, but this additional operation may not be necessary. A simple deletion of all field markers is sufficient. Removing field markers is the preferred option and eliminates the need to change the video signal to force another attribute to be measured in a subsequent recording attempt.

 An example of a video recorder according to the invention is shown in FIG. 2; it complements the encoding device of FIG. 1. An input digital video signal having field markers and watermarks is supplied from input 46 to a field marker detector 48, which detects each field marker and outputs a tag indicator on the control bus 50 to a substantially conventional watermark detector / verifier 54. The verifier 54 checks for the presence of the one-time-copy bit and normally performs a watermark check. Then, by means of the extraction device 56, 4 attribute bits are extracted from the tested watermark and transmitted via the bus 62 to the comparator 68. The attribute measurement circuit 58 also receives the input video signal and, in response to the signals on the bus 50, measures (calculates) a predetermined attribute of the marked frames, indicated on the control bus 50. The measured value of the attribute is supplied to the comparator 68 via bus 64. A recording circuit 70 other than the conventional one is included only when the comparator 68 detects a match. (The recording circuit is a regular digital video recorder with recording to tape or to disk). A recording circuit 72 of a field marker removal device and a circuit 74 are connected to the recording circuit 70 for changing the write once bit to a value corresponding to the total copy prohibition.

PROTOCOL PROTECTION
In order for a “hacker" (copyright infringer) to be able to cancel the operation of this system, that is, to change the legal video recording of the first generation so that it can be re-copied using video recorders corresponding to the invention, he must do the following (or implement complexity process). First, when playing the first (legal) record, it measures and stores the attribute of each field and decodes the watermark. Then he adds the field marker to the field whose attribute matches the one in the watermark.

 To “crack”, a video signal delay of many seconds is required at bit rates that comply with the Moving Image Expert Group (MPEG-2) (video compression) standard, watermark reader, and attribute measurement system. (The copied video signal usually has the MPEG-2 compression standard). Further details are provided below.

 Therefore, through the present process, the task of preventing “hacking” by most people can be easily realized, especially considering the minimum reward that will be obtained from breaking this part of a typical aggregate copy protection system. There is no need for the one-time copy scheme to be as “well protected against hacking” as the main watermark, because for the copyright holder, programs that are marked as “one-time copy” are usually less valuable in themselves, than programs with a "complete copy ban". In any case, a hacker who wants to get several copies can simply (and can be considered legal) to make them in parallel from the original video program intended for single copying.

ATTRIBUTE REQUIREMENTS
In accordance with the invention, an ideal image attribute:
1. It can be measured in a domestic digital video recorder with a minimum of additional circuits.

 2. It is relatively immune to common errors at the video signal level: non-linearity, noise, tilt, distortion of the amplitude-frequency characteristic, distortion due to sampling and compression, etc., available in various analog and digital transmission systems.

 3. It is such that the hacker could not easily change the video signal to force the introduction of a specific attribute value without seriously reducing the entertainment value of the program.

 This third requirement can be dispensed with, since, as applied to this single-copy protocol, it cannot significantly impede the work of a hacker.

ATTRIBUTE EXAMPLES
First example: The average DC voltage values of individual areas of a selected video frame are added up and subtracted in a way that is applicable to generate a common attribute value; for ordinary video images. The size and location of the image areas is chosen so as to obtain maximum immunity to tilt, noise and distortion. In order to eliminate the attribute measurement errors that may be caused by differences in the video signal gain in intermediate hardware or in the transmission path, the resulting value is divided by the average value of the constant component of the amplitude of the video frame.

 Second Example: It is a specific implementation of the above first example for a video signal with MPEG compression. Consider the MPEG-2 macroblock on an 8 x 8 grid of image elements (pixels), which is located symmetrically relative to the center of the video frame. Suppose that each macroblock is black or white in the form of a regular checkerboard. The attribute is [the sum of all the constant components of the white blocks minus the sum of all the constant components of the black blocks] divided by the sum of the constant components of all the blocks.

EXAMPLES OF FIELD MARKERS
First example of a field marker: The gray level in a video signal is set to 25% during the first 1.5 microseconds of the first horizontal line of each television field (or frame). Like the other field markers described here, this marker is positioned in the non-working part of the television frame so that it is not visible on the television screen. (However, this arrangement is not a limiting feature). To introduce a marker in a specific field, for example, the addition of a gray sinusoidal wave with a frequency of 2.5 MHz to this level is carried out with a full swing equal to 50 IRI units.

 Reliable detection of such a field marker can be carried out even after passing through a cable television channel having a low quality. However, the advantage is that it is not saved when a KVM (video cassette recorder) having a VHS or 8 mm system is passed through the signal processing and recording circuit, but nevertheless it is preserved when recording in the S-VHS system. This is because in a VHS or 8 mm VCR, this field marker is filtered by a comb signal filter. Thus, the field markers are effectively removed after recording and playback by means of a VHS or 8 mm VCR system, which prohibits the creation of second-generation copies by means of a video recorder according to the invention.

