JP5042972B2 - Data reproducing apparatus and data reproducing method - Google Patents

Description

  The present invention relates to a data reproducing apparatus and a data reproducing method.

  In a recording medium such as a magnetic disk, a specific code string (hereinafter, also referred to as a sync mark (SM)) representing a data head position SP is recorded in each sector as a data recording unit together with data. The data reproducing apparatus reads the reproduction signal from the disk by the reproducing head, detects SM from the reproduction signal, and decodes the data according to the head position SP represented by SM.

  The data reproducing apparatus cannot properly decode the data unless it detects the SM. For this reason, there is known a dual sync mark type data recording method in which data of each sector is divided into data parts 1 and 2 and SM1, data parts 1, SM2, and data part 2 are continuously recorded.

  When the data reproduction device of the dual sync mark method cannot detect SM1 but can detect SM2, the data included in the data portion 2 is decoded according to the head position SP represented by SM2, and the data included in the data portion 1 is detected. Is corrected with an error correction code. In addition, when the data reproducing apparatus cannot detect SM1 and SM2, the data reproducing apparatus estimates the head position SP of the data portion based on a read gate (RG) signal, and the data according to the estimated value SP ′ of the head position. Data included in parts 1 and 2 is decoded.

  Specifically, the data reproducing apparatus estimates the start position SP by counting the clocks based on the RG signal, and forcibly gives the estimated value SP ′ of the start position to the decoder, thereby estimating the start position. Attempt to decode the data according to the value SP ′. Further, if the data reproducing apparatus cannot properly decode the data in accordance with the estimated value SP ′ of the head position, the data reproducing apparatus performs the read operation on the same sector again after the disk has made one revolution.

JP 2003-16734 A

  However, since the RG signal and the reproduction signal are not completely synchronized, it is difficult to properly estimate the head position SP of the data, and it is necessary to repeat the read operation with the disk rotation waiting for the same sector. There is a problem that the data reproduction performance is remarkably deteriorated. Further, since SM2 is recorded in addition to SM1, there is a problem that the format efficiency is lowered, that is, the recording capacity is reduced or the recording density is increased.

  The present invention has been made in view of the above-described problems, and its object is to provide a new and improved technique capable of appropriately decoding data included in a sector by estimating the start position of the data included in the sector. Another object is to provide a data reproducing apparatus and a data reproducing method.

  In order to solve the above problems, according to a first aspect of the present invention, a storage unit that temporarily stores a reproduction signal read from a recording medium in units of sectors, and a reproduction signal read from the recording medium, A detection unit that detects a specific code string representing the head position of data included in the sector, and generates a head position estimation value based on the sector data structure, and changes the head position estimation value. When the change unit and the specific code string are not detected, the data is decoded according to the estimated value of the head position from the temporarily stored reproduction signal, and the data cannot be decoded according to the estimated value of the head position Includes a decoding unit that repeatedly decodes data from a reproduction signal temporarily stored in accordance with an estimated value of a head position that is changed each time decoding of data in the same sector. Apparatus is provided.

  According to this configuration, first, the reproduction signal read from the recording medium in units of sectors is temporarily stored, and detection of a specific code string is attempted from the reproduction signal. If the specific code string is not detected, the head position of the data is estimated based on the data structure of the sector, the temporarily stored reproduction signal is read, and the data is read according to the estimated value of the head position. Decrypted. Also, if the data could not be decoded according to the estimated value of the starting position, the estimated value of the starting position is changed every time the data of the same sector is decoded, and the reproduction signal temporarily stored is read again, Data is iteratively decoded according to the changed estimated value.

  Thereby, it is possible to appropriately decode the data included in the sector by repeating decoding while changing the estimated value of the head position with respect to the reproduction signal in units of sectors read at the same timing. Further, since it is not necessary to record two or more specific code strings in each sector in order to detect the specific code string, the format efficiency is not reduced.

  In order to solve the above problem, according to a second aspect of the present invention, there is provided a data reproduction method applicable to the data reproduction apparatus according to the first aspect of the present invention.

  In order to solve the above problems, according to a third aspect of the present invention, a storage unit that temporarily stores a reproduction signal read from a recording medium in units of sectors, and a reproduction signal read from the recording medium, A detection unit that detects a specific code string representing the head position of data included in the sector, and if the specific code string is not detected, generates an estimated value of the data head position based on the data configuration of the sector, A first position generating / changing unit that changes an estimated value of the starting position; a first reliability calculating unit that calculates data reliability information from a reproduction signal temporarily stored according to the estimated value of the starting position; A determination unit that determines whether or not the reliability information satisfies the threshold. If the reliability information does not satisfy the threshold, the reliability information is changed every time the reliability information is calculated for the data of the same sector until the reliability information satisfies the threshold. Head A second reliability calculation unit that repeatedly calculates reliability information from a temporarily stored reproduction signal according to the estimated value of the device, and if the reliability information satisfies a threshold value, based on the reliability information There is provided a data reproducing device including a decoding unit for decoding data.

  According to this configuration, first, the reproduction signal read from the recording medium is temporarily stored in units of sectors, and detection of a specific code string is attempted from the reproduction signal. Here, when the specific code string is not detected, the head position of the data is estimated based on the data structure of the sector, the temporarily stored reproduction signal is read, and the head is read from the read reproduction signal. Reliability information is calculated according to the estimated position value. Next, it is determined whether the reliability information satisfies a threshold value. Here, when the reliability information does not satisfy the threshold value, the estimated value of the head position is changed, the reproduction signal temporarily stored is read again, and the head position changed from the reproduction signal read again The reliability information is calculated according to the estimated value. Until the reliability information satisfies the threshold value, the determination and calculation of the reliability information are repeated while changing the estimated value of the head position each time the reliability information is calculated for the data in the same sector. Further, when the reliability information satisfies the threshold value, the data is decoded based on the reliability information.

