MXPA96003764A - Data registration device and method to prevent ile copying - Google Patents

Abstract

The unauthorized copying of a digital video program is prevented by designating a first block and a second data block in the bit stream encoded by a fixed length code. A portion of the first block is selected as the key data and inserted into the second block to indicate that the digital video program is a copy and to prevent illegitimate copying.

Description

"DATA REGISTRATION DEVICE AND METHOD TO PREVENT ILLEGAL COPYING" BACKGROUND OF THE INVENTION The present invention relates to preventing the data recorded in a recording medium from being copied illegally and, more particularly, to prevent the illegal copying of the registered data by coding the key data in legally reproduced copies. Private ownership of video tape recording devices has been widely dispersed in recent years so that copying of video programs has become a common occurrence. Video rental stores rent videotapes to consumers for home entertainment and some unauthorized consumers copy the video programs recorded on the rental videotapes. This problem is complicated by professional copiers or pirates who illegally copy video programs in bulk, to distribute the illegal copies for profit or profit. Even though measures have been taken to prevent the illegal copying of rented videotape video programs, the problem is not so serious because the copied video programs have a poor image quality. This is because illegally copied video programs were originally recorded as analog signals, which do not lend themselves to exact copying. The quality of the image of this analog signal after being copied several times, that is, after several generations, inevitably deteriorates. Due to this reason, the duplication of copies is limited and the problem of copying analog video programs is to a certain extent able to be handled. However, with the recent introduction of digital video recording devices that are capable of copying with superior quality, the problem of illegal copying is serious. Digital video, unlike its analog predecessor, has the advantage of reproducing with superior image quality and can be copied a number of times without deterioration. Therefore, the illegal copying program is much more serious in the case of digital video recording and the impediment of it is quite important for the digital video industry. Until now, proposals to prevent illegal copying of digital video programs have proven to be insufficient to prevent illegal copying. For example, it has been proposed to register a flag in the legal copies of the digital video program. In the period of withdrawal, indicating to a digital video recording device that the digital video program is a copy and should not be copied illegally. However, professional copiers have easily eliminated this anti-copying technique by building special digital circuits and software that ignore the backward period and illegally copy the digital video program. Since the backward period does not contain a significant part of the digital video program, the resulting illegal copies have a sufficiently high image quality and can be duplicated a plurality of times. Therefore, it is clear that a superior technique is needed to prevent illegal copying in the digital video industry.

OBJECTS AND COMPENDIUM OF THE INVENTION An object of the invention, therefore, is to provide a data record that prevents illegal copying. A further object of the invention is to provide a data record that prevents illegal copying by designating a first data block in a bitstream containing the key data. A further object of the invention is to provide a data record that prevents illegal copying by inserting the key data into a second data block in the bit stream. A still further object of the invention is to provide a data record that prevents illegal copying by indicating that the key data is in the second block. In accordance with the aforementioned objects, the present invention prevents illegal copying of a digital video program by designating a first block and a second data block in a bit stream encoded by a fixed length code. A portion of the first block is selected as the key data and inserted into the second block to indicate that the digital video program is a copy to prevent illegal copying.

BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned objects, features and advantages of the present invention will be apparent from the following detailed description of the illustrative modalities that will be taken into account in connection with the accompanying drawings, in which: Figure 1 illustrates the coding of groups of images (GOP); Figure 2 illustrates three DCT blocks in a GOP picture box shown in Figure 1, to prevent illegal copying in accordance with the present invention; Figure 3 illustrates another selection of three DCT blocks to prevent illegal copying in accordance with the present invention; Figure 4 illustrates a coding order of DC coefficients of the DCT blocks of Figure 1; Figure 5A illustrates a frame for a variable length coding technique for the DC coefficient in a luminance DCT block: Figure 5B illustrates a variable length coding frame of the DC coefficient in a one-component DCT block of color difference; Figure 6 illustrates a fixed-length coding table of a DC differential of the DCT blocks; Figure 7 illustrates the key datum to prevent illegal copying in accordance with the present invention; Figure 8 is a functional diagram of an encoder according to the present invention; Figure 9 is a functional diagram of a format preparer for encoding the key data in the DCT blocks to prevent illegal copying in accordance with the present invention; Figure 10 is a flow chart for explaining the operation of the format preparer shown in Figure 9; Figure 11 is a continuous flow chart of Figure 10; Figure 12 is a continuous flow chart of Figure 11; Figure 13 illustrates the selection of three DCT blocks for the explanation of step S18 of the flow chart shown in Figure 12; Figure 14 is a flow chart to explain the operation of the decision circuit shown in Figure 9; Figure 15 is a continuous flow chart of Figure 14; Figure 16 is a functional diagram of a video playback device in accordance with the present invention; Figure 17 is a schematic diagram for explaining the prevention of illegal copying with the present invention; and Figure 18 is a table of variable length codes and movement codes in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Referring now to the drawings, where like reference numerals designate identical or corresponding parts throughout the several views, the encoding process of the picture groups (GOPn) to which the present invention relates will be described with reference to Figure 1. Figure 1 shows an MPEG (Cinematographic Film Group of Experts) coding process for coding digital video programs that are composed of a series of picture frames that are to be presented in sequence on the monitor. video. In accordance with the MPEG standard, each picture frame in the series is divided into picture films that constitute a group of pictures (GOP). That is, a group of images includes a series of film images of the film. The MPEG states that the image films that make up the groups of images (GOPN) are encoded as an I image, a P image or a B image.