 Second Example: This example can be implemented in VCRs having systems such as VHS, S-VHS and 8 mm. The gray level during the first 1.5 microseconds of the first two lines of horizontal scanning of each field (or frame) is set equal to 25%. To introduce a marker in a specific field, a sine wave at a subcarrier frequency with a total amplitude of 50 IRI is added to this gray level, so that its phase relative to synchronization is the same in both scan lines (unlike the standard color signal, whose phase in alternating scan lines reverse).

 Reliable detection of this field marker can be carried out even after passing through a cable channel of poor quality. However, it is not saved after passing through the filter a color signal of any KVM of household type. During playback, the comb filter KVM reduces the color signal in the 1st scan line to 25 IRI units, and in the 2nd scan line to zero. The field marker detector in the VCR according to the invention is adjusted so that it detects this signal only in the 2nd scan line. In this way, the field markers are effectively removed after recording and playback by means of an analog VCR, which prohibits subsequent copying of the video signal by means of a video recorder according to the invention.

 Third Example: This field marker can be used in VCRs with VHS, S-VHS and 8 mm systems. First, a block of 24 x 4 picture elements is selected in, for example, the lower left corner of the television field (or frame). The next operation is to replace the color values in a block of 24 x 4 image elements with a constant marker image, for example, consisting of alternating values of blue and yellow. This marker must be preserved during compression according to the MPEG standard, so that it can be reliably detected even after passing through a cable channel having poor quality. However, it should not be saved when a household-type KVM color signal is passed through any filter. The field marker detector in the VCR according to the invention is adjusted so that it detects this signal only in the 2nd scan line. In this way, the field markers are effectively removed after recording and playback by means of an analog VCR, which prohibits the creation of second-generation copies by means of a video recorder according to the invention.

 The use of markers erased by KVM is a useful improvement of this system of single copy from the point of view of additional protection provided to copyright owners.

 To ensure full compatibility with MPEG compression, some of these marker insertion principles may be subject to minor modifications. They will be a useful improvement to this single-copy system in terms of providing additional protection for video material.

ADDITIONAL IMPLEMENTATION OPTION: FRAME MARKER AND WATER SIGN
1. In another embodiment, for encoding, a frame marker (or field) is added to a specific video frame in a pseudo-random manner, for example, in each window lasting 4 seconds. The frame marker is automatically deleted by KVM (as described above). (An example of such a marker is fixed values of the constant component of the color signal, and C _red (C _red ), and C _syn (C _blue ), in the first line of the first macroblock). For the marked frame, the attribute value is calculated and stored.

 2. In a pseudo-random location of the next window, for example, for 2 seconds, 4 bits of the watermark attribute are changed in such a way that it is equal to the attribute value of the previous marked frame.

 3. When encoding, operations 1 and 2 are repeated throughout the entire video program.

 4. Upon subsequent recording of a program for which, as described above, a single copy is allowed, the frame marker is deleted.

 In addition to the usual watermark bits, which are usually found in the low-frequency and mid-frequency DCT (discrete cosine transform) MPEG coefficients, and for only one copy in this embodiment, 4 additional resolution bits are added that should be contained in some high-frequency DCT coefficients MPEG If, based on the usual watermark bits, a one-time copy status is detected, then the VCR checks for 4 additional bits; if they are missing, the VCR does not copy. If they are present, then before creating a copy of the invention, the VCR adds an adequate noise level. This removes 4 extra bits and removes permission to create a copy.

 One of the advantages of this approach is that conventional (not corresponding to the invention) VCRs (not having copy control systems) automatically delete additional enable bits, which makes it impossible to overwrite the output signal with (digital) video recorders corresponding to the invention.

 In this embodiment, the watermark includes two separate parts, referred to as B31 and B32 (WM1 and WM2). B31 (WM1) contains a payload of 8 bits and is difficult to remove without compromising image quality. The payload bits are distributed according to the low-frequency / mid-frequency / high-frequency DCT coefficients MPEG in the form of macroblocks.

 B32 is, for example, a fixed set of 4 bits or a CRC value (cyclic redundancy code) of the payload bits. It is not difficult to remove B32, because B32 bits are distributed only at high frequencies and can be erased by a low-pass or other filter. B32 is retained when transmitting at 4.2 MHz, but not when recording in a 2.5 MHz VHS system. Most of the B32 energy can be distributed line by line in macroblocks so that it is easy and inexpensive to erase or invalidate it. For greater noise immunity, an additional CEC (4 bits) is additionally used.

 The “erase B32” circuit in a VCR according to the invention erases B32 using a low-pass filter or other filter for video information; thus a minimum of circuits is required. The cost of adding a B32 detection circuit to a B3 detection circuit (WM) is very small since most of the logical nodes used to detect B31 are reused in the B32 detection circuit.

 In FIG. 3 shows the modes for this embodiment. Figure 3 shows the contents of each watermark field for B31 and B32 in the top row of each column, and the related action performed by a VCR / video player according to the invention is indicated in the rest of the column. The upper half of FIG. 3 is a simpler embodiment of this embodiment; and the lower half is a more complex implementation using the CEC. In both versions, copying is allowed only when there is B31 with the enable one-time copy bit set, and B32 is valid (checked).