  As a result, the reliability information of the data contained in the sector is obtained by repeating the determination and calculation of the reliability information while changing the estimated value of the head position for the reproduction signal in units of sectors read at the same timing. It is possible to appropriately calculate and appropriately decode data included in the sector.

  In order to solve the above problem, according to a fourth aspect of the present invention, there is provided a data reproduction method applicable to the data reproduction apparatus according to the third aspect of the present invention.

  According to the present invention, it is possible to provide a data reproducing apparatus and a data reproducing method capable of appropriately decoding data included in a sector by estimating the head position of the data included in the sector.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  In the following, first, as a description of a data reproducing apparatus according to the prior art, a data reproducing apparatus 1 and a data reproducing apparatus 50 using LDPC (Low Density Parity Check) code and iterative decoding will be described. Next, as a description of the data reproducing apparatus according to the present invention, the data reproducing apparatuses 100 and 150 according to the first and second embodiments of the present invention will be described.

[1. Description of data reproducing apparatus according to prior art]
Hereinafter, the data reproducing apparatus 1 according to the related art will be described with reference to FIGS. 6 to 8, and the data reproducing apparatus 50 using the LDPC code and the iterative decoding according to the related art will be described with reference to FIG. To do.

[1-1. Data reproducing apparatus 1 according to prior art]
FIG. 6 shows a recording format of the disk D. 6A shows a plurality of cylinders Ci, Ci + 1, Ci + 2,... Arranged circumferentially on the disk D as data recording areas. In each cylinder C, reference position information representing at least one reference position RP is recorded.

  In FIG. 6B, a plurality of sectors # 0, # 1, # 2, # 3,..., #N arranged in each cylinder C are shown as data recording units. Data is recorded in each cylinder C at a predetermined time interval T. Specifically, the data of sector # 0 is recorded from the time point when the offset time T0 has elapsed from the reference position RP, and from time points 1T, 2T, 3T,. Data of sector # 2, sector # 3,..., Sector #n are recorded in each. Thereby, the data reproducing apparatus 1 can determine the timing of the read operation for a desired sector based on the elapsed time after the reference position information RP is detected. Although details are omitted in FIG. 6B, each cylinder C is provided with servo areas at regular intervals, and various gate signals are normally generated according to the timing of servo information recorded in the servo areas. Is done.

  FIG. 6C shows the data structure of sector S1 in the dual sync mark method. In the sector S1, a preamble used for synchronization control at the time of reading operation, SM1 representing the head position of the data part 1, SM2 representing the head position of the data part 1, the data part 2, and the data part 2 are continuously recorded. Yes. Further, in each sector S1, following the data portion 2, an ECC (Error Correct Code) used for error correction, a CRC (Cyclic Redundancy Check) used for error detection, and a pad representing the end of the sector S1 are continuously recorded. Has been. Normally, the data portion 1 is recorded with a data length that can be restored by ECC even when it is not decoded.

  FIG. 7 shows a data reproducing apparatus 1 according to the prior art. The data reproducing apparatus 1 includes a preamplifier 2, a read channel 4 (RDC: ReaD Channel), and a hard disk controller 6 (HDC: Hard Disk Controller). The preamplifier 2 includes an amplifier 8, and the amplifier 8 amplifies a reproduction signal read from the disk D by a reproduction head (not shown) and outputs the amplified signal to the RDC 4.

  The RDC 4 includes a variable gain amplifier 10 (VGA: Variable Gain Amplifier), a CT filter 12 (CTF: Continuous Time Filter), an AD converter 14 (ADC: Analog Digital Converter), an FIR (FIR: Finite Impulse Filter, and an automatic gain filter 16). It includes a control 18 (AGC: Automatic Gain Control), timing recovery 20 (TRC: Timing Recovery Circuit), an SM detection unit 22 (SMD: Synchronous Mark Detector), a switch A24, and a decoder 26.

  The VGA 10 amplifies the reproduction signal amplified by the amplifier 8 to a desired amplitude based on control by the AGC 18. The CTF 12 coarsely adjusts the signal characteristics by suppressing high frequency noise of the reproduction signal output from the VGA 10. The ADC 14 discretizes the reproduction signal output from the CTF 12 and converts the analog signal into a digital signal. The FIR 16 finely adjusts the signal characteristics of the reproduction signal output from the ADC 14 (waveform equalization, etc.). The AGC 18 controls the amplification factor of the VGA 10 based on the amplitude of the reproduction signal output from the FIR 16. The TRC 20 performs synchronization control based on the synchronization signal included in the preamble of each sector in order to perform sampling at a desired signal position by the ADC 14.

  The SMD 22 detects the SM representing the head position SP of the data portion from the reproduction signal, and outputs the SM detection result to the switch A24. The switch A24 is set to “0” when the SM is detected, and selectively outputs the head position SP represented by the SM to the decoder 26, and is set to “1” when the SM is not detected. As described later, the head position estimated value SP ′ output from the counter 36 is selectively output to the decoder 26. The decoder 26 decodes data from the reproduction signal output from the FIR 16 according to the start position SP or the estimated value SP ′ of the start position, and outputs it to the HDC 6.

