Patent Publication Number: US-2005140527-A1

Title: Information recording processor, information playback processor, method therefor, and information recording medium and computer program used therewith

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
      This application claims priority to Japanese Patent Application No. P2003-406197 filed on Dec. 4, 2003 and Japanese Patent Application No. P2004-022637 filed on Jan. 30, 2004, the disclosures of which are incorporated by reference herein.  
     BACKGROUND OF THE INVENTION  
      The present invention relates to information recording processors, information playback processors, methods therefor, and information recording media and computer programs used therewith. In particular, the present invention relates to an information recording processor, an information playback processor, and a method therefor in which, in a configuration capable of recording additional data, such as key information for use in decrypting content, content-playback control information, and copy-control information, on an information recording medium containing content, such as image data and music data, and reading the additional data, by setting additional data based on correspondence between the bit value of specific user control data (UCD) included in recorded data and DC control bits set in the recorded data, embedding of additional data that is difficult to analyze is realized. In addition, the present invention relates to a recording medium and computer program used with the information recording processor, the information playback processor, and the method therefor.  
      When data, such as music data and image data, is recorded in digital form on a recording medium, recording processing is performed in accordance with a predetermined recording format. For example, error-detecting/correcting codes are added to original data to be recorded, and the data is recorded in a form in which it is coded to have a format adapted for specific data recording/playback processing.  
      Regarding an information recording medium enabling high-density information recording, recently, an information recording medium based on a system using a blue laser to perform information recording and playback has been developed. In information recording using the blue laser, processing that converts two-bit data into three-bit data is basically performed.  
      Types of content to be recorded on the above information recording medium include, for example, movie data and music data. In general, rights of distribution, and the like, of many types of content, such as music data and image data, are owned by content creators or sellers. Therefore, in a common form for distributing the types of content, certain limitations in the use of the content are set, that is, by allowing only registered users to use the content, unauthorized reproduction, and the like, are prevented.  
      On a mass-storage recording medium, such as a recording medium using a blue-laser recording system capable of mass-storage recording, for example, a data capacity corresponding to one to several movies can be recorded. Since content can be easily recorded as described above in the form of digital information, many problems such as the spreading of unauthorized copies occur, so that reduction in profit of the copyright holder and distributor of the content becomes a large problem. In view of the present situation, it is an important issue to achieve protection of profits of the copyright holder and distributor by preventing unauthorized reproduction.  
      A system for preventing such unauthorized use of content has been proposed. In this system, content to be recorded on an information recording medium is recorded in encrypted form, and, simultaneously, encryption-key information for use as an encryption key for the encrypted content, information forming partial data of the encryption-key information, encryption-key generating information, such as data (e.g., a seed) required for generating an encryption key, or control information of various types, such as content-playback control information and copy-control information, is recorded as secret information on the information recording medium. In addition, a playback-processing program executed in a playback apparatus of a user reads the secret information, such as a key corresponding to the content to be played back, decrypts the content in accordance with the read secret information, and allows use of the content in accordance with playback-control information.  
      Regarding an example of the related art which discloses processing using embedding of secret information, Japanese Unexamined Patent Application Publication No. 2003-45128, in general, discloses a technology in which special data is embedded by using margin bits of eight-to-fourteen modulated data. Japanese Unexamined Patent Application Publication No. 2002-367282, in general, discloses a technology in which, in a system using transformation tables for modulating processing, data concerning one transformation table, which is used in modulation, is extracted and additional data is acquired based on the extracted data.  
      However, if the user or an authorized user of content acquires information representing the position of such an encryption key or control information on the information recording medium, that person can leak or alter the additional data. For example, a problem occurs, that is, information or copy-control information may be altered, or key information may leak out. Leaking of the encryption key or alteration of the control information will break a content-utilization form based on the valid right to use content, so that it is difficult to sufficiently protect the copyright of the content and the right to use the content.  
     SUMMARY OF THE INVENTION  
      The present invention in an embodiment provides an information recording processor, an information playback processor, and a method therefor in which, in a configuration capable of recording additional data, such as key information for use in decrypting content, content-playback control information, and copy-control information, on an information recording medium containing content, such as image data and music data, and reading the additional data, by setting additional data based on correspondence between bit values of specific user control data included in recorded data and DC control bits set in the recorded data, embedding of additional data that is difficult to analyze is realized, and to provide a recording medium and computer program used with the information recording processor, the information playback processor, and the method therefor.  
      According to an embodiment, an information recording processor is provided which includes a DC-control-bit selecting unit for executing DC-control-bit selecting processing in which the values of DC control bits set in a recording frame are set to be coincident or to be not coincident with user control data in response to the values of additional data component bits to be recorded on an information recording medium, and a modulated data generating unit for generating a modulated recording frame used as recording-unit data by executing processing for modulating data to be recorded and DC-control-bit setting processing, the modulated data generating unit selectively executing the DC-control-bit setting processing based on control of a digital sum variation and the DC-control-bit setting processing based on information input from the DC-control-bit selecting unit.  
      According to an embodiment, an information playback processor for executing processing for playing back information recorded on an information recording medium is provided. The information playback processor includes a data demodulating unit for executing demodulating processing on data read from the information recording medium, and an additional data decoding unit for executing determination of correspondence between DC control bits for determining a response to additional data, the DC control bits being acquired from a DC-control-bit storage frame for determining a response to additional data, and user control data for determining a response to additional data, and executing acquisition of additional-data-component-bit information on the basis of the result of the determination of correspondence.  
      According to an embodiment, an information recording medium including additional data recorded thereon is provided. The additional data is analyzable based on correspondence between bit values of specific user control data included in recorded data, and DC control bits set in the recorded data.  
      According to an embodiment, an information recording method is provided which includes a DC-control-bit selecting step of executing DC-control-bit selecting processing in which the values of DC control bits set in a recording frame are set to be coincident or to be not coincident with user control data in response to the values of additional data component bits to be recorded on an information recording medium, and a modulated data generating step in which a modulated recording frame used as recording-unit data is generated by executing processing for modulating data to be recorded and DC-control-bit setting processing, and in which the DC-control-bit setting processing based on control of a digital sum variation and the DC-control-bit setting processing based on information selected in the DC-control-bit selecting step are selectively executed.  
      According to an embodiment, an information playback method for executing processing for playing back information recorded on an information recording medium is provided. The information playback method includes a data demodulating step of executing demodulating processing on data read from the information recording medium, and an additional data decoding step of executing determination of correspondence between DC control bits for determining a response to additional data, the DC control bits being acquired from a DC-control-bit storage frame for determining a response to additional data, and user control data for determining a response to additional data, and executing acquisition of additional-data-component-bit information on the basis of the result of the determination of correspondence.  
      According to an embodiment, a computer program for executing processing for recording information is provided. The computer program includes a DC-control-bit selecting step of executing DC-control-bit selecting processing in which the values of DC control bits set in a recording frame are set to be coincident with user control data in response to the values of additional data component bits to be recorded on an information recording medium, and a modulated data generating step in which a modulated recording frame used as recording-unit data is generated by executing processing for modulating data to be recorded and DC-control-bit setting processing, and in which the DC-control-bit setting processing based on control of a digital sum variation and the DC-control-bit setting processing based on selecting information in the DC-control-bit selecting step are selectively executed.  
      According to an embodiment, a computer program for executing processing for playing back information recorded on an information recording medium is provided. The computer program includes a data demodulating step of executing demodulating processing on data read from the information recording medium, and an additional data decoding step of executing determination of correspondence between DC control bits for determining a response to additional data, the DC control bits being acquired from a DC-control-bit storage frame for determining a response to additional data, and user control data for determining a response to additional data, and executing acquisition of additional-data-component-bit information on the basis of the result of the determination of correspondence.  
      According to an embodiment, an information recording processor is provided which includes a DC-control-bit selecting unit for executing DC-control-bit selecting processing in which, when specific user control data selected from user control data to be recorded on an information recording medium is user control data including additional data, the values of DC control bits set in a DC-control-bit storage frame for specific user control data are set as bit values corresponding to the specific user control data, and in which, when the specific user control data is user control data including no additional data, the values of DC control bits set in a DC-control-bit storage frame for specific user control data are set to differ from bit values of the user control data including no additional data, and a modulated data generating unit for generating a modulated recording frame used as recording-unit data by executing processing for modulating data to be recorded and DC-control-bit setting processing, the modulated data generating unit selectively executing the DC-control-bit setting processing based on control of a digital sum variation and the DC-control-bit setting processing based on information input from the DC-control-bit selecting unit.  
      According to an embodiment, an information recording processor is provided which includes a DC-control-bit calculating unit for executing arithmetic processing using data included in specific user control data set in user control data to be recorded on an information recording medium, and additional data, and setting values obtained in the arithmetic processing as the values of DC control bits set in a DC-control-bit storage frame for specific user control data, and a modulated data generating unit for generating a modulated recording frame used as recording-unit data by executing processing for modulating data to be recorded and DC-control-bit setting processing, the modulated data generating unit selectively executing the DC-control-bit setting processing based on control of a digital sum variation and the DC-control-bit setting processing based on information input from the DC-control-bit selecting unit.  
      According to an embodiment, an information playback processor for executing processing for playing back information recorded on an information recording medium is provided. The information playback processor includes a data demodulating unit which executes demodulating processing on data read from the information recording medium, and an additional data decoding unit which executes determination of correspondence between DC control bits acquired from a DC-control-bit storage frame for specific user control data, and specific user control data, and determines, based on the result of the determination of correspondence, whether or not the user control data includes additional data, and which executes acquisition of the additional data on the basis of the result of the determination.  
      According to an embodiment, an information playback processor for executing processing for playing back information recorded on an information recording medium is provided. The information playback processor includes a data demodulating unit which executes demodulating processing on data read from the information recording medium, and an additional data decoding unit which executes arithmetic processing of DC control bits acquired from a DC-control-bit storage frame for specific user control data and specific user control data, and acquisition of additional data on the basis of the result of the arithmetic processing.  
      According to an embodiment, an information recording medium is provided which has a data recording configuration in which information indicating whether additional data is included in specific user control data selected from user control data included in recorded data is analyzable based on the values of DC control bits set in a DC-control-bit storage frame for specific user control data.  
      According to an embodiment, an information recording medium is provided which has a configuration in which bit information is recorded as the values of DC control bits set in a DC-control-bit storage frame for specific user control data, the bit information being calculated as the result of arithmetic processing using information of bits in specific user control data selected from user control data included in recorded data and information of additional data component bits.  
      According to an embodiment, an information recording method is provided which includes a DC-control-bit selecting step of executing DC-control-bit selecting processing in which, when specific user control data selected from user control data to be recorded on an information recording medium is user control data including additional data, the values of DC control bits set in a DC-control-bit storage frame for specific user control data are set as bit values corresponding to the specific user control data, and in which, when the specific user control data is user control data including no additional data, the values of DC control bits set in a DC-control-bit storage frame for specific user control data are set to differ from bit values of the user control data including no additional data, and a modulated data generating step in which a modulated recording frame used as recording-unit data is generated by executing processing for modulating data to be recorded and DC-control-bit setting processing, and in which the DC-control-bit setting processing based on control of a digital sum variation and the DC-control-bit setting processing based on information input from the DC-control-bit selecting unit are selectively executed.  
      According to an embodiment, an information recording method is provided which includes a DC-control-bit calculating step for executing arithmetic processing using data included in specific user control data set user control data to be recorded on an information recording medium, and additional data, and setting calculated values as the values of DC control bits set in a DC-control-bit storage frame for specific user control data, and a modulated data generating step in which a modulated recording frame used as recording-unit data is generated by executing processing for modulating data to be recorded and DC-control-bit setting processing, and in which the DC-control-bit setting processing based on control of a digital sum variation and the DC-control-bit setting processing based on information input from the DC-control-bit selecting unit are selectively executed.  
      According to an embodiment, an information playback method for executing processing for playing back information recorded on an information recording medium is provided. The information playback method includes a data demodulating step of executing demodulating processing on data read from the information recording medium, and an additional data decoding step in which determination of correspondence between DC control bits acquired from a DC-control-bit storage frame for specific user control data, and specific user control data is executed, and based on the result of the determination of correspondence, determination of whether or not the user control data includes additional data is performed, and in which acquisition of the additional data is executed based on the result of the determination.  
      According to an embodiment, an information playback method for executing processing for playing back information recorded on an information recording medium is provided. The information playback method includes a data demodulating step of demodulating processing on data read from the information recording medium, and an additional data decoding step of executing arithmetic processing of DC control bits acquired from a DC-control-bit storage frame for specific user control data and specific user control data, and acquisition of additional data on the basis of the result of the arithmetic processing.  
      According to an embodiment, a computer program for executing information recording processing is provided. The computer program includes a DC-control-bit selecting step for executing DC-control-bit selecting processing in which, when specific user control data selected from user control data to be recorded on an information recording medium is user control data including additional data, the values of DC control bits set in a DC-control-bit storage frame for specific user control data are set as bit values corresponding to the specific user control data, and in which, when the specific user control data is user control data including no additional data, the values of DC control bits set in a DC-control-bit storage frame for specific user control data are set to differ from bit values of the user control data including no additional data, and a modulated data generating step in which a modulated recording frame used as recording-unit data is generated by executing processing for modulating data to be recorded and DC-control-bit setting processing, and in which the DC-control-bit setting processing based on control of a digital sum variation and the DC-control-bit setting processing based on information input from the DC-control-bit selecting unit are selectively executed.  
      According to an embodiment, a computer program for executing information recording processing is provided. The computer program includes a DC-control-bit calculating step for executing arithmetic processing using data included in specific user control data set user control data to be recorded on an information recording medium, and additional data, and setting calculated values as the values of DC control bits set in a DC-control-bit storage frame for specific user control data, and a modulated data generating step in which a modulated recording frame used as recording-unit data is generated by executing processing for modulating data to be recorded and DC-control-bit setting processing, and in which the DC-control-bit setting processing based on control of a digital sum variation and the DC-control-bit setting processing based on information input from the DC-control-bit selecting unit are selectively executed.  
      According to an embodiment, a computer program for executing processing for playing back information recorded on an information recording medium is provided. The computer program includes a data demodulating step of executing demodulating processing on data read from the information recording medium, and an additional data decoding step in which determination of correspondence between DC control bits acquired from a DC-control-bit storage frame for specific user control data, and specific user control data is executed, and based on the result of the determination of correspondence, determination of whether or not the user control data includes additional data is performed, and in which acquisition of the additional data is executed based on the result of the determination.  
      According to an embodiment, a computer program for executing processing for playing back information recorded on an information recording medium is provided. The computer program includes a data demodulating step of demodulating processing on data read from the information recording medium, and an additional data decoding step of executing arithmetic processing of DC control bits acquired from a DC-control-bit storage frame for specific user control data and specific user control-data, and acquisition of additional data on the basis of the result of the arithmetic processing.  
      As described above, an embodiment, additional data is set based on correspondence between bit values of specific user control data included in recording data to be recorded on an information recording medium and DC control bits set in the recording data. Thus, embedding of additional data that is difficult to analyze is realized.  
      In an embodiment, by executing selective processing in which the values of DC control bits set in a recording frame are set to be coincident with user control data in response to the values of additional data component bits to be recorded on the information recording medium, DC-control-bit selecting processing is performed. In addition, in information playback, by executing determination of correspondence between DC control bits for determining a response to additional data, the DC control bits being acquired from a DC-control-bit storage frame for determining a response to additional data, and user control data for determining a response to additional data, reading of the additional data can be performed.  
      As described above, additional data is set based on correspondence between bit values of specific user control data included in recorded data for an information recording medium and DC control bits set in the recorded data. Thus, embedding of additional data having high difficulty in analysis is realized.  
      According to an embodiment, when specific user control data is user control data including additional data, recording is performed so that specific-user-control-data storage bits are coincident with DC control bits set in a DC-control-bit storage frame for specific user control data. When the specific user control data is user control data which does not include additional data, recording is performed so that the specific-user-control-data storage bits are not coincident with the DC control bits set in a DC-control-bit storage frame for specific user control data. In playback processing, the bit values in the specific user control data are compared with the DC control bits set in the DC-control-bit storage frame for specific user control data. When both are coincident, specific-user-control-data storage data can be acquired as additional data.  
