JP2003115173A - Decoding device and method, and information reproducing device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a regenerative signal that is temporally short. SOLUTION: An amplitude reference value initial value storage part 10 for storing an ideal amplitude reference value, an update initial value storage part 11 for storing an update initial value, an amplitude reference value storage part 12 for storing an amplitude reference value, an update operating part 13 for updating the amplitude reference value of the amplitude reference value storage part 12, a switching part 14 for setting the update initial value to either the amplitude reference value initial value storage part 10 or an updated amplitude reference value, a gate counter 15 for counting read gate signals, a selection part 16 for selecting either the update initial value of the update initial value storage part 11 or an amplitude reference value updated by the update operating part 13 as an amplitude reference value, and a control part for controlling switching of update initial values in the switching part 14 and/or selection of an amplitude reference value in the selection part 16 are provided. According to this, an amplitude reference value initial value is selected and an amplitude reference value is updated on the basis of a read gate signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decoding device and a decoding method, and an information reproducing device and an information reproducing method, and more particularly, to an accurate PRML (Partial Response Maximum) by accurately reproducing a recording signal which is short in time. The present invention relates to a decoding device and a decoding method for executing the Likelihood) method, and an information reproducing device and an information reproducing method for executing the PRML method to reproduce signal information.

[0002]

2. Description of the Related Art In the field of so-called digital mass storage such as digital video tape recorders, hard disks, and optical disks, PRML (Partial Response) is used.
A reproduction equalization / detection method called the Maximum Likelihood method is used.

This PRML method is better than the identification for each bit by the partial response equalization that enables recording / reproduction in a narrow band, which is multi-valued, and recursively calculating the likelihood of state transition. It is a combination of maximum likelihood decoding that can obtain various error rates. A typical algorithm for maximum likelihood decoding is Viterbi decoding, and a decoding device that realizes this is called a Viterbi decoding device.

The Viterbi decoding device and the Viterbi decoding method are often used when decoding a reproduction signal reproduced from a recording medium in an information recording device typified by a magneto-optical disk device.

The Viterbi decoding method is a decoding method capable of reducing the bit error rate when decoding a reproduced signal containing white noise. In the Viterbi decoding method, a plurality of states are specified in advance according to the recording method for the recording medium, and the read clock is followed by the calculation processing performed at the timing according to the read clock based on the reproduction signal reproduced from the recording medium. At each time point, the most likely state transition is selected. Then, corresponding to the result of such selection, decoded data as a series of decoded data values of "1" or "0" is generated.

The calculation process based on the reproduced signal is performed with reference to an amplitude reference value determined by the type of Viterbi decoding method. In the ideal case where the reproduced signal is not affected by amplitude fluctuations or the like, the amplitude reference value may be theoretically determined from the type of Viterbi decoding method. However, in a general case where the reproduced signal is not ideal, in order to improve the accuracy of Viterbi decoding, the amplitude reference value is updated by updating the amplitude reference value according to the amplitude fluctuation of the reproduced signal. It is necessary to adapt to the reproduced signal.

As such a method, generally, for example, the amplitude of the reproduced signal is detected by means such as an envelope detector, and the amplitude reference value is updated every predetermined period based on the detected value. .

For example, in an information reproducing apparatus that uses a removable recording medium such as a magneto-optical disk apparatus, the characteristics of each recording medium vary greatly during recording or reproducing operation due to factors such as different manufacturers. . Therefore, it is necessary to perform the calibration operation when the recording medium is mounted, for example. The calibration operation is an operation for controlling the operating conditions of the constituent elements in the recording system or the reproducing system to be optimum for the characteristics of the recording medium.

In the third-generation 5.25-inch optical disk device, the laser power during recording (hereinafter referred to as recording laser power) is calibrated as follows.

First, the recording laser power is initialized, and a predetermined pattern is recorded under this initialization. Then, the recorded predetermined pattern is reproduced, and the peak-to-peak voltage and the center voltage of the envelope signal of the reproduction signal are A / D converted and fetched. The deviation of asymmetry, that is, the asymmetrical distortion of the reproduced signal waveform is measured based on the captured voltage value. Since the asymmetry and the recording laser power have a close relationship, it is possible to know the suitability of the recording laser power for the magneto-optical disk as the recording medium from the asymmetry measured as described above.

When it is determined that the recording laser power is not optimum, the optimum recording laser power is estimated based on the asymmetry value, and the recording laser power is initialized again. The above procedure is repeated until the recording laser power is optimized.

The peak-to-peak voltage and the center voltage used in the calibration with respect to the recording laser power are temporarily sampled and held from the reproduced signal, and then A / D converted and taken in.

For example, in a third-generation 5.25-inch optical disk or the like, the DC component added to the reproduction signal varies greatly. Therefore, the sample hold value changes depending on the timing of sample hold. Even if it is calculated based on such a sample hold value, it is difficult to calculate asymmetry with high accuracy. In order to improve the calculation accuracy of the asymmetry, it is also possible to average a plurality of sample hold values obtained by performing sample hold for each voltage value a plurality of times, and use the average value to calculate the asymmetry.

[0014]

The quality of an ID signal, which is a prepit of a recording medium such as a magneto-optical disk, is controlled by the disk manufacturer, but there is a deviation from the above-mentioned amplitude reference value. Is the reality. Among magneto-optical discs, for example, the asymmetry of the reproduction signal is largely changed vertically depending on the radial position of the disc, or the amplitude variation is remarkable. Since such a magneto-optical disk is often caused by improper setting of the cutting machine in the manufacturing process, the asymmetry and the amplitude that are significantly deviated continuously deviate.

Therefore, in order to deal with such a disc having a poor ID quality, a Viterbi decoder capable of more optimal decoding by updating the amplitude reference value itself is also considered. As a method of updating the amplitude reference value in the conventional Viterbi decoder of the amplitude reference value adaptive type, the method of resetting and updating the initial value of the amplitude reference value for each read gate signal, or the initial value of the amplitude reference value is always used. There are ways to update.

However, for example, on the disk surface of a magneto-optical disk, the data area has an area of at least 512 bytes, whereas the ID signal area has
Since it is a very short area of 5 or 6 bytes, the period required to read the ID signal described in such a narrow area is
In a very short period, when the initial value of the amplitude reference value is reset for each read gate signal as in the conventional case, the update of the amplitude reference value does not proceed. Therefore, if there is an ID signal whose asymmetry is significantly deviated, this ID signal cannot be accurately read.

In the latter method, in which the initial value of the amplitude reference value is constantly updated, the asymmetry is significantly deviated.
The D signal can also be read, but once updated to an inappropriate amplitude reference value due to a loss of the RF signal or the like, it takes some time to return to the appropriate amplitude reference value.
Therefore, during this period, the amplitude reference value is not updated and the reading performance is deteriorated.

Therefore, the present invention has been proposed in view of such a conventional situation, and a decoding device for correctly reading the asymmetry of a reproduction signal such as an ID signal, which is short in time, fluctuates remarkably. And a decoding method, and an information reproducing apparatus and an information reproducing method.

[0019]

In order to achieve the above-mentioned object, a decoding apparatus according to the present invention updates an amplitude reference value determined by intersymbol interference caused by a reproduced signal and executes maximum likelihood decoding. In the decoding device, amplitude reference value initial value storage means for storing an ideal amplitude reference value specific to the system,
An update initial value storage means for storing an update initial value for initializing the amplitude reference value, an amplitude reference value storage means for storing an actual amplitude reference value, and an amplitude reference value stored in the amplitude reference value storage means. Either the update calculation means, the ideal amplitude reference value stored in the amplitude reference value initial value storage means or the amplitude reference value updated by the update calculation means is selected and supplied to the update initial value storage means, and the update initial value is stored. Switching means for setting the updated initial value stored in the value storage means to either the amplitude reference value initial value or the updated amplitude reference value, and a read gate signal generated based on the read series of reproduced signals. And the amplitude reference value stored in the amplitude reference value storage means are selected as the amplitude reference value stored in the update initial value storage means or the amplitude reference value updated by the update calculation means. Comprises selection means, and control means for controlling on the basis of the counting result from the counting means to select the amplitude reference value in switching and / or selecting means updates the initial value in the switching means.

