Data recording method and apparatus

Abstract: A method of and apparatus for recording data onto a disc-shaped recording medium having a sector construction such as an optical disc increases the interleave length of recorded data to cope with burst error or the like by dividing input data into predetermined lengths, respectively two-dimensionally arranging the divided data, generating and adding error correction codes to the two-dimensionally arranged data by a predetermined series to thereby form n encoded blocks; changing the data arrangement among the n encoded blocks; and distributing and recording the changed data to each sector on the disc-shaped recording medium.

Description: The present invention relates to a data recording method which is suitable for use when data is recorded to, for instance, an optical disc and to apparatus for carrying out that method. The development of the WORM (write once, read many) type optical disc and the erasable and rewritable optical disc (for instance, magneto optical disc) has progressed in recent times. In such an optical disc, each data track is divided into a plurality of sectors and data is recorded/reproduced on a sector unit basis. For instance, in the recording format for 5.25 inch diameter optical discs each data track is divided into 17 sectors into which data can be recorded. EP-A-0,258,059 discloses optical recording methods which make use of two-dimensionally arranged data blocks. Parity data is added along one direction of the block and the data is read out and recorded along the orthogonal direction. EP-A-0,163,41 discloses a method and apparatus of recording data on a disc which stores digital data in a buffer memory and converts address data when reading and writing to be non-consecutive as seen from a recorded pattern of the disc and consecutive as seen from a peripheral device. Data is interleaved within data blocks on the disc. In the conventional optical disc, in order to cope with burst errors or the like, the data for each sector is encoded with an error correction code and a parity code for error correction is generated and added. For instance, among the recording formats of 5.25 inch optical discs, there is a format which uses an LDC (long distance code) as an error correcting method. In the recording format using the LDC, for instance, control data and a CRC code for error detection are added to each 512 bytes of the user's data, data is written into a buffer memory in the horizontal direction, error correction encoding is executed in which respective columns are used as an encoding series, and a parity code of 16 bytes per series (5 x 16 = 80 bytes per sector) is added. The data is read out from the buffer in the horizontal direction and recorded into the destination sector on the optical disc. As mentioned above, in the case of generating and adding a parity for error correction of 16 bytes to one series, the error correction can be executed for up to eight bytes per series. Data is arranged into five columns, the error correction code is added by using each column as an encoding series, and the reading/writing operations are executed in the horizontal direction, so that an interleave of five bytes is executed. Therefore, in this case, it is possible to cope with the generation of burst errors of up to 5 x 8 = 40 bytes. Defects of 40 bytes extent correspond to a length of about 300 µm at the innermost rim of the disc. As mentioned above, in the case of 5.25 inch optical discs, it is possible to cope with burst errors corresponding to for instance, 40 bytes by the LDC. However, in a recording medium such as an optical disc on which data is to be recorded at a high density, it can happen that fairly large burst errors are generated. In such a case, error correction cannot satisfactorily be executed by the LDC as mentioned above. Therefore, when recording data onto an optical disc, a verification is made to see if errors equal to or exceeding a predetermined value have been generated in the sector into which data is to be recorded or not. The sector in which errors of a predetermined value or more are generated is regarded as a defective sector. The data to be recorded into the defective sector is then recorded into an alternate sector. In this manner, the alternate sector process as mentioned above is performed. However, even if such an alternate sector process is executed, it is impossible to cope with large burst errors which are generated after data has been recorded. If large burst errors are generated in a read only disc, the alternate sector process cannot be executed. It is, therefore, an object of the present invention to provide a data recording method which can effectively execute error correction of large burst errors. Another object of the invention is to provide a data recording method which can improve the correcting capability for large burst errors without largely changing the required circuitry and format. According to one aspect of the present invention there is provided