JP3691415B2 - REPRODUCTION DEVICE, REPRODUCTION DEVICE SPECIFICING DEVICE, AND METHOD THEREOF - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a playback apparatus for AV (in this specification, only one of audio and video, or both audio and video (arbitrary mixing is arbitrary) is referred to as “AV”). The present invention relates to a technique for embedding an identification code or the like for specifying a playback device as an electronic watermark in an AV signal (playback signal) output from the playback device.
[0002]
The present invention also relates to a playback device specifying device for specifying a playback device that extracts a digital watermark from an AV signal (playback signal) and outputs the AV signal (playback signal).
[0003]
Here, the “reproducing apparatus” in this specification includes not only an apparatus having only a function of reproducing an AV signal from a recording medium, but also a function of reproducing and a function of recording an AV signal on a recording medium. Including devices that have.
[0004]
[Prior art]
Recently, AV data can be recorded and reproduced in various forms. AV data can be recorded and reproduced as an analog signal as in VHS, and can be recorded and reproduced as a digital signal as in DVD.
[0005]
AV data can also be composed of only audio signals or video (including not only moving images but also still images) signals, and can be recorded and reproduced as analog signals or digital signals.
[0006]
The present invention can be applied to AV data in various signal forms as described above.
[0007]
Particularly recently, digital contents (AV data using digital signals) have been widely used.
[0008]
Regardless of whether it is analog or digital, if the data recorded and reproduced as AV data has copyrighted properties, the copyright must be protected. In particular, it is important to prohibit unauthorized duplication.
[0009]
AV data based on analog signals can be duplicated. However, when duplication is performed, quality (such as sound quality or image quality) is inevitably deteriorated. Therefore, it can be said that it is difficult to duplicate.
[0010]
However, digital content has no quality degradation due to copying. In other words, you can easily duplicate the exact same as the original.
[0011]
Since illegally copied content (or content distributed from the content) is indistinguishable from the original as it is, it is difficult to provide evidence to prove the fraud. For this reason, establishment of a technical method for effectively protecting copyright is required.
[0012]
As one of the methods, use of “digital watermark” is being studied.
[0013]
“Digital watermark” is data that is embedded in AV data so that it cannot be perceived by the viewer, and is devised so that a digital watermark can be extracted from the embedded AV data.
[0014]
In order to protect the copyright, copyright information (for example, a copyright owner name and date) is embedded in the AV data as a digital watermark.
[0015]
Then, the embedded digital watermark (copyright information) is extracted from the AV data suspected of being illegally copied, the copyright holder of the content is identified, and the unauthorized copy is revealed. This is intended to prevent unauthorized duplication.
[0016]
A specific technique for embedding a digital watermark in AV data is described in detail, for example, in Kokoo Matsui, “Basics of Digital Watermarking—New Protect Technology for Multimedia” (Morikita Publishing 1998).
[0017]
Further, there is a document called Japanese Patent No. 2982768 regarding embedding an electronic watermark in an AV signal to prevent unauthorized copying of content.
[0018]
In the technique described in this document, an illegal duplication prevention control signal is embedded as an electronic watermark in an AV signal in advance.
[0019]
Then, when reproducing the AV signal, an illegal duplication prevention signal is extracted from the AV signal, and when the illegal duplication prevention signal is extracted, noise is newly added as a digital watermark.
[0020]
Therefore, when an illegally copied recording medium is viewed with this, noise is added to the AV signal every time it is reproduced or copied, and the quality (sound quality and image quality) of the AV signal is greatly deteriorated. Eventually, a large amount of noise is added to the AV signal and it can no longer withstand viewing, so that it is possible to prevent unauthorized duplication.
[0021]
[Problems to be solved by the invention]
(1) However, in the prior art, it is not possible to specify the playback device used for replication. This is because, in the prior art, the digital watermark embedded in the AV signal is information that has nothing to do with the playback device, such as the author's name or random noise having no meaning. Even if the author's name becomes clear, there is little practical benefit if there is no evidence of the fact that the unauthorized copy was made.
[0022]
If the playback device used for duplication can be identified, the owner or user of the playback device will be able to claim with high probability that it would have been involved in unauthorized duplication. It is impossible.
[0023]
Therefore, the conventional technique has a problem that illegal duplication cannot be effectively suppressed.
[0024]
A first object of the present invention is to provide a technique capable of specifying a playback device used for duplication.
[0025]
(2) In order to extract the embedded digital watermark according to the above document, the correlation value between all the noise sequences used for embedding and the signal embedded with the digital watermark is obtained, and the noise showing the maximum correlation value It is common to extract columns as embedded noise sequences. However, if the noise sequence to be embedded is arbitrarily selected, some noise sequences may accidentally show a large correlation value, and the embedded noise sequence may not be accurately extracted.