Thus, in the decoding device according to the present invention, the control means sets the amplitude reference value initial value and updates the amplitude reference value based on the read gate signal.

Here, the control means may reset the actual amplitude reference value to the ideal amplitude reference value stored in the amplitude reference value initial value storage means for each predetermined read gate signal. Further, the control means uses the updated initial value updated last time as the actual amplitude reference value during the predetermined read gate signal period, and when the predetermined read gate signal period has passed, the control means finally determines in the predetermined read gate signal period. Alternatively, the updated initial value updated in step 1 may be used as the actual amplitude reference value.

Further, in order to achieve the above-mentioned object, the decoding method according to the present invention is a decoding method for updating the amplitude reference value determined by the inter-symbol interference caused by a reproduced signal to execute maximum likelihood decoding, An update calculation step for updating the amplitude reference value stored in the amplitude reference value storage means for storing the actual amplitude reference value, and an amplitude reference value initial value storage means for storing the ideal amplitude reference value peculiar to the system. Either the ideal amplitude reference value or the amplitude reference value updated in the update calculation step is selected, and the selected amplitude reference value is supplied to the update initial value storage means for storing it as the update initial value. A switching step of setting the amplitude reference value to either an initial value or an updated amplitude reference value, a counting step of counting read gate signals generated based on a series of read signals read, As the amplitude reference value in the reference value storage means, the selection step of selecting which of the update initial value of the update initial value storage means and the amplitude reference value updated by the update calculation means is adopted, and the update initial value in the switching step And a control step of controlling the selection of the amplitude reference value in the switching and / or selection step based on the counting result from the counting step.

Thus, according to the decoding method of the present invention, in the control step, the setting of the initial value of the amplitude reference value and the updating of the amplitude reference value are executed based on the read gate signal.

Here, in the control step, the actual amplitude reference value may be reset to the ideal amplitude reference value stored in the amplitude reference value initial value storage means for each predetermined read gate signal. Further, in the control step, the update initial value updated last time is used as the actual amplitude reference value for the predetermined read gate signal period, and when the predetermined read gate signal period elapses, the final read gate signal period is finally determined. Alternatively, the updated initial value updated in step 1 may be used as the actual amplitude reference value.

Further, the decoding device according to the present invention is applied to the amplitude reference value adaptation unit of the information reproducing apparatus, and a predetermined calculation process is performed based on the amplitude reference value obtained by this amplitude reference value adaptation unit. The information reproducing apparatus is provided with a section and an operation control section that controls the operation of the constituent elements in the apparatus by referring to the output from the calculation processing section.

Such an information reproducing apparatus controls the switching of the update initial value by the switching means and / or the selection of the amplitude reference value by the selecting means in accordance with the operation control of the components in the operation control section.

Further, the decoding method according to the present invention is applied to the amplitude reference value adaptation step of the information reproducing method, and a predetermined calculation processing is performed based on the amplitude reference value obtained by the amplitude reference value adaptation step. And an operation control step of controlling the operation of the constituent elements in the apparatus with reference to the output from the calculation processing step.

According to such an information reproducing method, the switching of the update initial value in the switching step and / or the selection of the amplitude reference value in the selection step are controlled according to the operation control of the constituent elements in the operation control step.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The decoder shown as a specific example of the present invention performs PR (effective transmission) by applying intersymbol interference obtained from a combination of reproduced signals obtained by reproducing recorded signals on a recording medium to a waveform. Partial Response) Viterbi decoder that performs signal processing by combining equalization and Viterbi decoding that selects and reproduces the most probable sequence from pre-correlated data sequences, and stores the ideal amplitude reference value specific to the system. An amplitude reference value initial value storage unit, an update initial value storage unit that stores an update initial value that initializes the amplitude reference value, an amplitude reference value storage unit that stores an actual amplitude reference value, and an amplitude reference value storage unit An update calculation unit for updating the amplitude reference value stored in, and an update by selecting either the ideal amplitude reference value stored in the amplitude reference value initial value storage unit or the amplitude reference value updated by the update calculation unit. Initial value memory Based on a read-out series of reproduced signals, and a switching unit for setting the update initial value stored in the update initial value storage unit to either the amplitude reference value initial value or the updated amplitude reference value. Either the update initial value of the update initial value storage unit or the amplitude reference value updated by the update calculation unit is adopted as the amplitude reference value in the counting unit for counting the read gate signal generated by the above and the amplitude reference value storage unit. The amplitude reference value is provided by including a selection unit that selects whether or not the switching initial value and / or a control unit that controls the selection of the amplitude reference value in the selection unit based on the counting result from the counting unit. PRML (Partial Response Maximum Likelihoo)
It is an adaptive amplitude reference value Viterbi decoder that stabilizes d) and can accurately read a reproduction signal that is short in time.

In the adaptive amplitude reference value Viterbi decoder shown as a specific example of the present invention, when the maximum likelihood decoding is performed on a signal whose PR is PR (1,2,1) for a magneto-optical disk. The recording medium is a magnetic recording medium such as a floppy disk (registered trademark) or a DVD.
It may be an optical recording medium such as (Digital Versatile Disc). Further, it can be applied to the case of PR other than (1, 2, 1).

Further, P in the magneto-optical recording used here
R (1,2,1) is a partial response response to the PWM recording, and is 1-7R in the specific example of the present invention.
LL (Run Length Limited) + NRZI (Non Return t
o RLmin (minimum inversion width) such as Zero Inverted)
Viterbi decoding of 6-value and 4-state is performed for the modulation of = 2.

User data is recorded on the magneto-optical disk with a sector as a unit for recording / reproducing. An example of the sector format used in the magneto-optical disk will be described with reference to FIG.

As shown in FIG. 11A, one sector is divided into header, ALPC, gap, VFO3, sync, data field, and buffer areas according to the order of recording / reproduction. The numbers attached in Fig. 11 are
Indicates the number of bytes. Data that has been encoded, such as block encoding, is recorded on the magneto-optical disk. For example, 8 bits are converted into 12 channel bits and recorded.

As an example of this sector format, a format having a user data amount of 1024 bytes and a format having a user data amount of 512 bytes are prepared. In the format in which the user data amount is 1024 bytes, the number of bytes in the data field is 670 bytes, and in the format in which the user data amount is 512 bytes, the number of bytes in the data field is 1278 bytes. In these two sector formats,
63-byte preformatted header and ALP
The 18 bytes of C and the gap area are the same.

FIG. 11B shows an enlarged 63-byte header. The header is sector mark SM (8 bytes), VF
O field VFO1 (26 bytes), address mark AM (1 byte), ID field ID1 (5 bytes), VFO field VFO2 (16 bytes), address mark AM (1 byte), ID field ID
2 (5 bytes) and postamble PA (1 byte)
Are arranged in order.

FIG. 11C shows an enlarged 18-byte ALPC and gap area. This area has a gap field (5 bytes), a flag field (5 bytes),
It consists of a gap field (2 bytes) and ALPC (6 bytes).

Next, the fields in the sector will be described. The sector mark SM is a mark for identifying the start of a sector and has a pattern formed by embossing that does not occur with the RLL (1,7) code.