I is encoded using only the data inside the image film and is therefore called the intra-image frame (or an intra-image field). The P images, on the other hand, are encoded using the data of a previous image film. Similarly, the B images are encoded using both previous and subsequent image films. The coding technique for the P images and the B images is known as predictive coding and these encoded image films are referred to as inter-image frames (or fields) because they are encoded using the data in the other image films. These pictures of intra-image and inter-image (or fields) (I, P, B) are then compressed according to a discrete cosine transformation process (DCT) which will be discussed below. Figure 1 illustrates a DCT that compresses an intra-image (image I) wherein the present invention preferably inserts the key datum into the compressed intra-image of DCT (image I) of Figure 1. Since the intra-images they are not encoded with reference to other image films, the insertion of the key data in the intra-images does not alter other image films. Otherwise, inserting the key data into the inter-images (P images or B images) alters the coding arrangement of other image films and the encoded inter-images would not be decoded exactly. In addition, the first frame in an encoded group of images is a picture frame I, and determining the key data of this frame, therefore, will cause the illegal copying of the corresponding movie to be interrupted immediately.

In accordance with Figure 1, an intra-image (image I) to be coded with the key data is divided into macroblocks, with each macrobioque further subdivided into four blocks of DCT (for reasons of simplification only four blocks of DCT are shown) . It will be noted that each image film actually comprises two fields, a luminance field (Y) and a color difference field (Cb, Cr). These fields contain the luminance data (Y) and the color difference data (Cb, Cr) that is provided in each field according to a ratio of 4: 2: 2 (Y: Cb: Cr). That is, the luminance field (Y) has four data pixels for each pixel of the field data (Cb) and one pixel of the field data (Cr) in the color difference field. Accordingly, the luminance macroblocks (Y) shown in Figure 1 include four DCT blocks, while the color difference macroblocks (Cb, Cr) each include a single block of DCT. The DCT blocks each preferably comprise 64 pixels placed as shown in Figure 1 in an 8 x 8 matrix. In accordance with the DCT process, these pixels are orthogonally transformed by DCT compression of a signal based on time in a frequency-based signal that has DCT coefficients that correspond to the signal strength • of the 64 pixels at different frequencies. These DCT coefficients are placed in a DCT block in order of ascending frequency that is shown by the zigzag line that starts with a frequency component of zero (DC) in the upper left-hand corner and ending with the component of DCT more frequently in the lower corner on the right. The MPEG further notes that each DCT block is quantized in the order shown by the zig-zag line. In accordance with the MPEG standard, the DCT coefficients are quantified using an average quantization value that is determined from a difference between the DC components of the DCT blocks. The order to determine the difference between DC components is shown in Figure 1 as starting with the upper block on the left, continuing to the upper block on the right, followed by the lower block on the left and ending with the block lower on the right. Following this order for the determination and the difference between the DC components, the differences between each of the DC components in the DCT blocks is determined and the quantification of the DCT components is carried out based on these differences.

The present invention inserts the key data into the DCT blocks of an intra-image frame or field (image I) to prevent illegal copying. As shown in Figure 2, for example, three blocks of DCT (1, 2, 3) are used for this purpose. The first block (1) is selected from the DCT blocks encoded by the aforementioned process and the data within the first block (1) is selected as the key data. The present invention changes the data in the second block (2) to match the key data selected in the first block (1) in order to indicate that the corresponding video program is a copy and should not be copied illegally. The third block contains the correction data that corrects an anomaly caused during the compression of the DCT blocks that arises from the insertion of the key data in the second block (2). The present invention selects a block of DCT to be the first block (1) and the data in the first block is selected as the key datum. It will be appreciated that the key data in the first block (1) is the original image data and, therefore, the encoded film is not altered up to this point. The present invention places the data of the image in the second block (2) to coincide with the key data determined by the first block (1). That is, the difference in the image data between the first and second blocks (1, 2) is removed. Problematically, the DC component will be altered by removing this difference from the second block (2). The present invention corrects this problem by inserting a correction data representative of the difference between the first and second blocks (1, 2) towards the third block (3). When the DCT blocks are coded, the alteration caused by the change in the second block (2) is corrected by the third block (3) which contains the difference between the first and second blocks. In this way, the correction data in the third block (3) corrects the anomaly caused by the data in the second block (2). The present invention places the three blocks in the order of processing DCT to ensure that the third block (3) is processed after the second block (2), canceling the anomaly caused by the change in the second block (2). Preferably the third block immediately follows, that is, it remains adjacent to the second block as shown in Figures 2 and 3 so that the alteration is corrected immediately after the second block (2) is coded. The key data of the first block (1) is preferably selected from the DC differential so that the insertion of the key data can be carried out during the calculation of the DC differential. By selecting the three blocks (1, 2, 3) to be adjacent to each other as shown in Figure 3, these blocks are in sequence order of the DC component processing shown in Figure 1 with this component order of DC, the data in the second block (2) is placed in the key data immediately after the first block (1) and the anomaly caused by the second block (2) is canceled by the third block (3) immediately afterwards. As explained with reference to Figure 1, the order of the processing of the DC component starts with the upper DCT block on the left and ends with the lower DCT block on the right. The order of processing the DC components has been described with reference to a macrobioche of luminance (Y) signals. For the color difference signals having a single DCT block in each macrobioque (Cb, Cr), the order of processing the DCT component follows the sequence order of the color difference signal DCT blocks shown in the Figure 4. In the present invention, it is preferred to reserve the macroblocks of the luminance signal (Y) as the key data, but in the alternative, the macroblocks of color difference (Cb, Cr) can be reserved for the key data of a similar way.