[0026]
A second object of the present invention is to provide a technique capable of accurately extracting an embedded digital watermark.
[0027]
(3) People who perform illegal copying may intentionally process AV signals so that information embedded as digital watermarks cannot be extracted. For example, the order of the signals is changed or a part of the signals is extracted. When such processing is performed, the embedded digital watermark cannot be correctly extracted by the conventional technique.
[0028]
A third object of the present invention is to provide a technique that can reliably extract a digital watermark even if a third party processes an AV signal.
[0029]
(4) In addition, people who perform illegal copying may intentionally embed a fake digital watermark by analyzing embedded information and an embedded method. In the prior art, if a third party succeeds in the analysis, the copyright protection is insufficient.
[0030]
A fourth object of the present invention is to provide a technology that can counter even if a third party successfully analyzes a digital watermark.
[0031]
[Means for Solving the Problems]
A playback device according to a first aspect of the present invention is a playback device that plays back an AV signal, based on an identification code generation unit that generates an identification code that identifies the playback device itself, and an identification code generated by the identification code generation unit. In a playback device including a digital watermark embedding unit that embeds an electronic watermark in an AV signal and generates an embedded AV signal and an output unit that outputs the embedded AV signal to the outside, the playback device and playback based on the embedded AV signal The playback device specifying device for specifying a device shares a plurality of signal sequences and corresponding relationships so as to have the same content, and the plurality of signal sequences is composed of a finite number of signal sequences that can be embedded in an AV signal, The correspondence relationship is based on a correspondence table that defines the relationship between the content of the identification code and the signal sequence embedded in the AV signal and belonging to a plurality of signal sequences corresponding to this content. The correspondence table defines the correspondence between the contents of the bit string when the identification code is bit expanded and the signal series embedded in the AV signal corresponding to the contents of the bit string and belonging to a plurality of signal series. The embedding unit embeds signal sequences belonging to a plurality of signal sequences in the AV signal based on the correspondence.
[0033]
In the playback device according to the second invention, the identification code stores the device ID of the playback device, the card ID of the IC card connected to the playback device, the user ID of the user, the material ID of the AV signal, and the AV signal. One or a combination of two or more of the media ID and playback date / time of the media.
[0034]
In the playback device according to the third aspect, the correspondence table corresponds to a bit position having a value of “0” or “1” in the binary bit string in which the identification code is expanded and belongs to a plurality of signal sequences. Based on this correspondence, the digital watermark embedding unit determines a bit position having a value of “0” or “1” in a binary bit string in which an identification code is expanded based on this correspondence. And signal sequences belonging to a plurality of signal sequences are embedded.
[0035]
In the playback device according to the fourth invention, the digital watermark embedding unit corresponds to a bit position having a value of “0” or “1” in the binary bit string in which the identification code is expanded, and a plurality of signal sequences A plurality of signal sequences belonging to the above are defined, and a plurality of signal sequences determined for each predetermined unit of the AV signal are embedded.
[0036]
In the reproduction apparatus according to the fifth aspect, the digital watermark embedding unit corresponds to a bit position having a value of “0” or “1” in the binary bit string in which the identification code is expanded, and a plurality of signal sequences A plurality of signal sequences belonging to the above are defined, and the determined plurality of signal sequences are randomly embedded in the AV signal at the same rate per fixed time.
[0037]
A playback device specifying device according to a sixth invention is a playback device specifying device that specifies a playback device based on an embedded AV signal, and the playback device, the plurality of signal sequences, and the correspondence table have the same contents. The signal sequence recording unit is shared, and the plurality of signal sequences are composed of a finite number of signal sequences that can be embedded in the embedded AV signal, and the correspondence table shows the contents of the bit sequence when the identification code is bit-expanded and this Corresponding to the signal sequence embedded in the embedded AV signal and belonging to a plurality of signal sequences corresponding to the contents of the bit string, the playback device specifying device further includes an input unit for inputting the embedded AV signal, and an input Calculates the correlation value between the embedded AV signal input by the section and all signal sequences included in the correspondence table, and outputs the maximum correlation value among the obtained correlation values And a threshold value setting unit for setting a threshold value of a correlation value used for comparison with the maximum correlation value output by the correlation value calculation unit, and a threshold value set by the maximum correlation value output by the correlation value calculation unit and the threshold value setting unit A comparison unit that outputs a signal sequence whose maximum correlation value exceeds a threshold value, an identification code determination unit that determines an identification code from a signal sequence output from the comparison unit and a correspondence table, and outputs a predetermined identification code And an identification code output unit.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the outline | summary of the reproducing | regenerating apparatus identification system of this form is demonstrated using FIG.