The VFO field is the VFO in the PLL section.
This is for synchronizing (Variable Frequency Oscillator) and is composed of VFO1, VFO2 and VFO3. V
FO1 and VFO2 are formed by embossing. The VFO 3 is written magneto-optically when the recording operation is performed on the sector. VFO1, VF
O2 and VFO3 each have a pattern (2T pattern) in which "0" and "1" of channel bits appear alternately. Therefore, when the time corresponding to the time length of one channel bit is T, when the VFO field is reproduced, a reproduction signal whose level is inverted every 2T is obtained.

The address mark AM is used to provide the device with byte synchronization for the subsequent ID field and has an embossed pattern that does not occur in the RLL (1,7) code. The ID field has a sector address, that is, track number and sector number information, and a CRC byte for error detection with respect to these information. The ID field consists of 5 bytes, and I
The same address information is doubly recorded by D1 and ID2. The postamble PA has a pattern (2T pattern) in which "0" and "1" of channel bits appear alternately. ID1, ID2 and postamble P
A is also formed by embossing. Thus, the header area is a preformatted area in which pits are formed by embossing.

Targeting the above-mentioned magneto-optical disk, PR
A specific example of a decoder that performs maximum likelihood decoding on a signal of PR (1,2,1) will be described below in detail with reference to the drawings.

The adaptive amplitude reference value Viterbi decoder 1 shown as a specific example of the present invention is particularly adapted to amplitude reference value adaptation (RAA; Reference Amplitude Adaptiv) for updating the amplitude reference value.
e) has a feature, and more specifically, this R
As shown in FIG. 1, the AA unit includes an amplitude reference value initial value storage unit 10 in which an ideal amplitude reference value unique to each storage medium such as a magneto-optical disk is stored in advance, and an update for initializing the amplitude reference value. An updated initial value storage unit 11 that stores an initial value and an amplitude reference value storage unit 12 that temporarily stores an amplitude reference value to be used.
An update calculation unit 13 for updating the amplitude reference value stored in the amplitude reference value storage unit 12, and an ideal amplitude reference value stored in the amplitude reference value storage unit 12 and the amplitude reference updated by the update calculation unit 13. One of the values is selectively supplied to the update initial value storage unit 11, and the update initial value stored in the update initial value storage unit 11 is either the ideal amplitude reference value storage unit 10 or the updated amplitude reference value. A switching unit 14 for setting a crab, a gate counter 15 for counting the number of read gate signals based on a series of read reproduction signals, and an amplitude reference value storage unit 1
As the amplitude reference value in 2, the selection unit 16 that selects which of the update initial value of the update initial value storage unit 11 and the amplitude reference value updated by the update calculation unit 13 is used, and the update initial value in the switching unit 14 are selected. Switching and / or selecting unit 1
By including the control unit for controlling the selection of the amplitude reference value in No. 6, the updating of the amplitude reference value can be executed by a more detailed method.

The amplitude reference value initial value storage unit 10 is a register for storing the initial value of the amplitude reference value, and is an output value in the case of PR (1, 2, 1) which is unique and ideal for the recording medium, that is, 1-7 RLL (Run Length Limited) + NRZI
In 6-value 4-state Viterbi decoding for (Non Return to Zero Inverted) modulation, the ideal amplitude reference value is 4-value 4
The state becomes 0, 1, 3, and 4. However, these values may be set externally.

The amplitude reference value storage unit 12 is a register for storing the amplitude reference value actually used in the Viterbi operation, and the amplitude reference value is overwritten after the update operation in the update operation unit 13. Further, the switching unit 14 selects the initial value of the updated initial value storage unit 11. Gate counter 15
Is a counter that measures the read gate signal generated based on the reproduction signal, and supplies a signal to the selection unit 16 every predetermined gate count.

In the adaptive amplitude reference Viterbi decoder 1, each of the above-mentioned configurations has a CPU (Central Processing) (not shown).
Unit), the amplitude reference value is updated based on each operation mode described later, and maximum likelihood decoding is executed.

The adaptive amplitude reference value Viterbi decoder 1 shown as a specific example of the present invention includes the RAA section described above.
It has a basic configuration as shown in FIG. That is, the adaptive amplitude reference value Viterbi decoder 1 calculates the relative value (branch metric) of the Euclidean distance between the reproduction signal and the amplitude reference value (hereinafter, referred to as B branch metric calculation circuit).
MC: Branch Metric Calculator. ) 20 and a path metric that is the sum of the branch metric and the past branch metric, the maximum likelihood path is selected and a new path metric is calculated.
ACS: Add Compare & Select. ) 21 and a status memory unit (hereinafter referred to as SMU; Status Memory Unit) 22 for storing the state transition of the path metric. Further, the amplitude reference value is the RAA unit 23 described above.
And the decoding process is performed by the Merge circuit 24.

The adaptive amplitude reference value Viterbi decoder 1
May include a channel quality signal generation circuit that generates a channel quality signal for evaluating the channel quality based on the signal from the RAA unit 23.

A general amplitude reference value updating method in the adaptive reference value Viterbi decoder 1 will be described. PR (1,2,1) as in this example can be generally expressed as PR (a, b, c) due to the asymmetry of the recording waveform. The original recorded data (reproduced signal) to be decoded is a _k = {0,1},
Since PWM records at a mark edge, if the recorded data is b _k = {0,1}, b _k is represented by the following equation (1), and the read data y at this time is
_k can be expressed by the equation (2), and the Viterbi decoding at this time is in the 6-value 4-state.

[0048]

[Equation 1]

The state transition at this time is shown in FIG.
In this example, since 1-7 RLL + NRZI modulation is used, the state transitions of c ₁₀₁ and c ₀₁₀ are eliminated, and 4
Value 4 is entered. In FIG. 3, c _ijk represents a possible value of y _k , that is, an amplitude reference value, and represents an output amplitude at the time of transition from each state to the next state. Incidentally, i, j, k, respectively _{b k-2, b k-} 1, b k
Is shown.

The BMC 20 uses the AD conversion value z of the reproduced signal.
The relative value (branch metric) of the Euclidean distance between [k] and the amplitude reference value is calculated. In the case of 4-value 4-state Viterbi decoding, the branch metric is as shown in the following Expression (3).

[0051]

[Equation 2]

However, here, c ₀₀₁ and c ₁₀₀ ,
In order to distinguish between c ₁₁₀ and c ₀₁₁ , calculation for 6 values is executed.

The ACS 21 selects the maximum likelihood path from the path metric which is the sum of the branch metric and the past branch metric, and calculates a new path metric by the calculation shown in the following equation (4).

[0054]

[Equation 3]

In the above equation, m _jk [k] is the time t =
It represents the path metric of state s _ij at k.
The selected path metric m _jk [k] indicates which state has transited to which state. The state of the transition state is stored in the SMU 22. Here, ACS
The state transition in the SMU 22 is performed by the select signal corresponding to the result of the metric selection in.

FIG. 4 shows the structure of the SMU 22.
Inside the SMU 22, there are as many sub-blocks as there are states. Here, since there are four states, there are four sub-blocks. The path movement of these sub-blocks is
This corresponds to the state transition diagram shown in FIG.

The inside of the sub-block has an n-stage register structure as shown in FIGS. 5 (a) and 5 (b). Each register has a bit width corresponding to the number of states,
In this case, it is 2 bits. The kth stage register is k
The maximum likelihood state for the input before time is shown.
When the number of stages n of 22 is sufficiently large, the register values of the nth stage of the four sub-blocks match. The length of this step is called Viterbi length.

