JP2008090901A - Content management system and content management method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a content management system and content management method which can fully protect against illegal copy of contents from a practical viewpoint by preventing reproduction of a part of the content transferred from a source recording medium as much as possible when transfer of the content is interrupted. <P>SOLUTION: A boundary is sequentially set for every interval in which overlapping of the content is permitted in the source recording medium and a destined recording medium from a starting point of recording in the content, and key data is changed for every set boundary to encrypt. Following transfer of the content, reproduction disapproval positions are sequentially set between the starting point of the transferred content of the source recording medium and a position tracking back by the interval in which overlapping of the content is permitted from the starting point of the transferred content, and the transferred content of the source recording medium is controlled in such a manner as reproduction is disapproved between the starting point of recording and the reproduction disapproval position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a content management apparatus and a content management method suitable particularly when moving content recorded on a recording medium and prohibited from being copied based on a copyright to another recording medium.

  As is well known, when content recorded on a recording medium is to be recorded on another recording medium, if copying of the content is prohibited based on copyright, This recording medium needs to be in a state in which the content does not exist, and content transfer processing is executed instead of so-called copying.

  For example, in television receivers that receive digital broadcasts, products that have a recording function and can record programs have been put on the market, but such products have a large recording capacity as a recording medium. Using a hard disk drive (HDD), a broadcast program (content) is recorded in a sloppy manner, and a program that is particularly desired to be kept later is selected and recorded on, for example, a DVD (digital versatile disk). May be.

  In this case, the necessary content is reproduced from the HDD and recorded on the DVD, but if the content is protected by copyright and copying is prohibited, the content is recorded on the DVD. Later, it is necessary to delete the content on the HDD side (make playback impossible).

  In this way, when moving content from the source recording medium to the destination recording medium, it is necessary to delete the source content, but this process is automatically performed by software after the content movement is completed. To be executed. However, if the moving process ends abnormally, such as when the power of the device is turned off immediately before the completion of moving the content, the deleting process is not executed and the content remains in a reproducible state at the moving source.

  Thus, the phenomenon that the power of the device is turned off immediately before the movement of the content is completed can be artificially realized by the user, thereby making it possible to execute unauthorized copying of the content. . As can be seen from this example, it is currently difficult to strictly manage copyright-protected content.

  On the other hand, when moving content recorded on a recording medium to another recording medium, an agreement that allows a part of the content to exist on both recording media is ARIB (association of radio industries and businesses) (TR-B14, 8th edition, 5.5.4 move function) is currently established, but it is also difficult to cope with the establishment when the power is cut off.

  In Patent Document 1, when moving content read from a moving source recording medium to a moving destination recording medium, the moving tip position of the moving source recording medium and a period allowing content duplication from the moving tip position are traced back. An unreproducible boundary position is set between the recorded position and the non-reproducible boundary position, and this is written in the non-volatile memory so that the content on the recording leading end side cannot be reproduced from the unreproducible boundary position.

If the movement process changes and the unreproducible boundary position is likely to deviate from within the position that is allowed to overlap for the overlap allowable period from the moving tip position, the position is moved to a position near the moving tip and the position is newly written to the nonvolatile memory. Then, a method is disclosed in which the process of making the recording leading end unreproducible is performed until the movement is completed.
JP 2005-339743 A

  However, according to the technique described in Patent Document 1, dummy data is added to the head portion of content recorded on the transfer source recording medium, and the content length is illegally manipulated to record the content in the nonvolatile memory. Further, since the position of the content indicated by the unreproducible boundary position can be shifted from the original position, there is a problem that it is possible to reproduce the moved content portion from the movement source recording medium.

  Therefore, the present invention has been made in consideration of the above circumstances, and when the content movement processing is interrupted, the content portion that has been moved is prevented from being reproduced from the recording medium of the movement source as much as possible. It is an object of the present invention to provide a content management apparatus and a content management method capable of sufficiently protecting from illegal copying in practice.