[0044]
FIG. 1 is a block diagram of a playback device specifying system according to an embodiment of the present invention.
[0045]
In the example shown in FIG. 1, it is assumed that the duplicator 10 reproduces the original recording medium 1 with the reproducing apparatus 3 and performs illegal duplication to the duplicate recording medium 2 using the AV signal recording apparatus 4.
[0046]
Then, the reproduction recording medium 2 is presented as evidence of unauthorized duplication by the duplicator 10 and the reproduction apparatus specifying apparatus 5 tries to clarify the fact that the reproduction recording medium 2 has been copied using the reproduction apparatus 3. And
[0047]
It is assumed that the duplicator 10 does not have the right to copy the recording medium 1 and that the duplicator 10 is the owner or the user of the playback apparatus 3 in advance.
[0048]
Here, the signal form in the recording medium 1 and the duplicate recording medium 2 is arbitrary, and may be either analog or digital. Further, the recording medium formats of the recording medium 1 and the duplicate recording medium 2 are arbitrary, and various types such as a disk, a tape, and a hard disk may be selected.
[0049]
Here, the playback device 3 is generally distributed in large quantities in the market, and the playback device specifying device 5 is an organization that manages the copyright of the recording medium 1, a police or other governmental organization that controls copyright violations. A form such as possession is conceivable.
[0050]
For the convenience of illustration, the playback device 3 and the playback device specifying device 5 are displayed at the same place, but the playback device 3 and the playback device specifying device 5 are usually present in different locations and used. The time will usually be different.
[0051]
And according to this system of the present invention, the unauthorized duplication of the duplicator 10 can be verified by the process described later.
[0052]
In the system shown in FIG. 1, when the duplicator 10 performs illegal duplication, the duplicator 10 sets the recording medium 1 in the playback device 3, and connects the playback device 3 and the AV signal recording device 4 with a cable or the like. Connected, and set the duplicate recording medium 2 in the AV signal recording device 4.
[0053]
Further, the replicator 10 connects the playback device 3 or the AV signal recording device 4 to the playback device 6 in order to monitor the AV signal.
[0054]
Here, as the playback device 6, when the AV signal includes both audio and video, a television device or the like will be used. If the AV signal is only audio, an amplifier and a speaker (or headphones) or the like will be used as the playback device 6.
[0055]
As described above, the AV signal may be either analog or digital, but the playback device 6 may be one that is compatible with the AV signal system to be used.
[0056]
Alternatively, the reproduction device 6 may be omitted if the duplicator 10 considers that the monitor is unnecessary.
[0057]
Next, the playback device 3 will be described. In the playback device 3, the AV signal playback means 31 reads the AV signal from the set recording medium 1 in the direction of the arrow N1.
[0058]
The digital watermark generation means 32 generates a digital watermark indicating attribute information that can identify the playback device 3. This generation method may be a conventional method such as the method described in the book introduced in the section of the prior art. What is important is that the attribute information can identify the playback device 3.
[0059]
The digital watermark embedding unit 33 receives the AV signal from the AV signal reproduction unit 31 and the digital watermark from the digital watermark generation unit 32. The digital watermark embedding unit 33 generates an embedded AV signal in which the digital watermark is embedded in the AV signal.
[0060]
The output unit 34 outputs the embedded AV signal generated by the digital watermark embedding unit 33 to the playback device 6 and the AV signal recording device 4 connected to the playback device 3.
[0061]
Here, even if the duplicator 10 uses the playback device 6 to monitor the AV signal, the digital watermark is data that is embedded so that it cannot be perceived by the viewer as described above. Normally, the user does not notice that a digital watermark is embedded in the AV signal being monitored.
[0062]
Now, in the present invention, unlike the technique described in the above-mentioned publication, the quality of the AV signal is not significantly degraded by the digital watermark. Therefore, if the duplicator 10 simply monitors the AV data recorded on the recording medium 1 without performing illegal duplication, it can be monitored with good quality.
[0063]
The present invention is superior to the technique described in the above publication even in this respect (a point in which good quality is maintained if only a proper monitor is used).
[0064]
Next, the playback device specifying device 5 will be described. In the playback device specifying device 5, the AV signal playback means 51 reads an AV signal from the set duplicate recording medium 2 (in this case, the embedded AV in which the attribute information of the playback device 3 is embedded as a digital watermark). Signal will be read).
[0065]
The digital watermark extraction unit 52 extracts a digital watermark from the AV signal (embedded AV signal) read by the AV signal reproduction unit 51. This extraction method is the reverse of the processing of the digital watermark embedding unit 33.