The kth stage register is adapted to be input by shifting from the k-1th stage register. For example, the k-th stage inputs of the sub-blocks SM ₀₁ and SM ₁₀ are shift-input from the k−1th stage SM ₀₀ and SM ₁₁ , respectively. The input to SM _{1 1} and SM ₀₀ is
It is determined by the select signal from the ACS 21. When the path length (the number of path memory stages n) is sufficiently large, the register values of the four sub-blocks at the n-th stage are all the same, so that the data at any final stage can be decoded. Here, the output value sm [k + from SM ₁₀ is
n] and sm [k + (n + 1)] are used for decoding. This decoding process is performed in the Merge circuit 24. Here, sm [k + n] to sm [k + (n
+1)] to the state transition.

The amplitude reference value c _ijk is an important parameter for predicting the state of state transition, but it actually varies depending on the recording state, defocus (signal loss) and the like. That is, PR (1,2,1) is equal to PR (0.8,2.0,0.
It changes like 9). Therefore, a general Viterbi decoder is provided with a step of judging the signal quality of an actual reproduced signal. Therefore, the adaptive amplitude reference value Viterbi decoder 1 absorbs these variations by applying adaptive control to this amplitude reference value, and calculates a more accurate characteristic value of the reproduced signal. Specifically, the amplitude reference value is sequentially adapted and updated according to the input amplitude and the decoding result of the Viterbi decoder.

For example, the AD conversion value z of the input reproduction signal
As a result of performing the Viterbi decoding process on [k], the maximum likelihood path transition is sm [k + n] = 01, sm [k + (n + 1)].
= 11, the amplitude reference value at this time is c
It is ₀₁₁ . Therefore, in equation (5) below,
The amplitude reference value is updated according to the original reproduction signal.

[0061]

[Equation 4]

Here, a represents a modified gain.
If this correction gain is set to a large value, the update will be quicker, but it may be oversensitive to the loss of the reproduction signal and the update may not catch up. for that reason,
This modified gain can be freely set from an external register.

The amplitude reference value updating process described above is executed in the RAA unit 23 described above. Since the update of the amplitude reference value is executed after the timing is determined by the Viterbi decoding process, the adaptive amplitude reference value Viterbi decoder 1 uses the Viterbi length shift register for storing the input reproduction signal z [k]. 25 are provided.

Next, the operation mode for updating the amplitude reference value of the adaptive amplitude reference Viterbi decoder 1 shown as a specific example of the present invention will be described with reference to FIG. 6 and Table 1.

In FIG. 6, counting is performed by the gate counter 15.
Read gate signal active, low,
Show how to update the amplitude reference value in each operation mode
There is. In FIG. 6, A₀Is the amplitude reference value initial value storage unit
The ideal amplitude reference value stored in 10 is shown.
The ideal amplitude reference value is read. A_s1, A_s2, A
_s3・ ・ ・ ・ ・ ・ A_s7Is updated in the update calculation unit 13.
Amplitude reference value that has been updated
Show that Viterbi decoding is being performed using the reference value.
is doing.

[0066]

[Table 1]

Table 1 explains how to update the amplitude reference value in each operation mode. “Number” in Table 1 indicates the order of the read gate signals, f
Indicates the fall of the read gate signal, and r indicates the rise of the read gate signal. A represents the initial value of the amplitude reference value, and B, C, D and E represent the updated amplitude reference value. Table 1 shows how the amplitude reference value updated with respect to the initial value of the amplitude reference value changes over nine read gate signals. The alphabet described below at the trailing edge indicates the initial value of updating, and the alphabet described at the rising edge indicates the result of updating.

The operation mode mode 1 is a mode for updating the amplitude reference value using the amplitude reference value initial value stored in the amplitude reference value initial value storage unit 10 for each read gate signal. The RAA unit 23 shown in FIG. 1 stores the six amplitude reference value initial values stored in the amplitude reference value initial value storage unit 10 in the update initial value storage unit 11 via the switching unit 14 and the amplitude. It is stored in the reference value storage unit 12.

The gate counter 15 counts the read gate signal from the rising edge r of the gate to a predetermined comparison number. In the operation mode mode1, the number of comparisons is
It is 1. When the gate counter 15 reaches the predetermined comparison number and detects the falling edge f of the read gate signal, the selection unit 1
6, the selection unit 16 receives the signal from the gate counter 15, and controls the amplitude reference value storage unit 12 to read the amplitude reference value initial value from the update initial value storage unit 11. To supply.

In the operation mode mode1, since the comparison number is set to 1, the amplitude reference value storage unit 12 is initialized to the value of the amplitude reference value initial value storage unit 10 for each read gate signal. While the read gate signal is active, the amplitude reference value storage unit 12 receives the calculation result from the update calculation unit 13 and continues to update the amplitude initial value. Therefore, in the operation mode mode1, the amplitude reference value is continuously updated for one read gate signal and the amplitude reference value B is set as the update result. When the reproduced signal of the next read gate signal is read, the amplitude reference value initial value is set. The value is always reset to the amplitude reference value initial value A stored in the amplitude reference value initial value storage unit 10. The switching unit 14 always selects the amplitude initial value initial value from the amplitude reference value initial value storage unit 10. However, Table 1
Then, the amplitude reference value B indicates the updated value, and does not necessarily indicate an equal value.

Therefore, in the operation mode mode1,
Since the amplitude reference value is updated based on the ideal initial value of the amplitude reference value for each read gate signal, the reproduction signal whose asymmetry is not greatly shifted is appropriately updated.
In the case of a reproduction signal that is significantly deviated, updating may be insufficient within the interval of the read gate signal, and Viterbi decoding performance may not be sufficiently exhibited.

The operation mode mode 2 is an operation mode in which the previously updated amplitude reference value is always used as the amplitude reference value initial value regardless of the read gate signal. In the operation mode mode2, the RAA unit 23 firstly updates the six amplitude reference value initial values A stored in the amplitude reference value initial value storage unit 10 via the switching unit 14 to the update initial value storage unit 11 And the amplitude reference value storage section 12 as well. Here, since the update proceeds regardless of the number of gates counted by the gate counter 15, the switching unit 1
From 4, the amplitude initial value updated by the update calculation unit 13 is supplied to the amplitude reference value storage unit 12, and the amplitude initial value B, C, D, E ... Become.

Therefore, by executing the operation mode mode2, the amplitude initial value is updated one after another regardless of the read gate signal. Therefore, the adaptive amplitude reference value Viterbi decoder 1 has the asymmetry with the amplitude reference value initial value. Even if the reproduced signal is deviated from the ideal amplitude reference value stored in the value storage unit 10, the amplitude reference value is adapted to the asymmetry of the magneto-optical disk by reading consecutive sectors. Viterbi decoding performance is improved.

However, in the operation mode mode2, if the amplitude reference value is set to an inappropriate value, for example, when there is a missing portion in the reproduced signal, it takes time to return to the optimum value. .

The above-mentioned operation modes mode1 and mod
The e2 is a method that is also adopted in the conventional adaptive amplitude reference value Viterbi decoder.
The ode3 and the mode4 are features of the present invention. That is, in the adaptive amplitude reference value Viterbi decoder 1 shown as a specific example of the present invention, after the amplitude reference value initial value is updated according to the read gate signal, it is reset to the ideal amplitude reference value initial value A again. And the case where the finally updated amplitude reference value is used as the initial value of the amplitude reference value from the next time, and these operation modes are added to the conventional operation mode or used together with the conventional operation mode. It is what you do.