  The HDC 6 includes an ECC / CRC decoder 28. The ECC / CRC decoder 28 corrects the error of the decoded data by ECC, inspects it by CRC, and outputs it as reproduced data.

  The counter 36 counts the clock with reference to the RG signal transmitted from the HDC 6, generates an estimated value SP ′ of the head position based on the clock count value, and outputs it to the decoder 26 through the switch A 24. Thereby, when the SM is detected, the decoder 26 decodes the data according to the head position SP represented by the SM. When the SM is not detected, the decoder 26 estimates the head position SP ′ based on the RG signal. Decrypt data according to

  Below, operation | movement of the data reproduction apparatus 1 is demonstrated. In the data reproducing apparatus 1, the SMD 22 tries to detect SM1 from the reproduced signal. When SM1 is detected, the switch A24 is set to “0”, and the decoder 26 receives the data according to the head position SP represented by SM1. Decrypt. If SM1 is not detected, the SMD 22 tries to detect SM2. If SM2 is detected, the decoder 26 determines the data included in the data portion 2 according to the head position SP represented by SM2. Decrypt. In this case, the ECC / CRC decoding unit 28 corrects the data included in the data unit 1 by the ECC recorded in each sector.

  On the other hand, when SM1 and SM2 are not detected, the switch A24 is set to “1”, and the decoder 26 decodes the data according to the estimated value SP ′ of the head position generated by the counter 36. Specifically, the counter 36 counts the clock with reference to the RG signal transmitted from the HDC 6, generates the estimated value SP ′ of the leading position based on the counted value of the clock, and decodes the estimated value SP ′ of the leading position. Forced to vessel 26. Further, if the data reproducing apparatus 1 cannot properly decode the data in accordance with the estimated value SP ′ of the head position, the data reproducing apparatus 1 waits until the disk D makes one revolution, and after the disk D makes one revolution, the data reproducing apparatus 1 again performs the read operation for the same sector. Do.

  FIG. 8 shows a method for generating the estimated value SP ′ of the head position. In the data reproducing apparatus 1, the HDC 6 enables the RG signal when a predetermined time (for example, T0 + iT in the sector #i) elapses after the reference position RP recorded in each cylinder is detected. The read operation for each sector is started. When a predetermined time has elapsed after the start of the read operation, the HDC 6 disables the RG signal, whereby the read operation for each sector is completed. In each sector, the data recorded as a preamble and SM is set to have a predetermined amount.

  Therefore, by counting the clock with reference to the RG signal transmitted from the HDC 6, the head position SP of the data portion can be estimated to some extent based on the count value of the clock. However, since the RG signal and the reproduction signal are not completely synchronized, the probability that the estimated value SP ′ of the leading position that matches the leading position SP of the data portion can be generated is not necessarily high.

  As described above, in the data reproducing apparatus 1 according to the prior art, since the RG signal and the reproduced signal are not completely synchronized, it is difficult to appropriately generate the estimated value SP ′ of the head position, and the same sector On the other hand, it is necessary to repeat the read operation accompanied by waiting for the rotation of the disk D, and the data reproduction performance is significantly deteriorated. Further, since SM2 is recorded in addition to SM1, the format efficiency is reduced, that is, the recording capacity is reduced or the recording density is increased.

[1-2. Data reproducing apparatus 50 according to prior art]
FIG. 9 shows a data reproducing apparatus 50 using LDPC code and iterative decoding according to the prior art. The data reproducing device 50 includes a preamplifier, RDC, and HDC. FIG. 9 shows only the configuration of the RDC.

  The RDC includes a VGA 52, a CTF 54, an ADC 56, an FIR 58, an AGC 60, a TRC 62, an SMD 64, an APP (A Posteriori Probability Check) decoder 66, an LDPC (Low Density Parity Check) decoder 68, a determiner 70, and an RLL (Run Length) decoding. A device 72 is included. Note that the APP decoder 66 and the LDPC decoder 68 are configured with a predetermined number of stages as the APP decoders 66-1 to 66-m and the LDPC decoders 68-1 to 68-m. Among the RDCs, the VGA 52, CTF 54, ADC 56, FIR 58, AGC 60, and TRC 62 have the same functions as the respective components of the data reproducing apparatus 1 shown in FIG.

  The SMD 64 detects the SM representing the head position SP of the data part from the reproduction signal output from the APP decoder 66-1, and outputs it to the LDPC decoder 68-1. Here, the SM is referred to as code frame information when the LDPC decoder 68 calculates data reliability information for the regularity of the LDPC code, as will be described later.

  The APP decoder 66-1 calculates the posterior probabilities of “0” and “1” from the reproduced signal output from the FIR 58 using SOVA (Soft Output Viterbi Algorithm) or the like, and outputs it to the LDPC decoder 68-1. To do. The LDPC decoder 68-1 calculates data reliability information with respect to the regularity of the LDPC code in consideration of the posterior probability output from the APP decoder 66-1. Next, the reliability information calculated by the LDPC decoder 68-1 is output to the second-stage APP decoder 66-2.