PROCESS AND DEVICE FOR CANCELING THE PROCESS
In addition to the above single-copy embodiments of FIG. 4 shows the above-described method of undoing the operation of the single-copy process, where both the undo process and the hardware are graphically shown. "Cancellation of a process" means creating a record, which in turn can be copied, this of course violates what the real one-time copy system is intended for. Therefore, manufacturers of video recorders will not allow the present method and device of cancellation to be available for purchase in the usual way, and their disclosure is given here for completeness. (The use of such a method or device of cancellation usually entails a violation of copyright).

 In FIG. 4 shows several conventional units, which include a conventional cable television set-top box 100 to a television (“set-top box”), which is connected to a cable television cable 102 and “attached” to a subscriber’s television (not shown). In this case, the video recorder 106 corresponding to the invention, which is the digital video recorder including the functions of FIG. 2, is connected to the set-top box 100. A person who wants to cancel the operation of the current single-copy process connects a “black box” 104 that cancels the action of the present process between his cable box 100 and its corresponding VCR 106. Details of the device of this “black box” are given below; in the "black box" 104 posted a cancellation scheme.

 In step 1 of FIG. 4, through a cable box 100, a video program is received via cable 102 having a one-time copy protection, which includes a field marker, and transmitted through the “black box” 104 to the VCR 106 according to the invention. Black Box 104 includes a circuit that adds a “label” (a special field marker) to that first frame of a video signal that has a detected (original) field marker. (The "black box" 104 includes its own field marker detector, as does the device of Figure 2). This label has special parameters, which are described below. Then, the black box 104 stores in its internal memory a table of time intervals between the field markers detected in the video program. This table provides timing information for these source field markers. Then, the video signal with the label added to the first frame with the marked field is supplied to the video recorder 106 according to the invention, the type of which corresponds to that shown in FIG. 2.

 Then, the VCR 106 of the invention records the allowed one-time copy on the first tape (or disc) 110. As described above, the VCR 106 of the invention deletes all of the original field markers. However, it does not delete the tag (s) that was added (s) by the black box 104 because each of these tags is a special type of field marker, which, unlike the original field markers, cannot be deleted using the delete device circuit in VCR 110 .

 Then, in step 2, which is shown in the lower half of FIG. 4, a recorded tape (or disc) 110 is reproduced on a video player (or on a VCR) 114. The reproduced video signal, of course, does not include any of the original field markers. Reproduction of this video signal is carried out through the black box 104 ', which is reconfigured to the playback mode. (In other words, the “black box” 104 'is the same as that shown in the upper half of FIG. 4, but now it is programmed to be in playback mode rather than recording mode). The black box 104 'detects the label (s) added by the black box 104 during the write operation 1, uses the first marked frame as a pointer, and then reinserts new field markers of the same type as in the original video material, according to the time intervals indicated in the table, which were previously saved (during operation 1) in the black box 104 '.

 Therefore, the video output from the black box 104 'is substantially identical to the original video and includes all reinserted field markers. This video signal can then be recorded using a VCR 106 according to the invention, which outputs a second-generation video onto a second tape or disc 116, which again has no field markers, but which is still suitable for viewing (but not for copying). Therefore, using the method of FIG. 4, it is possible to create a second-generation video recording on a tape or disc 116, which thereby cancels the action of the present protection process by a single copy.

 The internal black box arrangement 104, 104 'is shown in FIG. 5. The upper half of FIG. 5 shows the configuration of the “black box” 104 when it performs operation 1. The input video signal from the set-top box 100 is fed to input 120, and then fed to the frame marker detector 122, which detects the original frame markers (fields). The control bus 124 provides an indication of the presence of detected frame markers to the label recording circuit 128, which subsequently adds the label (s) to at least the first frame with the marked field and outputs this marked video signal to output 132, which, like 4 is connected to a video recorder 106 according to the invention. In a similar manner, a pointer to the detected frames is transmitted via a bus 124 to a memory 136, which includes a table for storing time intervals between detected frame markers pa

The lower half of FIG. 5 shows the configuration of the black box 104 'when it performs step 2. Here, the video signal (from the playback device 114) is input to the black box 120, which in turn is connected to the tag detector 140, which detects the tags inserted by mark recording circuitry 128. On the control bus 142 serves a pointer to each such detected label, which indicates specific frames having such a label (s). The bus 142 controls the frame marker recorder 150, which adds frame markers corresponding to those in the original video signal at the required time intervals. These time intervals are set previously saved in the table.
memory 136 data, which in this case is output to the control bus 146 for controlling the time of the actual addition of the frame markers by the frame marker recording circuit 150.

 Then, the video signal with the new frame markers, the insertion of which was carried out by the frame marker recording circuit 150, is supplied to the output of the black box 132, which in turn is connected (in FIG. 4) to the input of the video recorder 106 according to the invention. This version of such a black box shown for clarity and is not limiting.

