JP2005085400A - Data recording medium, method and device for recording data, method and device for reproducing data, and method for transmitting/receiving data - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain information on an encryption key or the like with an existing decoder by using two error correction encoding methods. <P>SOLUTION: An encrypter 53 encrypts input data, and a CIRC4 encoder subjects the resultant data to error correction encoding. The CIRC7 key encoder 56 subjects the data to error correction encoding by using the CIRC7, and a symbol for generating error correction is inserted by the C2 decoding of the CIRC4. In data substitution 66, the data are changed after C1 encoding so that a C1 mark indicating the presence of an error is attached to the symbol where the error correction occurs during decoding. The recording area of encrypted contents data encoded by the CIRC4 and the recording area including the data containing the encryption key encoded by the CIRC7 are formed on an optical disk 62. The reproduced data of these areas are decoded by the decoder of the CIRC 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a data recording medium on which content data is recorded, a data recording method and apparatus, a data reproduction method and apparatus, a data transmission method, and a data reception method.

Conventionally, when data is recorded on a data recording medium such as a CD (Compact Disc), a DVD (Digital Versatile Disc) or the like, error correction coding is used as an error countermeasure. An error correction method in CD is called CIRC (Cross Interleaved Reed-Solomon Code), and generally performs coding and decoding processes with the configuration shown in FIG.

  In FIG. 1, digital audio data of 24 symbols is supplied from an input terminal indicated by reference numeral 101, and is error correction encoded by a C2 encoder 102. The C2 encoder 102 encodes the (28, 24, 5) Reed-Solomon code on GF (2 <8>) and generates a 4-symbol Q parity. One word (16 bits) of the audio signal is divided into upper 8 bits and lower 8 bits, and each 8 bits is made one symbol.

  28 symbols of the output of the C2 encoder 102 are supplied to the interleave circuit 103. The interleave circuit 103 assigns each symbol a delay amount that varies in an equal manner to 0, D, 2D,..., Where D is a unit delay amount (hereinafter referred to as an interleave length). The arrangement of one is changed to the second arrangement.

  The output of the interleave circuit 103 is supplied to the C1 encoder 104. The (32, 28, 5) Reed-Solomon code on GF (2 8) is used as the C1 code. Four symbol P parity is generated from the C1 encoder 104. The minimum distance between the C1 code and the C2 code is both 5. Therefore, correction of 2 symbol errors and erasure correction of 4 symbol errors (when the position of the error symbol is known) are possible.

  32 symbols from the C1 encoder 104 are recorded on the recording medium 105. The recording medium 105 is a master used for mastering (a glass disk coated with a photoresist). A reproduction signal of a CD (not shown) manufactured from the recording medium 105 is supplied from the input terminal 106 to the C1 decoder 107. The recording medium 107 is not limited to a ROM type and may be a recordable one. That is, it may be a recordable optical disc or a re-recordable optical disc. The C1 decoder 107 outputs data as a result of C1 decoding and a C1 mark (sometimes called a C1 pointer) generated during C1 decoding.

  The output of the C1 decoder 107 is supplied to the deinterleave circuit 108. The deinterleave circuit 108 gives an equal difference delay amount of 27D, 26D,..., D, 0 to 28 symbols so as to cancel the delay amount given by the interleave circuit 103.

  The output of the deinterleave circuit 108 is supplied to the C2 decoder 109, where the C2 code is decoded. The 24-symbol reproduction data and the interpolation flag are extracted from the C2 decoder 109 to the output terminals 110 and 111. Data indicating an error by the interpolation flag is interpolated by an interpolation circuit (not shown).

  As described above, in CIRC, error correction encoding is performed in the C1 sequence in the vertical direction, and error correction encoding is performed in the C2 sequence in the diagonal direction, and double error correction encoding is performed. In addition, error correction capability for burst errors is improved by interleaving.

  In the CD, the interleave length D of the interleave circuit 103 is set to D = 4. This error correction encoding method will be referred to as CIRC4. In addition, an error correction method for interleaving length D = 7 has been proposed. This is called CIRC7. CIRC7 has a longer interleave length than CIRC4, and has a higher correction capability for burst errors than CIRC4.

  In the above-described CIRC4, after encoding, specific data detected as an error is added, and the error correction decoder of the player detects the content and position of the error, detects the presence of the specific data, Patent Document 1 below describes a method for determining that a CD is an original CD if data is present and determining a copied disk if specific data is not present. In Patent Document 1, specific data that can be error-corrected is intentionally added to obtain error-corrected reproduction data, and the presence or absence of specific data is detected.

Japanese Patent Laid-Open No. 11-25000

  The method described in Patent Document 1 described above requires a decoder having a function capable of analyzing the content and position of an error as a decoder for error correction. Therefore, there is a problem that the error correction decoder of the existing player cannot be used and the compatibility with the existing player is not achieved.

  Further, CIRC7 described above is not taken into consideration, and CIRC4 and CIRC7 are not combined. For example, when playing back one disc on which both CIRC4 encoded data and CIRC7 encoded data are recorded, an existing player having only a CIRC4 error correction decoder records on the CIRC7. There was a problem that the used data could not be used.

  Therefore, an object of the present invention is to provide a data recording medium, a data recording method and apparatus, a data reproduction method and apparatus, which can obtain specific information such as an encryption key by an error correction decoder provided in an existing player, The object is to provide a data transmission method and a data reception method.

In order to solve the above-described problem, the present invention provides a data recording medium having an area in which data encoded by a first error correction encoding method in which two or more error correction codes are combined is recorded.
Two or more error correction codes are combined, and at least one of the error correction codes is decoded by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. To be done,
In the decoding method, when it is determined that there is no error correction in a specific block when one error correction code is decoded, the symbols included in the specific block are corrected when the other error correction code is decoded. In the case of miscorrection,
Changing the value of one or a plurality of symbols to another value during encoding output of a common error correction code in the first and second error correction encoding methods to avoid erroneous determination A data recording medium characterized by the above.

The present invention relates to a data recording method for recording on a data recording medium data encoded by a first error correction encoding method combining two or more error correction codes.
Two or more error correction codes are combined, and at least one of the error correction codes is decoded by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. To be done,
In the decoding method, when it is determined that there is no error correction in a specific block when one error correction code is decoded, the symbols included in the specific block are corrected when the other error correction code is decoded. In the case of miscorrection,
Changing the value of one or a plurality of symbols to another value during encoding output of a common error correction code in the first and second error correction encoding methods to avoid erroneous determination A data recording method characterized by the above. In addition, the present invention is a recording apparatus that avoids being determined as erroneous correction.