a method for recording data onto a disc shaped recording medium having a sector construction, comprising the steps of: dividing input data into n predetermined lengths, where n is an integer greater than 1; arranging each of said predetermined lengths into a separate two-dimensional input data array; generating, for each input data array, error correction codes for predetermined one-dimensional series in the respective input data array and adding said error correction codes to said predetermined series in said respective input data array to form a respective encoded array, thereby forming n encoded arrays; recording the n encoded data arrays to n sectors on said disk-shaped recording medium; wherein said n encoded arrays are recorded by sequentially recording from each of said n encoded arrays data having the same two-dimensional coordinates in their respective encoded arrays. According to another aspect of the present invention there is provided an apparatus for recording data onto a disc shaped recording medium having a sector construction, comprising: means for dividing input data into n predetermined lengths, where n is an integer greater than 1; means for arranging each of said predetermined lengths into a separate two-dimensional input data array; means for generating, for each input data array, error correction codes for predetermined one-dimensional series in the respective input data array and adding said error correction codes to said predetermined series in said respective input data array to form a respective encoded array, thereby forming n encoded arrays; means for recording the n encoded data arrays to n sectors on said disk-shaped recording medium; wherein said means for recording is operative to record said n encoded arrays by sequentially recording from each of said n encoded arrays data having the same two-dimensional coordinates in their respective encoded arrays. In this invention, the input data is stored into buffer memories and encoded by the LDC, respectively. The encoded data is controlled by a buffer memory access controller so that the interleave length becomes substantially long and is recorded into each sector on the disc. In the case where the input data is divided into, for instance, four encoding blocks and the data is rearranged among the four encoded blocks and is recorded, the interleave length is substantially increased four times as compared with that in the case where the data is not rearranged. Therefore, the error correcting capability for burst errors can be increased. The invention will be further described by way of non-limitative example with reference to the accompanying drawings, in which:- Figure 1 is a functional block diagram which is used in explanation of a preferred embodiment of the present invention; Figure 2 is a plan view showing the data arrangement of a disc for use in the embodiment of the invention depicted in figure 1; Figure 3 is a flowchart which is used in explanation of the encoding in the embodiment of the invention depicted in figure 1; Figures 4A, 4B, 4C and 4D are schematic diagrams which are used in explanation of the encoding blocks in the embodiment of the invention depicted in figure 1; Figures 5A, 5B, 5C and 5D are schematic diagrams which are used in explanation of the recording of data in each sector in the embodiment of the invention depicted in figure 1; Figures 6A, 6C, 6C, 6D and 7A, 7B, 7C and 7D are schematic diagrams which are used in explanation of the embodiment of the invention depicted in figure 1; Figure 8 is a flowchart which is used in explanation upon decoding in the embodiment of the invention depicted in figure 1; and Figures 9A, 9B, 9C and 9D are schematic diagrams which are used in explanation of another embodiment of the invention. A preferred embodiment of the present invention will be described hereinbelow with reference to the drawings. In figure 1, reference numeral 1 denotes an input/output terminal for recording or reproduction data; 2 indicates an input/output terminal for data which is recorded or reproduced onto or from a disc 6 (figure 2); 3 an encoding/decoding circuit to perform the encoding and decoding of an LDC (long distance code); 4A to 4D buffer memories; and 5 a buffer memory access controller. When data is recorded onto the disc 6, input data from the input/output terminal 1 is stored once in the buffer memories 4A to 4D. A parity for error correction is generated and added to the input data which was two-dimensionally arranged and stored in the buffer memories 4A to 4D by using each column as an encoding series by means of the encoding/decoding circuit 3. When reproducing data from the disc 6, the reproduced data of the disc 6 is received at the input/output terminal 2 and is stored once in the buffer memories 4A to 4D. The error correcting process of the reproduction data of the disc 6 stored in the buffer memories 4A to 4D is executed by the encoding/decoding circuit 3. The buffer memory access controller 5 controls the read or write