 The device of such a “black box” is well known in the framework of the qualification of an ordinary person skilled in the art, taking into account the information about the properties of field markers and general information on the video recording technique available to a specialist. A “black box” is essentially a digital device that has the function of adding a label to specific frames of a video signal, recognizing the original field markers, and writing them to a table. Typically, a black box is a microprocessor controlled device including a storage device. A real black box scheme may have many varieties in which the above functions are implemented.

APPLYING LABELS FOR VARIOUS VIDEO DELIVERY METHODS
For the one-time copy marking system described above, you need to consider a process that includes preparing content, delivering content, and viewing / recording content. The following is an analysis of the process in terms of various ways of delivering a video signal: analogue delivery by cable and through television broadcasting; digital delivery through an existing installed base system of digital set-top boxes that do not have a digital (usually referred to as P1394) output; digital delivery through an existing installed base system of digital set-top boxes with a digital output signal; and digital delivery via new digital set-top boxes.

 For analogue delivery by cable and through television broadcasting, content (programs) are prepared before delivery, and the process of converting a single-copy resolution to a prohibition of further copying is carried out in a recording device, and this can only happen in the video signal area.

 For digital delivery via an installed base system of digital set-top boxes without a digital (P1394) output, the content is preferably prepared prior to authorization / MPEG encoding, but it can also be prepared together with authorization / MPEG encoding. However, single copy marks must be retained during MPEG encoding / decoding. In this case, the conversion of the resolution of a single copy to the prohibition of further copying is also performed in the recording device, and this can only happen in the video signal region.

 Digital delivery via the installed base system of digital set-top boxes with a digital output signal is similar, however, the conversion of the resolution of a single copy to a prohibition of further copying takes place in the MPEG region.

 Finally, for digital delivery via the new digital set-top boxes, marking once can also be done in the set-top box itself. In addition, in the case of the output signal P1394, the conversion of the single-copy resolution to a prohibition of further copying can also occur in the set-top box as long as the set-top box transmits the copy permission to the decoding device.

 For analogue delivery by cable and television broadcasting, the present system includes a permanent watermark of permission to once copy / prohibit further copying with an added frame or field mark attached to randomly selected television frames or to a sequence of television frames to recognize material for which single copying is allowed. Converting a single-copy permission to a prohibition of further copying is performed by removing or degrading the quality of the mark. In addition, to provide additional protection, the attribute of the tagged frame or frame sequence is encoded in the watermark. To provide an even higher degree of protection, a random delay of the watermark attribute code is performed.

 Examples of attributes include displaying the video characteristics of the marked frame (s), the position of the marked frame (s), or the length of the marked sequence (which is randomly selected to provide protection).

 Tags are those that are automatically deleted using conventional VCRs and even MPEG encoding devices that do not correspond to the invention. For example, alternating lines of complementary colors having relatively low amplitudes (label pattern) can be removed by MPEG encoders and VHS when converting a field to a frame. The label, for example, is placed at the edge of the lower left corner (the area of the label is, for example, 64 pixels x 4 lines in each field) of the television frame, and it is not visible on TVs (due to the presence of an inoperative area of the screen). To improve protection during the marking process, the color signal in the mark area is removed in all television frames, and a tag pattern is added to the marked frames. Remote tags are performed by removing a color signal.

 In the case of digital delivery via the installed base system of digital set-top boxes that do not have a digital output signal, the marking system should be preserved during MPEG compression / decompression and, as far as possible, maintained during MPEG recording and on VCR, except for the case when marking performed in the encoding device itself or when restrictions are imposed on the encoding process.

 To maximize the efficiency of a single-copy system, the VCRs of the invention support two marking methods. For analog systems or for compatible encoding devices, a “stronger” label is selected, which is described above. For incompatible encoding devices, a "weaker" label is selected, which has the form of a periodic structure from alternating colors changing along the line with relatively low amplitudes.

 For digital delivery via an installed base system of digital set-top boxes with a digital output signal, it is preferable to convert the one-shot resolution to a prohibition of further copying by a digital video recorder, ensuring a minimum of costs.

 One approach is to add and remove an extra label placed directly in the bitstream itself. However, it is necessary that the watermark / mark in the video information also supports the set-top box output signal, and the digitally recorded copy is marked as prohibited for further copying in the bit stream and as authorized for single copying in the video signal. In this case, to ensure that no further copies will be made, it is required that each video player includes a synchronization system.

Another, more preferred approach is to minimize the additional requirements for tag detection / tag removal. Common operations required to read a watermark in an MPEG stream are:
- Demultiplexing the transport stream.

 - Decoding video stream up to 1 frame.

 - Decoding of all layers in a 1-frame.

 - Processing of all macroblocks (MB).

 - Processing of all brightness units.

Since in this case only I-frames are used in the watermark reading process (they are a frame type in MPEG standard), the tag detection / deletion process should be carried out using only I-frames using the following operations:
- Processing color blocks in the label area to perform detection.