  That is, the content management apparatus according to the present invention is intended for a device that moves the content to be moved from the recording medium on which the content is recorded to the recording medium that is the movement destination sequentially from the recording head. Then, for the content to be recorded on the source recording medium, a boundary is sequentially set from the recording head to the source recording medium and the destination recording medium for each period during which content overlap is allowed. Encryption means for changing the key data to perform encryption processing; as the content moves from the movement source recording medium to the movement destination recording medium, the movement tip position of the movement source recording medium; Setting means for setting a non-reproducible boundary position between the moving tip position and a position that is backed by a period allowing content duplication; setting the content to be moved on the moving recording medium as the recording head And a control means for controlling the reproduction to be impossible with respect to the non-reproduction boundary position set by the means.

  In addition, the content management method according to the present invention is directed to a method of moving the content to be moved from the recording medium on which the content is recorded to the recording medium to which the content is moved sequentially from the recording head. Then, for the content to be recorded on the source recording medium, a boundary is sequentially set from the recording head to the source recording medium and the destination recording medium for each period during which content overlap is allowed. A step of performing an encryption process by changing the key data; and a moving tip position of the source recording medium as the content moves from the source recording medium to the destination recording medium; A step of setting a non-reproducible boundary position between the position and a position retroactive by a period that allows content duplication; and the content to be moved on the recording medium at the movement source and the non-reproducible boundary position. And a step of controlling the reproduction so as not to be reproducible.

  According to the above-described invention, in the content to be recorded on the source recording medium, the boundary is sequentially set for each period in which the duplication of the content is permitted from the recording head to the source recording medium and the destination recording medium, Since the encryption process is performed by changing the key data for each set boundary, when the content movement process is interrupted, the moved content part is reproduced from the source recording medium. It is possible to prevent as much as possible and to protect the content from unauthorized copying.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an outline of a content recording / playback apparatus 100 described in this embodiment. That is, the content recording / playback apparatus 100 includes a recording / playback processing unit 101, a first recording unit 102, and a second recording unit 103.

  Among these, the first recording unit 102 includes a recording medium 104 for recording / reproducing content, a controller 105 for controlling recording / reproducing processing of content on the recording medium 104, and a recording / reproducing processing unit 101. And an interface 106 for performing content transmission and reception processing.

  Similarly, the second recording unit 103 also includes a recording medium 107 for recording / reproducing content, a controller 108 for controlling recording / reproduction processing of content on the recording medium 107, and a recording / reproduction processing unit 101. Interface 109 for performing content transmission and reception processing.

  In this case, the recording media 104 and 107 of the first and second recording units 102 and 103 may be fixedly provided inside, or may be removable. Is.

  The first and second recording units 102 and 103 may be integrally provided in the casing of the recording / reproducing processing unit 101, or one or both of them may be recorded / reproduced. The processing unit 101 may be provided separately.

  Here, the recording / playback processing unit 101 has a function of acquiring content from the outside, encrypting the content based on predetermined key data, and recording the encrypted content on the first or second recording unit 102 or 103. In addition, the recording / playback processing unit 101 has a function of selectively playing back the content recorded in the first and second recording units 102 and 103, decrypting and decrypting the encryption, and outputting the decrypted content. Furthermore, the recording / playback processing unit 101 has a function of moving content data between the first and second recording units 102 and 103. For encryption, key data is set so that only the recording / playback processing unit 101 itself can decrypt it.

  In order to realize the processing of the functions as described above, the recording / playback processing unit 101 includes a CPU (central processing unit) 110 that performs overall control. The CPU 110 is connected to a memory 111 having a ROM (read only memory) section storing programs for executing various processes and a RAM (random access memory) section as a work area.

  In addition, the CPU 110 receives a digital television broadcast, performs demodulation, demultiplexing, and the like and performs a TS (transport stream) including an ES (elementary stream) that configures a MPEG (moving picture experts group) 2 broadcast program. ) Is connected. The receiving unit 112 is connected to an antenna 113 for catching broadcast radio waves.

  Furthermore, an interface 114 for exchanging contents with the first recording unit 102 is connected to the CPU 110 with the interface 106 of the first recording unit 102. Similarly, an interface 115 for exchanging contents with the second recording unit 103 is connected between the CPU 110 and the interface 109 of the second recording unit 103.

  The CPU 110 is connected to a decoder 116 for decoding the ES output from the receiving unit 112 and outputting it as uncompressed digital video and audio signals. The decoder 116 is connected to the display unit 117, and the display unit 117 constructs a standard television signal based on the signal supplied from the decoder 116 and displays it.