The difference value of the DC component is represented both by the size of the DC component and the actual value (DC differential) that corresponds to the size of the DC component). The size of the DC component is represented by a variable length code (VLC), and the DC differential is represented by a fixed length code (FLC) as defined by the MPEG format. An example of the size of the DC component for the luminance signal (Y) is shown in Figure 5A and the size of the color difference signals (CB, CR) is shown in Figure 5B. It will be noted that the DC component, ie the size of both luminance and color difference signals, is represented by the variable length codes in these figures. In contrast, the DC differential is shown in Figure 6, where the DC differential for the DC component having the size of three bits is represented by the fixed length codes. In this example, where the size of the DC component is 3 and the actual value is -6, the difference value is provided by the fixed length code 101001, the prefix 101 indicating the size of the DC component, indicating the subscript 001 the real value of -6. An advantage of selecting the key data of the DC differential and the DC component is that this data is coded using a fixed length code as shown in Figure 6, which is of uniform length for all the DCT blocks. The least significant bit of the DC differential in the first block of preference is selected as the key data in order to least alter the DCT compression. Therefore, the present invention places a corresponding least significant bit of the DC differential in the second block at this value. As shown in Figure 6, for example, a three-bit DC differential of the second block has its least significant bit placed. When the least significant bit of the DC differential having the value of "000" in Figure 6 is set to "1", for example, the DC differential for the second block becomes "001" as shown by the arrows It will be appreciated that the least significant bit of the second block results in a change in value and that therefore, it has a minimal impact on the motion picture. This impact is minimized in an additional way when it is considered that the third block will cancel immediately after the anomaly created by the loading of the second block. In accordance with this embodiment, the LSB of the DC differential of the second block is set to the same value as the LSB of the DC differential of the first block. For example, when the DC differential of the first block is 010 and the DC differential of the second block is 101. The LSB of the DC differential of the second block is rewritten to zero to be the DC differential of 100. As another example, when the DC differential of the first block is 001 and the DC differential of the second block is 010, the LSB of the DC differential of the second block is converted to write to one in order to make the DC differential of 011. therefore, in accordance with this mode, the DC differential of the second block is rewritten as shown by the arrows in Figure 6. When the value of the DC differential is 001 and the LSB is rewritten to zero, for example, the value of the DC differential is rewritten as 000, but not as 010. As another example, when the value of the DC differential is 010 and the LSB of this value is changed to "1", the differential of DC is rewritten as 011. As yet another example, how much If the value of the DC differential is 011 and the LSB is changed, the value is rewritten as 010. In this way, only the LSB is rewritten. It will be appreciated that, when the LSB of the first and second blocks are equal, the LSB of the second block does not need to be changed. It will be noted that, when the LSB of the DC differential of the second block, the values in the left column in Figure 6) are rewritten in this way, the actual value of the DCT coefficient (the value in the right column in Figure 6) It increases or decreases by one. If left uncorrected, this increase or decrease in one of the DCT coefficient would cause a slight alteration in the reproduced image. The third block corrects this slight alteration by changing the value of its DC differential in such a way as to absorb the increase or decrease in the real value of the DCT coefficient. More specifically, when the LSB of the DC differential of the second block is rewritten from zero to one, the actual value of the DCT coefficient is increased by one. To absorb this increase, the DC differential of the third block is rewritten in such a way that the DCT coefficient decreases by one. On the other hand, in the case where the LSB of the DC differential of the second block is rewritten from one to zero, the value of the DCT coefficient is decreased by one. In this DC situation of the third block, this decrease is absorbed by writing in such a way that the real value of the DCT coefficient is increased by one. For example, suppose that 010 of the DC differential of the second block is rewritten as 011, as shown in Figure 6. Therefore, the actual value of the DCT coefficient is increased by one, ie, -5 to -4. The DC differential of the third block is 110, for example, the present invention rewrites the DC differential of the third block as 101. By doing so, the DC differential of the third block causes the DCT coefficient to be decreased by one, that is, from 6 to 5. As another example, in the case where the DC differential of the second block is rewritten from 011 to 010, the actual value of the DCT coefficient is decreased by one, that is, from - 4 to -5. In this case, the DC differential of the third block that can, for example, be set to 110, is rewritten as 111 in order to increase the real value of the DCT coefficient by one, that is, from 6 to 7. In this way, the third block absorbs the increase or decrease in the real value of the DCT coefficient. The present invention also provides the placement of the key data of a plurality of macroblocks. For this object, a string of key data bits (n) derived from the least significant bit of the DC differential in a plurality of first blocks is inserted into the least significant bits of the respective second blocks. With this provision, it would be virtually impossible for a professional copier to determine all the second blocks and remove the key data in order to illegally copy the corresponding film. Despite the multiplicity of key data blocks, these numerous blocks are decoded quickly and efficiently because the blocks of the key data are placed in the known order of processing the DC component. An encoder that encodes the cinematic film of the source or original source in a stream of bits to be recorded on a master disk or a master tape according to the present invention, is shown in Figure 8. A picture of the current picture of the motion picture is stored in a frame memory, and a motion prediction image stored in a subtraction prediction memory 10 by a subtraction apparatus 2. The frame of the subtracted image is then processed by DCT by the DCT circuit 3, quantized by the quantization circuit 4 and compressed by the variable length coding circuit 5 (VLC) in a bit stream to be recorded on a master disk. The motion prediction image is generated in the motion compensation circuit by predicting the current frame of a motion vector of the frame previous detected by the motion vector detection circuit 11 and a reconstructed version of the previous frame. The reconstructed version of the above table is generated by the adder 8 which adds the previous motion production image to the decoded previous image by a reverse quantization circuit 6 and a reverse discrete cosine transformation (IDCT) circuit 7. An explanation of the encoder will be provided by way of example of its operation starting in a period of time when the current frame is stored in the memory 1 of the frame. During this moment, the motion prediction image has already been stored in the prediction memory 10 generated from the previous frame. This motion prediction image is a prediction of the current frame based on the motion vector of the previous frame detected by the motion vector detection circuit 11 and the reconstructed version of the previous frame. The motion prediction image of the current frame represents the image decoded by a decoder. By subtracting this decoded image representative of the current frame, the subtraction apparatus 2 generates the difference in data between the current motion vector and the current encoded frame. This difference data of the current frame that encodes and transmits to the decoder to be decoded and used to reconstruct the current frame. The difference data that is much smaller in data size than the current frame is not subtracted, it is now ready to be compressed. The circuit 3 of DCT transforms the data into the output of the subtraction apparatus 2 by an orthogonal transformation to the blocks of the DCT coefficients (DCT [u], [v]). These DCT coefficients are quantified by the cunatification circuit 4 in the corresponding quantization coefficients (QF [u], [v]) and are compressed by the variable length coding circuit 5. The resulting compressed bit stream is recorded in a master means 12, such as a magnetic tape or a high density disk. It will be appreciated that the inverse quantization circuit 6 and the IDCT circuit 7 are used to simulate the decoder on the decoding side (Figure 16). The decoded data includes errors in the encoded data inadvertently generated by the DCT circuit 3 and the quantization circuit 4. These errors are added together with the decoded data to the motion prediction image to reconstruct the data as it was immediately before being encoded. This reconstructed data is used to generate the motion prediction image of the current frame subtracted from the current frame by the recording apparatus 2. In this way, the errors generated by the coding are subtracted from the current frame, resulting in a more accurate coding process. The motion compensation circuit generates the motion prediction image by comparing this reconstructed image of the previous frame with the motion vector of the previous frame. The movement vector indicates the movement of the previous frame. From this motion vector, the motion compensation circuit provides a prediction of the arrangement of the images in the current frame. This prediction is stored in the prediction memory 10 and subtracted from the current frame by the subtraction apparatus as described. The encoded bits are recorded in a master media and the master media is used by the legal copiers to create the legal copies. Without further ado, illegal copiers would be able to illegally copy these copies of the illegal master disk. To prevent this illegal copying, the present invention provides a preparer of formats shown in Figure 9 that inserts the key data into the coded bit stream. It will be appreciated that, as an alternative, the format preparer can repair a format of the coded bit stream output directly from the encoder without first registering in the legal master medium.