The operation mode mode3 is the operation mode mo.
In de1, this is an operation mode in which the initial value of the amplitude reference value is reset to a predetermined gate count number. In the operation mode mode 3, the RAA unit 23 firstly updates the six amplitude reference value initial values A stored in the amplitude reference value initial value storage unit 10 via the switching unit 14 to the update initial value storage unit 1.
1 and the amplitude reference value storage unit 12. For example, when the number of comparisons in the gate counter 15 is 3, the RAA unit 23 keeps the amplitude initial value updated in the update calculation unit 13 from the switching unit 14 until the gate counter 15 counts three gates. The value is supplied to the value storage unit 12, and the initial amplitude value is updated to B, C, D, and so on. When the number of counts reaches 3, the switching unit 14 selects reading of the amplitude reference value initial value A stored in the amplitude reference value initial value storage unit 10, and the amplitude reference value initial value in the update initial value storage unit 11 becomes The amplitude reference value initial value A is reset.

Therefore, by executing the operation mode mode3, the adaptive amplitude reference value Viterbi decoder 1
In order to return the amplitude reference value initial value to the ideal amplitude reference value initial value stored in the amplitude reference value initial value storage unit 10 after the predetermined number of read gate signals have been counted. While continuing to update the amplitude reference value,
For example, when there is a missing portion in the reproduced signal, there is no fear that the amplitude reference value will be set to an inappropriate amplitude reference value, and the asymmetry is ideal amplitude stored in the amplitude reference value initial value storage unit 10. It is possible to read the reproduced signal more accurately even if the reproduced signal deviates greatly from the reference value.
That is, the operation mode mode3 is an improvement of the drawbacks of the mode2.

In the operation mode mode4, the case where the initial value of the amplitude reference value is reset for each read gate signal,
This is an operation mode having a case where it is executed every predetermined number of gate counts. In the operation mode mode 4, the RAA unit 23 first stores the six amplitude reference value initial values A stored in the amplitude reference value initial value storage unit 10 into the update initial value storage unit 11 via the switching unit 14. At the same time, it is stored in the amplitude reference value storage unit 12. For example, when the comparison number in the gate counter 15 is 3, the RAA unit 23 keeps the switching unit 14 until the gate counter 15 counts three gates.
From the above, the amplitude initial value updated by the update calculation unit 13 is supplied to the amplitude reference value storage unit 12, and the amplitude initial value is B,
Updated as C and D. When the count reaches 3,
The switching unit 14 selects reading of the amplitude reference value initial value A stored in the amplitude reference value initial value storage unit 10, and the amplitude reference value initial value in the update initial value storage unit 11 is reset to the amplitude reference value initial value A. It Subsequent updates will be performed for each gate,
The RAA unit 23 sets the last amplitude reference value updated at the third gate as the update result to the amplitude reference value initial value D of the subsequent read gate signal, and continues the update while the read gate signal is active and continues to the amplitude reference value E. To get After that, the amplitude reference value initial value is set to the amplitude reference value initial value D for each read gate signal.
The amplitude reference value is updated as. However, in Table 1, the amplitude reference value E indicates the updated value, and
It does not always indicate equal values.

Therefore, the adaptive amplitude reference value Viterbi decoder 1 is executed by executing the operation mode mode4.
After counting the predetermined number of gates, the amplitude reference value initial value is set to the amplitude reference value initial value storage unit 10 for each read gate.
By returning to the last amplitude reference value stored in, the amplitude reference value is set to an inappropriate amplitude reference value while the amplitude reference value is being updated, for example, when there is a missing portion in the reproduced signal. Even if it is a reproduced signal whose asymmetry is largely deviated from the ideal amplitude reference value stored in the amplitude reference value initial value storage unit 10, the read Viterbi decoding performance can be more accurately exhibited.

That is, the operation mode mode4 is mo
In de3, after the predetermined number of read gates has been counted, not the ideal amplitude reference value but the last amplitude reference value that matches the asymmetry of the magneto-optical disk is restored. ,
This is an operation mode in which the Viterbi decoding performance is further improved.

Next, a magneto-optical disk device to which the above-mentioned adaptive amplitude reference value Viterbi decoder 1 is applied will be described with reference to FIG. FIG. 7 shows the overall configuration of a magneto-optical disk device 30 having a reproducing system for performing the adaptive amplitude reference value Viterbi decoding.

The magneto-optical disk device 30 has a host computer 31, a controller 32, and a laser power control unit (hereinafter, referred to as LPC) 33. During recording, the controller 32 causes the host computer 31 to operate.
Receive the data to be recorded according to the instructions from
This is encoded to generate encoded data of RLL (1,7) code. This encoded data is supplied as recording data to the laser power control unit (hereinafter, referred to as LPC) 33. In addition to such processing, the controller 32 performs operations such as decoding processing, control of each mode such as recording, reproduction, and erasing, and communication with the host computer 31.

Further, the magneto-optical disk device 30 has an optical pickup 34 and a magnetic head 35 as a recording / reproducing system, and performs recording / reproducing with respect to the magneto-optical disk 36.
The LPC 33 controls the laser power of the optical pickup 34 according to the supplied recording data,
Recording data is recorded by forming a pit train having magnetic polarity on the recording medium 6. During this recording, the magnetic head 3
A bias magnetic field 5 is applied to the magneto-optical disk 36. Actually, mark edge recording as described later is performed based on the precode output generated based on the recording data.

The control of the recording position, that is, the pit formation position is performed by a means for positioning the magnetic head 35, the optical pickup 34, etc., although not shown. Therefore, when the optical pickup 34 passes through the address section or the like during the recording operation, an operation similar to the operation during reproduction as described later is performed.

A method of associating each pit formed as described above with each bit in the precode output generated as described below based on the recording data will be described with reference to FIG.

A recording method in which a pit is formed for "1" and a pit is not formed for "0" during precode output is called a mark position recording method. On the other hand, a recording method in which the inversion of the polarity at the boundary of each bit in the precode output represented by the edge of each pit corresponds to, for example, "1" is called a mark edge recording method.
At the time of reproduction, the boundary of each bit in the reproduction signal is recognized according to the read clock DCK generated as described later.

Next, the structure and operation of the reproducing system in the magneto-optical disk device 30 will be described. The optical pickup 34 irradiates the magneto-optical disk 36 with laser light, receives reflected light generated thereby, and generates a reproduction signal.
The reproduction signal is composed of four types of signals: a sum signal R +, a difference signal R-, and a focus error signal and a tracking error signal (not shown). The sum signal R + is supplied to the changeover switch 39 after gain adjustment and the like by the amplifier 37. Further, the difference signal R− is supplied to the changeover switch 39 after gain adjustment and the like by the amplifier 38. Further, the focus error signal is supplied to a means (not shown) for eliminating the focus error. On the other hand, the tracking error signal is supplied to a servo system (not shown) and used in those operations.

A changeover signal S, which will be described later, is supplied to the changeover switch 39. The changeover switch 39 supplies the sum signal R + or the difference signal R− to the filter section 40 in accordance with the changeover signal S as follows. That is, in the sector format of the magneto-optical disk 36, which will be described later, the sum signal R + is supplied to the filter unit 40 during a period in which a reproduction signal reproduced from a portion formed by embossing is supplied to the changeover switch 39. . Further, the difference signal R− is supplied to the filter unit 40 during the period in which the reproduction signal reproduced from the portion that is magneto-optically recorded is supplied to the changeover switch 39.

The switching signal S is generated as follows, for example. That is, first, a signal reproduced from a predetermined pattern defined in the sector format is detected from the reproduced signal. As such a predetermined pattern, for example, a sector mark SM described later or the like is used. Then, the switching signal S is generated at a predetermined time point recognized by a method such as counting a read clock described later with reference to the time point at which the detection is performed.