addresses in the buffer memories 4A to 4D. An erasable and rewritable optical disc, for instance, a magneto-optical disc can be used as the disc 6. As shown in figure 2, spiral or annular tracks T are formed on the disc 6. Each of the tracks T is divided into a plurality of physical sectors S₁, S₂, S₃, S₄, . . . and data is recorded there. The invention can be also similarly applied to a WORM type optical disc and to a read only optical disc. In addition, the invention can be also likewise applied to a magnetic disc such as a hard disc or the like. First, the operation in the case of recording data onto the disc 6 will be described with reference to the flowchart shown in figure 3. The data to be recorded onto the disc 6 is input at the input terminal 1. Input data of 512 bytes from data D₁ 1 to D₁ 512 is sequentially written into the buffer memory 4A in the horizontal direction. 512 bytes of subsequent data D₂ 1 to D₂ 512 is sequentially written into the buffer memory 4B in the horizontal direction. Subsequently, input data of 512 bytes, D₃ 1 to D₃ 512, is sequentially written into the buffer memory 4C in the horizontal direction. Lastly, 512 bytes of subsequent data D₄ 1 to D₄ 512 is sequentially written into the buffer memory 4D in the horizontal direction (step 11). The data written into the buffer memories 4A to 4D is two-dimensionally arranged as shown in figures 4A to 4D. That is, as shown in figure 4A, the data D₁ 1 to D₁ 512 are two-dimensionally arranged in the buffer memory 4A into four columns and 128 rows. A row of control data P₁ 1 to P₁ 4 and a row of CRC codes CRC₁ 1 to CRC₁ 4 for error detection are added to these data. Similarly, as shown in figure 4B, the data D₂ 1 to D₂ 512 are two-dimensionally arranged in the buffer memory 4B in 128 rows and 4 columns. A row each of control data P₂ 1 to P₂ 4 and CRC codes CRC₂ 1 to CRC₂ 4 for error detection are added to these data. In figure 4C, the data D₃ 1 to D₃ 512 are likewise two-dimensionally arranged in the buffer memory 4C. The control data P₃ 1 to P₃ 4 and CRC codes CRC₃ 1 to CRC₃ 4 for error detection are added to these data. Finally, as shown in figure 4D, the data D₄ 1 to D₄ 512 are two-dimensionally arranged in the buffer memory 4D. Control data P₄ 1 to P₄ 4 and CRC codes CRC₄ 1 to CRC₄ 4 for error detection are added to these data. As shown in figures 4A to 4D, error correction codes are generated and added to the two dimensionally arranged data by the encoding/decoding circuit 3 by using each column as an encoding series (step 12 of figure 3). That is, 16-byte parity codes E₁ 1,1 to E₁ 1,16, E₁ 2,1 to E₁ 2,16, E₁ 3,1 to E₁ 3,16 and E₁ 4,1 to E₁ 4,16 for error correction are generated and added to each of the respective columns of the encoding block shown in figure 4A. Similarly, 16-byte parity codes E₂ 1,1 to E₂ 1,16, E₂ 2,1 to E₂ 2,16, E₂ 3,1 to E₂ 3,16, and E₂ 4,1 to E₂ 4,16 for error correction are generated and added to each of the respective columns of the encoding block shown in figure 4B. Parity codes E₃ 1,1 to E₃ 1,16, E₃ 2,1 to E₃ 2,16, E₃ 3,1 to E₃ 3,16 and E₃ 4,1 to E₃ 4,16 for error correction of 16-bytes are generated and added to each of the respective columns of the encoding block shown in figure 4C. Finally, 16-bytes parity codes E₄ 1,1 to E₄ 1,16, E₄ 2,1 to E₄ 2,16, E₄ 3,1 to E₄ 3,16 and E₄ 4,1 to E₄ 4,16 for error correction are generated and added to each of the respective columns of the encoding block shown in figure 4D. As shown in figures 4A to 4D, by adding the 16 rows of parity codes for error correction to each column, error correction can be performed for up to eight bytes per individual series. The data in the buffer memories 4A to 4D is read out under the control of the buffer memory access controller 5 and is output from the input/output terminal 2 and is recorded onto the disc 6. At this time, the reading operations of the buffer memories 4A to 4D are controlled by the buffer memory access controller 5 so that the interleave length becomes substantially long (step 13 of figure 3). That is, for instance, when one data is read out of the buffer memory 4A, one data is then read out of the buffer memory 4B. Next, one data is read out of buffer memory 4C and one data is sequentially read out of the buffer memory 4D. By alternately reading out the data from the four buffer memories 4A to 4D as mentioned above, the sequence of the data is rearranged and the data is recorded in the physical sectors S₁ to S₄ on the disc 10 as shown in figures 5 A to 5E. That is, as shown in figure 5A, the data is sequentially recorded into the physical sector S₁ in accordance with the sequence of the data D₁ 1, D₂ 1, D₃ 1, D₄ 1, D₁ 2, D₂ 2, D₃ 2, D₄ 2, . . . and so forth until the data D₁ 146, D₂ 146, D₃ 146 and D₄ 146 so that data comprising 584 bytes is recorded. As shown in figure 5B, the data is sequentially recorded into the physical sector S₂ in accordance with the sequence of the data D₁ 147, D₂ 147, D₃ 147, D₄ 147, D₁ 148, D₂ 148, D₃ 148, D₄ 148, ... and so forth until