  The second-stage APP decoder 66-2 calculates the posterior probability while considering the reliability information calculated by the LDPC decoder 68-1, and outputs the posterior probability to the LDPC decoder 68-2. -2 updates data reliability information. After the processes by the APP decoders 66-3 to m and LDPC decoders 68-3 to m having a predetermined number of stages are repeated, the determiner 70 is output from the last stage LDPC decoder 68-m. The reliability information is subjected to threshold processing and output to the RLL decoder 72. Further, the RLL decoder 72 generates a reproduction value of the data and outputs it to an HDC (not shown).

  As described above, in the data reproducing device 50 according to the prior art, the reliability information of the data is calculated according to the SM referred to as the frame information of the code. Therefore, if the SM is not detected, the data of the data included in the sector is calculated. The reliability information cannot be calculated properly, and the data included in the sector cannot be decoded properly.

[2. Description of Data Reproducing Device According to the Present Invention]
Hereinafter, the data reproducing apparatus 100 according to the first embodiment will be described with reference to FIGS. 1 to 3, and the data reproducing apparatus 150 according to the second embodiment will be described with reference to FIGS. 4 and 5. explain.

[2-1. Data reproducing apparatus 100 according to first embodiment]
FIG. 1 shows a data reproducing apparatus 100 according to the first embodiment. The data reproduction device 100 includes a preamplifier 12, an RDC 14, and an HDC 16. The preamplifier 12 has the same configuration as the preamplifier 2 of the data reproducing apparatus 1 according to the related art. In addition to the VGA 110, CTF 112, ADC 114, FIR 116, AGC 118, TRC 120, SMD 122, switch A 124, and decoder 126, the RDC 104 includes a buffer 130, an error determination / head position generation unit 132, and a switch B 134. The HDC 106 includes an ECC / CRC decoder 128.

  Among the RDCs 104, the VGA 110, the CTF 112, the ADC 114, the FIR 116, the AGC 118, and the TRC 120 have the same functions as the corresponding components of the data reproducing apparatus 1 according to the related art. The data reproducing apparatus 100 according to this embodiment is a single sync mark type disk reproducing apparatus that decodes data in accordance with the head position SP represented by one SM recorded in each sector.

  The SMD 122 detects the SM indicating the head position SP of the data portion from the reproduction signal, outputs the SM detection result to the switch A124, and if SM is not detected, an SM detection error is determined as an error determination / head position generation. Notification to the unit 132. The switch A 124 is set to “0” when the SM is detected, and selectively outputs the head position SP indicated by the SM to the decoder 126, and is set to “1” when the SM is not detected. As described later, the head position estimated value SP ′ output from the error determination / head position generation unit 132 is selectively output to the decoder 126 as described later.

  The buffer 130 temporarily stores the reproduction signal output from the FIR 116 in units of sectors, and in response to an output instruction from the error determination / head position generation unit 132, the buffer 130 temporarily stores the reproduction signal stored in the switch B134. Output. The error determination / head position generation unit 132 is notified of the SM detection error from the SMD 122 according to the SM detection result, or, as will be described later, according to the CRC check result of the decoded data, the ECC / CRC decoding A CRC check error is notified from the device 128.

  When the error determination / leading position generation unit 132 is notified of the SM detection error or is notified of the CRC check error after the notification of the SM detection error, the error determination / leading position generation unit 132 generates an estimated value SP ′ of the start position and outputs the estimated value SP ′ The output instruction is notified to the buffer 130. The switch B 134 is set to “0” when SM is detected, selectively transmits the reproduction signal output from the FIR 116 to the decoder 126, and is set to “1” when SM is not detected. The reproduction signal set and output from the buffer 130 is selectively transmitted to the decoder 126. The decoder 126 decodes the data based on the reproduction signal output from the FIR 116 or the buffer 130 and outputs the data to the ECC / CRC decoder 128.

  The ECC / CRC decoder 128 corrects the error of the decoded data by ECC, inspects it by CRC, and outputs it as reproduced data. Further, the ECC / CRC decoder 128 notifies the error check / head position generation unit 132 of the CRC check error when an error is detected by the CRC check after the SM detection error occurs.

  Thus, the decoder 126 decodes the data according to the data head position SP represented by the SM when the SM is detected, and generates the error determination / head position generation unit 132 when the SM is not detected. The data output from the buffer 130 is decoded according to the estimated value SP ′ of the head position.

  Hereinafter, the operation of the data reproducing apparatus 100 will be described with reference to FIG. In the data reproducing apparatus 100, a reproduction signal is read from the disk D in units of sectors (step S10), and is transmitted from the preamplifier 102 to the RDC 104 to perform processing such as waveform equalization. The buffer 130 temporarily stores the reproduction signal output from the FIR 116 in units of sectors (S12).

  The SMD 122 tries to detect the SM from the reproduction signal (S14). When the SM is detected (when the determination result of S14 is “No”), the switch A124 and the switch B134 are set to “0”. Is performed. In this case, the decoder 126 decodes the data according to the start position SP indicated by the SM, and the ECC / CRC decoder 128 performs error correction / error check on the decoded data to determine whether a CRC check error is detected. To do. If no error is detected by the CRC check, the decoded data is output as reproduction data. If an error is detected, the decoding process is performed after a read operation involving waiting for rotation of the disk D is performed. Is done again.

  On the other hand, when the SM is not detected in the process of step S14, the SMD 122 notifies the error determination / leading position generation unit 132 of an SM detection error.

