JP2003018012A - Digital signal modulation method, digital signal modulator, and digital signal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for generating a digital modulation signal for DSV(digital sum value) control with high performance producing no low frequency component in the case of generating the digital modulation signal by run length coding and NRZI(non return to zero inverted recording) conversion by a prescribed method. SOLUTION: A synchronous word generating means 123 generates 1st and 2nd synchronous words from which number of inversion times, resulting in different polarities are obtained through the NRZI conversion, an address generating section 122 generates 1st and 2nd coded sequence data by allocating generated coded data to the two synchronous words, while referring to a run length coding table 13, a peak value comparison section 129 compares DSV arithmetic result stored in DSV arithmetic peak value memories 126, 127 receiving coded sequence data with a smaller DC component caused at the NRZI conversion among the coded sequence data and selects and obtains the coded sequence data obtained as the smaller DC component data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal modulation system for recording a digital information signal on a recording medium, and particularly to p (p is a positive integer) bit digital information signal data, q (q is p). When converting to a high-density recording medium such as an optical disk, a magnetic disk, or a magnetic tape by a code sequence that is converted into a code word of a larger integer) bit and that satisfies a predetermined run length limited limit, the low range of the recording code sequence is used. The present invention relates to a digital signal modulation method, a digital signal modulation device, and a digital signal recording medium capable of accurately performing low-frequency component suppression control for suppressing a component.

[0002]

2. Description of the Related Art Conventionally, as a modulation method of a digital signal for recording a digital information signal on a digital recording medium, a modulation method in which a DC signal component contained in a modulated signal is small has been developed, and the modulation method is mounted. The digital signal recording device has been put to practical use.

NRZ as a basic digital modulation method
There is a (Non Return to Zero) method, but this method uses a direct current component when digitally modulating a long-lasting digital information signal of 0 or 1, and the direct current component is used for magnetic recording, for example, which cannot reproduce the direct current signal. Unable to
Modulation methods such as mirror code and mirror square code that do not generate much DC component have been developed.

The mirror code is a method of generating a digital modulation signal by a combination of T, 1.5T, and 2T with respect to the bit interval T, and a slight DC component still remains in the modulation signal. The mirror square code is inverted at the center of 1 when 1 continues for a long time in the information signal,
Alternatively, it is a digital modulation method in which the DC signal component is further reduced by adaptively selecting one having a small DC component causing no inversion.

In the Miller square code in which the DC signal component is reduced, the minimum bit inversion interval is T and the maximum bit inversion interval is 3T or more. Therefore, the ratio of the maximum frequency component to the minimum signal frequency of the digital modulation signal is a value of 3 or more, and the signal of such frequency band is recorded on the recording medium.

On the other hand, in the recent information society realized by transmission and recording of digital information signals, the number of types of information handled is increasing and the amount of information is increasing, and the digital information signals tending to increase. The emergence of a highly efficient digital modulation system for efficiently transmitting and recording data has been awaited.

The highly efficient digital modulation method is to perform digital modulation with a modulation signal frequency component which is as low as possible, so that many digital information signals can be recorded on a digital signal recording medium having a predetermined recording frequency capacity. It tries to be able to do it.

The digital modulation signal recorded on the digital signal recording medium is a low DC component due to the magnetic reproduction characteristic in the case of magnetic recording, but in the case of a disc type high density recording medium such as an optical disc. However, it is required to reduce the level of the direct current component contained in the digital modulation signal in order to perform tracking control for obtaining the digital modulation signal while tracking directly above the recording track.

As described above, the characteristics of the digital modulation signal in the present day are such that the frequency of the modulation signal is in a low frequency band and the DC frequency component is obtained as much as possible. A transform coding method is often used to obtain such a modulated signal.

The transform coding is, for example, 25 bits of 8 bits.
6 kinds of information signals can be expressed by 10 bits 10
Encoding is performed by selecting 256 types of codes having a low DC component in which the numbers of 1s and 0s are almost equal from the 24 codes 8-10
It is a method like block conversion, and the method is DAT.
It is also used in (digital audio tape recorders).

A CD (Compact Disc) converts an 8-bit signal into a 14-bit signal sequence by an EFM (Ei).
The ght to Fourteen Modulation method is used, and the EFM modulation method uses a code sequence in which redundant bits are set to further suppress the DC component.