The present invention provides a data reproduction method for reproducing a data recording medium having an area in which data encoded by a first error correction encoding method combining two or more error correction codes is recorded.
Accessing the area and playing back the data;
Two or more error correction codes are combined, and at least one of the error correction codes is decoded by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. A decoding step
In the decoding step, when it is determined that there is no error correction in the specific block when decoding one error correction code, the symbols included in the specific block are corrected when decoding the other error correction code. In such a case, it is determined that the error is corrected and information that cannot be corrected is output.
When it is determined that there is an error correction in a specific block at the time of decoding one error correction code, if a symbol included in the specific block is corrected at the time of decoding the other error correction code, it is determined as an error correction. Without a symbol,
This is a data reproduction method in which information output as a result of the decoding step is used to process reproduction data. The present invention is also a data reproduction apparatus that uses information output as a result of the decoding step to process reproduction data.

The present invention relates to a data transmission method for transmitting data encoded by a first error correction encoding method in which two or more error correction codes are combined.
Two or more error correction codes are combined, and at least one of the error correction codes is decoded by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. To be done,
In the decoding method, when it is determined that there is no error correction in a specific block when one error correction code is decoded, the symbols included in the specific block are corrected when the other error correction code is decoded. In the case of miscorrection,
Changing the value of one or a plurality of symbols to another value during encoding output of a common error correction code in the first and second error correction encoding methods to avoid erroneous determination A data transmission method characterized by the above.

In this invention, in the data receiving method for receiving the transmission data encoded by the first error correction encoding method combining two or more error correction codes,
Decoding that combines two or more error correction codes, and at least one of the error correction codes decodes received data by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method Has steps,
In the decoding step, when it is determined that there is no error correction in the specific block when decoding one error correction code, the symbols included in the specific block are corrected when decoding the other error correction code. In such a case, it is determined that the error is corrected and information that cannot be corrected is output.
When it is determined that there is an error correction in a specific block at the time of decoding one error correction code, if a symbol included in the specific block is corrected at the time of decoding the other error correction code, it is determined as an error correction. Without a symbol,
This is a data receiving method in which information output as a result of the decoding step is used to process received data.

  In the present invention, specific information such as an encryption key can be obtained by an error correction decoder provided in an existing player.

  Embodiments of the present invention will be described below with reference to the drawings. The correspondence between terms used in the claims of the present specification and terms used in the embodiments will be described below.

  First error correction encoding method: CIRC7, second error correction encoding method: CIRC4, error correction code: C1 code and C2 code.

  In the present invention, when the data recorded by CIRC7 is reproduced and decoded by CIRC4, the CIRC4 decoder generates an error correction, and the CIRC4 decoder does not detect the error correction and is decoded from the CIRC4 decoder. Data is output. First, error correction will be generally described.

  The process of error correction code decoding, which estimates the transmitted word from the received word, divides the reception space consisting of a set of received words into areas corresponding to each code word, and which area the received word is in. Can be considered as a process of determining that the corresponding code word has been sent. At this time, an area corresponding to each codeword is called a decoding area of the codeword. Since only one transmission word is estimated, the decoding areas should not overlap.

FIG. 2 shows error correction of a block-coded code having a minimum Hamming distance of dmin and an error correction capability of t. In the case of CIRC4 and CIRC7, the dmin of the C1 code and the C2 code is 5, and t is 2. In FIG. 2, circles having a radius t indicate decoding regions, and the center indicates a code word. The distance between codewords is dmin.

  In the reception space, an area indicated by a hatched area remains in addition to the decoding area. If a received word enters this area, the transmitted word cannot be estimated and error detection is performed. Therefore, this area is called an error detection area.

  There are three possible error correction decoding results. The first decoding result is a case where the received word enters the area corresponding to the transmitted word and the transmitted word is correctly estimated. The second decoding result is a case where the received word enters a decoding area of a code word different from the transmission word and erroneous estimation is performed. The third decoding result is a case where information indicating that the received word enters the error detection area and the transmission word cannot be estimated correctly is output. The first decoding result is called correct decoding, the second decoding result is called error correction, and the third decoding result is called undecoding.

  When the data recorded by CIRC7 is reproduced and decoded by CIRC4, except for special data such as all zeros, the situation is the same as when all C2 parities of 4 symbols are in error. The C1 code and the C2 code are the same between CIRC4 and CIRC7. As described with reference to FIG. 1, the output of the C1 encoder 104 is supplied to the input of the C1 decoder 107 as described with reference to FIG. As a result, no error occurs. As is the case with the following description, it is assumed that no error occurs other than the theoretical error in the recording / reproducing process.

  As described above, since the error correction capability of the C2 code is 2 symbols, if all of the 4 symbols of C2 parity are in error, decoding becomes impossible. Further, since the C1 mark indicates no error, the C1 mark cannot indicate the error symbol position, and decoding is impossible.

However, erroneous decoding may occur when decoding with CIRC4. If the number of error symbols is equal to or greater than dmin−t (= 5-2 = 3), the code area may enter a decoding area of another codeword different from the original codeword, and erroneous correction occurs at this time. When the data recorded by CIRC7 is decoded by CIRC4, the C2 parity of all four symbols is in error, so that there is a possibility that erroneous correction will occur with a certain probability depending on the value of each symbol.

However, CIRC4 is configured to perform C2 decoding with reference to a C1 mark as a result of C1 decoding, and detects the possibility of erroneous correction. FIG. 3 shows an error correction detection method. The reproduced symbol data and parity data are decoded in C1 decoding. Error correction 1 means C1 decoding. When attention is paid to a certain symbol S, if it is determined that the block including the symbol S has no error or that the error has been corrected reliably (no error correction), the C1 mark has no error, for example, “0”. It is said. Otherwise, the C1 mark is set to “1”.

  Next, the symbol S is decoded by C2 decoding in response to the deinterleaving process. Error correction 2 means C2 decoding. If the symbol S is error-corrected in the C2 decoding and the C1 mark of the symbol S indicates no error, the possibility of erroneous correction is considered high. In that case, it is determined that the error correction 2 for the symbol S has failed (that is, erroneous correction). As a result, the interpolation flag passed to the interpolation circuit is set to a value indicating that there is an error, for example, “1”.