  When the SM detection error is notified, the switch A 124 and the switch B 134 are set to “1”, and the error determination / head position generation unit 132 generates the head position estimated value SP ′ (S 16), and the switch A 124. And an output instruction is notified to the buffer 130. In response to the output instruction, the buffer 130 outputs the reproduction signal temporarily stored in units of sectors to the decoder 126 through the switch B134 (S18). Thereby, the decoder 126 decodes data from the reproduction signal output in units of sectors from the buffer 130 in accordance with the estimated value SP ′ of the starting position generated by the error determination / starting position generating unit 132 (S20).

  Then, the ECC / CRC decoder 128 performs error correction / error check on the decoded data (S22), and determines whether no error is detected by the CRC check (S24).

  If no error is detected by the CRC check, the decoded data is output as reproduction data (S26). On the other hand, when an error is detected by the CRC check, the ECC / CRC decoder 128 notifies the error determination / head position generation unit 132 of the CRC check error. Then, when a CRC check error is notified, the processes of steps S16 to S20 are performed as in the case of the SM detection error. Accordingly, the decoder 126 decodes data from the reproduction signal output from the buffer 130 in accordance with the estimated value SP ′ of the starting position changed by the error determination / leading position generating unit 132. In the processes of steps S22 and S24, the error correction / error check is performed again on the decoded data, and the processes of steps S16 to S24 are repeated until no CRC check error is detected.

  FIG. 3 shows a method for generating / changing the estimated value SP ′ of the head position. In each sector S2, the data recorded as the preamble and SM is set to have a predetermined amount. For this reason, the head position SP of the data portion of each sector S2 can be estimated with high accuracy based on the data structure of the sector. That is, the error determination / leading position generation unit 132 generates a predetermined number of preamble and SM data to be processed prior to the data included in the data part as the estimated value SP ′ of the starting position.

  Here, the buffer 130 temporarily stores the reproduction signal output from the FIR 116 in units of sectors, and outputs it to the decoder 126 in response to an output instruction. That is, whenever the output instruction is notified, the buffer 130 outputs the same reproduction signal from the head of each sector S2 to the decoder 126 at the same timing. Therefore, the data reproducing apparatus 100 can appropriately decode the data included in the data portion of each sector S2 by repeating decoding while changing the estimated value SP ′ of the leading position based on the sector data configuration. .

  As shown in FIG. 3, the error determination / leading position generation unit 132 changes the estimated value SP ′ of the starting position according to a predetermined rule with reference to the estimated value SP ′ of the starting position based on the data structure of the sector. FIG. 3 shows an actual arrangement of the sector S2 based on the head position SP represented by SM and an arrangement of the sector S2 ′ based on the estimated value SP ′ of the head position based on the sector data configuration. .

  The estimated value SP ′ of the start position is, for example, + δ (SP1) with respect to the estimated value SP ′ (SP0) of the start position every time an SM detection error or a CRC check error is notified after notification of the SM detection error. , −δ (SP2), + 2δ (SP3), −2δ (SP4),... Here, “δ” is set, for example, as “4 bits” (considering the preamble period). In the case shown in FIG. 3, when the estimated value SP ′ of the head position is changed to SP3, the estimated value SP ′ of the head position matches the head position SP.

  As described above, in the data reproducing apparatus 100 according to the first embodiment, first, the reproduction signal read from the disk D is temporarily stored in units of sectors, and SM detection is attempted from the reproduction signal. If SM is not detected, an estimated value SP ′ of the data head position is generated based on the data structure of the sector, and the reproduction signal stored temporarily is read out to estimate the value of the head position. Data is decoded according to SP ′. If the data cannot be decoded according to the estimated value SP ′ of the start position, the estimated value SP ′ of the start position is changed every time the data of the same sector is decoded, and the reproduction signal temporarily stored is changed. The data is read again and the data is repeatedly decoded according to the estimated value SP ′ of the head position after the change.

  Thereby, it is possible to appropriately decode the sector data by repeating the decoding while changing the estimated value SP ′ of the head position with respect to the reproduction signal of the sector unit read at the same timing. Further, since it is not necessary to record two or more SMs in each sector in order to detect the SM, the format efficiency is not reduced.

  Further, even when data cannot be properly decoded in accordance with the estimated value SP ′ of the head position, the reproduction signal stored temporarily is read without waiting for the disk D to rotate, and decoding for the same sector is repeated. Thus, the data can be properly decrypted.

  However, when reading and decoding data of a plurality of sectors continuously, the decoding of the data of the same sector is repeated, so that the RDC 104 is occupied for decoding of the sector, and the read operation for the subsequent sector is delayed. End up.

[2-2. Data Reproducing Device 150 According to Second Embodiment]
FIG. 4 shows a data reproducing apparatus 150 using the LDPC code and iterative decoding according to the second embodiment. The data reproduction device 150 includes a preamplifier, RDC, and HDC. Note that FIG. 4 shows only the configuration of the RDC.

  RDC includes VGA152, CTF154, ADC156, FIR158, AGC160, TRC162, SMD164, APP decoder 166, LDPC decoder 168, determiner 170, and RLL decoder 172, as well as buffer 174, reliability determination / head position generation The unit 16 and the switch C178 are included. Note that the APP decoder 166, the LDPC decoder 168, the reliability determination / head position generation unit 176, and the switch C178 include an APP decoder 166-1 to m, an LDPC decoder 168-1 to m, and a reliability determination / head position. The position generation units 176-2 to m and switches C178-2 to m are configured with a predetermined number of stages.

  Among the RDCs, the VGA 152, the CTF 154, the ADC 156, the FIR 158, the AGC 160, the TRC 162, the determination unit 170, and the RLL decoder 172 have the same functions as the respective units of the data reproducing device 50 according to the related art.