Therefore, the format maker produces a large number of disks (ROM discs) from the legal master medium. As will be explained with reference to Figure 9, the format preparer detects when the master medium is a copy, ie, an illegal reproduction of the master medium. In this last case, the format preparer prevents illegal copying and a large number of discs can not be produced. - A calculation circuit 32 reads the bit stream to a predetermined position and calculates a position (X) of the first block that will determine the key data, for example, by using the equation (X = B / K), where (B) is the data extracted from the bitstream and (K) is a predetermined key stored in memory 31. A detection circuit 33 detects the first block at position (X) in the coded bit stream and causes the memory 34 extracts the key data thereof. A key insertion circuit 35 inserts the extracted key data into the second block and a correction circuit 36 forms the third block of the correction data to correct the anomaly of the key data inserted in the second block. A decision circuit 38 determines whether the coded bit stream is reproduced from a legal master disk of a copied version of the master disk, such as the disk being offered for sale, and the illegal master disk and causes the control circuit to allow that the coded bit stream is recorded by the recording apparatus 37 only in the first situation. Otherwise, the coded bit stream is judged as a stream from the illegal master disk and the recording apparatus is prevented from illegally copying the coded bit stream. The format preparer presents the decision of the decision circuit to an operator, through the presentation unit 40. The operation of the format preparer in the Figure 9 will be explained with reference to the flow charts of Figures 10 to 12. The format preparer begins a registration operation causing the calculation circuit 32 to continuously read the bit stream encoded in step SI. In accordance with the present invention, the key datum is inserted in a frame of the image I which is the first frame in each group of images and, therefore, the first frame in the motion picture. Therefore, the first bits of the frame of the image I are read by the calculation circuit and the data (B) is extracted in step S2, for example, from a sequence of the bits in the current corresponding to the header information The calculation circuit then calculates the position (X) of the first block in step S3 by using, for example, the equation (X = B / K), where the value of (K) is a predetermined value stored in the memory 31. It will be appreciated that the equation (X = B / K) provides additional protection against illegal copying.The value (K) stored in the memory 31 can be derived, for example, from an input of a password The value (B) can be derived from a secret area of the bit stream, together, the values (K) and (B) act as a double key, which is difficult for a Illegal copier can decipher In step S4, the calculation circuit specifies the position ions of the first and second blocks from position (X). For example, when (X) is a data byte, the calculation circuit can specify the four most significant bits (MSB) of the byte (X) as the position for the first block, and the next four least significant bits (LSB) of the byte (X) as the position for the second block. In the alternative, the six most significant bits (MSB) of (X) represent the position of the macrobioche and the next two least significant bits (LSB) of the byte (X) represent the position for the first block and the second block that follows immediately following the first block. Of course, the number of bits comprising the position of the first block can be variably selected in order to further prevent the illegal copiers from determining the position of the first block. The calculation circuit 32 generates the signal showing the position of the first and second blocks. Referring now to the portion of the flow chart illustrated in Figure 11, the operation of the format production device continues to step S5, wherein the detection circuit 33 reads the bitstream and detects when the position has been reached. of the first block in the bitstream as determined in the previous step. The present invention selects the least significant bit of the DC differential in the first block as the key data that is placed in the second block to prevent illegal copying. To detect the DC differential, the detection circuit detects the DC size for the block in the S7 query. If the size of DC is not zero, the operation of the format preparer advances to step 8 and a register (register_l) is placed in memory 34 in the least significant bit of the DC differential as the key data, by circuit 33 detection. Otherwise, the DC size is zero and the format preparer advances to step S8 where a register (register_l) is placed at "0" by the detection circuit 33.