  As described above, since there is no error in C1 decoding, it is determined that all C1 marks passed to C2 decoding are error-free, all symbols are erroneously corrected, and all symbols have an error flag. Will be attached. With this interpolation flag, in the case of audio data, the interpolation circuit performs the previous value hold or mute process, and the original data is not output. In the case of data such as a computer program, a read error occurs, the data is discarded, and no data is output from the decoder or drive.

  As described above, when data recorded by CIRC7 is reproduced and decoded by CIRC4, correction becomes impossible and no data is output from the decoder or drive. Therefore, even if specific information is recorded by CIRC7, CIRC4 No specific information is output from the decoder. Therefore, the data encoded by CIRC7 cannot be used by the CIRC4 decoder. Further, since it is difficult to distinguish from a true error, for example, a burst error, it is difficult to detect “whether it is CIRC7”.

  Therefore, in the present invention, in order to prevent erroneous correction in such an error correction decoder and to avoid being determined to be erroneous correction, the data resulting from C1 encoding of the CIRC7 encoder is intentionally added. An error is injected into this, and as a result, an error C1 mark is generated. If the C1 mark is attached to the symbol corrected by C2 decoding, the C2 decoder determines that the correction has been made correctly, and the corrected data is output from the decoder to obtain specific information.

  FIG. 4 and FIG. 5 are block diagrams represented along the flow of encoding according to the CIRC system. In the description of the CIRC encoding / decoding, the encoding of audio data is targeted for easy understanding.

  24 symbols (W12n, A, W12n, B,..., W12n + 11, A, W12n + 11, B) in which one word of the audio signal is divided into upper 8 bits and lower 8 bits (upper 8 bits Are indicated by A and the lower 8 bits are indicated by B) to the 2-symbol delay / scramble circuit 11. The two-symbol delay is executed for even-word data L6n, R6n, L6n + 2, R6n + 2,..., And interpolation is performed even when all the corresponding sequences in the C2 encoder 12 become errors. It has been made possible. The scrambling is performed so as to obtain the maximum burst error interpolation length.

  An output of 24 symbols (referred to as an information block) from the 2-symbol delay / scramble circuit 11 is supplied to the C2 encoder 12. The C2 encoder 12 encodes the (28, 24, 5) Reed-Solomon code on GF (2 8) and generates four-symbol Q parities Q12n, Q12n + 1, Q12n + 2, and Q12n + 3 To do.

  The 28-symbol output (referred to as a coding block) of the C2 encoder 12 is supplied to the interleave circuit 13. When the interleave length is D, the interleave circuit 13 gives each symbol a delay amount that changes in the same manner as 0, D, 2D,..., Thereby changing the first arrangement of symbols to the second arrangement. To change.

The output of the interleave circuit 13 is supplied to the C1 encoder 14. The (32, 28, 5) Reed-Solomon code on GF (2 8) is used as the C1 code. Four symbol P parities P12n, P12n + 1, P12n + 2, and P12n + 3 are generated from the C1 encoder 14. The minimum distance dmin between the C1 code and the C2 code is 5. Therefore, correction of 2 symbol errors and erasure correction of 4 symbol errors (when the position of the error symbol is known) are possible.

  32 symbols from the C1 encoder 14 are supplied to the 1-symbol delay circuit 15. The 1-symbol delay circuit 15 prevents the occurrence of a 2-symbol error due to an error straddling the boundary between symbols by separating adjacent symbols. Also, the Q parity is inverted by the inverter, so that an error can be detected even when the data and parity are all zero. An output of 32 symbols (= 24 symbols of data + 4 symbols of C1 parity + 4 symbols of C2 parity) is obtained at the output of the 1 symbol delay circuit 15. The 32 symbol output is supplied to an EFM modulator (not shown). This 32 symbol output is called an EFM frame or block.

  The interleave length D of the interleave circuit 13 differs between the CIRC4 system and the CIRC7 system. The interleave circuit 13 distributes burst errors.

  That is, in the case of the CIRC4 system, D = 4. In the case of the CIRC4 system, the maximum delay amount is 27D (= 108), and the total interleave length is 109. In the case of the CIRC7 system, D = 7. Thus, in the case of the CIRC7 system in which D = 7, the maximum delay amount is 27D (= 189), and the total interleave length is 190.

  6 and 7 are block diagrams represented along the decoding flow. The decoding process is performed in the reverse order to the above-described encoding process.

  First, 1 EFM frame (32 symbols) of reproduction data from an EFM demodulating circuit (not shown) is supplied to a 1 symbol delay circuit 21. The delay given by the one-symbol delay circuit 15 on the encoding side is canceled in this circuit 21.

  32 symbols from the 1-symbol delay circuit 21 are supplied to the C1 decoder 22. The output of the C1 decoder 22 is supplied to the deinterleave circuit 23. The deinterleave circuit 23 gives an equal differential delay amount of 27D, 26D,..., D, 0 to 28 symbols so as to cancel the delay amount given by the interleave circuit 13.

  The interleave length of the deinterleave circuit 23 is D = 4 frames in the CIRC4 system, and D = 7 frames in the CIRC7 system.

The output of the deinterleave circuit 23 is supplied to the C2 decoder 24, and the C2 code is decoded. The data corrected in the C1 decoder 22 and the C1 mark corresponding to the correction result of the C1 decoding are transmitted to the C2 decoder 24 via the deinterleave circuit 23. As an example, when there is no error in C1 decoding and when a single error is corrected, a C1 mark of “0” indicating no error is generated, and when a double error is corrected and a triple error or more In this case, a C1 mark “1” indicating that there is an error is generated.

  The C2 decoder 24 decodes the C2 code with reference to the C1 mark. The 24 symbols output from the C2 decoder 24 and the interpolation flag associated with each symbol are supplied to the 2-symbol delay / descramble circuit 25. From this circuit 25, decoded data of 24 symbols and an interpolation flag are obtained. In an interpolation circuit (not shown), a symbol indicating an error is interpolated by an interpolation flag.

  In the case of the CIRC4 system, as shown in FIG. 8, the interleave length D is (D = 4) and the total interleave length is 109 (= 108 + 1) frames, which is slightly larger than one sector. In the case of the CIRC7 system, as shown in FIG. 9, the interleave length D is (D = 7) and the total interleave length is 190 (= 189 + 1) frames, which is slightly smaller than two sectors.