  The buffer 174 temporarily stores the reproduction signal output from the FIR 158 in units of sectors, and outputs the temporarily stored reproduction signal from the reliability determination / leading position generation units 176-2 to m of each stage. In response to the instruction, the data is output to the switches C178-2 to m of each stage. The APP decoder 166-1 calculates the posterior probability from the reproduction signal output from the FIR 158, and outputs the posterior probability to the LDPC decoder 168-1. The SMD 164 detects SM from the reproduction signal output from the APP decoder 166-1.

  Here, when the SM is detected, the LDPC decoder 168-1 takes the reliability information of the data in accordance with the head position SP represented by the SM while considering the posterior probability output from the APP decoder 166-1. calculate. In this case, the switches C178-2 to m of each stage are set to “0”, and the APP decoders 166-2 to 16-m of the second and subsequent stages are respectively replaced with the LDPC decoders 168-1 to m− of the preceding stage. 1, the posterior probability is calculated and output to the LDPC decoders 168-2 to m of each stage, and the LDPC decoders 168-2 to m of each stage Update reliability information. Then, the determiner 170 performs threshold processing on the reliability information output from the LDPC decoder 168-m at the final stage using the second threshold, and outputs the reliability information to the RLL decoder 172. The RLL decoder 172 A reproduction value is generated and output to the HDC.

  On the other hand, when the SM is not detected, the SMD 164 notifies the SM detection error to the second-stage reliability determination / leading position generation unit 176-2. In this case, the second-stage switch C178-2 is set to “1”, and the reliability determination / head position generation unit 176-2, as described with reference to FIG. 2, starts the head position based on the data structure of the sector. Is estimated and output to the LDPC decoder 168-2 and the buffer 174 is notified of the output instruction. When notified of the output instruction, the buffer 174 outputs the reproduction signal temporarily stored in units of sectors to the APP decoder 166-2 through the switch C178-2.

  Then, the APP decoder 166-2 calculates the posterior probability from the reproduction signal output from the buffer 174 and outputs the posterior probability to the LDPC decoder 168-2. The LDPC decoder 168-2 determines the reliability and generates the head position. Data reliability information for the regularity of the LDPC code is calculated according to the estimated value SP ′ of the head position output from the unit 176-2.

  When the SM is not detected, the reliability determination / leading position generation units 176-3 to 176-3m in the third and subsequent stages receive the reliability output from the preceding LDPC decoders 168-2 to m-1. Threshold processing is performed on the degree information.

  When the reliability information satisfies the first threshold, the switches C178-3 to m at each stage are set to “0”, and the APP decoders 166-3 to m at the third stage and thereafter are set to Considering the reliability information calculated by the LDPC decoders 168-2 to m-1, the posterior probability is calculated and output to the LDPC decoders 168-3 to m of each stage, and the LDPC decoder 168 of each stage. −3 to m update the reliability information of each data.

  On the other hand, when the reliability information does not satisfy the first threshold value, the switches C178-3 to m of each stage are set to “1”. In addition, as described with reference to FIG. 2, the reliability determination / leading position generation units 176-3 to 176-3m at each stage include the head position generated by the reliability determination / leading position generation unit 176-2 at the second stage. The estimated value SP ′ is changed so as to be different from each other at each stage. Here, the estimated value SP ′ of the head position is, for example, + δ (SP1), − based on the estimated value SP ′ (SP0) generated by the reliability determination / head position generator 176-2 at the second stage. δ (SP2), + 2δ (SP3), −2δ (SP4),.

  Then, the reliability determination / leading position generation units 176-3 to 176-m at each stage output the changed estimated value SP ′ of the starting position to the LDPC decoders 168-3 to 168-m at each stage, and also to the buffer 174. Notify the output instruction. When notified of the output instruction, the buffer 174 outputs the reproduction signal temporarily stored in units of sectors to the APP decoders 166-3 to m of each stage through the switches C178-3 to m of each stage. .

  Then, the APP decoders 166-2 to 16-m at each stage calculate the posterior probability from the reproduction signal output from the buffer 174 and output the posterior probabilities to the LDPC decoders 168-3 to m at each stage. Units 168-3 to 168-m calculate data reliability information for the regularity of the LDPC code according to the estimated value SP ′ of the leading position output from the reliability determination / leading position generation unit 176-3 to m of each stage. To do.

  When the SM is not detected, it is determined that the reliability information satisfies the first threshold value by one of the reliability determination / leading position generation units 176-2 to 17-m of the second and subsequent stages. Until then, the determination and calculation of the reliability information are repeated while changing the estimated value SP ′ of the head position. For example, if the reliability determination / leading position generation unit 176-l in the l-th stage determines that the reliability information satisfies the first threshold value, the APP decoders 166-l to 166-l in the respective stages after the l-th stage. m and LDPC decoders 168-l-m update the reliability information of the data. Then, the determiner 170 performs threshold processing on the reliability information output from the LDPC decoder 168-m at the final stage using the second threshold, and outputs the reliability information to the RLL decoder 172. The RLL decoder 172 A reproduction value is generated and output to the HDC.

  Hereinafter, the operation of the data reproducing apparatus 150 will be described with reference to FIG. In the data reproducing device 150, a reproduction signal is read from the disk D in units of sectors (step S50), and is transmitted from the preamplifier to the RDC to be subjected to processing such as waveform equalization. The buffer 174 temporarily stores the reproduction signal read from the disk D and processed (S52).