  Further, the CPU 110 is connected to a nonvolatile memory 118 for storing pointer information. Details of the operation will be described later.

  The recording / reproducing operation in the first and second recording units 102 and 103, the channel selection operation in the receiving unit 111, and the like are executed by the user sending commands to the CPU 110. An operation input unit 120 is connected to the CPU 110 via an interface 119. The operation input unit 120 may be a remote controller, for example, and may be configured to include a plurality of operators provided on the front surface of the housing of the recording / playback processing unit 101.

  Hereinafter, the operation of the content recording / reproducing apparatus 100 configured as described above will be described. That is, when the user operates the operation input unit 120 to input a broadcast program recording command, the CPU 110 uses the key data stored in advance in the ROM unit of the memory 111 to output MPEG2- The TS is encrypted and sent as content to the first recording unit 102 via the interface 114.

  In this case, the first recording unit 102 receives the content supplied from the recording / playback processing unit 101 by the interface 106 and records it on the recording medium 104 via the controller 105.

  In order to reproduce the recorded content, a command is input to the CPU 110 from the operation input unit 120 via the interface 119. Then, the CPU 110 generates a list of contents recorded on the recording medium 104 of the first recording unit 102, and sends it to the display unit 117 via the decoder 116 for display.

  This list is generated in a GUI (graphical user interface) format. The user operates the operation input unit 120 to select content to be reproduced from the displayed list. In response to this selection operation, the CPU 110 reproduces necessary content from the recording medium 104 and takes it in via the interface 114, decrypts it based on the key data, and sends it to the decoder 116. The decoder 116 performs decoding in accordance with the MPEG2 standard and sends it to the display unit 117 for display.

  The above is a general recording / reproducing operation, and it is possible to cause the second recording unit 103 to perform a content recording / reproducing operation in the same manner as described above.

  Next, in the content recording / reproducing apparatus 100, the content recorded on the recording medium 104 of the first recording unit 102 or the recording medium 107 of the second recording unit 103 is stored in the recording medium 107 of the second recording unit 103 or When executing the process of moving to the recording medium 104 of the first recording unit 102, protection measures are taken so that unauthorized copying is not performed.

  In this embodiment, when moving content from the movement source (for example, the recording medium 104) to the movement destination (the recording medium 107), ARIB (TR-B14, volume 8, 5.5.4 move function) is performed. As shown in FIG. 5, it is assumed that an overlap allowance period of, for example, 1 minute is set between the recording media 104 and 107.

  Also in the content movement process, when the user operates the operation input unit 120, the CPU 110 causes the display unit 117 to display a setting screen indicating which of the first and second recording units 102 and 103 is the movement source. The list of content data recorded on the recording medium set as the movement source as a result of the user's selection is displayed on the display unit 117 so that the user can select content data to be moved. To.

  Here, it is assumed that the first recording unit 102 has been selected as the movement source. First, the CPU 110 uses the controller 105 of the first recording unit 102 to read the content selected as the content to be moved from the recording medium 104 and obtains it via the interface 114.

  Thereafter, the CPU 110 decrypts the encrypted content, and re-encrypts the content using another encryption method [for example, DTCP (digital transmission content protection) or CPRM (content protection for recordable media)]. 2 is recorded on the recording medium 107 by making full use of the controller 108.

  At this time, the CPU 110 first sets a flag indicating that the migration process is being performed in the nonvolatile memory 118. Further, as shown in FIG. 2, the CPU 110 specifies the read position of the content of the recording medium 104 that is the movement source by the number of bytes from the recording head of the content, and obtains the pointer data A that is the read movement leading position, Pointer data B is obtained by specifying the position of the recording medium 104 that is back from the pointer data A by the duplication allowable period by the number of bytes from the recording head.

  Then, the CPU 110 sets the pointer data C between the pointer data A and B, converts the pointer data C into data that cannot be read by the user, and stores the data in the nonvolatile memory 118.

  The pointer data A and B continuously change in conjunction with the transition of the content movement process while maintaining the same interval. On the other hand, the pointer data C is processed as having a fixed value as long as it is within the overlap allowable period, and gradually approaches the pointer data B as the movement process proceeds. When the pointer data C is likely to deviate from the overlap allowable period, the CPU 110 jumps to a position closer to the pointer data A and newly stores the updated data in the nonvolatile memory 118 as shown in FIG. .