      According to an embodiment, calculation using specific-user-control-data storage data set in user control data to be recorded on an information recording medium and additional data, for example, XOR or XNOR, is executed, and calculated values are set as the values of DC control bits set in a DC-control-bit storage frame for specific user control data. In playback processing, by executing calculation using specific-user-control-data storage data, and DC control bits set in the specific user control data for specific user control data, additional data can be acquired.  
      In an embodiment, an information recording processor and information playback processor is provided in which content, whose copyright must be protected, is recorded on a recording medium, and in which additional data, such as key information for use in decrypting the content, key-generating information, content-playback control information, or copy-control information, must be embedded in a hardly analyzable form. In another embodiment, an information recording medium used therewith is provided.  
      Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the Invention and the figures.  
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       FIG. 1  is a block diagram showing an information recording processor according to an embodiment.  
       FIG. 2  is a first illustration of processing in the modulated data generating unit in the information recording processor shown in  FIG. 1 .  
       FIG. 3  is a second illustration of processing in the modulated data generating unit in the information recording processor shown in  FIG. 1 .  
       FIG. 4  is an illustration of data in a transformation table for use in modulating processing in the information recording processor shown in  FIG. 1 .  
       FIGS. 5A and 5B  are illustrations of processing executed in the recording-signal processing circuit in the information recording processor shown in  FIG. 1 .  
       FIG. 6  is an illustration of detailed configurations of a BIS block and a BIS cluster.  
       FIG. 7  is an illustration of the arrangement of user control data in a BIS block.  
       FIG. 8  is an illustration of the arrangement of user control data in a BIS cluster.  
       FIG. 9  is an illustration of processing for generating an ECC cluster based on the LDC cluster and a BIS cluster.  
       FIG. 10  is an illustration of the configurations of a DC-control-bit storage frame for determining a response to additional data and a DC-control-bit storage frame for specific user control data.  
       FIGS. 11A and 11B  are illustrations of DC control bits in a DC-control-bit storage frame for determining a response to additional data which are set based on the values of additional data component bits.  
       FIG. 12  is an illustration of correspondence between DC control bits and user control data bits for determining a response to additional data, and additional data component bits.  
       FIG. 13  is an illustration of the configuration of a DC-control-bit storage frame for determining a response to additional data which is recorded on an information recording medium, and the configuration of a DC-control-bit storage frame for determining a response to additional data.  
       FIG. 14  is a flowchart illustrating an additional data recording process executed in the information recording processor according to an embodiment.  
       FIG. 15  is a block diagram showing an information playback processor according to an embodiment.  
       FIGS. 16A and 16   b  are block diagrams illustrating an example of processing in which additional data is applied in the information playback processor according to an embodiment.  
       FIG. 17  is a block diagram illustrating an example of processing in which additional data is applied in the information playback processor according to an embodiment.  
       FIG. 18  is a flowchart illustrating an additional data recording process executed in the information playback processor according to an embodiment.  
       FIG. 19  is a block diagram showing an information recording processor according to an embodiment.  
       FIG. 20  is a first illustration of processing in the modulated data generating unit in the information recording processor shown in  FIG. 19 .  
       FIG. 21  is a second illustration of processing in the modulated data generating unit in the information recording processor shown in  FIG. 19 .  
       FIG. 22  is an illustration of data in a transformation table for use in modulating processing in the information recording processor shown in  FIG. 19 .  
       FIGS. 23A and 23B  are illustrations of processing executed in the recording-signal processing circuit in the information recording processor shown in  FIG. 19 .  
       FIG. 24  is an illustration of detailed configurations of a BIS block and a BIS cluster.  
       FIG. 25  is an illustration of the arrangement of user control data in a BIS block.  
       FIG. 26  is an illustration of the arrangement of user control data in a BIS cluster.  
       FIG. 27  is an illustration of processing for generating an ECC cluster based on the LDC cluster and a BIS cluster.  
       FIG. 28  is an illustration of the configurations of a DC-control-bit storage frame for specific user control data and specific user control data, and correspondence therebetween.  
       FIGS. 29A and 29B  are illustrations of setting of DC control bits in a DC-control-bit storage frame for specific user control data.  
       FIG. 30  is an illustration of correspondence between specific user control data and additional data on the basis of coincidence and non-coincidence between DC control bits for specific user control data and specific user control data bits.  
       FIG. 31  is an illustration of a technique for setting different specific user control data items in clusters.  
       FIG. 32  is an illustration of the configurations of a DC-control-bit storage frame for specific user control data which is recorded on an information recording medium and specific user control data.  
       FIG. 33  is a flowchart illustrating an additional data recording process executed in the information recording processor according to an embodiment.  
       FIG. 34  is a block diagram showing an information playback processor according to an embodiment.  
       FIGS. 35A and 35B  are illustrations of an example of processing in which additional data is applied in the information playback processor according to an embodiment.  
       FIG. 36  is a block diagram illustrating an example of processing in which additional data is applied in the information playback processor according to an embodiment.  
       FIG. 37  is a flowchart illustrating an additional data recording process executed in the information playback processor according to an embodiment.  
       FIG. 38  is a block diagram showing an information recording processor according to an embodiment.  
       FIG. 39  is an illustration of processing for recording additional data in an embodiment.  
       FIG. 40  is a flowchart illustrating an additional data recording process executed in the information recording processor according to an embodiment.  
       FIG. 41  is a block diagram showing an information playback processor according to an embodiment.  
       FIG. 42  is a flowchart illustrating the additional data recording process executed in the information playback processor according to an embodiment.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention relates to information recording processors, information playback processors, methods therefor, and information recording media and computer programs used therewith. In particular, the present invention relates to an information recording processor, an information playback processor, and a method therefor in which, in a configuration capable of recording additional data, such as key information for use in decrypting content, content-playback control information, and copy-control information, on an information recording medium containing content, such as image data and music data, and reading the additional data, by setting additional data based on correspondence between the bit value of specific user control data (UCD) included in recorded data and DC control bits set in the recorded data, embedding of additional data that is difficult to analyze is realized. In addition, the present invention relates to a recording medium and computer program used with the information recording processor, the information playback processor, and the method therefor.  
      An information recording processor, information playback processor, and method therefor according to various embodiments and an information recording medium and computer used therewith are described below, in greater detail with reference to the accompanying drawings.  
      In an embodiment, the configuration and processing of the information recording processor are described with reference to  FIG. 1 .  
      The information recording processor described below includes a mastering apparatus that is an apparatus for producing a so-called “master disk”, and includes an apparatus having an information recording medium drive, which is usable by a general user, such as a DVD (digital versatile disk) recording/playback apparatus or a personal computer. In other words, the meaning of the information recording processor includes an information processing apparatus capable of recording data not only to a master disk, but also to various information recording media of recordable and rewritable types.  
      As shown in  FIG. 1 , the information recording processor includes an information recording medium  101  on which data can be recorded, a pickup  102  for outputting a data recording signal to the information recording medium  101 , a spindle motor  103  for driving the information recording medium  101 , a servo circuit  104  for controlling the pickup  102  and the spindle motor  103 , an additional-data error-correcting encoding unit  105 , an error-correcting-encoding-and-interleaving unit  106  for main data, an additional-data recording-area control unit  107 , a switch  108 , a modulated data generating unit  109 , a DC-control-bit setting unit  110 , a recording-signal processing circuit  111 , an error-correcting-encoding-and-interleaving unit  112  for user control data, an ECC cluster generating unit  113 , a DC-control-bit selecting unit  114 , and a main-data encrypting circuit  116 .  
      Recording data to be recorded on the information recording medium  101  includes main data formed by substantial data of data (such as content) to be played back, user control data (UCD) including various types of control data such as playback-control information, and additional data such as key information for use in decrypting content, content-playback control information, and copy-control information. The additional data is set as acquirable data based on correspondence between bit values of specific user control data and DC control bits set in the recording data.  
      The DC-control-bit selecting unit  114  executes selecting the values of DC control bits which are set in a DC-control-bit storage recording frame for determining a response to additional data. Specifically, the DC-control-bit selecting unit  114  performs DC-bit selecting processing in which, in response to the additional data component bit “0” or “1”, DC control bits to be set in a DC-control-bit storage recording frame for determining a response to additional data are set as bit values equal to the bit value (eight bits) of specific user control data, or as bit values being not equal to the bit value of the user control data. Details of the DC-bit selecting processing are described later.  
      Content data to be recorded on the information recording medium  101  is, for example, encrypted content data. The main data is encrypted by using an encryption key in the main-data encrypting circuit  116 . The main-data encrypting circuit  116  generates encryption main data by receiving, for example, a 64-bit DES (data encryption standard) encryption key, 128-bit AES (advanced encryption standard) encryption key, information of a component of the encryption key, or a seed which is encryption-key generating information, and executing block-encryption processing, such as DES algorithm or AES algorithm, on the main data, such as content data, by using an encryption key generated based on the input information.  
      The encrypted main data is input to the error-correcting-encoding-and-interleaving unit  106 . The error-correcting-encoding-and-interleaving unit  106  generates error-correcting codes and performs coding of the input data, and also performs interleaving processing. Details of these processes are described below.  
      The error-correcting-encoding-and-interleaving unit  112  generates error-correcting codes and performs coding of also on the user control data including the various types of control data, such as playback-control information, and performs interleaving processing.  
      The ECC cluster generating unit  113  generates ECC clusters based on the interleaving-processed main data and user control data, and the modulated data generating unit  109  receives the ECC clusters and executes modulating on the received ECC clusters. The modulated data generating unit  109  executes modulation based on the RLL (run length limited) (1, 7) modulation system in which modulation of two-bit data into three-bit data is basically performed.  
      In the modulation based on the (1, 7) RLL modulation system, data transformation is performed to produce modulated data in accordance with run-length limitation of (1, 7) RLL in which the number of consecutive 0&#39;s is a minimum of one and a maximum of seven. In this transformation processing, a transformation table is used. A specific example of using the transformation table is described later.  
      Based on modulated data based on the (1, 7) RLL system, a recording unit in which a synchronizing signal is set, which is called a “recording frame”, is generated and is recorded on the information recording medium  101  through the recording-signal processing circuit  111 .  
      The modulating processing is performed after the DC-control-bit setting unit  110  selects “0” or “1” as each DC control bit for insertion so that the absolute value of a digital sum variation (DSV) decreases at regular intervals of the input main data.  
      The digital sum variation is a DC balance index of an NRZI (nonreturn to zero change on one) transformation signal generated as a recording signal for the information recording medium  101 . Specifically, by totaling bits of a recording bit series (NRZI transformation signal), with each bit “0” as “−1”, and each bit “1” as “+1”, the total is obtained and is used as a digital sum variation. After the DC control bit “0” or “1” is selectively inserted so that the divergence of the digital sum variation from “0” is minimum, the modulating processing is performed. Details of the NRZI transformation processing are described later.  
      In an embodiment, in this DC control bit setting, for a selected specific recording frame, that is, a DC-control-bit storage recording frame for determining a response to additional data, bit values selected by the DC-control-bit selecting unit  114  is set as DC control bits without using DC-control-bit setting in accordance with the above rule. In other words, DC-bit setting is performed in which, in response to the additional data component bit “0” or “1”, DC control bits are set to have a bit string coincident with the bit values (eight bits) of specific user control data, or to have a bit string not coincident with the bit values. Information of the DC control bits is output from the DC-control-bit selecting unit  114  to the modulated data generating unit  109  through a switch  108  controlled by the additional-data recording-area control unit  107 . Details of the DC-control-bit setting based additional data are described later.  
      Details of ECC-cluster setting processing and modulated-data generating processing, which are based on main data and user control data, are described below, with reference to  FIGS. 2 and 3 .  
      The ECC-cluster setting processing and the modulated-data generating processing are executed by the error-correcting-encoding-and-interleaving unit  106 , the error-correcting-encoding-and-interleaving unit  112 , the ECC cluster generating unit  113 , and the modulated data generating unit  109 , which are shown in  FIG. 1 .  
      As shown in portion (a) of  FIG. 2 , the recording data is constituted by user data  201  as main data, and user control data  211 . The user data  201  corresponds to the main data including the substantial data of data to be played back, such as content. The user control data  211  includes various types of control data such as playback-control information.  
      The user data  201  is set in  32 -frame units, each consisting of 2048-byte data and 4-byte parity. The user control data  211  is formed by 32 units of 18-byte data.  
      Based on the user data  201 , which has 32 frames by (2048+4) bytes, a data block  202  is formed. The data block  202  has an arrangement of 304 columns by 216 rows. One column by one row stores one-byte data (eight bits).  
      For the data block  202 , an LDC block  203  is generated as a data block with parity of 32 rows added in each column. Interleaving processing on the LDC block  203  generates an LDC cluster  204  of 152 columns by 496 rows.  
      In addition, the user control data  211  is combined with physical address data  221  having 16 by 9 bytes to generate an access block  212  of 24 columns by 30 rows. After that, a BIS block  213  is generated as a data block in which parity of 32 rows is added in each column in the access block  212 . Interleaving of the BIS block  213  generates a BIS cluster  214  of 3 columns by 496 rows.  
      Portion (d) of  FIG. 3  shows data identical to that shown in portion (d) of  FIG. 2 , that is, the LDC cluster  204  of 152 columns by 496 rows which is generated based on the user data  201 , and the BIS cluster  214  of 3 columns by 496 rows.  
      As shown in portion (d) of  FIG. 3 , the LDC cluster  204  of 152 columns by 496 rows is divided into four parts I to IV in 38-column units. The BIS cluster  214  of 3 columns by 496 rows is divided into three parts i to iii in column units. By combining the parts I to IV and the parts i to iii, the ECC cluster  231 , shown in portion (e) of  FIG. 3 , of 155 columns by 496 rows is generated.  
      As shown in portion (f) of  FIG. 3 , the ECC cluster  231  is set as a cluster  232  partitioned into 28 parts  0  to  27 . Only part  0  has 25 bits, and the other parts  1  to  27  each have 45 bits. The numbers of bits, shown in portion (f) of  FIG. 3 , are values per row.  
      As shown in portion (g) of  FIG. 3 , a 20-bit synchronizing (Sync) part is set. In addition, in the parts  0  to  27  shown in portion (f) of  FIG. 3 , a one-bit DC-control-bit part is set between two parts.  
      This sets a physical cluster  233  of [1240 bits+20 bits (Sync)+(1 DC-control bit×28)=1288 bits]×496 rows. Each row of the physical cluster  233  is used as a recording frame  234  which is a modulated-data generating unit.  
      The DC control bits are a DC balance index of an NRZI transformation signal generated as a recording signal for the information recording medium  101 . Specifically, by totaling bits of a recording bit series (NRZI transformation signal), with each bit “0” as “−1”, and each bit “1” as “+1”, the total is obtained and is used as a digital sum variation. After the DC control bit “0” or “1” is selectively inserted so that the divergence of the digital sum variation from “0” is minimum, the modulating processing is performed.  
      As described above, in the present invention, in this DC control bit setting, for a selected specific recording frame, that is, a DC-control-bit storage recording frame determining a response to additional data, bit values selected by the DC-control-bit selecting unit  114  are set as DC control bits without using DC-control-bit setting in accordance with the above rule. In other words, DC-bit setting is performed in which, in response to the additional data component bit “0” or “1”, DC control bits are set to have a bit string coincident with the bit values (eight bits) of specific user control data, or to have a bit string not coincident with the bit values. Details of this processing are described below.  
      Modulating processing on a frame in which the DC control bits, that is, the recording frame  234  shown in portion (g) of  FIG. 3  which is formed by 1288-bit data, is performed. In the modulating processing, 2-bit data is transformed into 3-bit data. This data transformation executes (1, 7) RLL data transformation that produces modulated data in accordance with run-length limitation in which the number of consecutive 0&#39;s is a minimum of one and a maximum of seven, whereby the modulated recording frame  235  is generated.  