The filter section 40 is composed of a low-pass filter for noise reduction and a waveform equalizer for waveform equalization. As will be described later, the waveform equalization characteristic used in the waveform equalization processing at this time is adapted to the Viterbi decoding method performed by the Viterbi decoder 42. The A / D converter 12 supplied with the output of the filter unit 40 samples the reproduction signal value z [k] according to the read clock DCK supplied as described later.

The Viterbi decoder 42 reproduces the reproduced signal value z [k].
The decoded data is generated by the Viterbi decoding method based on The decoded data here is the maximum likelihood decoding sequence for the recorded data recorded as described above. Therefore,
If there is no decoding error, the decoded data matches the recorded data.

The output of the filter section 40 is also supplied to the PLL section 43. The PLL unit 43 generates the read clock DCK based on the supplied signal. The read clock DCK is the controller 32, the A / D converter 1
2, supplied to the Viterbi decoder 42 and the like. Controller 3
2. The operations of the A / D converter 12 and the Viterbi decoder 42 are performed at the timing according to the read clock DCK.
Further, the read clock DCK is supplied to a timing generator (not shown). The timing generator generates a signal for controlling operation timing such as switching of recording / reproducing operation.

The optical disk device 30 to which the adaptive amplitude reference Viterbi decoder 1 shown as a specific example of the present invention is applied also corresponds to a reproduction signal having a low amplitude obtained from a poor ID signal or an asymmetry greatly deviated from the center position. it can.

Using a Viterbi decoder which is not of the amplitude reference value adaptive type, for example, when decoding asymmetry in which the center position is detected and the amplitude is small by about 10%, and when the amplitude is normal and the center position is about 10%, Consider the case of decoding asymmetry that is offset. Normally, Viterbi decoding is effective for random noise, but asymmetry in which the center position is detected as a normal value can be detected as an accurate reproduced signal, but the center position is In the case of a system having deviated asymmetry, this is equivalent to the detection of non-random noise, so that the Viterbi decoder that is not the amplitude reference value adaptive type does not sufficiently exhibit the effect of Viterbi decoding. That is, in order to accurately detect the reproduced signal, the asymmetry should be at least ±
It is preferable to be within an error range of about 2%.

When the adaptive amplitude reference Viterbi decoder 1 is used, the amplitude reference value is adapted to such a system, and the PR (1,2,1) system is converted into, for example, PR (1.2). ，
2, 1.2), it is possible to eliminate asymmetries that are greatly deviated.

Since some magneto-optical disks have ID signals having an asymmetry shift of about 15%, it is necessary to adapt the amplitude reference value to remove the shifted asymmetry.

As an example, consider the case of decoding an ID signal having an asymmetry shift of about 15%. The reproduced signal has an amplitude of 40, an amplitude of 2T, and an amplitude of 20,
If it deviates from the ideal value by about 15%, the asymmetry in this case is expressed by the following equation (6).

[0098]

[Equation 5]

Since the offset due to this asymmetry is 40 × 0.165 = 6.6, c
₁₁₁ , c ₁₁₀ , c ₀₁₁ and c ₀₀₁ , c ₁₀₀
Then, the amplitude of c ₀₀₀ becomes as shown in FIG. That is, the amplitude detected here as 10 is up to 3.4,
Also, the amplitude detected as -10 must be updated to -16.6.

When the number of updates is calculated with the update gain a = 0.015625, it becomes about 460 times. The actual update is
Assuming that the 6 reference values are updated almost in sequence, 4
60 × 6 = 2760 updates are required. This is 3
It corresponds to 45 bytes. Since the number of bytes to be updated in one ID signal is 47 bytes, 345/7 =
7.340, and at least 8 to update the amplitude reference value.
It can be seen that individual ID signals are required.

As described above, in the magneto-optical disk device 30, if the seek head landing target sector is set to be about 8 sectors before the read sector under the above-mentioned asymmetry conditions, before the head reaches the read start sector. Since the updating of the amplitude reference value is completed, ideal Viterbi decoding is executed. However, since the specific condition is illustrated here, it is not always necessary to set the read sector approximately 8 sectors in front. If the target sector for landing is set too close to the front, the seek arrival will be delayed, so the target sector for landing can be set within a range that does not hinder the seek operation.

Next, FIG. 10 shows an example of the switching operation of the amplitude reference value updating operation mode in the magneto-optical disk device 30 to which the adaptive amplitude reference value Viterbi decoder 1 of the present invention is applied.
Will be explained.

The magneto-optical disk device 30 operates in the operation mode mode1 when it is not in the reading operation, that is, in the standby state.
Is selected. Magneto-optical disk device 30
When the reading operation of the magneto-optical disk 36 is started,
In step S1, the address currently detected by the optical pickup 34 is confirmed. At this time, the operation mode changes from the operation mode mode1 to the operation mode mode.
Moved to 4.

Subsequently, in step S2, the magneto-optical disk device 30 calculates search information (seek profile) from the current address to the target address, and in step 3, switches the operation mode to the operation mode mode1 and performs seek operation. To start. During the seek operation in step S4, the operation mode mode1 is selected.

The magneto-optical disk device 30 operates in step S5.
In step 2, the optical pickup 34 is landed slightly before the target address, for example, as described above, at 8 sectors, and the operation mode for updating the amplitude reference value is switched from the operation mode mode1 to the mode4.

In step S6, the magneto-optical disk device 30 reproduces the record data of the target address. When the read target sector including the target address has passed, the operation mode is switched from the operation mode mode4 to the mode1 in step S7, and the standby state is entered.

Therefore, the magneto-optical disk device 30 shown as a specific example of the present invention can select the updating method of the amplitude reference value according to the above series of steps, that is, the seek operation or the read operation. it can. In the seek operation, the ideal amplitude reference value that is stored in advance as the initial value of the amplitude reference value is always used, and in the reading operation, the ideal amplitude reference value that is stored in advance as the initial value of the amplitude reference value is used in a series of reading areas. By updating the amplitude reference value obtained by updating from the amplitude reference value as the initial value of the amplitude reference value, the Viterbi decoding process that is more accurate is performed on the reproduced signal having an extreme asymmetry deviation. it can.

The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0109]

As described above in detail, the decoding apparatus according to the present invention is a decoding apparatus that updates the amplitude reference value determined by the intersymbol interference generated by a reproduced signal and executes maximum likelihood decoding. Amplitude reference value initial value storage means for storing a unique ideal amplitude reference value, update initial value storage means for storing an update initial value for initializing the amplitude reference value, and amplitude reference value for storing an actual amplitude reference value Storage means, update calculation means for updating the amplitude reference value stored in the amplitude reference value storage means, ideal amplitude reference value stored in the amplitude reference value initial value storage means, and amplitude reference updated by the update calculation means One of the values is selected and supplied to the update initial value storage means, and the update initial value stored in the update initial value storage means is set to either the amplitude reference value initial value or the updated amplitude reference value. means A counting means for counting a read gate signal generated based on a set of reproduced signals read, as the amplitude reference value in the amplitude reference value storing means,
Selection means for selecting which of the update initial value of the update initial value storage means and the amplitude reference value updated by the update calculation means, and switching of the update initial value in the switching means and / or amplitude reference value in the selection means By including the control means for controlling the selection of the selection based on the counting result from the counting means, the setting of the amplitude reference value initial value and the updating of the amplitude reference value are executed based on the read gate signal,
Even if the asymmetry of a reproduction signal such as an ID signal, which is short in time, fluctuates significantly, it can be read correctly.