the data D₁ 292, D₂ 292, D₃ 292 and D₄ 292 so that data comprising 584 bytes is recorded. As shown in figure 5C, the data is sequentially recorded into the physical sector S₃ in accordance with the sequence of the data D₁ 293, D₂ 293, D₃ 293, D₄ 293, D₁ 294, D₂ 294, D₃ 294, D₄ 294, ... and so forth until the data D₁ 438, D₂ 438, D₃ 438 and D₄ 438 so that data comprising 584 bytes is recorded. As shown in figure 5D, the data is sequentially recorded into the physical sector S₄ in accordance with the sequence of the data D₁ 439, D₂ 439, D₃ 439, D₄ 439, D₁ 440, D₂ 440, D₃ 440, D₄ 440, ... and so forth until the data E₁ 4,16, E₂ 4,16, E₃ 4,16 and E₄ 4,16 so that data comprising 584 bytes is recorded. By recording the data onto the disc 6 by this rearranging method, the interleave length is substantially increased four times as compared with that in the case where the data is not rearranged. That is, as shown in figures 4A to 4D, by arranging the data at four columns and adding parities for error correction of 16 bytes to every column, error correction of up to eight bytes per one series can be executed. In the case where the data is not rearranged, an interleave of four bytes is performed. Therefore, in the case where the data stored in the buffer memories 4A to 4D is recorded into the corresponding physical sectors on the disc 6 without rearranging the data, it is possible to cope with burst errors of only up to 8 x 4 = 32 bytes. On the other hand, when the data ia rearranged and recorded onto the disc 6 as mentioned above, the interleave length is further increased four times. Therefore, it is possible to cope with burst errors of up to 4 x 32 = 128 bytes. For instance, assume that defects occurred on the disc 6 in the data recording areas of 128 bytes, for example, in the data D₁ 1 to D₄ 32 in the physical sector S₁ 1 shown as hatched portions in figure 6A. In this case, as shown by hatched portions in figures 7A to 7D, the errors are generated in the data of the first to eight rows in each encoding block. Since the error correction codes of 16 bytes have been added to each column in each of the encoding blocks of figures 7A to 7D, error correction of up to eight bytes in each encoding series can be executed. Thus, all of the errors which were generated at that time can be corrected. The operation during data reproduction will now be described. The operation upon reproduction is the inverse of that during recording. That is, as shown in the flowchart of figure 8, the data from the physical sectors S₁ to S₄ on the disc 6 is sequentially reproduced. As mentioned above, the data has been rearranged and recorded in the physical sectors S₁ to S₄ on the disc 6. This rearranged, reproduced data is input at the input/output terminal 2 and the sequence of the data is returned to the original sequence under the control of the buffer memory access controller 5 and the data is sequentially stored into the buffer memories 4A to 4D (step 21 of figure 8). That is, the sequence of the reproduced data of the disc 6 based on the sequence as shown in figures 5A to 5D is rearranged under the control of the buffer memory access controller 5. The data D₁ 1, D₁ 2, D₁ 3, D₁ 4, ... is sequentially stored into the buffer memory 4A in the horizontal direction. The data D₂ 1, D₂ 2, D₂ 3, D₂ 4, . . . is sequentially stored into the buffer memory 4B in the horizontal direction. The data D₃ 1, D₃ 2, D₃ 3, D₃ 4, ... is sequentially stored into the buffer memory 4C in the horizontal direction. The data D₄ 1, D₄ 2, D₄ 3, D₄ 4, ... is sequentially stored into the buffer memory 4D in the horizontal direction. Thus, the reproduced data is returned to the original two-dimensional arrangement as shown in figures 4A to 4D. For the data stored in the buffer memories 4A to 4D, the error correcting process is executed by the encoding/decoding circuit 3 by using each column as an encoding series. As mentioned above, the error correction can be executed for up to eight bytes by such an error correcting process by each encoding series. Therefore, it is possible to cope with burst errors of up to 128 bytes (step 22 of figure 8). The data, once error correction processed, is sequentially read out of the buffer memories 4A to 4D and output from the input/output terminal 1 (step 23 of figure 8). In the preferred embodiment, as shown in figures 5A to 5D, the data is rearranged in accordance with the sequence of the data D₁ 1, D₂ 1, D₃ 1, D₄ 1, D₁ 2, D₂ 2, D₃ 2, D₄ 2, .... However, the rearranging method of data is not limited to this manner. It is possible to use any rearranging method such that the interleave length becomes substantially long. For instance, as shown in figures 9A to 9D, the data D₁ 1, D₁ 2, D₁ 3 and D₁ 4 of the first row in the encoding block in figure 4A is recorded into the physical sector S₁, the data D₁ 5, D₁ 6, D₁ 7 and D₁ 8 of the second row is recorded into the physical sector S₂, the data D₁ 9, D₁ 10, D₁ 11 and D₁ 12 of the third row is recorded into the physical sector S₃, and the