      The modulated recording frame  235 , shown in portion (h) of  FIG. 3 , has a total of 1932 channel bits consisting of 30 (synchronizing) channel bits (modulated data bits) and 1902 channel bits consisting of (1288−20) synchronizing bits×⅔.  
      In the data modulating processing for transformation from 2-bit data to 3-bit data in accordance with the (1, 7) RLL run-length rule, a transformation table is used. A specific example of the transformation table is shown in  FIG. 4 .  
      As shown in  FIG. 4 , the transformation table indicates correspondence between strings of modulated data bits and corresponding strings of input bits. For example, when input data is “00000000”, a corresponding string of modulated data bits is “010100100100”. When input data is “11”, if precedent modulated data bits are “xx1”, corresponding modulated data bits are “000”, and if precedent modulated data bits are “xx0”, corresponding modulated data bits are “101”.  
      By using this transformation table to execute transformation from 2-bit data into 3-bit data, modulated data bits is generated in accordance with the (1, 7) RLL run-length rule.  
      Referring back to  FIG. 1 , the configuration and processing of the information recording processor is continuously performed as described below.  
      In the modulated data generating unit  109  shown in  FIG. 1 , the modulated data generating processing, described with reference to FIGS.  2  to  4 , is executed, and the recording-signal processing circuit  111  generates a recording signal based on the generated modulated data.  
      The recording-signal processing circuit  111  generates a NRZI signal in which the polarity of each pulse is inverted in response to the value “0” or “1” of the modulated data generated in the modulated data generating unit  109 . The recording-signal processing circuit  111  records the NRZI signal as a recording signal on the information recording medium  101 .  
       FIG. 5A  shows the configuration of the recording-signal processing circuit  111  in which processing for generating the NRZI signal as a recording signal is executed. Channel bits output from the modulated data generating unit  109 , which are modulated data bits, are input to the recording-signal processing circuit  111 , which includes an NRZ transformation unit  121 , an XOR  122 , and a delay unit  123 . In  FIG. 5B , portion (a) shows channel bits, portion (b) shows an output signal from the NRZ transformation unit  121 , and portion (c) shows NRZI transformed pulses which are finally output as a recording signal from the recording-signal processing circuit  111 . The recording signal is output to the pickup  102 , and recording information is recorded on the information recording medium  101  under the control of a servo circuit  104 .  
      In an embodiment, additional data, such as key information for use in decrypting content, content-playback control information, and copy-control information, is set, as acquirable data, based on correspondence between specific user control data, that is, the bit values (8 bits) of user control data for additional data, and eight DC control bits included in a DC-control-bit storage recording frame for determining a response to additional data.  
      For example, in the above setting, when the 8-bit value of the specific user control data coincides with the eight DC control bits included in the DC-control-bit storage recording frame for determining a response to additional data, it is indicated that each bit forming the additional data is “0”, while, when the 8-bit value of the specific user control data does not coincide with the eight DC control bits included in the DC-control-bit storage recording frame for determining a response to additional data, it is indicated that each bit forming the additional data is “1”.  
      When modulation of the DC-control-bit storage recording frame for determining a response to additional data is executed in the modulated data generating unit  109 , the additional-data recording-area control unit  107  shown in  FIG. 1  controls the switch  108  to be on, so that the DC control bit values selected in the DC-control-bit selecting unit  114  are output to the modulated data generating unit  109 .  
      At DC-control-bit setting positions for additional data in the DC-control-bit storage recording frame for determining a response to additional data, the modulated data generating unit  109  sets, not DC control bits having values determined based on the above DSV measurement, but the DC control bit value selected by the DC-control-bit selecting unit  114 .  
      The configuration shown in  FIG. 1  is shown in the form of a schematic block diagram illustrating the configuration and processing of the information recording processor according to the first embodiment of the present invention. For example, processing, such as control processing for DC control bits to be set for additional data, can be executed such that a controller, such as a central processing unit, executes a program describing a processing sequence. Accordingly, in the information recording processor according to the first embodiment, hardware corresponding to the switch and other component blocks shown in  FIG. 1  is not essential. The processing for generating the recording frame is executable on hardware including a CPU, which serves as a controller for executing processing in accordance with a predetermined program, and as a data processor, and a memory as a means of storing parameters, etc.  
      Additional data is encryption-key information for use as an encryption key for encrypted content, information forming partial data of the encryption-key information, encryption-key generating information, such as the data (e.g., seed) required for generating an encryption key, secret information, such as a password, control information of various types, such as content-playback control information ad copy-control information, or a bit string of data (e.g., “0, 0, 0, 1, 0, 0, 0, . . . ”) forming content attribute information. This bit string includes error-correcting codes set for the additional data in the additional-data error-correcting encoding unit  105 . In an embodiment, bit information forming the additional data bit string is set by the above-described configuration.  
      In other words, by setting, in the DC-control-bit storage recording frame for determining a response to additional data, a DC control bit string coincident with eight bits of specific user control data, it is indicated that the additional data component bit is “0”. In addition, by setting, in the DC-control-bit storage recording frame for determining a response to additional data, a DC control bit string which is not coincident with eight bits of specific user control data, it is indicated that the additional data component bit is “1”.  
      One form of setting may be employed between setting in which: 
          when UCD=“DC control bits”, “additional data bit”=“0”; and     when UCD≠“DC control bits”, “additional data bit”=“1”, and setting in which:     when UCD=“DC control bits”, “additional data bit”=“1”; and     when UCD e DC control bits, the additional data bit=“0”.        

      The configuration of additional data in the first embodiment of the present invention is described below.  
       FIG. 6  shows details of the BIS block  213  and BIS cluster  214  generated based on the user control data  211  in the modulated data generating processing described with reference to  FIGS. 2 and 3 .  
      As described with reference to  FIGS. 2 and 3 , by combining the physical address data  221  of 16×9 bytes with the user control data  211 , the access block  212  of  24  columns by  30  rows is generated. After that, the BIS block  213  is generated as a data block in which parity of 32 rows is added in each column. The generated block  213  is shown in portion (A) of  FIG. 6 .  
      By performing interleaving of the BIS block  213 , the BIS cluster  214  of  3  columns by 496 rows is generated. The generated BIS cluster  214  is shown in portion (B) of  FIG. 6 .  
      As shown in portion (B) of  FIG. 6 , a 3-row physical address, 12-row user control data (UCD), and 16-row parity constitute one unit of 3 columns×31 rows. Sixteen units  0  to  15  constitute the BIS cluster  214  of 3 columns×496 rows.  
       FIG. 7  shows details of the configuration in storage of the BIS block  213 .  FIG. 8  shows a detailed arrangement of user control data in the BIS cluster  214 .  
      As shown in portion (Al) of  FIG. 7 , the BIS block  213  is constituted by a physical address of 24 columns×6 rows, user control data (UCD) of 24 columns×24 rows, and parity of 24 columns×32 rows.  
      As shown in portion (A 2 ) of  FIG. 7 , the user control data (UCD) of 24 columns×24 rows is constituted by 576 (24×24) user-control-data-forming data items “UC 0,0” to “UC 17,31”, each data item having one byte (8 bits). By performing interleaving of the BIS block  213  having the user control data arrangement of 24 columns×24 rows, the BIS cluster  214  is generated.  
      As shown in portion (B 1 ) of  FIG. 8 , the BIS cluster  214  has an arrangement of 3 columns×496 rows. A 3-row physical address and 12-row user control data (UCD), and 16-row parity constitute one unit of 3 columns×31 rows. Sixteen units  0  to  16  constitute the BIS cluster  214  of 3 columns×496 rows.  
      Portion (B 2 ) of  FIG. 8  shows user control data of 3 columns×12 rows in unit  0 . The user control data in unit  0  stores 36 (=3×12) user-control-data-forming data items “UC 0,12” to “UC 4,25”, each data item having one byte (8 bits). Each of sixteen units  0  to  15  stores 36 (=3×12) user-control-data-forming data items. Accordingly, the BIS cluster  214  stores a total of  576  (=36×16) user-control-data-forming data items.  
      The user-control-data-forming data items stored in the BIS cluster  214  are arranged in distributed form in units  0  to  15  in the BIS cluster  214  by performing the interleaving of the BIS block  213  shown in portion (A 2 ) of  FIG. 7 .  
      The user control data is set as a storage area for storing various types of information, such as content-playback control information, and its part is set as a reserve area or the like, in which arbitrary data can be written.  
      As shown in  FIG. 9 , each column of the BIS cluster  214  including the user control data is inserted among four-divided data items I to IV of the LDC cluster  204  set based on the user data such as content (as described with reference to  FIGS. 2 and 3 ), whereby the ECC cluster  231  is generated.  
      As shown in  FIG. 9 , the ECC cluster  231  is set as a cluster in which a BIS cluster of 3 columns×496 rows is combined with an LDC cluster of 152 columns×496 rows.  
      As described with reference to  FIG. 6 , one of the physical address, the user control data, and the parity is set as each column of the BIS cluster. Therefore, the BIS cluster (i, ii, iii) included in each of 496 rows of the ECC cluster  231  is a type of data among a physical address, user control data, and parity.  
      As shown in  FIG. 10 , a specific row selected from 496 rows constituting the ECC cluster  231  is set as: 
          (A) a DC-control-bit storage frame  311  for determining a response to additional data, or     (B) a UCD storing frame  321  for determining a response to additional data.     (A) The DC-control-bit storage frame  311  for determining a response to additional data is a frame storing the value of bits forming additional data such as an encryption key, and adjusted DC control bits having values determined based on user control data for determining a response to additional data. Part of the DC control bits set in the DC-control-bit storage frame  311  is determined by the DC-control-bit selecting unit  114  shown in  FIG. 1  based on the value of bits forming additional data such as an encryption key, and user control data for determining a response to additional data.     (B) The UCD storing frame  321  for determining a response to additional data is a frame storing user control data for determining a response to additional data.        

      Although (A) the DC-control-bit storage frame  311  for determining a response to additional data and (B) the UCD storing frame  321  for determining a response to additional data may be set as separate frames, a single frame may be set both as the DC-control-bit storage frame  311  and as the UCD storing frame  321 .  
      As shown in  FIG. 10 , in the UCD storing frame  321 , user control data for use in determining a response to additional data, for example, the user control data “UC 0,0” formed by 8-bit data, is stored in user-control-data area (i)  322  which is a-BIS-cluster setting position.  
      It is assumed that the user control data “UC 0,0” formed by 8-bit data be set as user control data for determining a response to additional data. The user control data “UC 0,0” for determining a response to additional data has, for example, “00111101”.  
      In this case, among DC control bits to be stored in the DC-control-bit storage frame  311  for determining a response to additional data, eight bits (DC control bits) are adjusted. When the additional data component bit=“0”, eight bits (DC control bits) which are coincident with the 8-bit data “00111101” of “UC 0,0” is set. When the additional data component bit=“1”, eight bits (DC control bits) which are not coincident with the 8-bit data “00111101” of“UC 0,0” is set.  
      In the configuration shown in  FIG. 1 , the additional data is input to the additional-data error-correcting encoding unit  105 . The additional-data error-correcting encoding unit  105  performs encoding for adding error-correcting codes to the input data. The additional data is encryption-key information for use as an encryption key for encrypted content, information forming part of the encryption-key information, encryption-key generating information such as the data (e.g., a seed) required for generating an encryption key, secret information such as a password, control information such as content playback control information or copy-control information, or other information such as content-attribute information.  
      A string of bits of the additional data having error-correcting codes added thereto is input to the DC-control-bit selecting unit  114 . For example, the bit string “0, 0, 0, 1, 0, 0, 0, . . . ” is input. This bit string includes, for example, one type of additional data of encryption-key information, encryption-key generating information, content-playback control information, content copy control information, a password, and other content-attribute information, and the error-correcting codes set to the additional data by the additional-data error-correcting encoding unit  105 .  
      Information of component bits of user control data for determining a response to additional data is input to the DC-control-bit selecting unit  114 . For example, in the above example, the 8-bit data “00111101” of the user control data “UC 0,0” is input.  
      The DC-control-bit selecting unit  114  sequentially acquires, bit by bit, the bit string of the additional data having error-correcting codes added thereto. When the additional data component bit=“0”, the DC-control-bit selecting unit  114  selects DC control bit values so as to set DC control bits coincident with the 8-bit data “00111101” of the user control data “UC  0 , 0 ”, and outputs information of the selected DC control bit values to the modulated data generating unit  109  through the switch  108 .  
      The modulated data generating unit  109  executes generating a DC-control-bit storage frame (for determining a response to additional data) having the DC control bit values input from the DC-control-bit selecting unit  114 , and modulating the DC-control-bit storage frame.  
      The additional-data recording-area control unit  107  controls the switch  108  to be on with modulating-processing executing timing associated with the DC-control-bit storage frame so that the selected bit information from the DC-control-bit selecting unit  114  is output to the modulated data generating unit  109 .  
      When executing processing for generating a frame other then the DC-control-bit storage frame for determining a response to additional data and modulating the frame, the switch  108  is controlled to be off. The DC-control-bit setting unit  110  executes normal DC-control-bit setting processing, that is, DC-control-bit setting processing based on digital-sum-variation measurement.  
      As shown in  FIG. 10 , in a DC-control-bit storage frame  331  for determining a response to additional data, synchronizing bits (20 bits) are set. In each of frame parts # 0  to # 27  each having 45 bits, one DC control bit is set.  
      As described above, the DC-control-bit storage frame  331  stores a total of 28 DC control bits in frame parts # 0  to # 27 . Among these DC control bits, eight DC control bits are set as DC control bits for determining a response to additional data which are used to determine coincidence or non-coincidence with specific user control data, that is, user control data for determining a response to additional data.  
      The other DC control bits are set as DC control bits having bit values determined based on the normal bit-value setting processing, that is, digital-sum-variation measurement.  
      Details of the configuration of the DC-control-bit storage frame for determining a response to additional data are described below with reference to  FIGS. 11A and 11B .  
       FIG. 11A  shows details of the configuration of the DC-control-bit storage frame when the additional data component bit is “0”, and  FIG. 11B  shows details of the configuration of the DC-control-bit storage frame when the additional data component bit is “1”.  
      In this example, when the additional data component bit is “0”, DC control bits which are coincident with the bit values of user control data for determining a response to additional data are set in the DC-control-bit storage frame for determining a response to additional data. When the additional data component bit is “1”, DC control bits which are not coincident with the bit values of user control data for determining a response to additional data are set in the DC-control-bit storage frame for determining a response to additional data.  
      In  FIG. 11A , the additional data component bit is “0”, and user control data for determining a response to additional data is the eight bits “00111101” of the user control data “UC 0,0”. In this case, the eight bits “00111101” are stored at response-determining DC-control-bit storage positions in the DC-control-bit storage frame for determining a response to additional data.  
      Here, the response-determining DC-control-bit storage positions in the DC-control-bit storage frame for determining a response to additional data are eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 . The above response-determining DC-control-bit storage positions are examples. The DC control bits may be set at arbitrary positions. When valid playback-processing program is executed, from each bit position, a DC control bit is read. It is determined whether the read DC control bit is coincident with response-determining user control data, and the bit values of additional data are acquired. Details of the playback processing are described later.  
      In the example shown in  FIG. 11B , the additional data component bit is “1”, and the user control data for determining a response to additional data is the eight bits “00111101” of the user control data “UC 0,0”. In this case, bits different from the eight bits “00111101” are stored at DC-control-bit storage positions (for determining a response to additional data) in a DC-control-bit storage frame  352  for determining a response to additional data, that is, frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 . An arbitrary bit string may be used as the above eight DC control bits if different from the bits “00111101”. In the example shown in  FIG. 11B , the bits “10010100” are stored at DC-control-bit storage positions in the DC-control-bit storage frame  352 , that is, frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 .  
      As described above, in an embodiment, part of user control data included in data recorded on a recording medium (disk) is set as user control data for determining a response to additional data, and depending on whether an additional data component bit is “0” or “1”, DC control bits set in a DC-control-bit storage frame for determining a response to additional data is controlled to be coincident with or not to be coincident with user control data for determining a response to additional data. By using a plurality of DC-control-bit storage frames for determining a response to additional data, additional data information, such as encryption-key information, is embedded.  