Further, the control means resets the actual amplitude reference value to the ideal amplitude reference value stored in the amplitude reference value initial value storage means for each predetermined read gate signal. While the updating is continued, the asymmetry is stored in the amplitude reference value initial value storage unit without fear that the amplitude reference value is set to an inappropriate amplitude reference value, for example, when there is a missing portion in the reproduced signal. Even if the reproduced signal is largely deviated from the ideal amplitude reference value, it can be read more accurately.

Further, the control means uses the update initial value updated last time as the actual amplitude reference value for the predetermined read gate signal period, and when the predetermined read gate signal period has passed, the predetermined read gate signal period. By using the updated initial value that was finally updated as the actual amplitude reference value, the final amplitude reference value that was updated to match the asymmetry of the recording medium was obtained after counting the predetermined number of read gates. Therefore, the decoding device according to the present invention further improves the performance of decoding a reproduction signal that is short in time.

Further, the decoding method according to the present invention is a decoding method for executing maximum likelihood decoding by updating the amplitude reference value determined by intersymbol interference generated by a reproduced signal, and the amplitude for storing the actual amplitude reference value. Update calculation step for updating the amplitude reference value stored in the reference value storage means, and ideal amplitude reference value and update calculation step stored in the amplitude reference value initial value storage means for storing the ideal amplitude reference value specific to the system In the selected amplitude reference value, and supplies the selected amplitude reference value to the update initial value storage means that stores the selected amplitude reference value as the update initial value, and the update initial value is updated to the amplitude reference value initial value or updated. A switching process for setting one of the amplitude reference values,
A counting step of counting the read gate signal generated based on the read series of reproduced signals, and the amplitude reference value in the amplitude reference value storage means is updated by the update initial value of the update initial value storage means and the update calculation means. A selection step of selecting which of the amplitude reference values to be adopted, and a control step of controlling the switching of the update initial value in the switching step and / or the selection of the amplitude reference value in the selection step based on the counting result from the counting step. Since the setting of the initial value of the amplitude reference value and the updating of the amplitude reference value are performed based on the read gate signal in the control process,
Even if the asymmetry of a reproduction signal that is short in time, such as a signal, fluctuates significantly, it can be read correctly.

In the control step, the actual amplitude reference value is reset to the ideal amplitude reference value stored in the amplitude reference value initial value storage means for each predetermined read gate signal. While continuing to update, for example,
There is no fear that the amplitude reference value will be set to an inappropriate amplitude reference value when there is a missing portion in the playback signal, and the asymmetry is set to the ideal amplitude reference value stored in the amplitude reference value initial value storage unit. Even if the playback signal is greatly deviated,
It becomes possible to read more accurately.

Further, in the control step in the decoding method according to the present invention, the predetermined read gate signal period uses the update initial value updated last time as the actual amplitude reference value, and when the predetermined read gate signal period passes. , By using the updated initial value finally updated in the predetermined read gate signal period as the actual amplitude reference value, it is not the ideal amplitude reference value after counting the predetermined number of read gates, but the magneto-optical disk, etc. Since the last amplitude reference value that matches the asymmetry of the recording medium is restored, the decoding method according to the present invention further improves the performance of decoding a reproduction signal that is short in time.

Also, the decoding device according to the present invention is applied to the amplitude reference value adaptation unit of the information reproducing apparatus, and a predetermined calculation process is performed based on the amplitude reference value obtained by this amplitude reference value adaptation unit. If an information reproducing apparatus is provided with a control section and an operation control section that controls the operation of the constituent elements in the apparatus by referring to the output from the calculation processing section, this information reproducing apparatus is configured to operate the constituent elements in the operation control section. According to the control, the switching of the update initial value by the switching means and / or the selection of the amplitude reference value by the selecting means can be controlled.

Further, since such an information reproducing apparatus can select the updating method of the amplitude reference value depending on whether it is the seek operation or the read operation, in the seek operation,
The ideal amplitude reference value that has been stored in advance as the initial value of the amplitude reference value is always used, and in the reading operation, within the series of reading areas, the ideal amplitude reference value that is stored in advance as the initial value of the amplitude reference value is updated. By updating the obtained amplitude reference value as the initial value of the amplitude reference value at any time, more accurate decoding processing can be efficiently executed even for a reproduction signal having an extreme asymmetry shift.

Further, a calculation processing step in which the decoding method according to the present invention is applied to the amplitude reference value adaptation step of the information reproducing method and a predetermined calculation processing is performed based on the amplitude reference value obtained in the amplitude reference value adaptation step. And an operation control step of controlling the operation of the constituent elements in the apparatus by referring to the output from the calculation processing step, the information reproduction method allows the update initial value of the switching step to be changed. The selection of the amplitude reference value in the switching and / or selection process can be controlled according to the operation control of the component in the operation control process.

Further, in such an information reproducing method, the updating method of the amplitude reference value can be selected depending on whether the operation is a seek operation or a read operation.
The ideal amplitude reference value that has been stored in advance as the initial value of the amplitude reference value is always used, and in the reading operation, within the series of reading areas, the ideal amplitude reference value that is stored in advance as the initial value of the amplitude reference value is updated. By updating the obtained amplitude reference value as the initial value of the amplitude reference value at any time, more accurate decoding processing can be efficiently executed even for a reproduction signal having an extreme asymmetry shift.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating an RAA unit in an adaptive amplitude reference value Viterbi decoder shown as a specific example of the present invention.

FIG. 2 is a configuration diagram illustrating an adaptive amplitude reference value Viterbi decoder shown as a specific example of the present invention.

FIG. 3 is a schematic diagram illustrating a state transition of read data in an adaptive amplitude reference value Viterbi decoder shown as a specific example of the present invention.

FIG. 4 is a configuration diagram illustrating the inside of an SMU in an adaptive amplitude reference value Viterbi decoder shown as a specific example of the present invention.

5A is a configuration diagram illustrating a sub-block SM ₀₀ inside an SMU in an adaptive amplitude reference value Viterbi decoder shown as a specific example of the present invention, and FIG. 5B is a block diagram illustrating the sub-block SM ₁₀ . It is a block diagram explaining.

FIG. 6 is a diagram illustrating an update of the amplitude reference value in each operation mode with respect to active and low of the read gate signal counted by the gate counter of the RAA unit in the adaptive amplitude reference value Viterbi decoder shown as a specific example of the present invention. It is a figure explaining the method of.

FIG. 7 is a configuration diagram illustrating a magneto-optical disk device to which an adaptive amplitude reference value Viterbi decoder according to the present invention is applied.

FIG. 8 is a diagram illustrating a method of associating each pit with each bit in the precode output generated based on the recorded data in the magneto-optical disk device to which the adaptive amplitude reference value Viterbi decoder according to the present invention is applied. Is.

FIG. 9 is a magneto-optical disk device to which the adaptive amplitude reference value Viterbi decoder according to the present invention is applied.
4 is a diagram for explaining a case of decoding an ID signal having an asymmetry with an amplitude of 20 and deviated by about 15% from an ideal value. FIG.

FIG. 10 is a flow chart for explaining the updating of the amplitude reference value by the adaptive amplitude reference value Viterbi decoder in the magneto-optical disk device shown as the specific example of the present invention.

FIG. 11 is a diagram illustrating a sector format of a magneto-optical disk applied to a magneto-optical disk device shown as a specific example of the present invention.