 - Buffering the bitstream and replacing in the macroblock marks the bit sequence of the “color block” block with a pre-computed bit sequence of the “no color block” block while ensuring that there is no effect on the size (bbv) (vbv) of the video verifier buffer.

 Since label deletion is carried out only in I-frames and in macroblocks, the following problems and requirements arise.

 For incompatible encoding devices, there must be a sequence of tagged frames, and it must be long enough to ensure that it contains one I-frame. It can be one frame, or the distribution of tagged frames should be such that among them there are a sufficient number of I-frames. If a sequence of tagged frames is used, those sequence attributes must be subtracted from the attributes of the I-frame (frames). The best solution for this is to use a frame location or frame sequence length as an attribute. In the method using the location of the frame, the tagged frame has a special watermark code and the untagged frames have a different one. Any discrepancy between the watermark code and the label state creates a prohibition of further copying. In the method using the frame sequence length, the length of the frame sequences is randomly changed from 3xD to 5xD, where D is a number that exceeds the largest allowable size (maxGI) (maxGOP) of an image group (GOP). In this method, the presence of a separate labeled I-frame and a sequence of I-frames including a total number of frames less than maxGOP indicates a prohibition of further copying. This result is obtained in the case of a sequence of I-frames including a total number of frames greater than D and less than 3D compared with a 5xD code in a watermark, or a sequence of I-frames including a total number of frames greater than 3D compared with a 3xD code in a watermark. The latter method is preferred.

 When using the tag sequence, none of the frame labels preceding the first I-frame from the sequence will be deleted. This is solved by the methods described above using location and sequence length. Removing labels from I-frames makes it necessary to frequently remove labels from other frames of the GUI. This happens when there is no movement in the mark area, and improvement can be made by forcedly zeroing the motion vectors in the mark area during coding. Removing a label from I-frames should not create significant spurious distortions in other frames of the GUI. This may be due to the fact that the label region could be used to predict any nearby macroblock in subsequent P and B frames. This is one of the reasons why complementary colors are used in the label in one embodiment. Removing a label should not cause visible changes in the color signal. Removing a label by replacing the calculated chroma block implies either deleting the entire chroma signal in the region of 54 x 16, which creates spurious distortions visible on some television sets, or introducing a bit stream into user data, the generation of which must be carried out by a compatible encoding device.

 For compatible encoding devices, label generation by the encoding device is performed only for I-frames. In subsequent P and B frames, the motion vectors are forcibly nullified, and no intra-block coding is allowed in these frames. In motion prediction for blocks that do not have tags, they are not forced to use tag blocks.

 For digital delivery by means of a new generation of digital set-top boxes, marking of the frame is carried out only in the output video signal in the same way as the generation of ACP. Labels in the pre-watermarked content are inputted through a video encoder (using a strong tag) using the tag location information contained in the bit stream. As for the output of P1394, the prefix allows the output of the signal P1394 when recognizing a VCR corresponding to the invention. This system even allows you to specify whether the copy can be independently executed via analog or digital output. The transfer of copyright information and related data (label position) in the bit stream is carried out in the same way as ACP information is currently being transmitted.

 The following is a disclosure of three possible systems. All three systems use the same VCR and they have the same structure. They do not cause any spurious distortions (such that do not have any visible effect on the program viewer) in the source material or in video copies (unlike MPEG copies). In the case of a single copy structure for compatible encoding devices, labels are entered only in I-frames. For incompatible encoding devices, tag sequences lasting 3 seconds and 5 seconds are randomly added to the video signal, and after an arbitrary delay time, the “tag length identifier” bit in the watermark is set to 0 for a 3-second sequence and 1 for a 5-second sequence. Each time a new sequence of labels is accessed, another bit (change bit) is switched (thereby reducing the number of watermarks to 10). The label uses line or frame periodic structures from complementary colors with relatively low amplitudes in the 8 lower rows of the four lower left macroblocks. The 11th and 12th bits are used to distinguish between the systems designated here as systems 1, 2, and 3.

 1. System 1 has analog delivery and digital delivery with a compatible encoding / authorization device. Vertical periodic structures are used in this system, which allows tag deletion by means of a VHS VCR and by some MPEG encoding devices that are not in accordance with the invention. Labeling was performed by blanking the eight lower lines of the video signal in the VCR to the sixteen lower lines of the video signal in MPEG video recorders.

 For compatible encoding devices, label insertion is performed after converting the field to a frame, only I-frame labels are used, force vector vectors for lower macroblocks are forced to zero, the use of lower macroblocks for predicting motion in other macroblocks is forcibly prohibited, and interior coding for label region macroblocks in P- is prohibited / In frames.

 2. System 2 has digital delivery without a compatible encoding / authorization device. This system uses lowercase periodic structures. Label removal in the MPEG region is performed by removing the color signal in the macroblock labels. On some televisions, some spurious distortion may be visible in the tag area of digitally copied content. The protection provided by this system for MPEG copies may not be very reliable, since a “pirate” may respond to the fact that in the tagged frames there are no 16 color lines in the tag area, while in untagged frames only eight are missing.