      As  FIG. 12  shows, in a case in which DC-control-bit information (8 bits) in the DC-control-bit storage frame for determining a response to additional data is represented by A, and bit information of user control data for determining a response to additional data is represented by B, when A=B, the additional data component bit=“0”, and when A≠B, the additional data component bit=“1”. Under these conditions, data recording and playback are executed.  
      Additional data recording/storing processing, based on determination of correspondence between DC control bits (for determining a response to additional data) on a recording medium and user control data for determining a response to additional data, is described below with reference to  FIG. 13 .  
      On a recording medium (disk)  361 , items of main data, such as content, and ECC clusters (see  FIG. 3 ) generated based on user control data (UCD), such as control information, are set. Recording-data generating processing is executed in each cluster unit. A recording frame having DC control bits set therein is set, and a recording signal based on the recording frame is generated and recorded.  
      In the case of recording additional data in the configuration according to the first embodiment of the present invention, one user control data item for determining a response to additional data is set in, for example, an ECC cluster-A  371 . For example, it is assumed that eight bits of the user control data “UC 0,0” are used as a user control data item included in the ECC cluster-A  371 , and are set as user control data  381  for determining a response to additional data. In addition, a plurality of frames included in the ECC cluster-A  371  are set as DC-control-bit storage frames  382 - 1  to  382 -P for determining a response to additional data. By sequentially comparing the p DC-control-bit storage frames  382  with the UCD bits of the user control data  381 , and performing determination so that, when both have correspondence (coincidence), the additional data component bit=0, and when both have not correspondence (non-coincidence), the additional data component bit=1, additional-data-forming-bit information of p bits is acquired in one ECC cluster. In the case of a disk containing N ECC clusters, additional data of p×N bits can be stored.  
      Although  FIG. 13  shows a case in which one user control data item for determining a response to additional data is set in one ECC cluster, a construction may be employed in which a plurality of user control data items for determining a response to additional data are set and a user control data item, which executes response determination, is changed in each DC-control-bit storage frame.  
      Based on information set beforehand, the additional-data recording-area control unit  107  shown in  FIG. 1  identifies a DC-control-bit storage frame for determining a response to additional data. When the modulated data generating unit  109  performs modulating processing on the DC-control-bit storage frame, by changing over the switch  108 , it controls the DC-control-bit selecting unit  114  to output the set values of DC control bits (for determining a response to additional data) included in the DC-control-bit storage frame to the modulated data generating unit  109 .  
      Bit information of user control data for determining a response to additional data, and an additional data bit are input to the DC-control-bit selecting unit  114 . When the additional data bit is “0”, bit values which are coincident with the bit information of the user control data for determining a response to additional data are selected as DC control bits and are output to the modulated data generating unit  109 . When the additional data bit is “1”, bit values which are not coincident with the bit information of the user control data for determining a response to additional data are selected as DC control bits and are output to the modulated data generating unit  109 .  
      Based on the bit values input from the DC-control-bit selecting unit  114 , the modulated data generating unit  109  sets the input bit values at DC-control-bit setting positions for determining response to specific additional data in the DC-control-bit storage frame, and performs modulating processing.  
      An additional data recording process executed in the information recording processor according to the first embodiment of the present invention is described below with reference to  FIG. 14 .  
      In step S 101 , error-correcting coded additional data is input. The input data is data output from the additional-data error-correcting encoding unit  105  shown in  FIG. 1 . The additional data is encryption-key information for use as an encryption key for encrypted content, information forming partial data of the encryption-key information, encryption-key generating information such as the data (e.g., a seed) required for generating an encryption key, secret information such as a password, control information such as content-playback control information or copy-control information, or other data. A bit string of additional data to which error-correcting codes are added, for example, the data string “0, 0, 0, 1, 0, 0, 0, . . . ” is input.  
      In step S 102 , from the input data string “0, 0, 0, 1, 0, 0, 0 . . . ”, each bit is sequentially extracted as a recording bit.  
      In step S 103 , bit information of user control data for determining a response to additional data is performed. The bit information is, for example, the 8-bit information “UC 0,0”.  
      In step S 104 , it is determined whether the additional data component bit acquired in step S 102  is “0”.  
      When the additional data component bit is “0”, the process proceeds to step S 105 , and DC control bits set in the DC-control-bit storage frame for determining a response to additional data, for example, eight bits set in eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24  are set to have values coincident with the bit values of the user control data acquired in step S 103 .  
      In step S 104 , when the additional data component bit is “1”, the process proceeds to step S 106 , and DC control bits set in the DC-control-bit storage frame for determining a response to additional data, for example, eight bits set in eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , are set to have values not coincident with the bit values of the user control data acquired in step S 103 .  
      Proceeding to step S 107 , the DC-control-bit storage frame for determining a response to additional data is modulated.  
      In step S 103 , it is determined whether processing on the end bit of the additional data has finished. If there is unprocessed data, steps S 102  and the subsequent steps are repeatedly executed.  
      In step S 108 , if the process has determined that there is no unprocessed data, the process ends. In other words, in the above-described process, recording data in which the additional data bits are inserted is generated.  
      Although the flowchart in  FIG. 14  shows only processing on the DC-control-bit storage frame for determining a response to additional data, for each frame other the DC-control-bit storage frame, a recording frame in which DC control bits based on digital-sum-variation measurement are set is generated and modulation thereof is performed. In addition, regarding eight bits set at positions for setting DC control bits for determining a response to additional data in the DC-control-bit storage frame for determining a response to additional data, that is, in eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , values selected in accordance with the above process are set as DC control bits. However, in frame parts other than the DC-control-bit storage frame, DC control bits based on digital-sum-variation measurement are set.  
      Positions at which DC control bits for determining a response to additional data are stored in the DC-control-bit storage frame are not limited to frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , but may be arbitrarily set.  
      In the above embodiment, all the eight bits of the user control data for determining a response to additional data are set as response-determining bits.  
      However, only part of the eight bits, for example, upper four bits may be used, as the response-determining bits. In this case, also the positions at which the DC control bits for determining a response to additional data are stored in the DC-control-bit storage frame are limited to only four positions.  
      The above embodiment describes an example of a process in which, depending on whether the bit values of the user control data for determining a response to additional data are coincident with the DC control bits in the DC-control-bit storage frame, it is determined whether the additional data component bit is “0”. However, when the bit values of the user control data for determining a response to additional data are coincident with the DC control bits in the DC-control-bit storage frame, the bit values itself of the user control data for determining a response to additional data may be set as additional data component bits.  
      In the case of the above setting, the DC-control-bit selecting unit  114  performs a process of changing the user control data (for determining a response to additional data) in response to additional data. According to the above-described construction, eight bits constituting one user control data item can be associated with the additional data.  
      Next, the configuration and playback processing of an information playback processor for performing a process of playing back an information recording medium containing the above-described additional data and content (main data) such as movie and music are described below.  
      The configuration and process of the information playback processor are described with reference to  FIG. 15 .  
      The information playback processor includes an information recording medium  401 , a pickup  403  for reading data from the information recording medium  401 , a spindle motor  402  for driving the information recording medium  401 , a servo circuit  404  for controlling the pickup  403  and the spindle motor  402 , an RF circuit unit  405  for performing signal processing, such as gain adjustment of a read signal, and generating an RF signal, a synchronization detecting unit  406  for extracting a synchronizing signal from the RF signal, a data-demodulation processing unit  407  for. executing a data demodulating process, a switch  410  for outputting only an additional data area of a read signal from the information recording medium  401  to an additional-data decoding unit  408 , an additional-data-recording-area detecting unit  411  for detecting the additional data area and controlling the switch  410 , an additional-data decoding unit  408  for executing an additional data decoding process, a data dividing unit  412  which, based on demodulated data output from the data-demodulation processing unit  407 , divides main data and user control data, an error-correcting-and-deinterleaving unit  413  for main data which performs error correction of main data and a deinterleaving process, an error-correcting-and-deinterleaving unit  414  for user control data which performs error correction of user control data and a deinterleaving process, and an additional-data error-correcting unit  409  for performing an additional-data error-correction process.  
      The content data recorded on the information recording medium  401  is, for example, encrypted content data. The additional data recorded on the information recording medium  401  is encryption-key information for use as an encryption key for encrypted content, information constituting part of the encryption-key information, encryption-key generating information such as the data (e.g., seed) required for generating an encryption key, secret information such as a password, control information such as content-playback control information or copy-control information, or other information such as content-attribute information.  
      Data read from the information recording medium  401  through the pickup  403  is processed (signal processing such as gain adjustment) in the RF circuit unit  405 , and the processed signal is input to the synchronization detecting unit  406 . The synchronization detecting unit  406  detects a synchronizing signal from the recorded signal and outputs the detected signal to the additional-data-recording-area detecting unit 411 .  
      Based on the synchronizing signal input from the synchronization detecting unit  406 , the additional-data-recording-area detecting unit  411  identifies an additional data recording area and controls the switch  410  based on the identification information. By controlling the switch  410 , a recording frame in the area required for decoding additional data, that is, an additional-data-set recording frame in which DC control bits based on the additional data are set, is input from the data-demodulation processing unit  407  to the additional-data decoding unit  408 , which executes an additional data decoding process.  
      Based on the DC-control-bit storage frame for determining a response to additional data which is input from the data-demodulation processing unit  407  through the switch  410 , and user control data for determining a response to additional data which is input from the error-correcting-and-deinterleaving unit  414  for user control data, the additional-data decoding unit  408  detects the correspondence between DC-control-bit information for determining a response to additional data and user-control-data-bit information, that is, whether both are coincident, and executes a decoding process for acquiring the additional data.  
      In other words, an additional-data-component-bit identifying process is performed in which, when the DC-control-bit information is coincident with the user-control-data-bit information, the additional data component bit=“0”, and when the DC-control-bit information is not coincident with the user-control-data-bit information, the additional data component bit=“1”.  
      As described above in the configuration of the information recording processor, in a case in which, when the DC control bits for determining a response to additional data is associated with the user control data for determining a response to additional data, that is, when there is coincidence between both, a recording process is performed with the eight bits of the user control data set as additional data component bits, the additional-data decoding unit  408  determines whether the DC control bits for determining a response to additional data is associated with the user control data for determining a response to additional data, and acquires, based on the affirmative determination, bits constituting the user control data as additional data component bits.  
      In the playback processor, when data processed by the data-demodulation processing unit  407  is a DC-control-bit storage frame for determining a response to additional data, the data of the frame is input to the additional-data decoding unit  408  through the switch  410 . The additional-data decoding unit  408  acquires specific DC control bits of the DC-control-bit storage frame and executes a process of identifying additional data component bits on the basis of determination of coincidence with the user control data bits. While the data-demodulation processing unit  407  is executing processing the DC-control-bit storage frame, the additional-data-recording-area detecting unit  411  controls the switch  410  to be on.  
      By executing similar processing based on the additional-data-set recording frame, which is intermittently input, the additional-data decoding unit  408  acquires additional data such as n-bit information used as key information, key-information generating information, content-playback control information, copy-control information, or other content-attribute information. As mentioned in the above description of the information recording processor, the additional data includes error-correcting codes. The additional data is output after the additional-data error-correcting unit  409  performs error correction.  
      When the additional data is key information for use in, for example, content decryption, it is output to a decrypting processing unit for executing a content decrypting process. When the additional data is content-playback control information, it is output to a playback control unit.  
      In addition, ordinary data other than the additional data is output from the synchronization detecting unit  406  to the data-demodulation processing unit  407 . By sequentially executing data conversion inverse to that described with reference to  FIGS. 2 and 3 , the data-demodulation processing unit  407  acquires playback data.  
      Based on demodulated data output from the data-demodulation processing unit  407 , the DCT unit  412  divides the main data and the user control data. The error-correcting-and-deinterleaving unit error-correcting-and-deinterleaving unit  413  for main data executes error correction and the deinterleaving process on the main data. The error-correcting-and-deinterleaving unit  414  for user control data executes error correction and the deinterleaving process on the user control data, and outputs the processed user control data.  
      When the output main data is, for example, encrypted content, the encrypted content is decrypted by using an encryption key generatable based on key-generating information output as additional data, and the decrypted content is output through an output unit such as a display and a speaker.  
      The configuration shown in  FIG. 15  is a schematic block diagram illustrating the configuration and process of the information playback processor according to the first embodiment of the present invention. For example, a process of acquiring a DC-control-bit storage frame for determining a response to additional data, and processes of acquiring and analyzing additional data can be executed such that a control unit, such as a CPU, executes a program describing the processes, etc. Therefore, in the information playback processor according to the first embodiment of the present invention, items of hardware which correspond to the switch  410  shown in  FIG. 15  and component elements in the other blocks shown in  FIG. 15  are not essential. On hardware including a control unit for executing processing in accordance with a predetermined program, a CPU used as a data processing unit, and a memory used for storing data and parameters, processes of acquiring and playing back additional data are executable.  
      An application of the additional data acquired by the information playback processor is described below with reference to  FIGS. 16A, 16B , and  17 .  
      As described above, the additional data is, for example, encryption-key information for use as an encryption key for encrypted content, information forming part of the encryption-key information, encryption-key generating information such as the data (e.g., a seed) required for generating an encryption key, secret information such as a password, control information such as content playback control information or copy-control information, or other information such as content-attribute information.  
       FIG. 16A  shows an example of processing in a case in which the additional data is encryption-key information for use as an encryption key for encrypted content, information forming part of the encryption-key information, or encryption-key generating information such as the data (e.g., a seed) required for generating an encryption key. The information playback processor uses the acquired encryption-key information to execute a main data decrypting process. This plays back content such as music and video. An encryption algorithm, such as DES or AES, is applied to the decrypting process.  
       FIG. 16B  shows an example of a process in a case in which the additional data is content-playback control information corresponding to content recorded as the main data. In this case, control of playback of the main data (content) is executed in accordance with the content-playback control information acquired as the additional data. In the case of playing back the content, for example, control of a playback allowable range, such as output-form control such as 5.1-channel output control, and control of an introduction part of the content, are executed in accordance with the content-playback control information.  
       FIG. 17  shows an example of processing in a case in which the additional data is secret information such as a password, and content playback is allowed by checking the password. A password  511  is input as the additional data to a secret information checking unit  512 . The secret information checking unit  512  compares the input password  511  with password information input from an external input device or the like. Only when both match each other does the secret information checking unit  512  set a switch  513  to be on. This allows the content as the main data, for example, data, such as music and video, to be played back.  
      Next, a playback process including reading of the additional data is described below with reference to  FIG. 18 . The process shown in  FIG. 18  is executed by the information playback processor shown in  FIG. 15 .  
      In step S 201 , an RF signal is generated based on the information recording medium  401 . In step S 202 , demodulating processing based on the RF signal is executed. As data in the process of demodulation, demodulated data of the DC-control-bit storage frame for determining a response to additional data is acquired.  
      The additional-data-recording-area detecting unit  411  shown in  FIG. 15  recognizes timing of demodulating the DC-control-bit storage frame, whereby the DC-control-bit storage frame is output from the data-demodulation processing unit  407  to the additional-data decoding unit  408 .  
      In addition, in step S 203 , the additional-data decoding unit  408  acquires, from the DC-control-bit storage frame input from the data-demodulation processing unit  407 , the value of DC control bits set at positions at which the DC control bits for determining a response to additional data are stored, for example, eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 . The value of DC control bits is referred to as DC bit information A.  
      In step S 204 , the additional-data decoding unit  408  acquires user control data for determining a response to additional data from the error-correcting-and-deinterleaving unit  414 . The acquired user control data is referred to as UCD bit information B.  
      In step S 205 , the additional-data decoding unit  408  determines whether the relationship “DC bit information A”=“UCD bit information B” holds.  
      When the relationship “DC bit information A”=“UCD bit information B” holds, in step S 206 , it is determined that the additional data bit=0.  