[0066]
The printing unit 53 includes a printer and prints the digital watermark extracted by the digital watermark extraction unit 52 on a sheet. Of course, it is sufficient that a digital watermark can be concretely understood by a human being, and it is needless to say that a display or the like may be used instead.
[0067]
Now, when it is clear that the digital watermark extracted from the duplicate recording medium 2 indicates the unique attribute information of the reproduction apparatus 3, the duplication person 10 who is the owner of the reproduction apparatus 3 is the duplication recording medium. It will be easy to understand that the suspicion of the second illegal duplication has become rich.
[0068]
As described above, according to the present invention, the copyright of the recording medium 1 can be effectively protected by embedding the attribute information unique to the reproducing apparatus 3 as a digital watermark in the reproduced AV signal.
[0069]
Here, from the standpoint of the duplicator 10, even if the playback device 6 monitors, it usually does not notice that the digital watermark is embedded. This means that the medium 2 is engraved with evidence of the unauthorized duplication.
[0070]
Therefore, the duplicator 10 who knows this situation will not be able to make unauthorized duplication easily by fearing that the reproduction apparatus specifying apparatus 5 will expose the fraud later.
[0071]
Thus, the present invention can prevent unauthorized duplication.
[0072]
Next, a typical encoded AV signal is taken up as an AV signal to be recorded on the recording medium 1, and a preferred embodiment thereof will be described more specifically.
[0073]
2 and 3 are configuration diagrams of the playback device and the playback device specifying device according to the embodiment of the present invention.
[0074]
FIG. 2 shows a basic configuration of a playback device that embeds an identification code as an electronic watermark in an AV signal. FIG. 3 shows a playback device specifying device that extracts an identification code from an AV signal in which the identification code is embedded as a digital watermark. Is shown.
[0075]
In FIG. 2, the reproduction apparatus includes an encoded signal input unit 101, a decoding unit 102, an identification code generation unit 103, a digital watermark embedding unit 104, and an output unit 105.
[0076]
Here, in this example, the encoded signal input unit 101 and the decoding unit 102 correspond to the AV signal reproducing means 31 of FIG. The identification code generation unit 103 corresponds to the digital watermark generation unit 32, the digital watermark embedding unit 104 corresponds to the digital watermark embedding unit 33, and the output unit 105 corresponds to the output unit 34.
[0077]
In FIG. 3, the playback apparatus specifying apparatus includes an input unit 201, a signal sequence recording unit 202, a correlation value calculation unit 203, a threshold setting unit 204, a comparison unit 205, an identification code determination unit 206, and an identification code output unit 207. .
[0078]
Here, in this example, the input unit 201 corresponds to the AV signal reproducing means 51 of FIG. The signal sequence recording unit 202, the correlation value calculation unit 203, the threshold setting unit 204, the comparison unit 205, and the identification code determination unit 206 correspond to the digital watermark extraction unit 52, and the identification code output unit 207 corresponds to the printing unit 53. Correspond.
[0079]
The correlation value calculation unit 203 obtains a correlation value S (k) defined as follows.
S (k) = Σ (Xi × Ni (k)) (i = 1, 2,..., I)
Where X: series of input AV signals
N: All signal sequences in the correspondence table, for example: N (k) k = 1, 2,..., M
m: Number of signal sequences in the correspondence table
[0080]
Hereinafter, a reproduction method for embedding an identification code as an electronic watermark in an AV signal will be described with reference to FIG. FIG. 4 is a flowchart showing processing performed by the playback apparatus that embeds the identification code of FIG. 2 as a digital watermark.
[0081]
The encoded signal input unit 101 reads the encoded AV signal from a recording medium (for example, DVD, DV, HDD, etc.), receives a broadcast, or downloads from a network (for example, the Internet). Obtained and sent to the decoding unit 102 (step 301). Next, the decoding unit 102 decodes the AV signal encoded according to a rule such as compression or transmission protocol to generate a baseband AV signal (step 302).
[0082]
Next, the process (step 303) of the identification code generation unit 103 will be described with reference to FIG. FIG. 5 is a flowchart showing a processing flow of the identification code generation unit 103.
[0083]
The identification code generation unit 103 stores the device ID of the playback device, the card ID of the IC card connected to the playback device, the user ID of the user, the material ID of the AV signal, and the AV signal as unique attribute information of the playback device. An identification code is created from the media ID of the recorded recording medium, the reproduction date and time, or a combination thereof (step 401).
[0084]
For example, the device ID of the playback device is “152”, which is the identification code.
[0085]
Next, the identification code is expanded into a binary bit string of “0” and “1” (step 402). When the device code “152” is expanded into a bit string, “10011000” is obtained.
[0086]
Next, a signal sequence corresponding to a bit position that is 1 in the bit-developed identification code is searched from a correspondence table prepared in advance (step 403).