  The total interleaving length defines the correction capability for burst errors in which a large number of data is continuously erroneous due to fingerprints attached to the disc, scratches on the disc, and the like. The longer the length, the higher the burst error correction capability. Therefore, CIRC7 has a higher correction capability for burst errors than CIRC4.

  As described above, the present invention relates to processing when data recorded by CIRC7 is reproduced and decoded by CIRC4. That is, the data encoded by the CIRC7 encoder in which D = 7 in FIGS. 4 and 5 is recorded on the recording medium, and the data reproduced from the recording medium is D = 4 in FIGS. Is decoded by the decoded CIRC4 decoder.

  Then, in order to avoid erroneous correction at the decoder and to avoid being determined as erroneous correction, the data resulting from C1 encoding of the CIRC7 encoder cannot be corrected by C1 decoding or erroneous correction. An error is deliberately injected so that it is treated as a possible error correction, that is, an errored C1 mark is generated.

  In the configuration of the encoder of FIG. 5, by replacing, changing or overwriting (hereinafter simply referred to as replacement) data of two or more symbols in the stage after the output of the C1 encoder 14 and before the EFM modulation. An error is injected. The EFM frame subjected to the replacement process appears with a probability of 1/4 to 1/2. In this way, at least the EFM frame subjected to the replacement process becomes an error that cannot be corrected by C1 decoding, or error correction (two symbol correction) that may be erroneously corrected, and there is an error for all symbols of this EFM frame. A C1 mark is attached.

  In the decoder, when deinterleaving is performed after C1 decoding and passed to the C2 decoder 24, symbols with C1 marks with errors are scattered apart, so that the average is 1/4 to 1/2 symbols. It will be in the state with C1 mark. If the C2 decoder 24 corrects the symbol with the C1 mark having an error as a result of the error correction, the decoder outputs the corrected data without recognizing the error correction.

  As described above, erroneous correction can be caused with a certain probability using the randomness of data, and a C1 mark indicating the presence of an error is randomly generated with a certain probability, and this C1 mark is C2 decoded. Thus, it is possible to avoid matching with a symbol that has been erroneously corrected at a certain probability, and determining that it is erroneously corrected.

  Furthermore, it is possible to control the occurrence of erroneous correction to a more intended one. For example, in a CIRC7 encoder, after performing C2 encoding and before C1 encoding, decoding by CIRC4 is performed, and an operation for obtaining a C2 error is performed, so that it is possible to know in advance whether or not erroneous correction occurs. it can. In other words, a combination of symbols in which erroneous correction occurs is obtained, and a part of the symbols is replaced before C1 coding so as to make such a combination, thereby forcibly causing erroneous correction.

  If it is desired to control the value of a specific symbol after erroneous correction to a desired value, the other symbols are replaced so that erroneous correction occurs with the specific symbol fixed to that value. Furthermore, when it is desired to decode correctly in the CIRC7 decoder, the symbols are exchanged within a range of up to two symbols in the CIRC7 code block. In this way, it is possible to control the occurrence of erroneous correction to a more intended one.

  When the occurrence of error correction is controlled in this way, the position of the correction symbol at the time of error correction is also known. Therefore, the C1 mark with an error is always attached to the symbol. Specifically, after C1 encoding, two or more symbols in the EFM frame including the symbol are replaced with different values. By doing so, it is possible to reliably attach a C1 mark with an error to the correction symbol at the time of error correction.

  As described above, erroneously corrected data can be read from the decoder. Thereby, for example, the following applications are possible.

1. 1. Data that can be decoded is obtained by any of the methods CIRC4 and CIRC7. When decoding CIRC4, use it to indicate that it is a portion encoded with CIRC7 (and vice versa)
3. 3. Use miscorrected data that can be read as confidential data. 4. Use pattern information based on the presence or absence of error correction as a key or part of a key. 5. Use the miscorrected data itself as a key or part of a key. Used in copy protection to determine if it is original.

  FIG. 10 shows an example of the format of an optical disc to which the present invention is applied. The example shown in FIG. 10A is an example in which a plurality of, for example, two sessions are formed on an optical disc. A first lead-in area LI1, a first program area PA1, and a first lead-out area LO1 are provided from the inner periphery side of the disc to form a first session. Audio data is recorded in the first program area PA1 in the same recording format as the CD-DA. The data in the first program area PA1 has the same recording format as the CD-DA and is not encrypted, so that it can be played back by a normal player for playing music.

  A second session composed of the second lead-in area LI2, the second program area PA2, and the second lead-out area LO2 is provided outside the first lead-out area LO1. For example, compressed audio data is encrypted and recorded as content data in the second program area PA2.

  DES (Data Encryption Standard) can be used as an encryption method. DES is one of block ciphers that blocks plaintext and performs cryptographic conversion for each block. DES performs cryptographic conversion using a 64-bit key (56-bit key and 8-bit parity) on a 64-bit input, and outputs 64 bits. Encryption other than DES may be used. For example, DES is a common key method that uses the same key data for encryption and decryption, but RSA encryption, which is an example of public key encryption that uses different key data for encryption and decryption, may be employed. Furthermore, the content data is compression-coded by ATRAC3 (Adaptive TRansform Acoustic Coding 3), MP3 (MPEG1 Audio Layer-3), AAC (MPEG2 Advanced Audio Coding), TwinVQ, etc. as necessary.

  Further, the second program area PA2 includes two areas AR1 and AR2 having different error correction encoding methods. The data in the area AR1 is recorded with the error correction encoded data using the same CIRC4 as that of a normal CD-DA disc or CD-ROM disc. The data in the area AR2 is recorded with the error correction encoded data by CIRC7. The area AR2 includes information output from the CIRC4 decoder, such as encryption key information, as described above.

  In the program area area AR1, data is error-correction encoded by CIRC4 in order to achieve compatibility with existing CDs.

  In the example of FIG. 10B, the first lead-in area LI is provided on the innermost circumference of the optical disc, the program area PA is provided on the outer circumference, and the lead-out area LO is provided outside the program area PA. . The program area is divided into an area AR11 and an area AR12. In the area AR11, data is encrypted, and error-correction encoded by CIRC4 is recorded. In the area AR12, data is recorded after being subjected to error correction coding by CIRC7, and includes information that can be output from the decoder of CIRC4. In such a disc, the encryption key can be generated from the reproduction data in the area AR12.