      When the relationship “DC bit information A”=“UCD bit information B” does not hold, in step S 207 , it is determined that the additional data bit=1.  
      In step S 208 , it is determined whether the end bit of the additional data has been processed. If there is an unprocessed bit, step S 202  and the subsequent steps are repeatedly executed, and the process ends when the end bit of the additional data has been processed.  
      The configuration and processing of information recording processor according to an embodiment are described below with reference to  FIG. 19 .  
      The information recording processor described below includes a mastering apparatus that is an apparatus for producing a so-called “master disk”, and includes an apparatus having an information recording medium drive, which is usable by a general user, such as a DVD (digital versatile disk) recording/playback apparatus or a personal computer. In other words, the information recording processor includes an information processing apparatus capable of recording data not only to a master disk, but also to various information recording media of recordable and rewritable types.  
      As shown in  FIG. 19 , the information recording processor includes an information recording medium  1101  on which data can be recorded, a pickup  1102  for outputting a data recording signal to the information recording medium  1101 , a spindle motor  1103  for driving the information recording medium  1101 , a servo circuit  1104  for controlling the pickup  1102  and the spindle motor  1103 , a specific-UCD-positional-information-counter-and-data-extracting circuit  1105 , an error-correcting-encoding-and-interleaving unit  1106  for main data, an additional-data recording-area control unit  1107 , a switch  1108 , a modulated data generating unit  1109 , a DC-control-bit setting unit  1110 , a recording-signal processing circuit  1111 , an error-correcting-encoding-and-interleaving unit  1112  for user control data, an ECC cluster generating unit  1113 , a DC-control-bit selecting unit  1114 , and a main-data encrypting circuit  1116 .  
      Recording data to be recorded on the information recording medium  1101  includes main data formed by substantial data of data (such as content) to be played back, and user control data (UCD) including various types of control data such as playback-control information, and additional data such as encryption-key information for use as an encryption key for encrypted content, information forming partial data of the encryption-key information, encryption-key generating information, such as the data (e.g., seed) required for generating an encryption key, secret information such as a password, or control information such as content-playback information or copy-control information.  
      The additional data is set as acquirable data based on correspondence between bit values of specific user control data and DC control bits set in the recording data.  
      Content data to be recorded on the information recording medium  101  is, for example, encrypted content data. The main data is encrypted by using an encryption key in the main-data encrypting circuit  1116 . The main-data encrypting circuit  1116  generates encryption main data by receiving, for example, a 64-bit DES (data encryption standard) encryption key, 128-bit AES (advanced encryption standard) encryption key, information of a component of the encryption key, or a seed which is encryption-key generating information, and executing block-encryption processing, such as DES algorithm or AES algorithm, on the main data, such as content data, by using an encryption key generated based on the input information.  
      The encrypted main data is input to the error-correcting-encoding-and-interleaving unit  1106 . The error-correcting-encoding-and-interleaving unit  1106  generates error-correcting codes and performs coding of the input data, and also performs interleaving processing. Details of these processes are described below.  
      The error-correcting-encoding-and-interleaving unit  1112  generates error-correcting codes and performs coding of also on the user control data including the various types of control data, such as playback-control information, and performs interleaving processing.  
      In the configuration of the second embodiment, in at least one part of the user control data, data corresponding to additional data, such as the key information for use in decrypting content, content-playback control information, or copy-control information, or data for use in additional data derivation, is stored.  
      User control data which has a possibility of storing the additional data is called “specific user control data (UCD)”. Specific user control data has two states. In one state, the specific user control data stores additional data, and in the other state, the specific user control data stores no user control data. Based on correspondence between bits (eight bits) stored in specific user control data and DC control bits set in a DC-control-bit storage frame (for determining response to specific user control data) which is included in the recording data, it is determined whether the specific user control data stores additional data. Details of this determination are described later.  
      The specific-UCD-positional-information-counter-and-data-extracting circuit  1105  includes a circuit that counts storage positions or storage-start positions of specific user control data in units of “clusters”, each of which is a constitutional unit of user control data, on the basis of disk-internal-data address information  1117 .  
      The DC-control-bit selecting unit  1114  executes bit-value selecting processing on DC control bits set in a frame (DC-control-bit storage frame for specific user control data) designated by bit information of additional-data-information storing user control data and an address representing an additional data storage position or storage-start position, which are input from the specific-UCD-positional-information-counter-and-data-extracting circuit  1105 .  
      Specifically, the component bit “0” or “1” of the additional data stored in specific user control data storing the additional data, and a DC control bit set in the DC-control-bit storage frame for specific user control data are set to be equal. In addition, in the case of specific user control data storing no additional data, DC-control-bit selecting processing is executed in order to the bit values of the specific user control data and the DC control bit set in the DC-control-bit storage frame for specific user control data are set to differ. Details of the processing are described later.  
      The ECC cluster generating unit  1113  generates ECC clusters based on the interleaving-processed main data and user control data, and the modulated data generating unit  1109  receives the ECC clusters and executes modulating on the received ECC clusters. The modulated data generating unit  1109  executes modulation based on the RLL (run length limited) (1, 7) modulation system in which modulation of two-bit data into three-bit data is basically performed.  
      In the modulation based on the (1, 7) RLL modulation system, data transformation is performed to produce modulated data in accordance with run-length limitation of (1, 7) RLL in which the number of consecutive 0&#39;s is a minimum of one and a maximum of seven. In this transformation processing, a transformation table is used. A specific example of using the transformation table is described later.  
      Based on modulated data based on the (1, 7) RLL system, a recording unit in which a synchronizing signal is set, which is called a “recording frame”, is generated and is recorded on the information recording medium  1101  through the recording-signal processing circuit  1111 .  
      The modulating processing is performed after the DC-control-bit setting unit  110  selects “0” or “1” as each DC control bit for insertion so that the absolute value of a digital sum variation (DSV) decreases at regular intervals of the input main data.  
      The digital sum variation is a DC balance index of an NRZI (nonreturn to zero change on one) transformation signal generated as a recording signal for the information recording medium  101 . Specifically, by totaling bits of a recording bit series (NRZI transformation signal), with each bit “0” as “−1”, and each bit “1” as “+1”, the total is obtained and is used as a digital sum variation. After the DC control bit “0” or “1” is selectively inserted so that the divergence of the digital sum variation from “0” is minimum, the modulating processing is performed. Details of the NRZI transformation processing are described later.  
      In an embodiment, in the DC-control-bit setting, for a selected specific recording frame, that is, a DC-control-bit storage frame for specific user control data, DC control bits in accordance with the above rule are not set, but bits selected by the DC-control-bit selecting unit  1114  are set as DC control bits. In other words, processing is executed, such as setting of the additional data component bit “0” or “1” set in the user control data and a DC control bit set in the DC-control-bit storage frame for specific user control data to be equal or differ.  
      Details of ECC-cluster setting processing and modulated-data generating processing, which are based on main data and user control data, are described below with reference to  FIGS. 20 and 21 .  
      The ECC-cluster setting processing and the modulated-data generating processing are executed by the error-correcting-encoding-and-interleaving unit  1106 , the error-correcting-encoding-and-interleaving unit  1112 , the ECC cluster generating unit  1113 , and the modulated data generating unit  1109 , which are shown in  FIG. 19 .  
      As shown in portion (a) of  FIG. 20 , the recording data is constituted by user data  1201  as main data, and user control data  1211 . The user data  1201  corresponds to the main data including the substantial data of data to be played back, such as content. The user control data  1211  includes various types of control data such as playback-control information.  
      The user data  1201  is set in 32-frame units, each consisting of 2048-byte data and 4-byte parity. The user control data  211  is formed by 32 units of 18-byte data.  
      Based on the user data  1201 , which has 32 frames by (2048+4) bytes, a data block  1202  is formed. The data block  1202  has an arrangement of 304 columns by 216 rows. One column by one row stores one-byte data (eight bits).  
      For the data block  1202 , an LDC block  1203  is generated as a data block with parity of 32 rows added in each column. Interleaving processing on the LDC block  1203  generates an LDC cluster  1204  of 152 columns by 496 rows.  
      In addition, the user control data  1211  is combined with physical address data  1221  having 16 by 9 bytes to generate an access block  1212  of 24 columns by 30 rows. After that, a BIS block  1213  is generated as a data block in which parity of 32 rows is added in each column in the access block  1212 . Interleaving of the BIS block  1213  generates a BIS cluster  1214  of 3 columns by 496 rows.  
      Portion (d) of  FIG. 21  shows data identical to that shown in portion (d) of  FIG. 20 , that is, the LDC cluster  1204  of 152 columns by 496 rows which is generated based on the user data  1201 , and the BIS cluster  1214  of 3 columns by 496 rows.  
      As shown in portion (d) of  FIG. 21 , the LDC cluster  1204  of 152 columns by 496 rows is divided into four parts I to IV in 38-column units. The BIS cluster  1214  of 3 columns by 496 rows is divided into three parts i to iii in column units. By combining the parts I to IV and the parts i to iii, the ECC cluster  1231 , shown in portion (e) of  FIG. 21 , of 155 columns by 496 rows is generated.  
      As shown in portion (f) of  FIG. 21 , the ECC cluster  1231  is set as a cluster  1232  partitioned into 28 parts  0  to  27 . Only part  0  has  25  bits, and the other parts  1  to  27  each have 45 bits. The numbers of bits, shown in portion (f) of  FIG. 21 , are values per row.  
      As shown in portion (g) of  FIG. 21 , a 20-bit synchronizing (Sync) part is set. In addition, in the parts  0  to  27  shown in portion (f) of  FIG. 21 , a one-bit DC-control-bit part is set between two parts.  
      This sets a physical cluster  233  of [1240 bits+20 bits (Sync)+(1 DC-control bit×28)=1288 bits]×496 rows. Each row of the physical cluster  1233  is used as a recording frame  1234  which is a modulated-data generating unit.  
      The DC control bits are a DC balance index of an NRZI transformation signal generated as a recording signal for the information recording medium  1101 . Specifically, by totaling bits of a recording bit series (NRZI transformation signal), with each bit “0” as “−1”, and each bit “1” as “+1”, the total is obtained and is used as a digital sum variation. After the DC control bit “0” or “1” is selectively inserted so that the divergence of the digital sum variation from “0” is minimum, the modulating processing is performed.  
      As described above, in an embodiment, in this DC control bit setting, for a selected specific recording frame, that is, a DC-control-bit storage recording frame determining a response to additional data, bit values selected by the DC-control-bit selecting unit  1114  are set as DC control bits without using DC-control-bit setting in accordance with the above rule. In other words, DC-bit setting is performed in which, in response to the additional data component bit “0” or “1”, DC control bits are set to have a bit string coincident with the bit values (eight bits) of specific user control data, or to have a bit string not coincident with the bit values. Details of this processing are described below.  
      Modulating processing on a frame in which the DC control bits, that is, the recording frame  234  shown in portion (g) of  FIG. 21  which is formed by 1288-bit data, is performed. In the modulating processing, 2-bit data is transformed into 3-bit data. This data transformation executes (1, 7) RLL data transformation that produces modulated data in accordance with run-length limitation in which the number of consecutive 0&#39;s is a minimum of one and a maximum of seven, whereby the modulated recording frame  1235  is generated.  
      The modulated recording frame  235 , shown in portion (h) of  FIG. 21 , has a total of 1932 channel bits consisting of 30 (synchronizing) channel bits (modulated data bits) and 1902 channel bits consisting of (1288−20) synchronizing bits×⅔.  
      In the data modulating processing for transformation from 2-bit data to 3-bit data in accordance with the (1, 7) RLL run-length rule, a transformation table is used. A specific example of the transformation table is shown in  FIG. 22 .  
      As shown in  FIG. 22 , the transformation table indicates correspondence between strings of modulated data bits and corresponding strings of input bits. For example, when input data is “00000000”, a corresponding string of modulated data bits is “010100100100”. When input data is “11”, if precedent modulated data bits are “xx1”, corresponding modulated data bits are “000”, and if precedent modulated data bits are “xx0”, corresponding modulated data bits are “101”.  
      By using this transformation table to execute transformation from 2-bit data into 3-bit data, modulated data bits is generated in accordance with the (1, 7) RLL run-length rule.  
      Referring back to  FIG. 19 , the configuration and processing of the information recording processor according to the second embodiment of the present invention is continuously performed below.  
      In the modulated data generating unit  1109  shown in  FIG. 19 , the modulated data generating processing, described with reference to FIGS.  20  to  22 , is executed, and the recording-signal processing circuit  1111  generates a recording signal based on the generated modulated data.  
      The recording-signal processing circuit  1111  generates a NRZI signal in which the polarity of each pulse is inverted in response to the value “0” or “1” of the modulated data generated in the modulated data generating unit  1109 . The recording-signal processing circuit  1111  records the NRZI signal as a recording signal on the information recording medium  1101 .  
       FIG. 23A  shows the configuration of the recording-signal processing circuit  1111  in which processing for generating the NRZI signal as a recording signal is executed. Channel bits output from the modulated data generating unit  1109 , which are modulated data bits, are input to the recording-signal processing circuit  1111 , which includes an NRZ transformation unit  1121 , an XOR  1122 , and a delay unit  1123 . In  FIG. 23B , portion (a) shows channel bits, portion (b) shows an output signal from the NRZ transformation unit  121 , and portion (c) shows NRZI transformed pulses which are finally output as a recording signal from the recording-signal processing circuit  1111 . The recording signal is output to the pickup  1102 , and recording information is recorded on the information recording medium  1101  under the control of a servo circuit  1104 .  
      In the construction of the second embodiment, additional data, such as key information for use in decrypting content, content-playback control information, and copy-control information, is stored in specific user control data.  
      For example, the 8-bit value of specific user control data is set as a component bit value of key information for use in decrypting content, content-playback control information, copy-control information, and the like.  
      When the eight bits of the specific user control data are equal to the values of eight DC control bits included in the DC-control-bit storage frame for specific user control data, the eight bits of the specific user control data are additional data component bits. When the eight bits of the specific user control data are not equal, they are not additional data component bits.  
      In data recording, when specific user control data, that is, eight bits of specific user control data are additional data such as encryption-key information, the values of eight DC control bits included in a DC-control-bit storage frame for specific user control data are adjusted to be equal to the eight bit values of specific user control data before a recording frame is set. When the eight bits of specific user control data are not additional data such as encryption-key information, the values of eight DC control bits included in a DC-control-bit storage frame for specific user control data are adjusted to be not equal to the eight bit values of specific user control data before a recording frame is set and recorded.  
      By performing comparison with the values of eight DC control bits included in the DC-control-bit storage frame for specific user control data, the information playback processor for executing playback of content and playback of additional data determines whether the eight bits of specific user control data are information of bits constituting additional data. Specifically, when the eight bit values of specific user control data are equal to the values of eight DC control bits included in the DC-control-bit storage frame for specific user control data, it is determined that the eight bits of the specific user control data are information of bits constituting additional data. When eight bit values of specific user control data are not equal, it is determined that the eight bits of the specific user control data are not information of bits constituting additional data.  
      When modulation of the DC-control-bit storage recording frame for specific user control data is executed in the modulated data generating unit  1109 , the additional-data recording-area control unit  1107  shown in  FIG. 19  controls the switch  1108  to be on, so that the DC control bit value selected in the DC-control-bit selecting unit  1114  is output to the modulated data generating unit  1109 .  
      At DC-control-bit setting positions for additional data in the DC-control-bit storage recording frame for specific user control data, the modulated data generating unit  1109  sets, not DC control bits having bit values determined based on the above DSV measurement, but the DC control bit values selected by the DC-control-bit selecting unit  1114 .  
      The configuration shown in  FIG. 19  is shown in the form of a schematic block diagram illustrating the configuration and processing of the information recording processor according to an embodiment. For example, processing, such as control processing for DC control bits to be set for specific user control data, can be executed such that a controller, such as a central processing unit, executes a program describing a processing sequence. Accordingly, in the information recording processor according to the first embodiment, hardware corresponding to the switch and other component blocks shown in  FIG. 19  is not essential. The processing for generating the recording frame is executable on hardware including a CPU, which serves as a controller for executing processing in accordance with a predetermined program, and as a data processor, and a memory as a means of storing parameters, and the like.  