 3. System 3 has digital delivery on new networks. This system is not backward compatible with systems 1 or 2. However, it provides a high-quality and low-cost solution for new networks or networks requiring the use of new set-top boxes to enable one-time encoding.

 For the case when the input signal is a video signal, upon detecting a watermark of a single copy, the VCR deletes the mark by removing the color signal in the 8 lower lines of the frame in the mark area.

 For a digital input signal when a single copy watermark is detected (system 1 or 2), the tag detector determines which system, 1 or 2, is used. For system 1, label removal is performed by replacing the lower layers with a previously stored layer (blanking the 16 lower lines of the video signal) and filling them with insignificant information so that this does not affect the bvv (vbv). For system 2, label removal is performed by replacing the lower blocks of the color labels with previously stored blocks (deleting the color and 4 macroblocks in the lower left).

 After detecting the watermark of a single copy of system 3, copying is performed until the identification protocol P1394 determines the availability of permission for a single copy.

VIDEO LABEL (FRAME / FIELD MARKER)
The “label” of the frame or field marker described above is a video signal inserted into the video stream or a signal modification that is essentially “transparent” for compression according to the MPEG-2 standard, but which is suppressed by the (at least) standard VCR VHS, and which after that can be read from the video signal to transmit information. In a preferred embodiment, the label is “transparent” for compression according to the MPEG-2 standard so that it can be inserted into the video signal before MPEG encoding, and therefore, no modifications to the MPEG encoding device are required. The information intended for transmission contains the copy protection state of the corresponding video signal, however, other variants of its application are also possible, and this type of label is not limited to the scope of copy protection. Other applications are authentication or data transfer.

 You can use a label with inverse color, in which successively selected lines have an input or added special sample of a color signal such that the modulated color signal in successive lines has an inverted phase. The goal is for the comb filter in the VCR to suppress this signal. However, due to the subsampling format for the color signal frame in the MPEG-2 coding system, it requires the presence of smoothing filtering by frame. One image consists essentially of a high-frequency change in signal level relative to a vertical scan in the spatial domain of a color signal, and the MPEG-2 smoothing filter is essentially a low-pass filter for vertical scanning. (In fact, the design of the KVM comb filter is identical in design to the MPEG-2 smoothing filter, and the smoothing filter usually has a more complex and lower cutoff filter than the comb filter). Such a smoothing filter eliminates the input color signal pattern in the same way as a comb filter; in this way, the introduced unwanted signal is eliminated in all formats of interest.

 The baseband of the chroma signal in the MPEG-2 system is approximately 1.4 MHz, which depends on the implementation. 6A shows a well-known spectrum of a VHS video signal with color spectrum transfer. The baseband of the color signal of the standard VHS VCR system is approximately 300 kHz and again depends on the implementation. Therefore, in the region of modulating frequencies of the color signal, there is a zone extending from approximately 300 kHz to approximately 1.4 MHz (bandwidth of 1.1 MHz), in which the signal transmitted through the MPEG-encoded / decoded path will still be suppressed 2, by means of a standard VCR (household type) of the VHS system (NTSC or PAL).

 It is desirable that the input mark signal is completely in this zone and only in it so that none of its components passes through the 300 kHz wide KVM color signal path. Filtering in the color channel by the VCR itself ensures that no component of the input tag signal appears in the luminance path of the VCR.

 One of the embodiments of the label signal (see Fig. 6B, which shows the spectrum of the inserted label according to the present invention, when compared with the spectrum in the color channel with the transfer of the color spectrum) is a color signal of a rectangular shape with a frequency of 844 kHz, consisting of repeating in rows a sample of four consecutive samples of the CCIR-601 4: 2: 0 green color signal according to the CCIR standard (International Broadcasting Advisory Committee)), followed by four consecutive samples of the color signal tnosti lavender. In the field of a video signal, it is a color signal, which approximately every two periods of the color signal (3.58 MHz) has its phase inversion and which can be considered as a signal with two sidebands and carrier suppression, having only two spectral components: one on frequency (3.58 MHz - 844 kHz), and the other at a frequency (3.58 MHz + 844 kHz). In particular, in the 300 kHz band at about 3.58 MHz, there are no spectral components. Fig. 6B shows the spectrum of the introduced label relative to the group spectrum of the color channel for MPEG-2, and Fig. 6G shows the shape of the modulated color signal of the introduced label.

 Other label options are also possible. The sample does not have to be in the form of a rectangular signal, although a rectangular signal is the simplest in terms of generating it; it can, for example, be a sine wave. Also, the sample does not have to have a frequency of 844 kHz; any frequency that is substantially above about 300 kHz and below about 1.4 MHz will be suitable. In an alternative embodiment, the frequency is 1.125 MHz and consists of three samples of green CCIR-601 and three samples of lilac. In addition, the sample does not need to be symmetrical, or even periodic — any sample or signal whose primary energy is below about 1.4 MHz but which has no content below about 300 kHz is well suited; this choice is made to simplify the implementation.