  Further, although not shown, the present invention can be applied to a multilayer optical disc. For example, the present invention may be applied to a multilayer optical disc in which the first session in FIG. 10A corresponds to the first layer and the second session corresponds to the second layer.

  As described above, according to the present invention, an encryption key can be recorded on a disk by using data that can be output from a CIRC4 decoder even if it is encoded by CIRC7. A data recording method and a reading method for the area AR2 (or AR12) in which data encoded by CIRC7 is recorded will be described more specifically.

  FIG. 11A shows the configuration of the area AR2 of the second program area PA2 in the optical disc shown in FIG. 10A. This area AR2 is subjected to error correction coding by CIRC7, and includes a capable data pattern that can be output from the decoder of CIRC4. In FIG. 11, data A, dummy data,..., Dummy data, data B, and data C are portions where data that can be output from the CIRC4 decoder is recorded. The other part (area hatched) indicates a part that is determined to be erroneously corrected and detected as uncorrectable when decoded by CIRC4.

When such an area AR2 is decoded by CIRC4, an error correction occurs in the data A portion or the like and the error correction is not determined, so there is no error (indicated by No in the figure). An error correction impossible result (indicated by “Yes” in the figure) is obtained. When performing error correction with CIRC4, 1 bit “0” corresponding to the portion in which error correction is impossible
And 1 bit “1” is assigned corresponding to the portion where there is no error (correctable), the data D of (0101... 01101) is obtained in the case of FIG. 11A.

As an example, data A, B, and C output from the CIRC4 decoder are used as an encryption key or a part of the encryption key. Further, the data D corresponding to whether the error is uncorrectable or correctable and error-free is used as an encryption key or a part of the encryption key. That is, if the encryption key is expressed as CIRC7-key,
CIRC7-key = f ₁ (A, B, C, D)
Generates an encryption key. f ₁ is a key generation function. Furthermore, dummy data is recorded in order to improve the confidentiality of the encryption key.

There are several methods for increasing the confidentiality of the encryption key. If the method shown in FIG. 11A is the first recording method, FIG. 11B shows the second recording method. Compared with the first recording method, the position of the data (A, B, C) output from the CIRC4 decoder is changed in the second recording method. In addition, the position where the error correction result is read is changed. Further, the key generation function is f ₂ different from f ₁ . When recording data on a recordable disc, the confidentiality of the encryption key can be increased by changing the first recording method and the second recording method for each recording. In the case of a read-only disk, such processing is performed during mastering. For example, a plurality of stampers are created.

  FIG. 12 shows an embodiment of a recording apparatus to which the present invention is applied. For simplicity, in one embodiment, data is recorded on an optical disc of one session as shown in FIG. 10B. In the case of a read-only disk, the configuration of FIG. 12 is applied to the mastering system. In FIG. 12, content data to be recorded is supplied to an input terminal denoted by reference numeral 51. An example of content is audio data compressed by ATRAC3, but the present invention is not limited to music data, and can also be applied when image data, music, image data, and the like are handled. Note that already encrypted content data may be supplied to the input terminal 51. Further, a part of the content data may be encrypted.

The input data is supplied to one input terminal of the switch circuit 52 and is encrypted by the encryptor 53 and then supplied to the other input terminal of the switch circuit 52. The switch circuit 52 is controlled by a controller (CPU) 54 that controls the entire recording apparatus, and is switched according to whether encrypted data is recorded or non-encrypted data is recorded. Although not shown, a display, operation switches, and the like are connected to the controller 54. The switch circuit 52 is controlled by the controller 54 according to the necessity of encryption. Further, an encryption key (CIRC7-key) is supplied from the controller 54 to the encryptor 53.

The output of the switch circuit 52 is supplied to the CIRC4 encoder 55 and the encryption key (CIRC7-key) encoder 56. As described above, the encryption key encoder 56 encodes the CIRC 7 so that erroneous correction occurs at a predetermined position. The controller 54 indicates the position at which erroneous correction occurs. The output of the encryption key encoder 56 is supplied to the data replacement circuit 66. The data replacement circuit 66 generates a C1 mark with an error and replaces two or more symbols in the EFM frame with another value so that the above-described erroneous correction is not detected.

  The output of the CIRC4 encoder 55 is supplied to one input terminal of the switch circuit 57. The output of the data replacement circuit 66 is supplied to the other input terminal of the switch circuit 57. The encryption key encoder 56 and the data replacement circuit 66 generate data (see FIG. 10B) recorded in the area AR12 encoded by the CIRC7.

  The switch circuit 57 is controlled by the controller 54. In the example shown in FIG. 10B, the switch circuit 57 is controlled by the controller 54 so that the data encoded by CIRC4 is recorded in the area AR11 and the data encoded by CIRC7 is recorded in the area AR12.

  Output data of the switch circuit 57 is supplied to the EFM modulator 59. Reference numeral 58 denotes a subcode encoder, and subcode information is supplied from the controller 54 to the subcode encoder 58. The output data of the subcode encoder 58 is supplied to the EFM modulator 59, and data of a predetermined format to which the subcode is added is formed. The data to which the subcode is added is EFM modulated by the EFM modulator 59. Further, it is supplied to the write strategy unit 60. The write strategy unit 60 is a circuit for controlling the data recording method. For example, in the area AR12, a process of performing multiple recording or changing a track for recording the encryption key is performed.

  The output of the light strategy 60 is supplied to the optical pickup 61. From the optical pickup 61, laser light modulated according to the output of the light strategy 60 is output. The laser light is irradiated onto the recording surface of the optical disc 62, and information is recorded on the optical disc 62.

  The optical disk 62 is placed on a turntable and rotated by a spindle motor 63. The spindle motor 63 is driven to rotate at a constant linear velocity (CLV) or a constant angular velocity (CAV) under the control of the servo unit 64. The servo section 64 generates various focus, tracking, sled, and spindle servo drive signals based on the focus error signal and tracking error signal from the RF section 65 and the operation command from the controller 54, and outputs them to the optical pickup 61. To do.