      Additional data is encryption-key information for use as an encryption key for encrypted content, information forming partial data of the encryption-key information, encryption-key generating information, such as the data (e.g., seed) required for generating an encryption key, secret information, such as a password, control information of various types, such as content-playback control information ad copy-control information, or a bit string of data (e.g., “0, 0, 0, 1, 0, 0, 0, . . . ”) forming content attribute information. This bit string includes error-correcting codes set for the additional data in the additional-data error-correcting encoding unit  1105 . In the first embodiment of the present invention, bit information forming the additional data bit string is set by the above-described configuration.  
      In other words, by setting, in a DC-control-bit storage frame for specific user control data, a DC-control-bit string coincident with eight bits of specific user control data, the set eight bits are used as component bits of encryption-key generating information, secret information such as a password, control information such as copy-forgery-inhibited-pattern-image printing-setting information or copy-control information, or content-attribute information.  
      Specifically, when “specific user control data”=“DC control bits for specific user control data, “8 bits constituting specific user control data”=“additional data component bits”.  
      When “specific user control data”≠“DC control bits for specific user control data, “8 bits constituting specific user control data”≠“additional data component bits”.  
      The configuration of additional data in the second embodiment of the present invention is described below.  
       FIG. 24  shows details of the BIS block  1213  and BIS cluster  1214  generated based on the user control data  1211  in the modulated data generating processing described with reference to  FIGS. 20 and 21 .  
      As described with reference to  FIGS. 20 and 21 , by combining the physical address data  221  of 16×9 bytes with the user control data  1211 , the access block  1212  of 24 columns by 30 rows is generated. After that, the BIS block  1213  is generated as a data block in which parity of 32 rows is added in each column. The generated block  1213  is shown in portion (A) of  FIG. 24 .  
      By performing interleaving of the BIS block  1213 , the BIS cluster  1214  of 3 columns by 496 rows is generated. The generated BIS cluster  1214  is shown in portion (B) of  FIG. 24 .  
      As shown in portion (B) of  FIG. 24 , a 3-row physical address, 12-row user control data (UCD), and 16-row parity constitute one unit of 3 columns×31 rows. Sixteen units  0  to  15  constitute the BIS cluster  1214  of 3 columns×496 rows.  
       FIG. 25  shows details of the configuration in storage of the BIS block  1213 .  FIG. 26  shows a detailed arrangement of user control data in the BIS cluster  1214 .  
      As shown in portion (A 1 ) of  FIG. 25 , the BIS block  1213  is constituted by a physical address of 24 columns×6 rows, user control data (UCD) of 24 columns×24 rows, and parity of 24 columns×32 rows.  
      As shown in portion (A 2 ) of  FIG. 25 , the user control data (UCD) of 24 columns×24 rows is constituted by 576 (24×24) user-control-data-forming data items “UC 0,0” to “UC 17,31”, each data item having one byte (8 bits). By performing interleaving of the BIS block  213  having the user control data arrangement of 24 columns×24 rows, the BIS cluster  1214  is generated.  
      As shown in portion (B 1 ) of  FIG. 26 , the BIS cluster  1214  has an arrangement of 3 columns×496 rows. A 3-row physical address and 12-row user control data (UCD), and 16-row parity constitute one unit of 3 columns×31 rows. Sixteen units  0  to  16  constitute the BIS cluster  1214  of 3 columns×496 rows.  
      Portion (B 2 ) of  FIG. 26  shows user control data of 3 columns×12 rows in unit  0 . The user control data in unit  0  stores 36 (3×12) user-control-data-forming data items “UC 0,12” to “UC 4,25”, each data item having one byte. Each of sixteen units  0  to  15  stores 36 (3×12) user-control-data-forming data items. Accordingly, the BIS cluster  1214  stores a total of (36×16)  576  user-control-data-forming data items.  
      The user-control-data-forming data items stored in the BIS cluster  1214  are arranged in distributed form in units  0  to  15  in the BIS cluster  214  by performing the interleaving of the BIS block  213  shown in portion (A 2 ) of  FIG. 25 .  
      The user control data is set as a storage area for storing various types of information, such as content-playback control information, and its part is set as a reserve area or the like, in which arbitrary data can be written.  
      As shown in  FIG. 27 , each column of the BIS cluster  1214  including the user control data is inserted among four-divided data items I to IV of the LDC cluster  1204  set based on the user data such as content (as described with reference to  FIGS. 20 and 21 ), whereby the ECC cluster  1231  is generated.  
      As shown in  FIG. 27 , the ECC cluster  1231  is set as a cluster a BIS cluster of 3 columns×496 rows is combined with an LDC cluster of 152 columns×496 rows.  
      As described with reference to  FIG. 24 , one of the physical address, the user control data, and the parity is set as each column of the BIS cluster. Therefore, the BIS cluster (i, ii, iii) included in each of 496 rows of the ECC cluster  231  is a type of data among a physical address, user control data, and parity.  
      In an embodiment, as shown in  FIG. 28 , a specific row selected from 496 rows constituting the ECC cluster  231  is set as a DC-control-bit storage frame  1311  for specific user control data.  
      When specific user control data, for example, the data item “UC x,y” of the data items “UC 0,0” to “UC 17,31” shown in portion (A 2 ) of  FIG. 25 , the values of eight DC control bits included in the DC-control-bit storage frame  1311  for specific user control data are set as bit values matching 8-bit data stored in the data item “UC x,y”, that is, correlated bit values.  
      As shown in  FIG. 28 , in a specific-user-control-data setting frame  1321 , specific user control data, that is, specific user control data “UC a,b” storing 8-bit data, is stored in user-control-data area (i)  1322 , which is a BIS cluster setting position.  
      A case in which the specific user control data “UC a,b” stores, for example, “00111101” as 8-bit data is described below.  
      When the eight bits “00111101” are additional data component bits, among the DC control bits stored in the DC-control-bit storage frame  1311  for specific user control data, eight DC control bits are adjusted to be equal to the eight bits “00111101” of the specific user control data “UC a,b”.  
      When the eight bits “00111101” of the specific user control data “UC a,b” are not additional data component bits, among the DC control bits stored in the DC-control-bit storage frame  1311  for specific user control data, eight DC control bits are adjusted to have different values from the values of the eight bits “00111101” of the specific user control data “UC a,b”.  
      In the example shown in  FIG. 28 , in one cluster, one DC-control-bit storage frame  1311  for specific user control data is set and the specific user control data “UC x,y” is set in one cluster. However, in order to set a plurality of DC-control-bit storage frames for specific user control data in one cluster, and associating the set frames with different specific user control data items “UC a,b”, “UC c,d”, and “UC e,f”, n specific user control data items may be set in one cluster, and additional data component bits composed of n×8 bits may be stored in one cluster.  
      In the configuration shown in  FIG. 19 , information of component bits of specific user control data is input to the DC-control-bit selecting unit  1114 . For example, in the above example, the 8-bit data “00111101” of the specific user control data item “UC a,b” is input.  
      The DC-control-bit selecting unit  1114  selects the values of additional data component bits so that, when the component bits of the specific user control data are additional data component bits, among the DC control bits stored in the DC-control-bit storage frame  1311  for specific user control data, eight DC control bits are adjusted to have values equal to the values of eight bits “00111101” of the specific user control data item “UC a,b”, and so that the component bits of the specific user control data are not additional data component bits, among the DC control bits stored in the DC-control-bit storage frame  1311  for specific user control data, eight DC control bits are adjusted to have values different from the values of eight bits “00111101” of the specific user control data item “UC a,b”. The DC-control-bit selecting unit  1114  outputs information the selected values of the DC control bits to the modulated data generating unit  1109  through the switch  1108 .  
      The modulated data generating unit  1109  executes generating a DC-control-bit storage frame (for specific user control data) having the DC control bit values input from the DC-control-bit selecting unit  1114 , and modulating the DC-control-bit storage frame.  
      The additional-data recording-area control unit  1107  controls the switch  1108  to be on with modulating-processing executing timing associated with the DC-control-bit storage frame for specific user control data so that the selected bit information from the DC-control-bit selecting unit  1114  is output to the modulated data generating unit  1109 .  
      When executing processing for generating a frame other then the DC-control-bit storage frame for user control data and modulating the frame, the switch  1108  is controlled to be off. The DC-control-bit setting unit  1110  executes normal DC-control-bit setting processing, that is, DC-control-bit setting processing based on digital-sum-variation measurement.  
      As shown in  FIG. 28 , in a DC-control-bit storage frame  331  for determining a response to additional data, synchronizing bits (20 bits) are set. In each of frame parts # 0  to # 27  each having 45 bits, one DC control bit is set.  
      As described above, the DC-control-bit storage frame  1331  stores a total of 28 DC control bits in frame parts # 0  to # 27 . Among these DC control bits, eight DC control bits are set as DC control bits which are used to determine coincidence or non-coincidence with specific user control data.  
      The other DC control bits are set as DC control bits having values determined based on the normal bit-value setting processing, that is, digital-sum-variation measurement.  
      Details of the configuration of the DC-control-bit storage frame for specific user control data are described below with reference to  FIGS. 29A and 29B .  
       FIG. 29A  shows a detailed configuration of the DC-control-bit storage frame for specific user control data in the case of “specific user control data”=“additional data component bits”, and  FIG. 29B  shows a detailed configuration of the DC-control-bit storage frame for specific user control data in the case of “specific user control data”≠“additional data component bits”.  
      In this example shown in  FIGS. 29A and 29B , the case of “component bits of specific user control data”=“00111101” is shown.  
      When “specific user control data”=“additional data component bits”, the eight bits “00111101” are stored at DC-control-bit storing positions selected from the DC-control-bit storage frame for specific user control data.  
      Here, the DC-control-bit storage positions in the DC-control-bit storage frame for specific user control data are eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 . The above DC-control-bit storage positions are examples. The DC control bits may be set at arbitrary positions. When valid playback-processing program is executed, from each bit position, each DC control bit is read. It is determined whether the read DC control bit is coincident with specific user control data, and the bit value of additional data is acquired. Details of the playback processing are described later.  
       FIG. 29B  shows the case of “specific user control data”≠“additional data component bits”, and Bits different from the eight bits “00111101” are stored at the DC-control-bit storage positions selected from the DC-control-bit storage frame for specific user control data.  
      In other words, bits different from the eight bits “00111101” are stored at the DC-control-bit storage positions in a DC-control-bit storage frame for specific user control data, that is, frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 . An arbitrary bit string may be used as the above eight DC control bits if different from the bits “00111101”. In the example shown in  FIG. 29B , the bits “10010100” are stored at DC-control-bit storage positions in the DC-control-bit storage frame  1352  for specific user control data, that is, frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 .  
      As described above, in an embodiment, part of user control data included in data to be recorded on the information recording medium is set as specific user control data. Depending on whether information of bits in the specific user control data is used as additional data component bits, DC control bits set in DC-control-bit storage frame for specific user control data are controlled to be coincident or not coincident with corresponding user control data. By using DC-control-bit storage frames, additional data information, such as encryption-key information, is embedded.  
      As  FIG. 30  shows, in a case in which DC-control-bit information (8 bits) in the DC-control-bit storage frame for specific user control data is represented by A, and bit information of specific user control data is represented by B, if A=B, “bit information of specific user control data”=“additional data component bits”, and if A≠B, “bit information of specific user control data”≠“additional data component bits”. Under the these conditions, data recording and playback are executed.  
      Next, a method of selecting and setting which user control data item as specific user control data, that is, a method of selecting a user control data item in which additional data is to be stored, is described below.  
      As described above with reference to  FIGS. 25 and 26 , in one cluster, many user control data items “UC 0,0” to “UC 17,31”, each item storing 8-bit data, are stored. From among the user control data items, one or plural items are selected as specific user control data items.  
      In one technique of selecting specific user control data, a user control data item common to all clusters, for example, the user control data item “UC 0,0”, is set in common as specific user control data.  
      In addition, in another technique, a plurality of user control data items, such as “UC 0,0”, “UC 0,5”, and “UC 0,10”, are selected at predetermined intervals and are all set as specific user control data items.  
      However, as described above, in a case in which common user control data items, that is, “UC 0,0” and “UC 0,5”, are set as specific user control data items in all clusters, if it is found, in a certain cluster, which of user control data items is used as a specific user control data item, by acquiring identical user control data items from all the clusters, a possibility that secret information may leak out can be generated. Accordingly, it is preferable to employ a technique of setting different specific user control data items for the clusters.  
      The technique of setting different specific user control data items for the clusters is described below with reference to  FIG. 31 .  
      On the information recording medium  1101 , data is recorded in units of physical sectors, which are predetermined data-recording units, and physical sector numbers are assigned to the physical sectors, as shown in  FIG. 31 .  
      The physical sectors numbers are data of 32 bits from PS 0  to PS 31 . The physical sector numbers PS 0  to PS 31 , composed of 32 bits, are associated with address unit numbers AU 0  to AU 31  serving as address information.  
      In address units AU 31  to AU 27 , the bit values “0000” are recorded, and in the address units AU 26  to AU 24 , a layer number is recorded. In address units AU 23  to AU 5 , a cluster number is recorded, and address unit AU 4  to AU 1  are used to perform counting in the inside of each cluster, and in address unit AU 0 , “0” is set.  
      User control data is formed in units of clusters. As described above with reference to  FIGS. 25 and 26 , in one cluster, the user control data items “UC 0,0” to “UC 17,31” are stored, each item storing 8-bit data.  
      Here, as specific cluster identification information, bit data of address units AU 23  to AU 5  having the cluster number recorded therein is used. As shown in  FIG. 31 , for example, the four bits of address units AU 12  to AU 9  are used as a specific-user-control-data (specific UCD) row information (address), and the four bits of address units AU 8  to AU 5  are used as a specific-UCD column information (address).  
      In a cluster in which lower eight bits (AU 12  to AU 5 ) of the cluster number are “00000000”, specific user control data is “UC 0000,0000”, that is, “UC 0,0”. In addition, a cluster in which lower eight bits (AU 12  to AU 5 ) of the cluster number are “00000001”, specific user control data is “UC 0000,0001”, that is, “UC 0,1”.  
      By employing the above setting, in clusters, different user control data items can be set as specific user control data items.  
      In the case of setting a plurality of specific user control data items in one cluster, intervals at which specific user control data items are determined beforehand. For example, user control data items at intervals of five columns are set as specific user control data items.  
      In the case of setting user control data items at intervals of five columns as specific user control data items, in clusters in which lower eight bits (AU 12  to AU 5 ) of the cluster number are “00000000”, specific user control data items are set as “UC 0,0”, “UC 0,5”, “UC 0,10”, etc. In clusters in which lower eight bits (AU 12  to AU 5 ) of the cluster number are “00000001”, specific user control data items are set as “UC 0,1”, “UC 0,6”, “UC 0,11”, and the like.  
      By employing the above-described setting of specific user control data, specific user control data items can be set at different positions in the clusters. This realizes a system having high resistance to leaking of secret information.  
      Next, processing for recording, on a recording medium (disk)  1361 , specific user control data and a DC-control-bit storage frame for specific user control data is described below with reference to  FIG. 32 .  
      On the recording medium (disk)  1361 , main data such as content, and plural ECC clusters (see  FIG. 21 ) generated based on user control data (UCD), such as control information, are set. Recording-data generating processing is executed in each cluster unit. A recording frame having DC control bits set therein is set, and a recording signal based on the recording frame is generated and recorded.  
      For example, in ECC cluster-A  1371 , a plurality of specific user control data items are set. It is assumed that “the lower eight bits of the cluster number of ECC cluster-A  1371 ”=00000000.  
      ECC cluster-A  1371  includes “UC 0,0” as a first specific UCD (user-control-data) item  1381 - 1 , “UC 0,5” as a second specific UCD item  1381 - 2 , and “UC 0,10” as a third specific UCD item  1381 - 3 .  
      In this case, by determining whether each specific UCD item is coincident with DC control bits in a DC-control-bit storage frame for specific user control data, each specific UCD item is identified as additional data component bits.  