Further, if the digital modulated signal in which the direct current component is suppressed can be generated without setting such a redundant bit, the coding efficiency can be further increased, so that the recording on the high density information recording medium is performed. A method has been developed in which a DSV (Digital Sum Value) control is performed on a code sequence to reduce a DC component.

The suppression of the low frequency component of the digital modulation signal in the high density disc type optical recording medium typified by the optical disk is performed at a high speed because the low frequency component of the recording signal series is mixed into the focus servo signal in addition to the tracking servo. This is to minimize the adverse effect on the performance for performing accurate servo control.When detecting an error signal for servo, the reference level for signal detection fluctuates and erroneous control operation is performed. The purpose is to reduce undesired servo control operations, such as accidents.

To reduce the signal component given to these undesired servo controls, for example, a DVD (Digital ve
rsatile Disc Digital versatile disc) DVD-ROM
The DSV control method is stipulated in the physical standard.

[0015]

By the way, the DVD
-In the DSV control method specified in the ROM physical standard, D
This is to reduce the generation of an undesired error signal by reducing the absolute value of the DSV value at the time of SV control, and it is possible to reduce the low frequency component of the digital modulation signal, but also at a time other than the time of DSV control. There is a demand for establishment of a method of generating a digital modulation signal for performing high-performance DSV control in which low frequency components do not occur.

A control method for detecting the peak voltage value of such a DSV signal to perform DSV control
No. 000-295109 discloses a "digital modulator", but the DSV control method is for optimizing the DSV control by using a data scrambling method, and for example, does not use the data scrambling method. It cannot be applied to a digital modulation method such as block conversion.

Therefore, the present invention has been made in view of the above-mentioned problems, and for example, the run-length limited coding is applied to a disk type high density recording medium such as an optical disk.
This is performed by using a coding table for converting bit data into q-bit codewords, which enables a DSV control method having a DC component suppression characteristic superior to the conventional one, and
An object of the present invention is to provide a method of modulating a digital signal, a structure of a digital signal modulator, and a digital signal recording medium for the purpose of providing a structure of a modulator equipped with the SV control method at a low cost.

[0018]

The present invention comprises the following means 1) to 11) in order to solve the above problems. That is,

1) The operation of converting the source data having the bit number p (p is a positive integer) into the code word data having the bit number q (q is an integer larger than p) is repeated a plurality of times to generate the code word data. A group of code words is generated at a predetermined bit interval, a code word data group is arranged following the code word generated, and the code word data group is obtained as a coded sequence signal. NRZI (Non Retur
n to Zero Inverse) conversion to obtain a signal to be supplied to a recording medium or a transmission medium as a signal, which is a method of modulating a digital signal, wherein the NRZI conversion obtains the number of inversions of different polarities depending on the sync word. A first step (123) of simultaneously generating one sync word and a second sync word respectively, and generating the code word data group based on a run length encoding method in which a run length is limited to a predetermined range. , Arranging the generated codeword data group following the first synchronization word to generate first encoded sequence data, and arranging the codeword data group following the second synchronization word And a second step (122, 124, 125) for generating second coded sequence data, and a first DC component data relating to a DC component generated when the first coded sequence data is NRZI converted. And a third step (126, 127) of obtaining the second DC component data relating to the DC component generated when the second coded sequence data is NRZI-converted, and the first DC component data. Comparing with the second DC component data and selecting and supplying either the first coded sequence data or the second coded sequence data that is obtained as the smaller DC component data. And (4) (128, 129), at least.

2) The operation of converting the source data having the bit number p (p is a positive integer) into the code word data having the bit number q (q is an integer larger than p) is repeated a plurality of times to generate the code word data. When generating the group, when the specific source data capable of generating the first code word data and the second code word data having different values with respect to one source data is supplied, the specific source data is supplied after the specific source data. The code word data group is generated from the source data, and the generated code word data group is obtained as a coded sequence signal that is arranged following the first code word or the second code word. NRZI (Non Return to Zer)
o Inverse) conversion to obtain a signal to be supplied to a recording medium or a transmission medium as a signal, which is a modulation method of a digital signal, wherein the NRZI conversion can obtain the number of times of inversion of mutually different polarities. A first step (122) of generating each of the second codewords, and the codeword data group is generated based on a run length encoding method in which the run length is limited to a predetermined range, and the generated code A word data group is arranged following the first code word to form a first code word.
Second step (122, 12) of generating the second encoded sequence data by generating the encoded sequence data of No. 1 and arranging the codeword data group subsequent to the second codeword.
4, 125) and NRZ the first encoded sequence data.
The first DC component data relating to the DC component generated when the I conversion is performed is obtained, and the second encoded sequence data is N
Third step (126, 127) of obtaining second DC component data relating to DC component generated when RZI conversion is performed
And the first coded sequence data or the second coded sequence data that is obtained as the smaller DC component data by comparing the first DC component data and the second DC component data. And a fourth step (128, 129) for selecting and supplying any one of the above, and a method of modulating a digital signal.