  The optical pickup 61 traces a track formed concentrically or spirally on the optical disc 62 while condensing the light beam of the semiconductor laser on the signal surface of the optical disc 62. The laser beam from the optical pickup 61 can be moved in the focus direction and the tracking direction by a biaxial mechanism. The entire optical pickup 61 can be moved in the radial direction of the disk by a thread mechanism.

  FIG. 13 shows an example of a playback apparatus for playing back the optical disk 62 recorded as described above. The optical disk 62 is placed on a turntable and rotated by a spindle motor 71. The spindle motor 71 is driven to rotate at a constant linear velocity (CLV) or a constant angular velocity (CAV) under the control of the servo unit 74.

  The servo unit 74 generates various servo drive signals for focus, tracking, sled, and spindle based on the focus error signal, tracking error signal, and operation command from the controller 83, and outputs them to the spindle motor 71 and the optical pickup 72. Yes. The controller 83 is used to control the entire playback device, and a display, operation switches, and the like are connected to the controller 83 (not shown). The optical pickup 72 traces a track formed concentrically or spirally on the optical disk 62 while condensing the light beam of the semiconductor laser on the signal surface of the optical disk 62. The entire optical pickup 72 is moved by the thread mechanism.

  The output of the optical pickup 72 is supplied to the synchronization detector 75 via the RF amplifier 73, and the output of the synchronization detector 75 is supplied to the demodulator 76 of the EFM. The EFM demodulator 76 demodulates the EFM. The output of the EFM demodulator 76 is supplied to a subcode decoder 77 and a CIRC4 decoder 78. The subcode decoder 77 separates and decodes the subcode data. The decoded subcode is supplied to the servo unit 74 and the controller 83. The CIRC4 decoder 78 decodes CIRC4.

  When reproducing the data of the optical disk 62, the optical pickup 72 is moved to a desired position, and the optical pickup 72 reproduces the program area PA1. This reproduction output is supplied to the CIRC4 decoder 78 via the RF amplifier 73, the synchronization detector 75, and the EFM demodulator 76.

  The CIRC4 decoder 78 performs the CIRC4 decoding process, and the output of the CIRC4 decoder 78 is supplied to the switch circuit 79. The switch circuit 79 is controlled by the controller 83, and is switched depending on whether non-encrypted data or encrypted data is reproduced. When reproducing the encrypted data, the encrypted content data selected by the switch circuit 79 is supplied to the decryptor 80.

  The reproduction data of the area AR2 is supplied to the CIRC7 key extractor 81. An encryption key is generated by the CIRC7 key extractor 81, and the encryption key is supplied to the decryptor 80. The decryptor 80 decrypts the encryption, and the reproduced data is output to the output terminal 82. When reproducing the non-encrypted data, the output data of the CIRC4 decoder 78 selected by the switch circuit 79 is taken out to the output terminal 82.

  The controller 83 is supplied with the TOC and address information of the optical disc 62 from the subcode decoder 77. Preferably, when the optical disc 62 is loaded, the area AR12 is accessed, and the optical pickup 72 reproduces the area AR12, generates an encryption key, and then reproduces the content data in the area AR11.

  By the way, in the above-described optical disc 62, the area AR12 is partly error-correction-encoded by CIRC7 and includes data output from the CIRC4 decoder. It is thought that it will become a sound. Therefore, in this part, it is conceivable to set all the upper bits of the PCM signal to 0 or 1 so that the sound is low.

  Further, if the sound generated in this portion is direct current or high frequency, the user is not likely to notice, and there is a risk of increasing the volume. Therefore, it is conceivable to embed 0 data and 1 data in a specific pattern to generate sound in the audible band. As an example, it is conceivable to repeat 0 and 1 at 7.35 kHz.

  In the above description, the example in which the present invention is applied to the data recording medium has been described. However, the present invention is not limited to the data recording medium, and the content data is encrypted and transmitted, and the encrypted data is transmitted. It can also be applied when receiving. That is, a predetermined period (frame, packet, etc.) of data to be transmitted / received is a data period encoded by CIRC7, and an encryption key can be embedded in the data period as described above.

  When the present invention is applied to data transmission / reception, the configuration of the recording system shown in FIG. 12 corresponds to the configuration of the transmission system, the output of the switch circuit 57 is supplied to the transmission unit, and the wired or wireless communication path is connected. Sent out. Further, the configuration of the reproduction system shown in FIG. 13 corresponds to the configuration of the reception system, and reception data is supplied to the RF amplifier 73. Then, the data received from the output terminal 82 and decoded is obtained.

  The present invention is not limited to the above-described embodiment of the present invention, and various modifications and applications can be made without departing from the gist of the present invention. For example, C1 decoding and C2 decoding may be repeated after performing C1 decoding and C2 decoding. In the above example, the data has been described as being correctable by CIRC4 and CIRC7. However, the present invention can also be applied to product codes used in DVDs. The DVD has an error correction code combining two block codes called PI (inner-code parity) and PO (outer-code parity), and the present invention is applied in the same manner as the C1 code and C2 code in CIRC. be able to. In the case of a DVD error correction code, the order of encoding (decoding) of the two error correction codes PI and PO is not particularly defined, and any error correction code may be encoded first.

It is a block diagram used for description of the error correction code | symbol which can apply this invention. It is an approximate line figure used for explanation of error correction operation of an error correction code. It is an approximate line figure used for explanation of error correction in an error correction code. It is a block diagram of an example of an encoder of CIRC to which the present invention can be applied. 2 is a more detailed block diagram of an example of a CIRC encoder. FIG. It is a block diagram of an example of the decoder of CIRC which can apply this invention. FIG. 4 is a more detailed block diagram of an example of a CIRC decoder. It is a basic diagram used for description of the interleaving in the case of CIRC4. It is an approximate line figure used for explanation of interleaving in the case of CIRC7. It is a basic diagram used for description of the recording format of the optical disk to which this invention is applied. It is a basic diagram used for description of the area | region encoded by CIRC7 of the optical disk to which this invention was applied. 1 is a block diagram of an example of an optical disk recording apparatus to which the present invention is applied. It is a block diagram of an example of an optical disk reproducing apparatus to which the present invention is applied.