data D₁ 13, D₁ 14, D₁ 15 and D₁ 16 of the fourth row is recorded into the physical sector S₄. It is possible to execute the rearrangement as mentioned above. In the above embodiment, the input data is divided into four encoding blocks by the four buffer memories 4A to 4D and encoded and the data rearrangement is performed among the four encoding blocks. However, the number of encoding blocks is not limited to four. For instance, it is also possible to divide the input data into two encoding blocks and to execute the data rearrangement between the two encoding blocks. By executing the data rearrangement between the two encoding blocks as mentioned above, the interleave length can be substantially doubled. The number of encoding blocks into which the input data is divided is determined in consideration of the length of the burst errors which will be generated in the disc and the capacities of the buffer memories which can be realised. The information indicative of the number of encoding blocks which were divided can be written as a flag onto a control track or onto an ID section of each sector. The invention is not limited to the LDC but can be also similarly applied to the case of using a product code. According to the invention, the data which was divided into, for instance, four encoding blocks and encoded is recorded into each sector on the disc by rearranging the data sequence. By executing the data rearrangement among a plurality of encoding blocks, the interleave length becomes substantially long and the error correcting capability for burst errors can be increased. Having described a specific preferred embodiment of the present invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to that precise embodiment, and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined in the appended claims.

Claims: A method for recording data onto a disc-shaped recording medium (6) having a sector construction, comprising the steps of: dividing input data into n predetermined lengths, where n is an integer greater than 1; arranging each of said predetermined lengths into a separate two-dimensional input data array; generating, for each input data array, error correction codes for predetermined one-dimensional series in the respective input data array and adding said error correction codes to said predetermined series in said respective input data array to form a respective encoded array, thereby forming n encoded arrays; recording the n encoded data arrays to n sectors (5) on said disc-shaped recording medium (6); characterised in that said n encoded arrays are recorded by sequentially recording from each of said n encoded arrays data having the same two-dimensional coordinates in their respective encoded arrays. A data recording method according to claim 1, wherein the data is recorded from the n-encoded arrays in the direction in the arrays of the one-dimensional series which are orthogonal to said first-mentioned one-dimensional series. An apparatus for recording data onto a disc-shaped recording medium (6) having a sector construction, comprising: means for dividing input data into n predetermined lengths, where n is an integer greater than 1; means for arranging each of said predetermined lengths into a separate two-dimensional input data array; means for generating, for each input data array, error correction codes for predetermined one-dimensional series in the respective input data array and adding said error correction codes to said predetermined series in said respective input data array to form a respective encoded array, thereby forming n encoded arrays; means for recording the n encoded data arrays to n sectors (5) on said disc-shaped recording medium (6); characterised in that said means for recording is operative to record said n encoded arrays by sequentially recording from each of said n encoded arrays data having the same two-dimensional coordinates in their respective encoded arrays. An apparatus according to claim 3, wherein said means for recording is operative to record the data from the n-encoded arrays in the direction in the arrays of the one-dimensional series which are orthogonal to said first-mentioned one-dimensional series. An apparatus according to either claim 3 or 4, said apparatus including a buffer memory, said input data being arranged into said input data arrays in said memory, and said error correction codes being added to said input arrays in said memory. Apparatus according to any one of claims 3 to 5 and including means for reading data from designated sectors of the disc, means for error-correction-processing the data and means for restoring the error-correction-processed data to its original arrangement prior to its two dimensional arrangement before recording.

Inventors: TOBITA MINORU C O SONY CORPORA, YOKONO SHIGERU C O SONY CORPOR, TOBITA, MINORU C/O SONY CORPORATION, YOKONO, SHIGERU C/O SONY CORPORATION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1989
Main classification: G11B20
IPC codes: G11B20, H03M13