  In other words, as the content moves from the movement source recording medium 104 to the movement destination recording medium 107, the movement leading edge position (pointer data A) of the movement source recording medium 104 and the content overlap from the movement leading edge position. The pointer data C is sequentially set between the position (pointer data B) that is traced back by a period that permits.

  Note that the movement leading end position of the recording medium 104 as the movement source is the head position where the content on the recording medium 104 is read, and the read content is accumulated in a reception buffer (not shown) in the recording / playback processing unit 101 by a predetermined amount. The timing can be defined at various timings, such as when the content to be written to the recording medium 107 is output from a transfer buffer (not shown) in the recording / playback processing unit 101.

  The content existing on the recording medium 104 that is the movement source in front of the position of the pointer data C (up to the recording head) is set in a state in which it cannot be reproduced by the CPU 110. That is, the pointer data C is also position information indicating a non-reproducible boundary.

  When the movement of all the contents to be moved is completed, the CPU 110 drops the flag indicating the movement process from the nonvolatile memory 118, deletes the pointer data C from the nonvolatile memory 118, and ends the process.

  If the process is interrupted in the middle of the movement process due to a power shutdown or the like, the flag indicating that the movement process of the nonvolatile memory 118 and the pointer data C are held as they are, and when the movement process is resumed, the CPU 110 Recognizes a flag indicating that the non-volatile memory 118 is being moved, then reads the pointer data C, and resumes moving the content from the position corresponding to the pointer data C on the recording medium 104. This timing is within the duplication allowable period for content data that has been moved to the recording medium 107 of the second recording unit 103, and is not an illegal copy.

  The pointer data C stored in the non-volatile memory 118 is stored in the non-volatile memory 118 in a format that cannot be read and tampered with by the user by encryption or the like. It is to be managed. In the content recording / playback apparatus 100 configured as described above, unauthorized copying can be prevented by executing content movement processing.

  By the way, the content recording / playback apparatus 100 described above is effective in preventing unauthorized copying by interrupting the process by shutting off the power supply during the transfer process, but as described above, the transfer source recording medium 104 The content position indicated by the pointer data C (non-reproducible boundary position information) recorded in the non-volatile memory 118 can be normalized by adding dummy data to the beginning of the content recorded in the file and illegally manipulating the content length. Therefore, it is possible to reproduce the content part that has been moved from the recording medium 104 that is the movement source, and illegal copying is possible.

  In addition, the content is always reproduced without reproducing the recording medium 104 from the position indicated by the pointer data C recorded in the nonvolatile memory 118 as designated by the content recording / reproducing apparatus 100 for the first recording unit 102. Even if unauthorized modification is made so that playback starts from the beginning of the file, unauthorized copying is possible.

  Therefore, in this embodiment, as shown in FIG. 3, when content is recorded on the recording medium 104 that is the movement source, a boundary is sequentially set to the content to be recorded from the head position for each overlap allowable period, The key data for encrypting the content is changed for each set boundary.

  In this case, each key data for encrypting the content is generated using a value indicating an offset position from the head of the content (a boundary position where the key data changes) as a parameter. The threshold value for changing the value of the offset position is set to an arbitrary value that does not exceed a period during which content duplication is allowed when moving the content.

  By sequentially changing the key data for encrypting the content in this way, when the content is read from the recording medium 104 as the transfer source and decrypted, it is decrypted from the value indicating the offset position from the top of the content. Therefore, even if it is possible to extract the moved content part from the recording medium 104 of the movement source by adding dummy data to the beginning part of the content and illegally manipulating the content length, Therefore, decryption fails and the content can be protected.

  4 and 5 are flowcharts summarizing the processing operations when the recording / playback processing unit 100 records content on the recording medium 104 of the first recording unit 102. FIG. That is, when the process is started (step S1), the recording / playback processing unit 100 obtains a key data seed Kcs for generating a random number and encrypting the content in step S2, and in step S3, Kcs Issue a content key management ID corresponding to. At the same time, the content key management ID is recorded in the content attribute information and the like, and the correspondence between the content and the content key management ID is taken.