Explanation of symbols

53 Encryptor 55 CIRC4 Encoder 56 CIRC7 Key Encoder 66 Data Replacement Circuit 78 CIRC4 Decoder 80 Decryptor 81 Key Extractor

Claims (42)

In a data recording medium having an area in which data encoded by the first error correction encoding method combining two or more error correction codes is recorded,
Two or more error correction codes are combined, and at least one of the error correction codes is reproduced data of the region by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. Is made to be decrypted,
In the decoding method, when it is determined that there is no error correction in a specific block at the time of decoding one error correction code, symbols included in the specific block are decoded at the time of decoding the other error correction code. If it is corrected, it will be judged as incorrect correction.
In the encoded output of the error correction code common to the first and second error correction encoding methods, the value of one or a plurality of symbols is changed to another value, and the error correction is determined. A data recording medium characterized by being avoided. In claim 1,
In the first and second error correction coding methods, the error correction code C1 is coded, interleaved, and the error correction code C2 is coded in order. The first and second error correction coding methods are used. A data recording medium in which only the interleaving length of the interleaving differs between methods. In claim 1,
In the first and second error correction coding methods, a plurality of symbols are encoded by an error correction code C2, the plurality of symbols and the parity symbol are interleaved, and the plurality of symbols and the parity subjected to the interleave processing are interleaved. A symbol is encoded by an error correction code C1,
A data recording medium in which the interleave length of the first error correction encoding method is 7, and the interleave length of the second error correction encoding method is 4. In claim 1,
In the first and second error correction encoding methods, a block is configured by a two-dimensional array of a plurality of symbols, and the block is aligned in any one of the first direction of the vertical direction, the horizontal direction, and the diagonal direction. A data recording medium for encoding an error correction code C1 on a plurality of symbols and encoding an error correction code C2 on a plurality of symbols aligned in a second direction different from the first direction. In a data recording method for recording data encoded by a first error correction encoding method combining two or more error correction codes on a data recording medium,
Two or more error correction codes are combined, and at least one of the error correction codes is reproduced data of the region by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. Is made to be decrypted,
In the decoding method, when it is determined that there is no error correction in a specific block at the time of decoding one error correction code, symbols included in the specific block are decoded at the time of decoding the other error correction code. If it is corrected, it will be judged as incorrect correction.
In the encoded output of the error correction code common to the first and second error correction encoding methods, the value of one or a plurality of symbols is changed to another value, and the error correction is determined. A data recording method characterized by avoiding. In claim 5,
In the first and second error correction coding methods, the error correction code C1 is coded, interleaved, and the error correction code C2 is coded in order. The first and second error correction coding methods are used. A data recording method in which only the interleaving length of the interleaving is different among the methods. In claim 5,
In the first and second error correction coding methods, a plurality of symbols are encoded by an error correction code C2, the plurality of symbols and the parity symbol are interleaved, and the plurality of symbols and the parity subjected to the interleave processing are interleaved. A symbol is encoded by an error correction code C1,
A data recording method, wherein the interleaving length of the first error correction coding method is 7, and the interleaving length of the second error correction coding method is 4. In claim 5,
In the first and second error correction encoding methods, a block is configured by a two-dimensional array of a plurality of symbols, and the block is aligned in any one of the first direction of the vertical direction, the horizontal direction, and the diagonal direction. A data recording method for encoding an error correction code C1 on a plurality of symbols and encoding an error correction code C2 on a plurality of symbols aligned in a second direction different from the first direction. In claim 5,
When encoding with the first error correction encoding method, it is checked whether or not error correction occurs when decoding with the second error correction encoding method when encoding the one error correction code. A data recording method in which when correction occurs, a symbol to be erroneously corrected is specified, and then, at the stage of encoding the other error correction code, at least a block including the specified symbol changes the value of the symbol. In claim 5,
When encoding with the first error correction encoding method, one or a plurality of error correction codes may be generated when decoding with the second error correction encoding method when the one error correction code is encoded. A data recording method for rewriting symbol values. In claim 5,
A data recording method for rewriting one or a plurality of symbol values so that when a symbol value is changed, a specific codeword is obtained when decoding is performed by the second error correction encoding method. In claim 5,
A data recording method for controlling whether or not an error correction is determined in the decoding method of the second error correction encoding method according to specific information when encoding is performed by the first error correction encoding method. In claim 12,
The data recording method, which is information for indicating that the specific information is encoded by the first error correction encoding method. In claim 12,
A data recording method wherein the specific information is information related to copy protection or security. In a data recording apparatus for recording data encoded by a first error correction encoding method combining two or more error correction codes on a data recording medium,
Two or more error correction codes are combined, and at least one of the error correction codes is reproduced data of the region by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. Is made to be decrypted,
In the decoding method, when it is determined that there is no error correction in a specific block at the time of decoding one error correction code, symbols included in the specific block are decoded at the time of decoding the other error correction code. If it is corrected, it will be judged as incorrect correction.
In the encoded output of the error correction code common to the first and second error correction encoding methods, the value of one or a plurality of symbols is changed to another value, and the error correction is determined. A data recording apparatus characterized by avoiding. In claim 15,
In the first and second error correction coding methods, the error correction code C1 is coded, interleaved, and the error correction code C2 is coded in order. The first and second error correction coding methods are used. A data recording apparatus in which only the interleaving length of the interleaving differs between methods. In claim 15,
In the first and second error correction coding methods, a plurality of symbols are encoded by an error correction code C2, the plurality of symbols and the parity symbol are interleaved, and the plurality of symbols and the parity subjected to the interleave processing are interleaved. A symbol is encoded by an error correction code C1,
A data recording apparatus, wherein the first error correction encoding method has an interleave length of 7, and the second error correction encoding method has an interleave length of 4. In claim 15,
In the first and second error correction encoding methods, a block is configured by a two-dimensional array of a plurality of symbols, and the block is aligned in any one of the first direction of the vertical direction, the horizontal direction, and the diagonal direction. A data recording apparatus for encoding an error correction code C1 for a plurality of symbols and encoding an error correction code C2 for a plurality of symbols aligned in a second direction different from the first direction. In claim 15,
When encoding with the first error correction encoding method, it is checked whether or not error correction occurs when decoding with the second error correction encoding method when encoding the one error correction code. A data recording device that, when correction occurs, specifies a symbol to be erroneously corrected, and then changes the value of the symbol at least in a block including the specified symbol in the stage of encoding the other error correction code. In claim 15,
When encoding with the first error correction encoding method, one or a plurality of error correction codes may be generated when decoding with the second error correction encoding method when the one error correction code is encoded. A data recording device that rewrites symbol values. In claim 15,