The operation of the format preparer then proceeds to step S10, wherein the reading is continued by the detection circuit 33 and the detection circuit 33 detects the second block in the read bit stream. Similar to step S6, the detection circuit in step Sil reads the size of DC for the current block. The detection circuit in query S12 detects that the DC size of the block is zero, therefore, the logic circuit is advanced to step S26 (Figure 12). Otherwise, the DC size of the block is not zero, the operation of the format preparer advances to step S13, where the least significant bit of the DC differential of the current block is sent as a register (register_2) in the memory 34 and it is placed in the record (record_2). In Query S14, the detection circuit 33 determines whether the value in register -1 and register -2 are equal and if so, the least significant bit of the DC differential in the second block is considered as having already essentially changed . In this situation, there is no need to write the LSB of the DC differential of the first block in the LSB of the DC differential of the second block, and the logic circuit deviates from the write step of S15 to step S26. On the other hand, when the values in the registers are not judged equal to the same, it is considered that the LSB of the DC differential of the second block has not been graduated to the LSB of the DC differential of the first block. In this latter situation, the logic circuit advances to step S15, wherein the detection circuit 33 generates the detection signal to the key insertion circuit 35 and the key insertion circuit 35 reads the LSB of the first differential DC. block from register -1 and overwrites the LSB of the DC differential of the second block with the LSB of the first block to indicate that the coded bit stream is a copy and should not be copied illegally. As a result of the aforementioned overwrite operation, which places the LSB of the second block, the original bitstream deviates only one from the decode image in the case where the DC component of each block is quantized to eight. bits by 0.5 in the case where the DC component of each block is quantized in nine bits, by 0.25 in the case where the DC component of each block is quantized in 10 bits, by 0.125 in the case where the component DC of each block is quantized in 11 bits. Then, a correction process is carried out to suppress a decoupling attributable to the placement of the LSB of the second block. The processing for the third block will be explained with reference to steps S16 to S25. Although the third block can be placed at any point in the bit stream, it is preferred that it immediately follows the second block. Therefore, the detection circuit continues to read the coded bitstream after the second block, and detects the third block below in step S16. The detection circuit in step S17 reads the DC size of the current block and determines a query S18 of whether the DC size is zero. As in the S7 and S12 queries, when the detected DC size is not zero, the operation of the format preparer advances to step S19. Otherwise, if the DC size is zero, the operation of the format preparer advances to step S16. Unlike the previous queries, in the query S19, the detection circuit 33 writes the entire DC differential, not only the LSB thereof of the third block in a third register (register_3) of the memory 34 when the DC size does not it's zero As an example, the DC differential can be represented by a three-bit fixed-length code as shown in Figure 6. In query S20, the detection circuit determines whether the value stored in register 1 (register_l) is "0" indicating that the second block was rewritten from "1" to "0" and proceeds to query S21. Otherwise, the detection circuit decides that the second block was written from "0" to "1" and advances to query S23. In queries S21 and S23, the detection circuit 33 determines whether the third block is appropriate for a correction block. If the third block is considered inappropriate, the next block in the bit stream is selected to be the third block. This is shown in Figure 3, where the third block (3) is changed from for example the block immediately after the second block to the next block afterwards. To explain, the third block is considered not to be appropriate, in the case where the DC differential LSB of the second block is converted from "1" to "0", that is, it decreases when it is already at an extreme value because an extreme value can not be increased to a higher value. For example, when the DC differential represented by the three bits shown in Figure 6 is equal to the extreme value "111" it is not possible to increase this extreme value by "1" to negate the decrease of the LSB of the second block. In query S21, the mathematical expression 2 (size DC) _? _ And 2 (size DC -1) _ are equal to the maximum positive and negative values, that is, the extreme value of the DC differential, where the size DC is the number of bits in the DC differential. In the example of Figure 6, the maximum positive values for three bits is 2 3) -1 = 7 ("111", value 7) and the maximum negative value is 2 (3-1) -1 = 3 ("011", value -4). Therefore, query S21 determines whether the value in register_3 is at the extreme values of "111" or "011" and if so, considers that the current block is inappropriate. Similarly, query S23 is equal to the minimum allowable positive and negative values when the third block is decreased to deny a change of the LSB of the second block from "0" to "1", ie, an increase. In this case, the minimum positive allowable value is 2 ^ 3-1) = 4 (binary "100") since the decrease of this value to "011" would result in -4 and not three. The other minimum value is zero since it is not possible to decrease "000". Therefore, in query S23, the third block is considered inappropriate when it contains the minimum values and will be decreased. In the situation where the third block is considered appropriate in query S21, the detection circuit advances to step S22 where the value of the third block in register_3 is increased to negate the anomaly caused by decreasing the second block. Similarly, when the third block is considered appropriate in query S23, the detection circuit advances to step S24, where the value of the third block of register 3 is decreased to negate the anomaly caused by increasing the second block. Next, the detection circuit sends the correction value in register_3 to the correction circuit 36 which overwrites the DC differential of the third block with the correction value in step S25. It will be appreciated that the present invention can suppress the third block and operate without a correction data. In this case, however, the anomaly caused by the insertion of the bit of the key data in the LSB of the DC differential of the second block, will cause a distortion in the motion picture during the decoding. This distortion is minimal because the anomaly changes the DC component only by one and is hardly noticeable in the brief presentation of that single frame. The anomaly can further be minimized as explained by increasing the number of bits in each DCT block to decrease the representative value of each bit as explained. In step S26, the calculation circuit 32 determines whether more I images will be encoded with the key data returning to the beginning or ending the coding process of the key data. In Figure 7, for example, the key data can be a string of bits, with each bit selected from a different first block. In this situation, the calculation circuit will continue to process the bitstream for a number of times (n) until all the bits of the key data in Figure 7 have been coded in the second blocks. With this arrangement, it is possible to encode the key data into multiple portions of the motion picture, thus greatly impeding the illegal copying of the motion picture. The recording apparatus 37 (Figure 9) then records the bit stream with the second key data on a disk. Since the key data indicates that the corresponding film is a copy of a master disc, an illegal copier can not copy the film of this illegal master without great difficulty. The manufacturer can use a die cutter that physically punches other discs to mass-produce stamped copies of a copy encoded with the key data. Since each die-cut disk carries the coded key data, each stamped copy will also be unable to be copied. The decision process by which the format preparer decides whether the coded bit stream is reproduced from a legal master disk and, therefore, is capable of being copied, is described with reference to the flow charts of Figures 14 and 15. In step S40, the control circuit 39 places a variable (N) of the counter representing the bit of the key data Nth checked in the string of key data bits (n) in Figure 7. Steps S41 a S44 are the same as steps SI to S4 (Figure 10) and for a detailed description those steps will refer to the corresponding sections. In this manner, the position (X) (step S43) of the first block is derived from the extracted value (B) (S42) of the continuously read bit stream (step S41) and the detection circuit 33 (FIG. 9) specifies which portion of the byte (X) is assigned for the position of the first block and the position of the second block (S44). The detection circuit continuously reads the bitstream until the first block is detected in step S46 (FIG. 15) and then determines the value of the DC component (DC size) of the first block in step S47. When the detection circuit determines that the DC size is "1" in the query S48, the detection circuit proceeds to step S49 and places the register_l in the LSB of the DC differential. On the other hand, when the DC value is "0", the detection circuit advances to step S50 and sets the register_l to "0". The