  This allows the corresponding Kcs to be extracted by designating the content key management ID. Although not particularly shown, this is simply an index indicating the corresponding Kcs from a table in which issued Kcs are arranged. It does n’t matter. A sufficiently large number of Kcs with respect to the number of contents handled by the content management apparatus may be prepared in advance, and a content key management ID indicating which Kcs may be designated by a random number. The method of generating Kcs and the content key management ID is not particularly limited as long as it is a method that can be managed without issuing frequently duplicated Kcs for the number of contents handled by the content management apparatus. The recording / playback processing unit 100 starts receiving broadcast content in step S4, and records the received content in one of a plurality of reception buffers (not shown) installed in the reception unit 112 in step S5.

  Thereafter, when the reception buffer is full of content in step S6, the recording / playback processing unit 100 switches the recording of the content to another reception buffer in step S7, and the recording of the content on the recording medium 104 is performed in step S8. It is determined whether or not all the processes have been completed.

  If it is determined that the recording of the content on the recording medium 104 has been completed (YES), the recording / playback processing unit 100 performs various processes accompanying the end of the recording of the content on the recording medium 104 in step S9. To finish the process (step S10).

  If it is determined in step S8 that the recording of the content on the recording medium 104 has not been completed (NO), the recording / playback processing unit 100 proceeds to the process of step S5 and receives it in step S11. The buffer content is encrypted and recorded in a transfer buffer (not shown) installed in the interface 114, and the transfer buffer content is recorded in the recording medium 104 in step S12.

  FIG. 6 is a flowchart summarizing the encryption processing operation in step S11. That is, when the process is started (step S13), the recording / playback processing unit 100 sets each offset position from the beginning of the content in step S14, and whether or not the key data switching timing has been reached in step S15. Is determined.

  If it is determined that the key data switching timing has been reached (YES), the recording / playback processing unit 100 generates key data from the key data type Kcs and the offset position value in step S16, and step S17. The generated key data is held.

  After this step S17 or when it is determined in step S15 that the key data switching timing has not been reached (NO), in step S18, the recording / playback processing unit 100 converts the content on the reception buffer into key data. And is recorded in the transfer buffer, and the process ends (step S19).

  FIG. 7 shows a flowchart summarizing processing operations when the recording / playback processing unit 100 moves content from the recording medium 104 of the first recording unit 102 to the recording medium 107 of the second recording unit 103. That is, when the process is started (step S20), the recording / playback processing unit 100 reads the content key management ID from the attribute information of the content to be played back from the recording medium 104 in step S21, thereby managing the content key corresponding to the content. An ID is designated, and key data seed Kcs is obtained in step S22.

  Then, in step S23, the recording / playback processing unit 100 reads the encrypted content from the recording medium 104 and records it in a playback buffer (not shown) installed in the interface 114, for example, and in step S24, the content on the playback buffer. Is subjected to decoding processing and recorded in the reproduction buffer.

  Thereafter, in step S25, the recording / playback processing unit 100 performs encryption processing on the plain content on the playback buffer using the key exchanged key data, and for example, for transfer (not shown) installed in the interface 115 or the like. Record in buffer. In step S26, the recording / playback processing unit 100 transfers the content stored in the transfer buffer to the recording medium 107 and records it.

  Next, in step S27, the recording / playback processing unit 100 determines whether or not the transfer of all the contents to be moved has been completed. If it is determined that the transfer has not ended (NO), the recording / playback processing unit 100 proceeds to the process of step S23. If it is determined that the process has been completed (YES), the key data seed Kcs corresponding to the content to be moved is deleted in step S28. The process is performed, and the process ends (step S30).

  FIG. 8 shows a flowchart summarizing the decoding processing operation in step S24. That is, when the process is started (step S31), the recording / playback processing unit 100 sets each offset position from the beginning of the content in step S32, and whether or not the key data switching timing has been reached in step S33. Is determined.

  If it is determined that the key data switching timing has been reached (YES), the recording / playback processing unit 100 generates key data from the key data type Kcs and the offset position value in step S34, and step S35. The generated key data is held.

  After step S35 or when it is determined in step S33 that the key data switching timing has not been reached (NO), in step S36, the recording / playback processing unit 100 converts the content on the playback buffer to key data. Is used for decoding, recording in the reproduction buffer, and the process is terminated (step S37).