A data recording apparatus that rewrites one or a plurality of symbol values so that a specific code word is obtained when the symbol value is changed by decoding with the second error correction encoding method. In claim 15,
A data recording apparatus that controls whether or not erroneous correction is determined in the second error correction encoding method according to specific information when encoding is performed by the first error correction encoding method. In claim 22,
A data recording apparatus, which is information for indicating that the specific information is encoded by the first error correction encoding method. In claim 22,
A data recording apparatus in which the specific information is information related to copy protection or security. In a data reproduction method for reproducing a data recording medium having an area in which data encoded by a first error correction encoding method combining two or more error correction codes is recorded,
Accessing the area and reproducing the data;
Two or more error correction codes are combined, and at least one of the error correction codes is reproduced data of the region by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. A decoding step for decoding
In the decoding step, when it is determined that there is no error correction in the specific block at the time of decoding one error correction code, the symbols included in the specific block are decoded at the time of decoding the other error correction code. If it is corrected, it will be judged as incorrect correction and information that cannot be corrected will be output.
When it is determined that there is an error correction in a specific block at the time of decoding one of the error correction codes, and a symbol included in the specific block is corrected at the time of decoding the other error correction code, The above symbol is output without being judged,
A data reproduction method for using information output as a result of the decoding step to process reproduction data. In claim 25,
In the first and second error correction coding methods, the error correction code C1 is coded, interleaved, and the error correction code C2 is coded in order. The first and second error correction coding methods are used. A data reproduction method in which only the interleaving length of the interleaving is different among the methods. In claim 25,
In the first and second error correction coding methods, a plurality of symbols are encoded by an error correction code C2, the plurality of symbols and the parity symbol are interleaved, and the plurality of symbols and the parity subjected to the interleave processing are interleaved. A symbol is encoded by an error correction code C1,
A data reproduction method, wherein the interleaving length of the first error correction coding method is 7, and the interleaving length of the second error correction coding method is 4. In claim 25,
In the first and second error correction encoding methods, a block is configured by a two-dimensional array of a plurality of symbols, and the block is aligned in any one of the first direction of the vertical direction, the horizontal direction, and the diagonal direction. A data reproduction method for encoding an error correction code C1 on a plurality of symbols and encoding an error correction code C2 on a plurality of symbols aligned in a second direction different from the first direction. In claim 25,
A data reproduction method which is information for indicating that the information output as a result of the decoding step is encoded by a second error correction encoding method different from the first error correction encoding method. In claim 25,
The data output method, wherein the information output as a result of the decryption step is information related to copy protection or security. In claim 25,
A data reproduction method for determining whether or not the information output as a result of the decoding step is an original. In claim 25,
A data reproduction method in which the information output as a result of the decryption step is an encryption key or a part of the encryption key. In a data reproduction apparatus for reproducing a data recording medium having an area in which data encoded by a first error correction encoding method combining two or more error correction codes is recorded,
Means for accessing the area and reproducing the data;
Two or more error correction codes are combined, and at least one of the error correction codes is reproduced data of the region by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. Decoding means for decoding
When the decoding means determines that there is no error correction in a specific block when decoding one error correction code, the decoding means converts a symbol included in the specific block when decoding the other error correction code. If it is corrected, it will be judged as incorrect correction and information that cannot be corrected will be output.
When it is determined that there is an error correction in a specific block at the time of decoding one of the error correction codes, and a symbol included in the specific block is corrected at the time of decoding the other error correction code, The above symbol is output without being judged,
A data reproduction apparatus that uses information output from the decoding means for processing reproduction data. In claim 33,
In the first and second error correction coding methods, the error correction code C1 is coded, interleaved, and the error correction code C2 is coded in order. The first and second error correction coding methods are used. A data reproducing apparatus in which only the interleaving length of the interleaving differs between methods. In claim 33,
In the first and second error correction coding methods, a plurality of symbols are encoded by an error correction code C2, the plurality of symbols and the parity symbol are interleaved, and the plurality of symbols and the parity subjected to the interleave processing are interleaved. A symbol is encoded by an error correction code C1,
A data reproducing apparatus, wherein the first error correction encoding method has an interleave length of 7, and the second error correction encoding method has an interleave length of 4. In claim 33,
In the first and second error correction encoding methods, a block is configured by a two-dimensional array of a plurality of symbols, and the block is aligned in any one of the first direction of the vertical direction, the horizontal direction, and the diagonal direction. A data reproducing apparatus that encodes an error correction code C1 on a plurality of symbols and encodes an error correction code C2 on a plurality of symbols aligned in a second direction different from the first direction. In claim 33,
A data reproducing apparatus which is information for indicating that the information output from the decoding means is encoded by a second error correction encoding method different from the first error correction encoding method. In claim 33,
A data reproducing apparatus in which the information output from the decryption means is information related to copy protection or security. In claim 33,
A data reproduction apparatus for determining whether or not the information output from the decoding means is original. In claim 33,
The information output from the decryption means is an encryption key or a data reproducing apparatus that is a part of the encryption key. In a data transmission method for transmitting data encoded by a first error correction encoding method combining two or more error correction codes,
Two or more error correction codes are combined, and at least one of the error correction codes is reproduced data of the region by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. Is made to be decrypted,
In the decoding method, when it is determined that there is no error correction in a specific block at the time of decoding one error correction code, symbols included in the specific block are decoded at the time of decoding the other error correction code. If it is corrected, it will be judged as incorrect correction.
In the encoded output of the error correction code common to the first and second error correction encoding methods, the value of one or a plurality of symbols is changed to another value, and the error correction is determined. A data transmission method characterized by avoiding. In a data reception method for receiving transmission data encoded by a first error correction encoding method in which two or more error correction codes are combined,
A combination of two or more error correction codes, and at least one of the error correction codes is decoded by the decoding method of the second error correction encoding method that is the same as the first error correction encoding method. A decoding step
In the decoding step, when it is determined that there is no error correction in the specific block at the time of decoding one error correction code, the symbols included in the specific block are decoded at the time of decoding the other error correction code. If it is corrected, it will be judged as incorrect correction and information that cannot be corrected will be output.
When it is determined that there is an error correction in a specific block at the time of decoding one of the error correction codes, and a symbol included in the specific block is corrected at the time of decoding the other error correction code, The above symbol is output without being judged,
A data receiving method that uses information output as a result of the decoding step to process received data.

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