[0087]
FIG. 6 is a correspondence table between bit positions of identification codes and signal sequences. FIG. 7 shows the bit position of the identification code.
[0088]
In the identification code “10011000” expanded in the bit string, the fourth bit, the fifth bit, and the eighth bit are “1” from the LSB, and therefore “1” using the correspondence table. Three signal sequences {N4, N5, N8} corresponding to the number of bits are obtained. The identification code generation unit 103 sends this signal sequence to the digital watermark embedding unit 104 (step 404).
[0089]
Note that when the identification code is expanded into a bit string, the identification code is expanded as a binary display. However, the method for expanding the identification code into the bit string is not limited to this. For example, a code table such as an ASCII code may be used.
[0090]
Further, when searching for a signal sequence from the correspondence table, the signal sequence is created from the bit position of “1”, but it may be created from the bit position of “0”.
[0091]
Next, processing (step 304) of the digital watermark embedding unit 104 will be described with reference to FIG. FIG. 8 is a flowchart showing the processing flow of the digital watermark embedding unit 104.
[0092]
The digital watermark embedding unit 104 embeds a plurality of signal sequences input from the identification code generation unit 103 at the same rate per fixed time T.
[0093]
This is because, if an AV signal for a certain time T is later taken out, a signal sequence can be taken out at a constant rate, which is convenient.
[0094]
That is, first, the number EMAX of each signal series to be embedded in a predetermined time T is set (step 701), and the number of times of embedding each signal series is cleared to 0 (step 702).
[0095]
Next, one of the signal sequences whose embedding frequency is not EMAX is selected at random, and the embedding frequency of the signal sequence is incremented (step 703).
[0096]
Next, the selected signal sequence is embedded as a digital watermark in a predetermined unit of the AV signal input from the decoding unit 102 by a conventionally used method (step 704).
[0097]
Until the number of embeddings of all signal sequences reaches EMAX, the processing from the selection of the signal sequence in step 703 is repeated, and the process proceeds to the next processing (step 705).
[0098]
Furthermore, when the embedding process in steps 703 to 705 is repeated, the process is repeated from the clearing of the number of embeddings in step 702. Otherwise, the embedding process is terminated (step 706).
[0099]
Next, the output unit 105 outputs the AV signal in which the identification code is embedded as a digital watermark by the digital watermark embedding unit 104 to a monitor, a speaker, a recording device, a network, or the like (step 305).
[0100]
FIG. 9 shows an example in which a signal sequence is embedded in a video signal. The signal sequence to be embedded is {N4, N5, N8}, the unit of the video signal in which one signal sequence is embedded (the predetermined unit) is 1 field, and the fixed time T for which the ratio of each signal sequence is the same is 9 fields, Each signal sequence is embedded three times in nine fields.
[0101]
Here, one signal sequence is embedded using one field as a predetermined unit, but one frame may be used as a predetermined unit, or several fields or several frames may be used as a predetermined unit.
[0102]
Next, a reproducing apparatus specifying method for extracting an identification code from an AV signal in which the identification code is embedded as a digital watermark and specifying a reproducing apparatus will be described with reference to FIG. FIG. 10 is a flowchart showing processing performed by the playback device specifying device of FIG.
[0103]
The input unit 201 divides the input AV signal into predetermined units in which one signal series is embedded, and sends it to the correlation value calculation unit 203 (step 901). The signal sequence recording unit 202 is a correspondence table between the bit position of the identification code and the signal sequence, and records the same contents as those used in the reproducing apparatus.
[0104]
Correlation value calculation section 203 calculates correlation values between all signal sequences and AV signals input from input section 201, and calculates the maximum correlation value from the correlation values (step 902). The maximum correlation value and the bit position corresponding to the signal sequence from which the correlation is extracted are sent to the comparison unit 205.
[0105]
For example, when the correspondence table of FIG. 5 is used, the correlation value calculation unit 203 obtains a correlation value between the m signal sequences {N1, N2,..., Nm} and the AV signal, and the maximum correlation value among them is obtained. Ask for. When the maximum correlation value SMAX is obtained by correlation with the signal sequence {N4}, the maximum correlation value SMAX and the bit position {4} corresponding to the signal sequence {N4} are sent to the comparison unit 205.
[0106]
Next, the threshold value setting unit 204 sets the threshold value of the correlation value of the comparison unit 205 (step 903). The comparison unit 205 compares the maximum correlation value with the threshold (step 904), and when the correlation value is large, sends the bit position corresponding to the signal sequence from which the correlation value is extracted to the identification code determination unit 206. If the maximum correlation value is equal to or less than the threshold value, the process is not performed.