  The APP decoder 166-1 calculates the posterior probability of the data from the reproduction signal read from the disk D (S54), and outputs it to the LDPC decoder 168-1. The SMD 164 tries to detect the SM indicating the head position SP of the data included in the sector from the reproduction signal read from the disk D (S56).

  When SM is detected in the processing of step S56 (the determination result of S56 is “No”), normal processing is performed according to the head position of the data represented by SM. On the other hand, if no SM is detected in the process of step S56 (the determination result of S56 is “Yes”), an SM detection error is output to the second-stage reliability determination / start position generation unit 176-2. The Then, the reliability determination / start position generation unit 176-2 at the second stage generates an estimated value SP ′ of the start position of the data based on the data structure of the sector (S58), and outputs it to the LDPC decoder 168-2. To do. In addition, the reliability determination / head position generation unit 176-2 notifies the buffer 174 of an output instruction, and the buffer 174 outputs the temporarily stored reproduction signal to the APP decoder 166-2 in units of sectors. (S60).

  The APP decoder 166-2 calculates the posterior probability from the reproduction signal output from the buffer 174, and outputs the posterior probability to the LDPC decoder 168-2. The LDPC decoder 168-2 calculates reliability information from the reproduced signal output from the buffer 174 in accordance with the estimated value SP ′ of the head position in consideration of the posterior probability (S62). It outputs to the head position generation part 176-3 (S64).

  In each of the third and subsequent stages, the reliability determination / head position generation units 176-3 to 176-m have the reliability information output from the preceding LDPC decoders 168-2 to m−1 satisfy the first threshold. Is determined (S66).

  Here, when the reliability information does not satisfy the first threshold value, the process returns to the process of step S58, the estimated value SP ′ of the head position of the data is changed, and the reproduction signal temporarily stored becomes the sector. Output in units. Then, the APP decoders 166-3 to m of each stage calculate a posteriori probability from the reproduction signal output from the buffer 174 and output the posterior probability to the LDPC decoders 168-3 to m of each stage. The LDPC decoders 168-3 to 168-m at each stage calculate reliability information according to the changed estimated value SP ′ of the head position from the temporarily stored reproduction signal in consideration of the posterior probability.

  Here, the reliability determination / leading position generation units 176-3 to 176-m of the third and subsequent stages estimate the starting position in the process of step S 58 when the reliability information does not satisfy the first threshold value. The value SP ′ is changed. For example, if the reliability information output from the second, third, and fourth LDPC decoders 168-2, 3, and 4 does not satisfy the first threshold, the third and fourth stages The reliability determination / leading position generation units 176-3, 4 and 5 in the fifth stage use + δ (SP1), −δ () with reference to the estimated value SP ′ (SP0) of the leading position based on the data structure of the sector. SP2), + 2δ (SP3), the estimated value SP ′ of the head position is changed.

  When the SM is not detected, it is determined that the reliability information satisfies the first threshold value by one of the reliability determination / leading position generation units 176-2 to 17-m of the second and subsequent stages. Until the estimated value SP ′ of the head position is generated (second stage) or changed (after the third stage), determination and calculation of reliability information are repeated. For example, if the reliability determination / leading position generation unit 176-l in the l-th stage determines that the reliability information satisfies the first threshold value, the APP decoders 166-l to 166-l in the respective stages after the l-th stage. The m and LDPC decoders 168-l to 168-m update the reliability information of each data (S68).

  When the update of the reliability information by the final stage APP decoder 166-m and the LDPC decoder 168-m is completed, the determiner 170 receives the reliability information output from the final stage LDPC decoder 168-m. Threshold processing is performed using the second threshold (S70), and the result is output to the RLL decoder 172. The RLL decoder 172 generates a reproduction value of the data and outputs it to an ECC / RCC decoder (not shown), and the ECC / RCC decoder outputs the reproduction data after error correction / error check (S72).

  As described above, in the data reproduction device 150 according to the second embodiment, first, the reproduction signal read from the disk D is temporarily stored in units of sectors, and SM detection is attempted from the reproduction signal. Here, when SM is not detected, an estimated value SP ′ of the head position of the data is generated based on the data structure of the sector, the temporarily stored reproduction signal is read, and the read reproduction Reliability information is calculated from the signal according to the estimated value SP ′ of the head position.

  Next, it is determined whether the reliability information satisfies a first threshold value. Here, when the reliability information does not satisfy the first threshold value, the estimated value SP ′ of the head position is changed, the temporarily stored reproduction signal is read again, and the reproduction signal read again is read out. Reliability information is calculated according to the changed estimated value SP ′ of the head position. Until the reliability information satisfies the first threshold value, the determination and calculation of the reliability information are repeated while changing the estimated value SP ′ of the head position each time the reliability information is calculated for the data in the same sector. Further, when the reliability information satisfies the first threshold value, data is decoded from the reproduction signal based on the updated reliability information.

  As a result, the reliability of the data included in the sector is repeated by repeating the determination and calculation of the reliability information while changing the estimated value SP ′ of the head position for the reproduction signal in units of sectors read at the same timing. It is possible to appropriately calculate information and appropriately decode data included in the sector.

  In addition, after the first stage processing for the first sector data is completed, the second stage processing for the first sector data is started and the first stage processing for the second sector data is started. can do. That is, data of a plurality of sectors that are continuously read out can be processed in parallel at each stage. As a result, like the data reproducing apparatus 100 according to the first embodiment, by repeatedly decoding the data of the same sector, the RDC is occupied in the decoding process of the sector, and the data reading operation of the subsequent sector is performed. There is no delay.