detection circuit then proceeds to step S52 to continuously read the bitstream until the second block is detected. During this time, the detection circuit determines whether or not the DC size of the second block is zero in query S53. If the size of DC is zero, the format preparer operation advances to step S54; if the DC value is not zero, the operation of the format preparer advances to step S57. The detection circuit in step S54 places the register_2 in the LSB of the DC differential of the second block and the decision circuit 38 (Figure 9) in step S55, determines whether the LSBs of the DC differential of the first and second blocks are equal indicating that the bit of the key data Nth is found and that the bit stream is reproduced from an illegal master disk or a disk offered for sale, not a legal master disk. No bits of the key data are found, ie, if the LSBs of the DC differential of the first and second blocks are not equal, the bitstream is considered reproduced from a master disk in step S59 and copying is allowed. If the illegal master disk or a disc offered for sale is indicated, that is, the LSBs of the DC differential of the first and second blocks are equal, the control circuit advances to step S56 and increments the counter N so that the preparer of formats will search for the next bit of key data in the string of Figure 7. Then, the control circuit advances to step S57 and if there are more key data bits to be found from the string of key data bits, the controller returns to step S41 of the flow chart in Figure 15 to place the next bit of key data in the string. Otherwise, all the key data bits were placed and the control unit prevents the recording apparatus from recording the bit stream since the bit stream is reproduced from an illegal master disk or a disk offered for sale. It will be appreciated that it is not known if any given disc includes a key datum. In the preferred embodiment, the presence of the key data is definitely known due to its position that is indicated in the header of the images I. Alternatively, the position data can be left intentionally ambiguous, in order to prevent illegal copiers from finding the data key of the header information. In this last situation, the key data is testing the first and second blocks to correspond to the images I. It will be appreciated that it is not known exactly if any given disk is coded with the key data, since the LSB in the positions of the First and second blocks can be the same by coincidence. In this situation, the controller must decide in step S58 whether it is likely that the given disk is an illegal master disk or a disk offered for sale based on the match number detected between the first and second blocks. When all the bits of the key data are matched, the probability that the given disk is an illegal master disk or a disk offered for sale increases with the number (N) of matching key data bits and is equal to (l- (l / 2 ^)). It will be appreciated that the probability can be increased to within one thousandth of 100 percent with as little as 10 bits of key data. The present invention in no way prevents the legal digital disc player device from reproducing copies of the master disc. Figure 16 is a functional diagram representing a portion of a reproduction device for reproducing the reproduced bitstream of a disk. The reproduced bit stream is decoded by a variable length decoding circuit (VLD) 61 into quantized and dequantized coefficients towards the DCT coefficients by an inverse quantization circuit 62. The DCT coefficients are transformed into pixels representing a portion of a frame of the motion picture, and these pixels are added to the motion prediction image stored in a prediction memory 66 to recreate the complete frame. The entire frame is offset in motion by the motion compensation circuit 65 and stored in the prediction memory 66 as the motion prediction image is used for the next frame. In this way, the bit stream is decoded and reconstructed in frames of the cinematographic film to be sent as a video data to a monitor and a similar device, for its presentation. Even though the present invention has been described as inserting bits of the key data data into the blocks of the luminance DC component (Y), it is equally practical to insert the key data into the color difference blocks (Cb, Cr). Of course, the key data can be determined from a block type, the luminance block (Y), for example, inserted in another type of block, such as the color difference blocks (Cr, Cb). The present invention may also be encompassed as a means capable of being read on a computer to direct a computer, such as the described format preparer to avoid illegal copying. A stream of reproduced bits recorded in the medium capable of being read on a computer is encoded in accordance with the MPEG standard which provides for the way in which the recorded data is encoded as images including intra-images and inter-images. The images are divided into DCT blocks of the DCT coefficients, with the DCT blocks having a difference of the DC components in the adjacent DCT blocks. A first block of DCT in a respective intra-image determines the key data and a second block of DCT in the respective intra-image receives the key data, indicating that the medium capable of being read on the computer is a copy. A third block of DCT in the respective intra-image includes the correction of data of the anomaly caused during the registration that is caused by the receipt of the key data through the second block. The DC differential from which the key data in the present invention is determined, has been described as being the fixed length coded blocks. Instead, the encoded residual-motion (FLC) of the differential value of the motion vector can be used with equal effect. According to the MPEG project, as explained with reference to Figure 8, the motion vectors of the image P and the image B are detected by the detection circuit 11 of the motion vector and these motion vectors are encoded and they are contained in a stream of bits for transmission. These motion vectors are represented by the code_of_ movement as VLC as shown in Figure 18, and by the "motion_residual", as a fixed-length code (FLC). The movement _code represents an approximate value of the motion vector, the residual movement represents a correction value to indicate an exact value and f__code represents the accuracy (amplification) of the code_motion. In the case where the f_code is 1, for example, the code_ movement represents a value with an accuracy of 0.5. A sufficiently accurate value, therefore, can be represented and, therefore, residual motion is not used in this case. In the case where f_code is 2, on the other hand, the code_show represents a value with an integer accuracy and the residual_shift a value with an accuracy of 0.5. In other words, the motion_residual is represented by a one-bit FLC indicating 0 or 0.5. Further, in the case where f_code is 3, the code_show represents a value with an accuracy of a multiple of 2, and the residual_shift provides a 2-bit CLF that represents 0, 0.5, 1.0 or 1.5. It will be appreciated that, as in the case of the DC difference, the residual motion does not exist for the code_movement of 0. In this way, the key data for preventing illegal copying can be recorded in the data of residual movement that constitutes a length code fixed (FLC) in the case of the DC differential mentioned above. It will be appreciated that the data of the residual motion is included both in the image P and in the image B. The exclusive use of the residual motion of the image B, however, can prevent the effect of inserting the key data into other images, since image B is not used for the prediction of other images. The present invention is particularly suitable for manufacturers wishing to protect their digital video programs from illegal copying. As shown in Figure 17, for example, a manufacturer mass copies a motion picture from a source or original source, such as an authentic master disc or an authentic master tape. Since the original source or source does not include the key data, the format preparation device does not detect any key data and allows the motion picture to be recorded to an object offered for sale, such as a copy of a disc, as shown through the circles marked in the block desigando as the format preparer. To prevent illegal copying, the format preparer detects the key data of the first blocks already existing in the motion picture and inserts this key data into the corresponding blocks. As explained, the item offered for sale can be legally reproduced by the reproduction device of Figure 16, but can not be copied by the format preparation device. In this way, an illegal copier can not make copies of the offered object for sale or an illegal master disc because the format preparation device will detect the key data indicating a copy as shown by "X" that is marked in the preparer of formats. In addition, the illegal copier can not make an illegal master disk or illegal master tape of the offered object for sale or illegal master disk because the resulting master disks can also include the key data that prevents it from being copied. Accordingly, the present invention securely prevents the illegal copying of a digital video program, thus greatly avoiding the danger of mass-produced copies illegally. Although the present invention has been described in specific detail with respect to the preferred embodiments, it should be noted that the invention is not limited thereto and that various changes and modifications can be made therein by a person skilled in the art without departing from the scope of the invention. scope of the invention which is intended to be defined by the appended claims.