  When recording the content on the recording medium 104, after the content size is determined after the recording is finished, the content size is recorded in the recorded content, and the content size is checked when the recording medium 104 is played back. In this case, when the reproduced content size is different from the recorded content size, it is possible to determine that the content length has been illegally manipulated by adding dummy data to the beginning of the content.

  In addition, when recording the key data with encrypted content, it is also possible to separately generate key data including the content size as a parameter, and to encrypt the key data with which the content is encrypted with this key data. is there.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by variously modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements according to different embodiments may be appropriately combined.

1 is a block diagram illustrating an outline of a content recording / reproducing apparatus according to an embodiment of the present invention. The figure shown in order to demonstrate the content movement processing operation | movement using the content recording / reproducing apparatus in the embodiment. The figure shown in order to demonstrate the principal part of the content movement processing operation | movement using the content recording / reproducing apparatus in the embodiment. The flowchart shown in order to demonstrate a part of recording process operation | movement of the content using the content recording / reproducing apparatus in the embodiment. The flowchart shown in order to demonstrate the remainder of the recording process operation | movement of the content using the content recording / reproducing apparatus in the embodiment. The flowchart shown in order to demonstrate the encryption process in the recording process operation | movement of the content using the content recording / reproducing apparatus in the embodiment. The flowchart shown in order to demonstrate the movement processing operation | movement of the content using the content recording / reproducing apparatus in the embodiment. The flowchart shown in order to demonstrate the decoding process in the movement processing operation | movement of the content using the content recording / reproducing apparatus in the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Content recording / reproducing apparatus, 101 ... Recording / reproducing process part, 102 ... 1st recording part, 103 ... 2nd recording part, 104 ... Recording medium, 105 ... Controller, 106 ... Interface, 107 ... Recording medium, 108 ... Controller, 109 ... interface, 110 ... CPU, 111 ... memory, 112 ... receiving unit, 113 ... antenna, 114, 115 ... interface, 116 ... decoder, 117 ... display unit, 118 ... non-volatile memory, 119 ... interface, 120 ... Operation input part.

Claims (5)

In a content management apparatus that moves content to be moved from a recording medium on which a content is recorded to a recording medium that is a movement destination sequentially from the recording head.
For the content to be recorded on the movement source recording medium, a boundary is sequentially set from the recording head to the movement source recording medium and the movement destination recording medium for each period during which content overlap is allowed. Encryption means for changing the key data to perform encryption processing,
Along with the movement of the content from the source recording medium to the destination recording medium, the moving leading position of the moving source recording medium and the period from which the overlapping of the content is allowed to go back from this moving leading position. Setting means for sequentially setting the non-reproducible boundary position between the position and
Control means for controlling the content to be moved on the recording medium of the movement source so as not to be reproducible between the recording head and a non-reproducible boundary position set by the setting means. Content management device.   2. The encryption unit according to claim 1, wherein the encryption unit generates key data for each boundary by using, as a parameter, a value indicating a boundary position from the recording head of the content to be recorded on the movement source recording medium. Content management device.   When the content encrypted by the encryption unit is recorded on the recording medium of the movement source, the content to be recorded is recorded including the content size in order to collate with the content reproduced from the recording medium. The content management apparatus according to claim 1.   Generating a key using the content size as a parameter, performing encryption processing on key data for encrypting the content for each boundary using the key, and recording the encrypted data on the transfer source recording medium The content management apparatus according to claim 3. In the content management method for moving the content to be moved from the recording medium from which the content is recorded to the recording medium to which the content is moved sequentially from the recording head.
For the content to be recorded on the movement source recording medium, a boundary is sequentially set from the recording head to the movement source recording medium and the movement destination recording medium for each period during which content overlap is allowed. Changing the key data to perform encryption processing;
Accompanying the movement of the content from the source recording medium to the destination recording medium, the moving leading position of the moving source recording medium and the period from which the overlapping of the content is allowed to go back from this moving leading position. A step of sequentially setting a non-reproducible boundary position between the position and the position;
And a step of controlling the content to be moved on the movement source recording medium to be unreproducible between the recording head and the unreproducible boundary position.

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