 One of the methods of transmitting information through this signal is that labels with several different lengths are inserted in such a way that they can be measured in units of I-frames, and then information is added to the accompanying watermark of the video signal in which the length of the mark is displayed. In this case, for the system before copying permission it is necessary that both of them coincide.

 To reduce the visibility of such a signal, it is desirable that its various components be as small as possible both horizontally and vertically and have the property of becoming invisible. Therefore, in another embodiment, the mark consists of small colored areas that alternate both horizontally and vertically, forming a pattern in the form of a "checkerboard". In one embodiment, the colors are green and lilac, since they are complementary colors with very similar brightness values and the eye tends to average them in space by one semitone; other colors are possible. Colored areas should be as small as consistent with the spatial resolution characteristics of the selected format; in the case of compression according to the MPEG-2 standard, the restriction is imposed by line and frame smoothing filters preceding the implementation of the subsampling of the color signal caused by this format.

 The details of this embodiment are implementation dependent. For a typical application in the case of MPEG-2 using a digital smoothing filter with coefficients of [-29, 0, 88, 0, -29] * 256 for both line and frame subsampling, one embodiment of the signal label is created by applying to the specified smoothing sequence filters from fully discretized (i.e., 13.5 MHz) image elements consisting of a green image element, two gray image elements, a lilac image element and two more gray elements about color. To create the desired pattern in the form of a "checkerboard" this sequence is duplicated both in horizontal and vertical directions and extended in both directions (or "repeated") as much as it is desirable and useful for this application for the invention.

 Separate image elements of green and lilac color form impulse functions supplied to the input of smoothing filters, and the output signal of the filter is a sequence of image elements corresponding to filter coefficients, that is, the output of one image element and the specified filter will lead to the presence of a sequence of image elements with a set amplitudes -29, 0, 88, 138, 88, 0, and -29. The total filter output is the linear sum of its responses to each of the input pixels. If in the embodiment described above, the lilac image element is encoded as “-1”, the gray image element is encoded as “0”, and the green image element is encoded as “+1”, then the steady-state response of the filter to the label sequence described above will be equal to ... 88, -88, -196, -83, 88, 196, 88, -38, -196, ..., which is a sinusoidal color signal with a frequency of 1.125 MHz.

 An image in the form of a chessboard is created by arranging the input signal in such a way that in any given marked scan line the specified image element corresponds to the specified spatial image, that is, if the image element 20 in the input signal line 460 is green, then the image element 20 in lines 461 and 462 should be gray, image element 20 on line 463 should be purple and image element 20 on lines 464 and 465 should be gray. Image elements 21 22, 24 and 25 must be gray in all marked lines, and all image elements in the marked parts of lines 461, 462, 464 and 465 must also be gray. Then the action of smoothing filters will cause blurring of monochromatic image elements into the desired sinusoidal waves in both horizontal and vertical directions.

 This disclosure is illustrative and not limiting; In view of the foregoing description of the invention, those skilled in the art will appreciate additional modifications that fall within the scope of patent claims of the appended claims.

Claims (45)