Claims (33)

R E I V I N D I C A C I O N E S:

1. A data recording apparatus for preventing the unauthorized copying of the encoded data subsequently reproduced as a stream of bits from a recording medium, the apparatus comprising: a designation means for designating a first data block and a second data block of the bitstream; and an insertion means for inserting at least a portion of the data included in the first data block as the key data to the second data block indicating that the data registered in the recording medium is a copy and should not be copied.

The apparatus according to claim 1, further comprising a recording means for recording the coded data including the key data in the recording medium.

3. The apparatus according to claim 2, wherein the recording means includes an orthogonal transformation means for transforming the bit stream into orthogonal transformation coefficients before coding.

The apparatus according to claim 3, wherein the recorded data is a video data encoded as inter-coded and inter-coded images formed from the blocks of the DCT coefficients, each block having a component of the DC differential representing a difference between the DCT DC coefficients in the adjacent blocks; wherein the first data block designated by the first designation means is a first block of the DCT coefficients in an intra-coded image; and wherein the second data block that is designated by the designation means is a second block of DCT coefficients in the same intracoded image.

The apparatus according to claim 4, wherein the insertion means inserts the key data into the second data block by writing a least significant bit of a first DC differential component in the first block as the least significant bit of a Second differential component of DC in the second block.

The apparatus according to claim 3, wherein the designation means further designates a third data block in the bit stream; and the furthermore comprises a correction means for correcting an anomaly during registration caused by the insertion of the key data in the second data block.

7. The apparatus according to claim 6, wherein the recorded data is a video data encoded as inter-coded and inter-coded images formed from the blocks of DCT coefficients, each block having a DC differential component representing a difference between the coefficients of DC of the DCT and the adjacent blocks; wherein the first data block designated by the designation means is a first block of the DCT coefficients in an intra-encoded image; wherein the second data block designated by the designation means is a second block of DCT coefficients in the same intra-encoded image; And the third data block designated by the designation means is a third block of DCT coefficient in the same intra-coded image.

The apparatus according to claim 7, wherein the insertion means inserts the key data in the second data block by writing a least significant bit of a first DC differential component in the first data block as the least significant bit of a second DC differential component in the second data block; and the correction means corrects the anomaly by inserting the least significant bit of the second differential component of DC into the least significant bit of a third DC differential component included in the third data block, thus negating the anomaly caused by the insertion of the key data in the second data block.

The apparatus according to claim 4, wherein the DCT coefficient blocks are grouped into coded macroblocks in a predetermined order, and the second data block is a last block in the predetermined order.