  In the data reproducing apparatus 150 according to the present embodiment, the decoding process is performed based on the reproduction signal output from the buffer 174 in accordance with the reliability determination result, so that the number of iterations of the decoding process is substantially reduced. Resulting in. However, since the data reproduction apparatus using iterative decoding is designed so that reliability information is saturated and error rate is almost saturated by decoding processing of a predetermined number of stages, the possibility that the error rate is deteriorated is low.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, this invention is not limited to the example which concerns. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

It is a block diagram which shows the structure of the data reproduction apparatus which concerns on 1st Embodiment. It is a flowchart which shows operation | movement of the data reproduction apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the production | generation / change method of the estimated value of the head position which concerns on 1st Embodiment. It is a block diagram which shows the structure of the data reproduction apparatus which concerns on 2nd Embodiment. It is a flowchart which shows operation | movement of the data reproduction apparatus which concerns on 2nd Embodiment. It is a figure for demonstrating the recording format (cylinder arrangement | positioning) of a disc. It is a figure for demonstrating the recording format (sector arrangement | positioning) of a disc. It is a figure for demonstrating the recording format (sector structure) of a disk. It is a block diagram which shows the structure of the data reproduction apparatus which concerns on a prior art. It is a figure for demonstrating the production | generation method of the estimated value of the head position based on a prior art. It is a block diagram which shows the structure of the data reproduction apparatus using the LDPC code and iterative decoding based on a prior art.

Explanation of symbols

122, 164 SMD
124 Switch A
126 Decoder 130, 174 Buffer 132 Error determination / head position generator 134 Switch B
166 APP decoder 168 LDPC decoder 176 Reliability determination / head position generation unit 178 Switch C

Claims (5)

A storage unit for temporarily storing a reproduction signal read from the recording medium in units of sectors;
A detection unit for detecting a specific code string representing a head position of data included in a sector from a reproduction signal read from the recording medium;
A head position generation / change unit that generates an estimated value of the head position of data based on the data structure of the sector and changes the estimated value of the head position;
When the specific code string is not detected, the data is decoded according to the estimated value of the head position from the temporarily stored reproduction signal, and the data cannot be decoded according to the estimated value of the head position Includes a decoding unit that repeatedly decodes data from the temporarily stored reproduction signal in accordance with the estimated value of the head position that is changed each time the data of the same sector is decoded.
A data reproducing apparatus comprising: Temporarily storing a reproduction signal read from the recording medium in units of sectors;
Detecting a specific code string representing a head position of data included in a sector from a reproduction signal read from the recording medium;
If the specific code string is not detected, an estimated value of the head position of data is generated based on the data configuration of the sector, the temporarily stored reproduction signal is read, and the read reproduction signal is read Decoding data according to the estimated value of the head position from:
If the data could not be decoded according to the estimated value of the head position, the estimated value of the head position is changed every time decoding is performed on the data in the same sector, and the reproduction signal stored temporarily is read again. Repetitively decoding data from the re-read reproduction signal according to the changed estimated value of the starting position;
Including a data reproducing method. A storage unit for temporarily storing a reproduction signal read from the recording medium in units of sectors;
A detection unit for detecting a specific code string representing a head position of data included in a sector from a reproduction signal read from the recording medium;
When the specific code string is not detected, an estimated value of the leading position of data is generated based on the data structure of the sector, and a leading position generating / changing unit that changes the estimated value of the leading position;
A first reliability calculation unit that calculates data reliability information from the temporarily stored reproduction signal according to the estimated value of the head position;
A determination unit for determining whether the reliability information satisfies a threshold;
If the reliability information does not satisfy the threshold, the temporary position is changed according to the estimated value of the head position that is changed each time the reliability information is calculated for the data of the same sector until the reliability information satisfies the threshold. A second reliability calculation unit that repeatedly calculates the reliability information from a reproduction signal stored in a stored manner,
When the reliability information satisfies a threshold, a decoding unit that decodes data based on the reliability information;
A data reproducing apparatus comprising: Temporarily storing a reproduction signal read from the recording medium in units of sectors;
Detecting a specific code string representing a head position of data included in a sector from a reproduction signal read from the recording medium;
If the specific code string is not detected, an estimated value of the head position of data is generated based on the data configuration of the sector, the temporarily stored reproduction signal is read, and the read reproduction signal is read calculating a signal Yoriyukido information according to the estimated value of the head position from
Determining whether the reliability information satisfies a threshold;
If the reliability information does not satisfy the threshold value, the estimated value of the head position is changed, the reproduction signal stored temporarily is read again, and the changed head is re-read from the reproduction signal read again. Calculating the reliability information according to a position estimate;
Repeating the determination and calculation of the reliability information while changing the estimated value of the head position for each calculation of the reliability information for the data of the same sector until the reliability information satisfies a threshold;
If the reliability information meets a threshold, decoding data based on the reliability information;
Including a data reproducing method. Further comprising the step of continuously reading a reproduction signal from the recording medium in units of sectors;
In the step of determining the reliability information, each time the reliability information is determined for the data included in a specific sector, the step of storing the reproduction signal for the data included in the subsequent sector is started. 5. The data reproduction method according to claim 4, wherein a reproduction signal continuously read out in units is continuously processed.

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