      For example, the first specific UCD item “UC 0,0”  1381 - 1  is compared with eight DC control bits in a corresponding DC-control-bit storage frame  1391  for specific user control data, for example, the eight DC control bits in frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , as described above with reference to  FIG. 29 .  
      When “8 bits of the specific UCD item “UC 0,0”  1381 - 1 ”=“8 DC control bits in the DC-control-bit storage frame  1391 - 1 ”, the eight bits of the specific UCD item “UC 0,0”  1381 - 1  are additional data component bits.  
      The second specific UCD item “UC 0,5”  1381 - 2  is compared with eight DC control bits in a corresponding DC-control-bit storage frame  1391 - 2  for specific user control data.  
      When “8 bits of the second specific UCD item “UC 0,5”  1381 - 2 ”≠“8 bits in the DC-control-bit storage frame  1391 - 2  for specific user control data”, it is determined that the 8 bits of the second specific UCD item “UC 0,5”  1381 - 2  are not additional data component bits.  
      The third specific UCD item “UC 0,10”  1381 - 3  is compared with eight DC control bits in a corresponding DC-control-bit storage frame  1391 - 3  for specific user control data.  
      When “8 bits of the third specific UCD item “UC 0,10”  1381 - 3 ”≠“8 DC control bits in the corresponding DC-control-bit storage frame  1391 - 3  for specific user control data, it is determined that the 8 bits of the third specific UCD item “UC 0,10”  1381 - 3  are additional data component bits.  
      Subsequently, similarly, a plurality of specific user control data items are extracted from ECC cluster-A  1371 , and from among the extracted items, only those coincident with the 8 DC control bits in the DC-control-bit storage frame for specific user control data are extracted as additional data items.  
      Assuming that ECC cluster-B  1372  has a cluster number whose lower 8 bits=“00000001”, ECC cluster-B  1372  includes “UC 0,1” as a first specific UCD item  1382 - 1 , and “UC 0,6” as a second specific UCD item  1382 - 2 .  
      The first specific UCD item “UC 0,1”  1382 - 1  is compared with 8 DC control bits in a corresponding DC-control-bit storage frame  1392 - 1  for specific user control data.  
      When “8 bits of the first specific UCD item “UC 0,1”  1382 - 1 ”=“8 DC control bits in the DC-control-bit storage frame  1392 - 1  for specific user control data”, the 8 bits of the first specific UCD item “UC 0,1”  1382 - 1 ” are additional data component bits.  
      The second specific UCD item “UC 0,6”  1382 - 2  is compared with 8 DC control bits in a corresponding DC-control-bit storage frame  1392 - 2  for specific user control data.  
      When “8 bits of the second specific UCD item “UC 0,6”  1382 - 2 ”≠“8 DC control bits in a corresponding DC-control-bit storage frame for specific user control data”, it is determined that the 8 bits of the second specific UCD item “UC 0,6”  1382 - 2  are not additional data component bits.  
      As described above, setting positions of specific user control data items are set to differ in clusters recorded on the disk  1361 , and determination of whether a specific user control data item is additional data component bits is performed depending on whether the specific user control data item is coincident with DC control bits in a corresponding DC-control-bit storage frame for specific user control data. This enables recording of additional data having high difficulty in analysis.  
      The additional-data recording-area control unit  1107  shown in  FIG. 19  identifies a DC-control-bit storage frame for specific user control data on the basis of information set beforehand. When the modulated data generating unit  1109  performs processing of modulating the DC-control-bit storage frame, by changing over the switch  1108 , the additional-data recording-area control unit  1107  allows the DC-control-bit selecting unit  1114  to output the set values of DC control bits for specific user control data to the modulated data generating unit  1109 .  
      Bit information of specific user control data is input to the DC-control-bit selecting unit  1114 .  
      When “bit information of specific user control data”=“additional data component bits”, the DC-control-bit selecting unit  1114  selectively outputs, to the modulated data generating unit  1109 , bit values coincident with the bit information of the specific user control data.  
      When “bit information of specific user control data”≠“additional data component bits”, the DC-control-bit selecting unit  1114  selectively outputs, to the modulated data generating unit  1109 , bit values which are not coincident with the bit information of the specific user control data.  
      Based on the bit values input from the DC-control-bit selecting unit  1114 , the modulated data generating unit  1109  generates a recording frame by setting the input bit values at specific positions for setting DC control bits for specific user control data in a DC-control-bit storage frame for specific user control data, and performs modulating processing.  
      Next, an additional data recording process executed in the information recording processor according to the second embodiment of the present invention is described below with reference to  FIG. 33 .  
      In step S 1101 , user control data is input. As described above, the user control data is constituted by a plurality of user control data items (“UC 0,0” to “UC 17,31”), each item including 8-bit data.  
      In step S 1102 , based on address positional information, that is, specific bits of an address unit corresponding to a physical sector number as described with reference to  FIG. 31 , in other words, some component bits of a cluster number, Row-position information and column-position information are acquired, and user control data corresponding to the acquired information is identified and acquired as specific user control data.  
      In step S 1103 , it is determined whether the acquired specific user control data stores additional data. The additional data is encryption-key information for use as an encryption key for encrypted content, information forming part of the encryption-key information, encryption-key generating information such as the data (e.g., a seed) required for generating an encryption key, secret information such as a password, control information such as content playback control information or copy-control information, or other information.  
      The information required to determine whether the acquired specific user control data stores additional data is externally input to the apparatus by the user beforehand.  
      When the specific user control data selected is user control data storing additional data, the process proceeds to step S 1104 , DC control bits set in the DC-control-bit storage frame for specific user control data, for example, eight bits set in eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , are set to have values coincident with the bit values of the specific user control data acquired in step S 1102 .  
      In step S 1103 , if the process has determined that the selected specific user control data is not user control data storing additional data, the process proceeds to step S 1105 . the DC control bits set in the DC-control-bit storage frame for specific user control data, for example, eight bits set in eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24  are set to have values which are not coincident with the bit values of the specific user control data acquired in step S 1102 .  
      Next, the process proceeds to step S 1106 , and executes processing of modulating the DC-control-bit storage frame for specific user control data.  
      In step S 1107 , it is determined whether processing on all items of the specific user control data in the same cluster has finished. If the processing has not finished yet, the process proceeds to step S 1108 . In step S 1108 , the next specific user control data is acquired and processing in steps S 1103  to S 1106  is repeatedly executed. The acquisition of the next specific user control data in step S 1108  is executed, for example, when the first specific user control data item in a cluster to be processed is “UC 0,0”, as processing in which “UC 0,5” is acquired as the next user control data item, with the column-position information incremented by a predetermined value.  
      If the process has affirmatively determined in step S 1107 , it proceeds to step S 1109 , and it is determined whether superimposition of additional data has finished. If there is unprocessed data, step S 1102  and the subsequent steps are repeatedly executed.  
      Determination of no unprocessed data in step S 1109  terminates the process. In other words, in the process, which has been described, recording data in which additional data bits are inserted is generated.  
      Although the flowchart shown in  FIG. 33  shows only processing on the DC-control-bit storage frame for specific user control data, for each frame other than the DC-control-bit storage frame, a recording frame in which DC control bits are set based digital sum variation measurement is generated and modulated. In addition, regarding eight bits set at positions for setting DC control bits for specific user control data in the DC-control-bit storage frame for determining a response to additional data, that is, in eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , values selected in accordance with the above process are set as DC control bits. However, in frame parts other than the DC-control-bit storage frame, DC control bits based on digital-sum-variation measurement are set.  
      Positions at which DC control bits for specific user control data are stored in the DC-control-bit storage frame are not limited to frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , but may be arbitrarily set.  
      In an embodiment, all the eight bits of the specific user control data are set or not set as additional data. However, only part of the eight bits, for example, upper four bits may be used as bit data of additional data.  
      In an embodiment, depending on whether the bit valued of specific user control data are coincident with DC control bits for determining response to specific user control data in the DC-control-bit storage frame for specific user control data, it is determined whether component bits of the specific user control data are additional data component bits. However, when the bit values of the specific user control data are coincident with the DC control bits for determining response to specific user control data, the additional data component bit may be set to be “1”. When both are not coincident, the additional data component bit may be set to be “0”. Alternatively, converse setting may be performed.  
      Next, the configuration and playback processing of an information playback processor for performing a process of playing back an information recording medium containing the above-described additional data and content (main data) such as movie and music are described below.  
      The configuration and process of the information playback processor are described with reference to  FIG. 34 .  
      The information playback processor includes an information recording medium  1401 , a pickup  1403  for reading data from the information recording medium  1401 , a spindle motor  1402  for driving the information recording medium  1401 , a servo circuit  1404  for controlling the pickup  1403  and the spindle motor  1402 , an RF circuit unit  1405  for performing signal processing, such as gain adjustment of a read signal, and generating an RF signal, a synchronization detecting unit  1406  for extracting a synchronizing signal from the RF signal, a data-demodulation processing unit  1407  for executing a data demodulating process, a switch  1410  for outputting only an additional data area of a read signal from the information recording medium  1401  to an additional-data decoding unit  1408 , an additional-data-recording-area detecting unit  1411  for detecting the additional data area and controlling the switch  1410 , an additional-data decoding unit  1408  for executing an additional data decoding process, a data dividing unit  1412  which, based on demodulated data output from the data-demodulation processing unit  1407 , divides main data and user control data, an error-correcting-and-deinterleaving unit  1413  for main data which performs error correction of main data and a deinterleaving process, an error-correcting-and-deinterleaving unit  1414  for user control data which performs error correction of user control data and a deinterleaving process, and a specific-UCD-positional-counter-and-data-extracting circuit  1416  which acquires the disk internal address information  1415  (see  FIG. 31 ) and calculates the position of user control data storing additional data, that is, the position of specific user control data, and which executes predetermined incrementing processing to selectively acquire the specific user control data.  
      The content data recorded on the information recording medium  1401  is, for example, encrypted content data. The additional data recorded on the information recording medium  1401  is encryption-key information for use as an encryption key for encrypted content, information constituting part of the encryption-key information, encryption-key generating information such as the data (e.g., seed) required for generating an encryption key, secret information such as a password, control information such as content-playback control information or copy-control information, or other information such as content-attribute information.  
      Data read from the information recording medium  1401  through the pickup  1403  is processed (signal processing such as gain adjustment) in the RF circuit unit  1405 , and the processed signal is input to the synchronization detecting unit  1406 . The synchronization detecting unit  1406  detects a synchronizing signal from the recorded signal and outputs the detected signal to the additional-data-recording-area detecting unit  1411 .  
      Based on the synchronizing signal input from the synchronization detecting unit  1406 , the additional-data-recording-area detecting unit  1411  identifies a recording area of the DC-control-bit storage frame for specific user control data and controls the switch  1410  based on the identification information. By controlling the switch  1410 , a recording frame in the area required for decoding additional data, that is, the DC-control-bit storage frame for specific user control data, is input from the data-demodulation processing unit  1407  to the additional-data decoding unit  1408 , which executes an additional data decoding process.  
      The additional-data decoding unit  1408  receives a DC-control-bit storage frame for specific user control data from the data-demodulation processing unit  1407  through the switch  1410 , and specific user control data from the specific-UCD-positional-counter-and-data-extracting circuit  1416 . The additional-data decoding unit  1408  compares the DC control bits for specific user control data and the bit values of the specific user control data, and executes processing of acquiring only coincident ones as additional data component bits.  
      The specific-UCD-positional-counter-and-data-extracting circuit  1416  acquires the disk-internal-data address information  1415  (see  FIG. 31 ) and calculates the position of user control data storing additional data, that, specific user control data. In addition, the specific-UCD-positional-counter-and-data-extracting circuit  1416  executes predetermined incrementing processing to selectively acquire the specific user control data.  
      For items of the specific user control data sequentially input from the specific-UCD-positional-counter-and-data-extracting circuit  1416 , the additional-data decoding unit  1408  selects only those storing additional data, and acquires additional data based on the bit information of those storing additional data.  
      In other words, only when DC-control-bit information for determining response to specific user control data is coincident with the bit information of specific user control data does the additional-data decoding unit  1408  determines that bit information stored in the specific user control data is additional data component bits. Based on the bit information, the additional-data decoding unit  1408  acquires the additional data.  
      In the playback processor, when data to be processed in the data-demodulation processing unit  1407  is a DC-control-bit storage frame for specific user control data, data of the frame is input to the additional-data decoding unit  1408  through the switch  1410 . The additional-data decoding unit  1408  acquires specific DC control bits in the DC-control-bit frame for determining response, and executes, based on determination of correspondence with the specific user control data bits, processing of determining whether the specific user control data is additional data component bits. The additional-data-recording-area detecting unit  1411  controls the switch  1410  to be one when the data-demodulation processing unit  1407  executes processing of the DC-control-bit storage frame for specific user control data.  
      By executing similar processing based an intermittently-input DC-control-bit storage frame (for specific user control data) and specific user control data, the additional-data decoding unit  1408  acquires additional data such as n-bit information used as key information, key-information generating information, content-playback control information, copy-control information, or other content-attribute information.  
      When the additional data is key information for use in, for example, content decryption, it is output to a decrypting processing unit for executing a content decrypting process. When the additional data is content-playback control information, it is output to a playback control unit.  
      In addition, ordinary data other than the additional data is output from the synchronization detecting unit  1406  to the data-demodulation processing unit  1407 . By sequentially executing data conversion inverse to that described with reference to  FIGS. 20 and 21 , the data-demodulation processing unit  1407  acquires playback data.  
      Based on demodulated data output from the data-demodulation processing unit  1407 , the DCT unit  1412  divides the main data and the user control data. The error-correcting-and-deinterleaving unit error-correcting-and-deinterleaving unit  1413  for main data executes error correction and the deinterleaving process on the main data. The error-correcting-and-deinterleaving unit  1414  for user control data executes error correction and the deinterleaving process on the user control data, and outputs the processed user control data.  
      When the output main data is, for example, encrypted content, the encrypted content is decrypted by using an encryption key generatable based on key-generating information output as additional data, and the decrypted content is output through an output unit such as a display and a speaker.  
      The configuration shown in  FIG. 34  is a schematic block diagram illustrating the configuration and process of the information playback processor according to the second embodiment of the present invention. For example, a process of acquiring a DC-control-bit storage frame for specific user control data, and processes of acquiring and analyzing additional data can be executed such that a control unit, such as a CPU, executes a program describing the processes, etc. Therefore, in the information playback processor according to an embodiment, items of hardware which correspond to the switch  1410  shown in  FIG. 34  and component elements in the other blocks shown in  FIG. 34  are not essential. On hardware including a control unit for executing processing in accordance with a predetermined program, a CPU used as a data processing unit, and a memory used for storing data and parameters, processes of acquiring and playing back additional data are executable.  
      An application of the additional data acquired by the information playback processor is described below with reference to  FIGS. 35A, 35B  and  36 .  
      As described above, the additional data is, for example, encryption-key information for use as an encryption key for encrypted content, information forming part of the encryption-key information, encryption-key generating information such as the data (e.g., a seed) required for generating an encryption key, secret information such as a password, control information such as content playback control information or copy-control information, or other information such as content-attribute information.  
       FIG. 36A  shows an example of a process in a case in which the additional data is encryption-key information for use as an encryption key for encrypted content, information forming part of the encryption-key information, or encryption-key generating information such as the data (e.g., a seed) required for generating an encryption key. The information playback processor uses the acquired encryption-key information to execute a main data decrypting process. This plays back content such as music and video. An encryption algorithm, such as DES or AES, is applied to the decrypting process.  
       FIG. 35B  shows an example of a process in a case in which the additional data is content-playback control information corresponding to content recorded as the main data. In this case, control of playback of the main data (content) is executed in accordance with the content-playback control information acquired as the additional data. In the case of playing back the content, for example, control of a playback allowable range, such as output-form control such as 5.1-channel output control, and control of an introduction part of the content, are executed in accordance with the content-playback control information.  