[Explanation of symbols]

1 adaptive type amplitude reference value Viterbi decoder, 10 amplitude reference value initial value storage unit, 11 update initial value storage unit, 12 amplitude reference value storage unit, 13 update calculation unit, 14 switching unit, 15 gate counter, 16 selection unit, 20 BMS, 21 A
CS, 22 SMU, 23 RAA section, 24 Merge
Circuit, 25 shift register, 30 magneto-optical disk device, 31 host computer, 32 controller,
33 laser power control section, 34 optical pickup, 35 magnetic head, 36 magneto-optical disk, 37
Amplifier, 38 amplifier, 39 changeover switch, 40 filter section, 41 A / D conversion section, 42 Viterbi decoder

Claims (14)

[Claims] 1. A decoding device for updating maximum amplitude decoding by updating an amplitude reference value determined by intersymbol interference generated by a reproduced signal, and storing an amplitude reference value initial value storing an ideal amplitude reference value specific to a system. Means, an update initial value storage means for storing an update initial value for initializing the amplitude reference value, an amplitude reference value storage means for storing an actual amplitude reference value, and an amplitude reference value stored in the amplitude reference value storage means And an ideal amplitude reference value stored in the amplitude reference value initial value storage means or an amplitude reference value updated by the update calculation means are supplied to the update initial value storage means. Switching means for setting the update initial value stored in the update initial value storage means to either the amplitude reference value initial value or the updated amplitude reference value, and the switching means for generating based on the read series of reproduced signals. The counting means for counting the read gate signal and the amplitude reference value in the amplitude reference value storage means, which of the update initial value of the update initial value storage means and the amplitude reference value updated by the update calculation means is selected is selected. And a control means for controlling the switching of the update initial value in the switching means and / or the selection of the amplitude reference value in the selection means based on the counting result from the counting means. apparatus. 2. The control means resets the actual amplitude reference value to the ideal amplitude reference value stored in the amplitude reference value initial value storage means for each predetermined read gate signal. The decoding device according to claim 1. 3. The control means uses the update initial value updated last time as the actual amplitude reference value for a predetermined read gate signal period, and when the predetermined read gate signal period has passed, the predetermined read gate The decoding device according to claim 1, wherein an updated initial value finally updated in a signal period is used as the actual amplitude reference value. 4. A decoding method for performing maximum likelihood decoding by updating an amplitude reference value determined by intersymbol interference generated by a reproduced signal, wherein the amplitude reference value storage means stores an actual amplitude reference value. An update calculation step for updating the amplitude reference value, an ideal amplitude reference value stored in the amplitude reference value initial value storage means for storing an ideal amplitude reference value specific to the system, and an amplitude reference value updated in the update calculation step. Is supplied to the update initial value storage means for storing the selected amplitude reference value as the update initial value, and the update initial value is either the amplitude reference value initial value or the updated amplitude reference value. Switching step of setting the read gate signal generated on the basis of the read series of read signals, and the above-mentioned updating as the amplitude reference value in the amplitude reference value storage means. A selection step of selecting which of the updated initial value of the initial value storage means and the amplitude reference value updated by the update calculation means is adopted, and switching of the updated initial value in the switching step and / or the amplitude reference in the selection step And a control step of controlling selection of a value based on the counting result from the counting step. 5. In the control step, the actual amplitude reference value is reset to the ideal amplitude reference value stored in the amplitude reference value initial value storage means for each predetermined read gate signal. The decoding method according to claim 4. 6. In the control step, the update initial value updated last time is used as the actual amplitude reference value for the predetermined read gate signal period, and when the predetermined read gate signal period has passed, the predetermined read gate signal period has passed. 5. The decoding method according to claim 4, wherein the updated initial value finally updated in the signal period is used as the actual amplitude reference value. 7. An information reproducing apparatus for performing maximum likelihood decoding by updating an amplitude reference value determined by intersymbol interference generated by a reproduction signal from a recording medium, and an amplitude for storing an ideal amplitude reference value specific to a system. Reference value initial value storage means, update initial value storage means for storing the update initial value for initializing the amplitude reference value, amplitude reference value storage means for storing the actual amplitude reference value, and storage in the amplitude reference value storage means Update calculation means for updating the calculated amplitude reference value, and the update initial value by selecting either the ideal amplitude reference value stored in the amplitude reference value initial value storage means or the amplitude reference value updated by the update calculation means. Switching means for supplying to the storage means and setting the update initial value stored in the update initial value storage means to either the amplitude reference value initial value or the updated amplitude reference value, and a series of read reproduction signals. Counting means for counting the read gate signal generated based on the above, and as the amplitude reference value in the amplitude reference value storage means, either the update initial value of the update initial value storage means or the amplitude reference value updated by the update calculation means is used. Amplitude having selection means for selecting whether to adopt, and control means for controlling switching of the update initial value in the switching means and / or selection of the amplitude reference value in the selection means based on the counting result from the counting means. A reference value adaptation unit, a calculation processing unit that performs a predetermined calculation process based on the amplitude reference value obtained by the amplitude reference value adaptation unit, and a component in the device with reference to the output from the calculation processing unit And an operation control unit that controls the operation of the information reproducing apparatus. 8. The control means in the amplitude reference value adaptation unit sets the actual amplitude reference value to the ideal amplitude reference value stored in the amplitude reference value initial value storage means for each predetermined read gate signal. The information reproducing apparatus according to claim 7, wherein the information is reset. 9. The control means in the amplitude reference value adaptation unit uses the update initial value updated last time as the actual amplitude reference value for a predetermined read gate signal period, and the predetermined read gate signal period is 8. The information reproducing apparatus according to claim 7, wherein when it has passed, the update initial value finally updated in a predetermined read gate signal period is used as the actual amplitude reference value. 10. The control unit in the amplitude reference value adaptation unit switches the update initial value in the switching unit and / or the amplitude reference value in the selection unit according to the operation control of the constituent elements in the operation control unit. 8. The information reproducing apparatus according to claim 7, wherein selection of is controlled. 11. An information reproducing method for performing maximum likelihood decoding by updating an amplitude reference value determined by intersymbol interference generated by a reproduction signal from a recording medium, and storing an amplitude reference value for storing an actual amplitude reference value. Update calculation step for updating the amplitude reference value stored in the means, and update in the update calculation step and the ideal amplitude reference value stored in the amplitude reference value initial value storage means for storing the system-specific ideal amplitude reference value Selected amplitude reference value, and supplies the selected amplitude reference value to an update initial value storage unit that stores the selected amplitude reference value as an update initial value, and the update initial value is the amplitude reference value initial value or the updated amplitude. A switching step of setting one of the reference values, a counting step of counting the read gate signals generated based on the read series of reproduced signals, and an amplitude in the amplitude reference value storage means. As a quasi value, a selection step of selecting which of the update initial value of the update initial value storage means and the amplitude reference value updated by the update calculation means is adopted, and switching of the update initial value in the switching step and / or Based on the amplitude reference value obtained by the amplitude reference value adaptation step, which has a control step for controlling the selection of the amplitude reference value in the selection step based on the counting result from the counting step, An information reproducing method comprising: a calculation processing step for performing a predetermined calculation processing according to the above; and an operation control step for controlling the operation of the constituent elements in the apparatus by referring to the output from the calculation processing step. 12. In the control step in the amplitude reference value adaptation step, the actual amplitude reference value is set to an ideal amplitude reference value stored in the amplitude reference value initial value storage means for each predetermined read gate signal. The information reproducing method according to claim 11, wherein the information is set again. 13. The control step in the amplitude reference value adaptation step uses the update initial value updated last time as the actual amplitude reference value for the predetermined read gate signal period, and the predetermined read gate signal period is 12. The information reproducing method according to claim 11, wherein when it has passed, an update initial value finally updated in a predetermined read gate signal period is used as the actual amplitude reference value. 14. The control step in the amplitude reference value adaptation step switches the update initial value in the switching step and / or the amplitude reference value in the selection step in accordance with operation control of components in the operation control step. 12. The information reproducing method according to claim 11, further comprising controlling the selection of.