[0107]
If a disturbance occurs due to illegal copying or the like, there may be a case where there is no correlation value greater than the threshold value or a plurality of correlation values greater than the threshold value. In such a case, the comparison unit 205 does not compare the threshold value and the correlation value as an exceptional process, but the maximum correlation value S1 is set to a certain condition (for example, S1> with respect to other correlation values Sn). Only when the condition (Sn) is satisfied, the bit position corresponding to the signal sequence should be extracted.
[0108]
Next, the processing (step 905) of the identification code determination unit 206 will be described in detail with reference to FIG. FIG. 11 is a flowchart showing the process flow of the identification code determination unit 206.
[0109]
The identification code determination unit 206 holds a plurality of bit positions obtained by obtaining correlations with a plurality of signal sequences obtained from at least an AV signal having a length equal to or longer than the predetermined time T used in the playback device (step 1001). ). Next, a bit string of an identification code is generated from a plurality of bit positions (step 1002), and an identification code is generated from the bit string (step 1003).
[0110]
Needless to say, the creation of the bit string and the generation of the identification code are the same as the interpretation and method of the playback apparatus. For example, when a plurality of bit positions obtained from an AV signal at a predetermined time T is {4, 5, 8}, the playback apparatus embeds a signal sequence at a bit position corresponding to “1” in the bit string of the identification code. Therefore, the bit string “1001100” is obtained.
[0111]
Further, in the reproducing apparatus, since the bit string is generated using conversion from decimal to binary, the identification code “152” is obtained from the bit string “1001100”.
[0112]
Next, the identification code output unit 207 outputs the identification code extracted by the identification code determination unit 206 (step 906).
[0113]
Further, the identification code generation unit 103 of the playback device and the signal sequence recording unit 202 of the playback device identification device change the contents of the correspondence table held by the change signal of the correspondence table. The correspondence table can be changed by any method. Several correspondence tables may be held in the identification code generation unit 103 and the signal sequence recording unit 202 in advance, and may be switched, or a new correspondence table may be input from the outside.
[0114]
The correspondence table between the identification code generation unit 103 and the signal sequence recording unit 202 is changed to the same content at the same time.
[0115]
As a result, the playback device can embed different signal sequences as digital watermarks in the AV signal even with the same identification code, and the playback device specifying device can correctly extract the embedded identification code.
[0116]
The plurality of signal sequences used in the correspondence table of the identification code generation unit 103 of the playback device and the signal sequence recording unit 202 of the playback device specifying device have a cross-correlation smaller than a preset value (cross-correlation threshold). Such a signal sequence is used. Selecting a signal sequence having a smaller cross-correlation improves the extraction accuracy of the embedded signal sequence and improves the extraction accuracy of the identification code. Preferably, a PN code, an M-sequence code, and a Gold code are used.
[0117]
As described above, according to the reproduction apparatus according to the present embodiment, the encoded AV signal is encoded, the identification code is converted into a plurality of signal sequences using the correspondence table, and the obtained plurality of The signal sequence is embedded as a digital watermark at the same rate per fixed time T.
[0118]
On the other hand, according to the playback device specifying device, the correlation value between the AV signal in which the digital watermark is embedded and the signal sequence included in the correspondence table is obtained and compared with a preset threshold value. Determine the signal sequence.
[0119]
Then, the identification code of the playback device is extracted from a plurality of signal sequences obtained from the AV signal having a length equal to or longer than the predetermined time T.
[0120]
Further, the correspondence table between the playback device and the playback device specifying device is changed to the same content at the same time. The signal sequence to be embedded can be changed even with the same identification code.
[0121]
【The invention's effect】
The present invention According to the above, it is possible to specifically specify the reproduction device used for duplication by using the digital watermark extracted from the illegally duplicated AV signal. Therefore, it is possible to assert that the owner of the specified playback device is involved in unauthorized copying, and it is possible to prevent unauthorized copying by establishing a copyright protection system.
[0122]
In addition, the present invention According to the above, it is possible to cope with the case where the AV signal is encoded, and it is possible to specify the reproduction apparatus used for the duplication by the identification code.
[0123]
In addition, the present invention According to this, it is possible to accurately specify the playback device and the duplicator used for duplication.
[0124]
In addition, the present invention According to the above, it is possible to extract the identification code of the playback device used at the time of duplication from the illegally duplicated AV signal, and to prevent illegal duplication.
[0125]
In addition, the present invention According to the above, even when an unauthorized duplicator performs processing for changing the temporal order of AV signals, the identification code can be reliably extracted from the illegally duplicated AV signal, and the playback device can be specified. .
[0126]
In addition, the present invention According to this, the extraction accuracy of the embedded signal sequence in the playback device specifying device is improved, and the extraction accuracy of the identification code is improved.