 1. A coding method for copy protection of a digital video signal, which includes the following operations: place a marker in the selected fields or frames of the video signal, measure the image attribute for each of the selected frames, and mark the video signal with a signal that contains information on the measured value in numerical form attribute of each field or frame that has a marker.  2. The method of claim 1, wherein the tagged signal is a watermark that is a digital signal.  3. The method according to claim 1, in which the measurement of the attribute is carried out by calculating the amplitude in a predetermined part of the selected frame.  4. The method of claim 1, wherein the signal includes at least one bit indicating that copying of the video signal is allowed.  5. The method according to p. 1, in which the marker is located in the non-working area of the frame.  6. The method according to p. 1, in which the marker is placed in the blanking interval of the reverse frame scan.  7. The method of claim 1, wherein the marker is a signal that is filtered out using a conventional analog video recorder.  8. The method of claim 1, wherein the signal comprises a portion that is a signal that is filtered out using a conventional analog video recorder.  9. The method of claim 1, wherein the marker is a repeating color signal.  10. The method of claim 9, wherein the marker is a repeating square wave.  11. The method according to p. 1, in which the marker has a frequency in the range from approximately 300 kHz to 1.4 MHz.  12. The method according to p. 9, in which the marker is an image in the form of a "chessboard" containing two additional colors.  13. A method for permitting the recording of a secure video signal, wherein the secure video signal contains at least one frame marker and has a signal associated with it, including numerically presented information about an attribute of a frame having a marker, said method comprising the following operations: detecting a marker for identifying a particular frame, detecting a signal associated with the frame, measuring the image attribute of the identified frame, comparing the measured attribute with lennoy numerically information about an attribute for the identified frame and allowed to record the video signal only if the comparison operation when a coincidence is established.  14. The method of claim 13, wherein the signal is a watermark that is a digital signal.  15. The method according to p. 13, in which the measurement of the attribute is carried out by calculating the amplitude in the selected part of the frame.  16. The method according to p. 13, further comprising the following operations: determine whether the signal contains a copy enable bit, and only allow copying when the copy enable bit is present.  17. The method according to p. 16, further comprising an operation in which the copy permission bit is changed during the recording of the video signal.  18. The method according to p. 13, in which the marker is located in the non-working area of the frame.  19. The method according to p. 13, in which the marker is located in the blanking interval of the reverse frame scan.  20. The method according to p. 13, in which the marker is a signal that is filtered through a conventional analog video recorder.  21. The method according to p. 13, in which the signal contains a part, which is the signal that is filtered out using a conventional analog video recorder.  22. The method according to p. 13, in which the marker is a repeating color signal.  23. The method of claim 22, wherein the marker is a repeating square wave.  24. The method according to p. 13, in which the marker has a frequency in the range from approximately 300 kHz to 1.4 MHz.  25. The method according to p. 22, in which the marker is an image in the form of a "chessboard" containing two additional colors.  26. A digital video recorder adapted for a one-time copy protocol for a video signal, said video recorder including a circuit for recording a video signal, an input for receiving a video signal, a marker detector that detects a mark in a frame of a received video signal, a detector that detects a signal associated with the frame, an attribute measurement circuit that measures the attribute of the image of the frame, and a comparison device that compares the measured attribute with the information presented in numerical form information about the attribute in the signal associated with the frame, and allows the functioning of the video recording scheme only when there is a match.  27. The digital video recorder of claim 26, wherein the detector also determines whether the copy enable bit is set to a digital signal containing a watermark, and the comparison device only allows copying when the copy enable bit is set.  28. The digital video recorder of claim 27, further comprising a circuit for changing a copy permission bit in a video recording process.  29. An encoding device for protecting a video signal, including an input for receiving a video signal, a marker input circuit that puts a marker in the selected frames of the received video signal, a measurement circuit that measures the image attribute in each of the selected frames, and a circuit that puts the video signal through signal, which contains the information in numerical form about the measured attribute of each frame that has a marker.  30. The device according to p. 29, in which the marker is located in the non-working area of the frame.  31. The device according to p. 29, in which the marker is located in the range of blanking reverse frame scan.  32. The device according to p. 29, in which the marker is a signal that is filtered out using a conventional analog video recorder.  33. The device according to p. 29, in which the signal contains a part, which is a signal that is filtered by a conventional analog video recorder.  34. A method for permitting copying of a protected video signal containing at least one frame marker and having a signal associated with it containing numerically represented image attribute information of at least one frame, said method comprising the following operations: detecting frames having a marker, mark one of the detected frames with a predetermined signal, store data indicating the time reference of each of the detected frames, record video signals Ala, the video signal is played back repeatedly in the VCR, when the video signal is played back, a marked frame is detected, and a marker similar to the marker contained in the protected video signal is inserted into the marked frame and the selected subsequent frames, and the insertion is carried out in accordance with the stored data.  35. The method of claim 34, wherein the predetermined signal is different from markers.  36. The method of claim 34, wherein the predetermined signal is a signal that is not removed by the digital video recorder.  37. The method of claim 34, wherein the associated signal is a watermark that is a digital signal.  38. A device for permitting copying of a protected video signal containing at least one frame marker and having a signal associated with it, comprising numerically represented information about the image attribute of the frame, including an input for receiving a protected video signal, a first detector, connected to the input and detecting frame markers, a circuit connected to a detector that records a predetermined signal in at least one of the marked frames, which stores property connected to the first detector, which stores data indicating the time reference of each of the detected marked frames, a second detector that detects a predetermined signal, and a circuit for inserting a frame marker in the video signal, which is similar to the markers available in the protected video signal, insertion is carried out in accordance with the stored data.  39. The device according to p. 38, in which a predetermined signal is different from the frame marker.  40. The device according to p. 38, in which a predetermined signal is a signal that is not deleted by means of a digital video recorder.  41. The device according to claim 38, in which the associated signal is a watermark, which is a digital signal.  42. A method of processing the original video signal to limit its copying, the original video signal having a watermark, which is a digital signal transmitting data related to copying restriction, said method including the following operations: a video signal marker is inserted into the original video signal, the video signal marker having an attribute providing a predetermined method to match the characteristics of the original video signal, while the above-mentioned correspondence indicates that the video signal is and a similar video signal, in response to a request for outputting a video signal for copying, a digital signal containing a watermark is detected and the video signal is verified as the original video signal, the check includes checking the video marker for a predetermined correspondence to the video signal, and only if it is confirmed that the video signal is the original video signal, then the initial video signal is processed to create a copy of it, moreover, in order for the video signal marker la it is no longer matched by said predetermined method, the copy is not identical to the original video signal, wherein subsequent checking of the copied video signal indicates that the video signal is not the original signal, whereby the restriction may be imposed on further copying.  43. The method according to p. 42, in which the processing includes changing the marker of the video signal.  44. The method of claim 43, wherein the processing includes removing a video marker.  45. The method according to p. 43, in which the processing includes converting the original video signal from digital to analog form. Priority on points:
10/08/1997 by claims 1-8, 13-21;
03/04/1998 PP 9-12, 22-25;
03.03.1998 PP 26-45.

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