       FIG. 36  shows an example of a process in a case in which the additional data is secret information such as a password, and content playback is allowed by checking the password. A password  1511  is input as the additional data to a secret information checking unit  1512 . The secret information checking unit  1512  compares the input password  1511  with password information input from an external input device or the like. Only when both match each other does the secret information checking unit  1512  set a switch  1513  to be on. This allows the content as the main data, for example, data, such as music and video, to be played back.  
      Next, a playback process including reading of the additional data is described below with reference to  FIG. 37 . The process shown in  FIG. 37  is executed by the information playback processor shown in  FIG. 34 .  
      In step S 201 , positional information of specific user control data is acquired based on the address information (see  FIG. 31 ) written in the disk  1401 . In step S 202 , demodulated data of a DC-control-bit storage frame for specific user control data is acquired. The additional-data-recording-area detecting unit  1411  shown in  FIG. 34  recognizes timing of demodulating the DC-control-bit storage frame for specific user control data, whereby the DC-control-bit storage frame for specific user control data is output from the data-demodulation processing unit  1407  to the additional-data decoding unit  1408 .  
      In step S 203 , the additional-data decoding unit  1408  acquires, from the DC-control-bit storage frame input from the data-demodulation processing unit  1407 , the value of DC control bits set at positions at which the DC control bits for determining a response to additional data are stored, for example, eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 . The value of DC control bits is referred to as DC bit information A.  
      In step S 204 , the additional-data decoding unit  1408  acquires specific user control data from the specific-UCD-positional-counter-and-data-extracting circuit  1416 . The acquired user control data is referred to as UCD bit information B.  
      In step S 1205 , the additional-data decoding unit  1408  determines whether the relationship “DC bit information A”=“specific-UCD bit information B” holds.  
      When the relationship “DC bit information A”=“specific-UCD bit information B” holds, in step S 1206 , it is determined that “specific-UCD bit information B”=“additional data component bits”.  
      When the relationship “DC bit information A”≠“specific-UCD bit information B” holds, in step S 1207 , it is determined that “specific-UCD bit information B”≠“additional data component bits”.  
      In step S 1208 , it is determined whether processing on all items of the specific user control data in the same cluster has finished. If the processing has not finished yet, the process proceeds to step S 1209 . In step S 1209 , the next specific user control data is acquired and steps S 1202  to S 1208  are repeatedly executed.  
      The acquisition of the next specific user control data in step S 1209  is executed, for example, when the first specific user control data item in a cluster to be processed is “UC 0,0”, as processing in which “UC 0,5” is acquired as the next user control data item, with the column-position information incremented by a predetermined value.  
      If the process has affirmatively determined in step S 1208 , it proceeds to step S 1210 , and it is determined whether extraction of additional data has finished. If there is unprocessed data, step S 1202  and the subsequent steps are repeatedly executed. If it is determined that all additional data has been acquired, the process ends.  
      Next, an example of processing according to an embodiment is described below. In the example of processing, values are calculated as the result of arithmetic processing (e.g., exclusive OR (XOR) or exclusive NOR (XNOR)) on data items in user control data and additional data, and the values are set as DC control bits set in a DC-control-bit storage frame for specific user control data.  
       FIG. 38  shows the configuration of an information recording processor according to the third embodiment. In  FIG. 38 , components identical to those shown in the information recording processor (shown in  FIG. 19 ) according to an embodiment are denoted by identical reference numerals.  
      In the information recording processor according to the third embodiment, for example, additional data  1600 , such as encryption-key information for use as an encryption key for encrypted content, information constituting part of the encryption-key information, encryption-key generating information such as the data (e.g., seed) required for generating an encryption key, secret information such as a password, control information such as content-playback control information or copy-control information, is processed for error-correcting encoding by an additional-data error-correcting encoding unit  1601 . The error-correcting-coded additional data is input to a DC-control-bit calculating unit  1602 .  
      The DC-control-bit calculating unit  1602  also receives specific user control data input from a specific-UCD-positional-information-counter-and-data-extracting unit  1105 .  
      The specific-UCD-positional-information-counter-and-data-extracting unit  1105  is similar to the specific-UCD-positional-information-counter-and-data-extracting unit  1105  (shown in  FIG. 19 ) according to the second embodiment. It executes processing of identifying and acquiring specific user control data.  
      By executing arithmetic processing based on additional data component bits and stored-bit information in the specific user control data, the DC-control-bit calculating unit  1602  determines the values of DC control bits to be set in the DC-control-bit storage frame for specific user control data.  
      The DC-control-bit calculating unit  1602  executes arithmetic processing on data items in the specific user control data and additional data, for example, XOR or XNOR. The DC-control-bit calculating unit  1602  outputs the calculated results to a modulated data generating unit  1109  through a switch  1108 . The modulated data generating unit  1109  generates a DC-control-bit storage frame (for specific user control data) in which DC control bits based on the calculated result are set.  
      The other components shown in  FIG. 38  are identical to those described with reference to  FIG. 19 . Accordingly, a description of them is omitted.  
      The arithmetic processing executed in the DC-control-bit calculating unit  1602  is described below with reference to  FIG. 39 .  
       FIG. 39  shows an example in which XOR is executed as arithmetic processing using data items in specific user control data and additional data and in which the result of XOR is set as DC control bits set in the DC-control-bit storage frame for specific user control data.  
      In the example shown in  FIG. 39 , the following settings are used: 
          “additional data component bits”=“01011010”; and     “specific UCD storing bits”=“00111101”.        

      The additional data component bits are some bits included in additional data, for example, encryption-key information for use as a key for encrypted content, information forming part of the encryption-key information, encryption-key generating information such as the data (e.g., seed) required for generating an encryption key, secret information such as a password, or control information such as content-playback control information or copy-control information.  
      The DC-control-bit calculating unit  1602  executes XOR of the additional data component bits “01011010” and the specific-user-control data storage bits “00111101”, and produces the arithmetic processing result “01100111”.  
      The resultant values “01100111” are used as DC control bits set in the DC-control-bit storage frame for specific user control data.  
      The resultant values are output to the modulated data generating unit  1109  through the switch  1108 , and a DC-control-bit storage frame for specific user control data in which DC control bits based on the resultant values are set is generated.  
      For example, in the DC-control-bit storage frame  1621  for specific user control data, shown in  FIG. 39 , in eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , the resultant values “01100111” are stored which are obtained by executing XOR of the additional data component bits “01011010” and the specific-user-control-data storage bits “00111101”.  
      Positions at which the DC control bits for user control data are stored are only illustrative. The DC control bits may be stored at arbitrary positions if they are set beforehand. When a valid playback processing program is executed, the DC control bits are read at the bit positions and are arithmetically processed (XORed) with the specific user control data, and additional data is acquired as the result of arithmetic processing.  
      In other words, in the information playback processor, the DC control bits “01100111” and the specific-user-control-data storage bits “00111101” are XORed, whereby the additional data component bits “01011010” are acquired.  
      Although, in  FIG. 39 , the case of executing XOR as arithmetic processing is shown, XNOR or other arithmetic processing may be executed. However, it is required for arithmetic processing to be executed so that, in data recording processing, DC control bits are calculated by arithmetically processing additional data and specific user control data, and so that, in data playback processing, additional data is calculated by arithmetically processing specific user control data and DC control bits.  
      Next, an additional data recording process executed by the information recording processor according to the third embodiment is described below with reference to  FIG. 40 .  
      In step S 1301 , user control data is input. As described above, the user control data is constituted by a plurality of user control data items (“UC 0,0” to “UC 17,31”), each item including 8-bit data.  
      In step S 1302 , based on address positional information, that is, specific bits of an address unit as address information corresponding to a physical sector number, described above with reference to  FIG. 31 , in other words, component bits included in a cluster number, row-position information and column-position information of user control data are acquired and user control data corresponding to the information of both is determined and acquired as specific user control data.  
      In step S 1303 , additional data component bits which are error-correcting-encoded are acquired. The additional data is encryption-key information for use as an encryption key for encrypted content, information forming part of the encryption-key information, encryption-key generating information such as the data (e.g., a seed) required for generating an encryption key, secret information such as a password, control information such as content playback control information or copy-control information, or other information such as content-attribute information.  
      Here, in order to execute arithmetic processing with the specific user control data (8 bits), that is, XOR or XNOR, the additional data is acquired in units of eight bits.  
      In step S 1304 , calculation using the specific user control data (8 bits) and the additional data, that is, XOR or XNOR, is executed.  
      In step S 1305 , DC control bits in the DC-control-bit storage frame for specific user control data are set to have bit values coincident with the result of the calculation. For example, eight bits in eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24  are set to the bit values calculated in step S 1304 .  
      The process proceeds to step S 1306 , and the DC-control-bit storage frame for specific user control data is modulated.  
      In step S 1307 , it is determined whether processing on all specific user control data in the same cluster has finished. If the processing has not finished yet, the process proceeds to step S 1308 . The next specific user control data is acquired, and steps S 1303  to S 1306  are repeatedly executed. In the processing of acquiring the next specific user control data in step S 1308 , when the first user control data in a cluster to be processed is “UC 0,0”, the column-position information is incremented by a predetermined value and “UC 0,5” is to be acquired as the next specific user control data.  
      In step S 1307 , if the process has determined that the processing on all specific user control data in the same cluster has finished, the process proceeds to step S 1309 . In step S 1309 , it is determined whether additional data superimposition has finished. If there is unprocessed data, step S 1302  and the subsequent steps are repeatedly executed.  
      In step S 1309 , determination of no unprocessed data terminates the process. In other words, in accordance with the above-described processing, recording data in which additional data bits are inserted is generated.  
      Although the flowchart shown in  FIG. 40  only shows processing on a DC-control-bit storage frame for specific user control data, in each frame other than the DC-control-bit storage frame for specific user control data, a recording frame in which DC control bits based on digital-sum-variation measurement are set is generated and modulated. In addition, regarding eight bits set at positions for setting DC control bits for specific user control data in the DC-control-bit storage frame for specific user control data, that is, in eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , values calculated in accordance with the above process are set as DC control bits. However, in frame parts other than the DC-control-bit storage frame, DC control bits based on digital-sum-variation measurement are set.  
      Positions at which DC control bits for specific user control data are stored in the DC-control-bit storage frame are not limited to frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 , but may be arbitrarily set.  
      Next, the configuration and playback process of the image playback processor according to the third embodiment are described below.  
       FIG. 41  shows the configuration of the information playback processor according to the third embodiment. In  FIG. 41 , component identical to those in the information playback processor according to the second embodiment described with reference to  FIG. 34  are denoted by identical reference numerals.  
      Based on the synchronizing signal input from a synchronization detecting unit  1406 , an additional-data-recording-area detecting unit  1411  identifies a recording area for a DC-control-bit storage frame for specific user control data and controls a switch  1410  based on the identification information. By controlling the switch  1410 , a recording frame in the area required for decoding additional data, that is, a recording frame including a DC-control-bit storage frame for specific user control data, is input from the data-demodulation processing unit  1407  to an additional-data decoding unit  1711 , which executes an additional data decoding process.  
      The additional-data decoding unit  1711  receives the DC-control-bit storage frame for specific user control data from the data-demodulation processing unit  1407  through the switch  1410 , and specific user control data from the specific-UCD-positional-counter-and-data-extracting circuit  1416 . The additional-data decoding unit  1711  executes arithmetic processing using DC control bits for specific user control data and specific-user-control-data bits.  
      Specifically, by executing arithmetic processing on the DC control bits for specific user control data and specific-user-control-data bits, that is, XOR or XNOR, the additional-data decoding unit  1711  acquires the result of arithmetic processing as additional data.  
      The specific-UCD-positional-counter-and-data-extracting circuit  1416  acquires disk-internal-data address information  1415  (see  FIG. 31 ) and calculates user control data storing the additional data, that is, the position of specific user control data, and executes predetermined incrementing processing to selectively acquire specific user control data.  
      In the information playback processor, when data to be processed in the data-demodulation processing unit  1407  is a DC-control-bit storage frame for specific user control data, data of the frame is input to the additional-data decoding unit  1711  through the switch  1410 , and the additional-data decoding unit  1711  acquires specific additional data component bits in the DC-control-bit storage frame for specific user control data and executes arithmetic processing with the specific-user-control-data bits to acquire additional data component bits.  
      While the data-demodulation processing unit  1407  is executing processing the DC-control-bit storage frame for specific user control data, the additional-data-recording-area detecting unit  1411  controls the switch  1410  to be on.  
      By executing similar processing based a DC-control-bit storage frame for specific user control data and specific user control data which are intermittently input, the additional-data decoding unit  1711  acquires additional data such as n-bit information used as key information, key-information generating information, content-playback control information, copy-control information, or other content-attribute information.  
      Next, a playback process including reading of the additional data is described below with reference to  FIG. 24 . The process shown in  FIG. 24  is executed by the information playback processor shown in  FIG. 23 .  
      In step S 1401 , based on the address information (see  FIG. 31 ) recorded on the disk, the positional information of specific user control data is acquired. In step S 1402 , demodulated data of the DC-control-bit storage frame for specific user control data is acquired. The additional-data-recording-area detecting unit  1411  shown in  FIG. 41  determines timing of demodulating the DC-control-bit storage frame for specific user control data, and The DC-control-bit storage frame for specific user control data is output from the data-demodulation processing unit  1407  to the additional-data decoding unit  1711 .  
      In addition, in step S 1403 , the additional-data decoding unit  1711  acquires, from the DC-control-bit storage frame input from the data-demodulation processing unit  1407 , the value of DC control bits set at positions at which the DC control bits for specific user control data are stored, for example, eight frame parts # 3 , # 6 , # 9 , # 12 , # 15 , # 18 , # 21 , and # 24 . The value of DC control bits is referred to as DC bit information C.  
      In step S 1404 , bit information of specific user control data is acquired from the specific-UCD-positional-counter-and-data-extracting circuit  1416 . The acquired information is referred to as specific-user-control-data bit information B.  
      In step S 1405 , the additional-data decoding unit  1711  performs calculation (e.g., XOR or XNOR) using DC-control-bit information C and specific-user-control-data bit information B.  
      In step S 1406 , the result of calculation using capacitor C and specific-user-control-data bit information B is set as additional data.  
      In step S 1407 , it is determined whether processing on all specific user control data in the same cluster has finished. If the processing has not finished yet, the process proceeds to step S 1408  and the next specific user control data is acquired. Steps S 1402  to S 1407  are repeatedly executed.  
      In acquiring the next specific user control data in step S 1408 , when the first specific user control data in a cluster to be processed is “UC 0,0”, the column-position information is incremented by a predetermined value and “UC 0,5” is acquired as the next specific user control data.  
      If the process has determined in step S 1407  that the processing on all specific user control data in the same cluster has finished, the process proceeds to step S 1409  and determines whether extraction of additional data has finished. If there is unprocessed data, step S 1402  and the subsequent steps are repeatedly executed. If the process has determined that all additional data has been acquired, the process ends.  
      Consecutive processing described herein can be executed one of hardware and software, or a configuration in which both are combined. When software processing is executed, it can be executed by installing a process-recorded program into a memory in a computer built-in dedicated hardware, or installing a program into a multi-purpose computer capable of executing various types of processing.  
      For example, the program can be recorded beforehand on a hard disk or on a read-only memory. Alternatively, the program can be temporarily or permanently stored (recorded) in a removable recording medium such as a CD-ROM (compact-disk read-only memory), an MO (magneto-optical disk), a DVD (digital versatile disk), a magnetic disk, or a semiconductor memory. The removable recording medium can be provided in the form of so-called “package software”.  
      The program is installed from the above removable recording medium to a computer. Moreover, the program is wirelessly transferred from a download site to the computer or is transferred by wire to the computer through a network such as the Internet. The computer can receive and install the transferred program into a built-in recording medium such as a hard disk.  
      Various types of processing described herein are not only executed in a time-series manner in accordance with the description, but also may be executed in parallel or separately depending on the processing capability of an apparatus executing the processing or as required. In addition, in this specification, the system means a logical set of a plurality of apparatuses, and is not limited to one having different apparatuses in a single housing.  
      It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.