[0127]
In addition, the present invention According to the above, by embedding different signal sequences, it is possible to make it difficult for a duplicator to see the method of embedding a digital watermark.
[0128]
In addition, the present invention According to the above, even when an unauthorized duplicator performs a process of extracting a part of the AV signal at regular intervals, the identification code can be reliably extracted from the illegally duplicated AV signal, and the playback device can be specified. .
[0129]
In addition, the present invention According to the above, even if the digital watermark embedding method or extraction method is leaked to a third party, these methods should be updated so as to correspond to each other in the playback device and the playback device specifying device. This can counter illegal copying by a third party.
[Brief description of the drawings]
FIG. 1 is a block diagram of a playback device specifying system according to an embodiment of the present invention.
FIG. 2 is a block diagram of the playback apparatus.
FIG. 3 is a block diagram of the playback device specifying device.
FIG. 4 is a flowchart of the playback apparatus.
FIG. 5 is a flowchart illustrating the identification code generation unit.
FIG. 6 is an exemplary diagram of a correspondence table between bit positions of the identification codes and signal sequences;
FIG. 7 is an explanatory diagram of bit positions of the identification code
FIG. 8 is a flowchart of the digital watermark embedding unit.
FIG. 9 is an explanatory diagram illustrating an example of embedding a signal sequence in the video signal.
FIG. 10 is a flowchart of the playback apparatus specifying apparatus.
FIG. 11 is a flowchart of the identification code determination unit.
[Explanation of symbols]
1 Recording medium
2 Duplicate recording media
3 Playback device
4 AV signal recording device
5 Playback device identification device
6 Playback devices
10 Duplicator
31 AV signal reproducing means
32 Digital watermark generation means
33 Electronic watermark embedding means
34 Output means
51 AV signal reproduction means
52 Electronic watermark extraction means
53 Printing means
101 Encoded signal input unit
102 Decoding unit
103 Identification code generator
104 Digital watermark embedding part
105 Output section
201 Input section
202 Signal sequence recording unit
203 correlation value calculation part
204 Threshold setting unit
205 comparison part
206 Identification code determination unit
207 Identification code output unit

Claims (12)

A reproduction device for reproducing an AV signal, wherein an identification code generation unit that generates an identification code for identifying the reproduction device itself, and an electronic watermark is embedded in the AV signal based on the identification code generated by the identification code generation unit In a playback device including a digital watermark embedding unit that generates an embedded AV signal and an output unit that outputs the embedded AV signal to the outside,
The playback device and the playback device specifying device that specifies the playback device based on the embedded AV signal share a plurality of signal sequences and corresponding relationships so as to have the same content.
The plurality of signal sequences are composed of a finite number of signal sequences that can be embedded in the AV signal,
The correspondence relationship is expressed by a correspondence table that defines the relationship between the content of the identification code and the signal sequence embedded in the AV signal and belonging to the plurality of signal sequences corresponding to the content,
The correspondence table defines the correspondence between the content of the bit string when the identification code is bit expanded and the signal series embedded in the AV signal corresponding to the content of the bit string and belonging to the plurality of signal series,
The digital watermark embedding unit embeds signal sequences belonging to the plurality of signal sequences in the AV signal based on the correspondence. The identification code includes the device ID of the playback device, the card ID of the IC card connected to the playback device, the user ID of the user, the material ID of the AV signal, the media ID of the media in which the AV signal is stored, and the playback date and time. 2. The playback apparatus according to claim 1, wherein the playback apparatus is one or a combination of two or more. The correspondence table defines a relationship with a signal sequence that corresponds to a bit position having a value of “0” or “1” in a binary bit string in which the identification code is expanded and belongs to the plurality of signal sequences. ,
The digital watermark embedding unit corresponds to a bit position having a value of “0” or “1” in the binary bit string obtained by developing the identification code in the AV signal based on the correspondence relationship, and 2. The reproducing apparatus according to claim 1, wherein signal sequences belonging to a plurality of signal sequences are embedded. The digital watermark embedding unit includes a plurality of signal sequences corresponding to a bit position having a value of “0” or “1” in a binary bit string obtained by developing the identification code and belonging to the plurality of signal sequences. 4. The playback apparatus according to claim 3, wherein a plurality of signal sequences determined for each predetermined unit of the AV signal are embedded. The digital watermark embedding unit includes a plurality of signal sequences corresponding to a bit position having a value of “0” or “1” in a binary bit string obtained by developing the identification code and belonging to the plurality of signal sequences. 4. The reproducing apparatus according to claim 3, wherein the plurality of defined signal sequences are embedded in the AV signal randomly at the same rate per fixed time. A playback device specifying device for specifying a playback device based on an embedded AV signal,
A signal sequence recording unit that shares the playback device and the plurality of signal sequences and the correspondence table so as to have the same content,
The plurality of signal sequences includes a finite number of signal sequences that can be embedded in the embedded AV signal.