The apparatus according to claim 1, wherein the recorded data is a video data and the bit stream is an encoded bit stream of MPEG including a fixed length code representing a motion vector.

The apparatus according to claim 10, wherein the MPEG encoded bitstream is formed from predictively encoded image frames including image frames B, and the designation means designates the first and second blocks of data in the vector of movement of a frame of image B.

12. A method of recording data to prevent the unauthorized copying of data reproduced subsequently as a bitstream of a recording medium, the apparatus comprises the steps of: designating a first data block and a second data block from the current of bits; and inserting at least a portion of the data included in the first data block as the key data in the second data block indicating that the data recorded in the second recording means is a copy and should not be copied.

The method according to claim 12, further comprising the step of registering the coded data that includes the key data in the recording medium.

The method according to claim 13, further comprising the step of transforming the bit stream into orthogonal transformation coefficients before coding.

The method according to claim 14, wherein the recorded data is a video data encoded as intra-coded and inter-coded images formed from blocks of DCT coefficients, each block having a DC differential component representing a difference between the DCT DC coefficients in the adjacent blocks; wherein the designation step designates a first data block of DCT coefficients in an intra-encoded image; and wherein the step of designating designates a second data block of the DCT coefficients in the same intra-encoded image.

The method according to claim 15, wherein the insert step inserts the key data in the second data block by writing a least significant bit of a first DC differential component in the first block as the least significant bit of a Second differential component of DC in the second block.

The method according to claim 14, wherein the step of de-assigning further designates a third data block in the bitstream, the method further comprising the step of correcting an anomaly during registration caused by the insertion of the key data. in the second data block.

18. The method according to claim 17, wherein the recorded data is a video data encoded as intra-encoded and inert-encoded images, formed of a DCT coefficient block, each block having a DC differential component that represents a difference between the DCT DC coefficients in the adjacent DCT blques; wherein the designation step designates a first data block of DCT coefficients as an intra-encoded image; wherein the design step designates a second data block of the DCT coefficients in the same intra-encoded image; and wherein the designation step designates a third data block of DCT coefficients in the same intracoded image.

The method according to claim 18, wherein the insert step inserts the key data in the second data block by writing a least significant bit of a first differential DC component in the first data block as a least significant bit of a second DC differential component in the second data block; and the correction step corrects the anomaly by inserting the least significant bit of the second differential component of DC into the least significant bit of a third DC differential component included in the third data block, thus negating the anomaly caused by the insertion of the key data of the second data block.

The method according to claim 15, wherein the DCT coefficient blocks are grouped into coded macroblocks in a predetermined order, and the second designated block is the last block in the predetermined order.

The method according to claim 12, wherein the recorded data is a video data and the bit stream is an MPEG encoded bit stream that includes a fixed length code representing a motion vector.

22. The method according to claim 21 further comprising the step of encoding the recorded data into an MPEG encoded bit stream that represents the frames of the predicted encoded image including frames of the B image., and the designation step further allocates the first and second data blocks in the motion vector of a frame of image B.

23. An apparatus for preventing the unauthorized copying of the registration data comprising: a detection means to detect a first data block and a second data block in a stream of data bits reproduced from the recorded data; a comparison means for comparing the predetermined data as the key data in the first data block with the data in the second data block; and a control means, which responds to the comparison means, to inhibit the copying of the reproduced data of the registered data if the key data compares with the data in the second data block.

24. The apparatus according to claim 23, further comprising a display means for displaying a result of the comparison means.

25. The apparatus according to claim 24, wherein the recorded data is a video data encoded as inter-coded and inter-coded images formed from DCT blocks, each block having a DC differential component representing a difference between the coefficients DCT in the adjacent blocks; wherein the first block of data detected by the detection means is a first block of DCT coefficients in an intra-coded image; and wherein the second block of data detected by the detection means is a second block of DCT coefficients in the same intracoded image.

26. A method for preventing the unauthorized copying of the recorded data comprising the steps of: detecting a first data block and a second data block in a stream of data bits reproduced from the recorded data; comparing the predetermined data as the key data in the first data block with the data of the second data block; and selectively inhibiting the copying of the reproduced data from the recorded data if the key data is compared with the data in the second data block.

27. The method according to claim 26, further comprising the step of presenting a comparison result.

The method according to claim 27 wherein recorded data is a video data encoded as inter-coded and inter-coded images formed from blocks of DCT coefficients, each block having a DC differential component representing a difference between the DC coefficients of the DCT in the adjacent blocks; the first detected data block is a first block of DCT coefficients in an intra-coded image; and the second detected data block is a second block of the DCT coefficients in the same intracoded image.

29. A means capable of being read in processor to instruct a processor to prevent the unauthorized copying of a reproduced bit stream recorded in the medium and encoded as inter-coded and inter-coded images formed from the DCT blocks of the DCT coefficients, each DCT block has a DC differential component that represents the difference between the DC components in the adjacent DCT blocks, where: the predetermined data in a first DCT block in an intra-coded image is the key datum; and the second predetermined data in a second DCT block in the same intracoded image indicates that the medium is a copy if the predetermined data in the second DCT block is equal to the key data.

30. The medium according to claim 29, wherein the third DCT block is the same intracoded image and includes a data that corrects an anomaly caused if the predetermined data in the second DCT block is equal to the key data.

The medium according to claim 30, wherein the predetermined data in the second DCT block is a least significant bit of a first DC differential component in the first DCT block, and is the least significant bit of a second differential component of DC in the second block of DCT.

32. The means according to claim 31, wherein the data included in the third DCT block is placed in the least significant bit of the second DC differential component before the key data inserts into the second block.

33. The medium according to claim 32, wherein the DCT blocks are grouped into macroblocks, the DCT blocks of each macrobioche is coded in a predetermined order and the second DCT block is a last DCT block in predetermined order.