The correspondence table defines a correspondence relationship between the contents of the bit string when the identification code is bit-expanded and the signal series embedded in the embedded AV signal and belonging to the plurality of signal series corresponding to the contents of the bit string. ,
The playback device specifying device further includes:
An input unit for inputting the embedded AV signal;
A correlation value calculation unit that calculates a correlation value between the embedded AV signal input by the input unit and all signal sequences included in the correspondence table, and outputs a maximum correlation value among the obtained correlation values When,
A threshold value setting unit for setting a threshold value of a correlation value used for comparison with the maximum correlation value output by the correlation value calculation unit;
A comparison unit that compares the maximum correlation value output by the correlation value calculation unit with the threshold set by the threshold setting unit, and outputs a signal sequence in which the maximum correlation value exceeds the threshold;
An identification code determination unit for determining an identification code from the signal sequence output from the comparison unit and the correspondence table;
An apparatus for identifying a playback apparatus, comprising: an identification code output unit for outputting a predetermined identification code. A reproduction device for reproducing an AV signal, wherein an identification code generation unit that generates an identification code for identifying the reproduction device itself, and an electronic watermark is embedded in the AV signal based on the identification code generated by the identification code generation unit In a playback method in a playback device including a digital watermark embedding unit that generates an embedded AV signal and an output unit that outputs the embedded AV signal to the outside,
The playback device and the playback device specifying device that specifies the playback device based on the embedded AV signal share a plurality of signal sequences and corresponding relationships so as to have the same content.
The plurality of signal sequences are composed of a finite number of signal sequences that can be embedded in the AV signal,
The correspondence relationship is expressed by a correspondence table that defines the relationship between the content of the identification code and the signal sequence embedded in the AV signal and belonging to the plurality of signal sequences corresponding to the content,
The correspondence table defines the correspondence between the content of the bit string when the identification code is bit expanded and the signal series embedded in the AV signal corresponding to the content of the bit string and belonging to the plurality of signal series,
A reproduction method comprising embedding signal sequences belonging to the plurality of signal sequences in the AV signal based on the correspondence relationship. The identification code includes the device ID of the playback device, the card ID of the IC card connected to the playback device, the user ID of the user, the material ID of the AV signal, the media ID of the media in which the AV signal is stored, and the playback date and time. 8. The reproduction method according to claim 7, wherein the reproduction method is one or a combination of two or more. The correspondence table defines a relationship with a signal sequence that corresponds to a bit position having a value of “0” or “1” in a binary bit string in which the identification code is expanded and belongs to the plurality of signal sequences. ,
Based on this correspondence, the AV signal corresponds to a bit position having a value of “0” or “1” in a binary bit string obtained by developing the identification code, and belongs to the plurality of signal sequences 8. The reproduction method according to claim 7, wherein the sequence is embedded. A plurality of signal sequences corresponding to a bit position having a value of “0” or “1” in the binary bit string in which the identification code is expanded and belonging to the plurality of signal sequences are determined, and a predetermined value of the AV signal is determined. 10. The reproducing method according to claim 9, wherein a plurality of signal sequences determined for each unit are embedded. In the binary bit string in which the identification code is expanded, a plurality of signal sequences corresponding to a bit position having a value of “0” or “1” and belonging to the plurality of signal sequences are determined, and a plurality of defined signals 10. The reproduction method according to claim 9, wherein a sequence is randomly embedded in the AV signal at the same rate per fixed time. A playback device specifying device for specifying a playback device based on an embedded AV signal, the playback device including a signal sequence recording unit that shares the playback device, a plurality of signal sequences, and a correspondence table so as to have the same contents. A playback device specifying method in a device specifying device, comprising:
The plurality of signal sequences includes a finite number of signal sequences that can be embedded in the embedded AV signal.
The correspondence table defines a correspondence relationship between the contents of the bit string when the identification code is bit-expanded and the signal series embedded in the embedded AV signal and belonging to the plurality of signal series corresponding to the contents of the bit string. ,
Inputting the embedded AV signal;
Calculating a correlation value between the embedded AV signal and all signal sequences included in the correspondence table, and outputting a maximum correlation value among the obtained correlation values;
Setting a correlation value threshold for comparison with the maximum output correlation value;
Comparing the output maximum correlation value with a set threshold and outputting a signal sequence in which the maximum correlation value exceeds the threshold;
Determining an identification code from the output signal sequence and the correspondence table;
And a step of outputting a predetermined identification code.

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