3) The method of modulating a digital signal according to item 1) or 2), wherein the DC component data in the third step is CDS (Code Word Digital Sum) data.

4) The method of modulating a digital signal according to item 1) or 2), wherein the DC component data in the fourth step is one having a smaller average value level.

5) The method of modulating a digital signal according to item 1) or 2), wherein the DC component data in the fourth step is one having a smaller peak value.

6) The selection of the coded sequence data in the fourth step is performed at the time when the sync word is generated, or the source data that can generate a plurality of code word data having different values for one source data. The method for modulating a digital signal according to the item 1) is performed at the time when is supplied.

7) The selection of the coded sequence data in the fourth step is performed at the time when the sync word is supplied, or when the source data capable of generating a plurality of code word data having different values with respect to the one source data. The method for modulating a digital signal according to the item 2), which is performed at the time of supply.

8) The operation of converting the source data having the bit number p (p is a positive integer) into the code word data having the bit number q (q is an integer larger than p) is repeated a plurality of times to generate the code word data. A group of code words is generated at a predetermined bit interval, a code word data group is arranged following the code word generated, and the code word data group is obtained as a coded sequence signal. NRZI (Non Retur
A digital signal modulator for obtaining a signal to be supplied to a recording medium or a transmission medium by performing n to Zero Inverse) conversion, wherein the NRZI conversion obtains the number of times of inversion of mutually different polarities depending on the synchronization word. Word and second
Sync word generating means (123) for simultaneously generating each of the sync words and the code word data group based on the run length coding method in which the run length is limited to a predetermined range,
The generated codeword data group is arranged following the first synchronization word to generate the first coded sequence data, and the codeword data group is arranged following the second synchronization word. Coded sequence data generation means (122, 124, 125) for generating second coded sequence data by
Second DC component related to the DC component generated when the second coded sequence data is NRZI-converted while obtaining the first DC component data related to the DC component generated when the NRZI-converted coded sequence data The DSV operation memory means (126, 127) for obtaining the data and the first code of the one obtained as the smaller DC component data by comparing the first DC component data with the second DC component data Code word output means (128, 12) for selecting and supplying either the encoded sequence data or the second encoded sequence data.
9) and a digital signal modulating device characterized by comprising at least.

9) The operation of converting the source data having the bit number p (p is a positive integer) into the code word data having the bit number q (q is an integer larger than p) is repeated a plurality of times to generate the code word data. When generating the group, when the specific source data capable of generating the first code word data and the second code word data having different values with respect to one source data is supplied, the specific source data is supplied after the specific source data. The code word data group is generated from the source data, and the generated code word data group is obtained as a coded sequence signal that is arranged following the first code word or the second code word. NRZI (Non Return to Zer)
o Inverse) conversion to obtain a signal to be supplied to a recording medium or a transmission medium as a signal, the digital signal modulating device,
Codeword generating means (122) for generating each of the first codeword and the second codeword that can obtain the number of inversions of polarities different from each other by RZI conversion, and a run with a run length limited to a predetermined range. The codeword data group is generated based on a length coding method, and the generated codeword data group is arranged following the first codeword to generate first coded sequence data, and Coded sequence data generation means (122, 12) for arranging a codeword data group following the second codeword to generate second coded sequence data.
4, 125) and NRZ the first encoded sequence data.
The first DC component data relating to the DC component generated when the I conversion is performed is obtained, and the second encoded sequence data is N
DSV operation memory means (126, 12) for obtaining second DC component data relating to the DC component generated when the RZI conversion is performed.
7) and the first DC component data and the second DC component data are compared with each other, and the first coded sequence data or the second encoded sequence data of the smaller one obtained as the smaller DC component data.
And a codeword output means (128, 129) for selecting and supplying any one of the coded sequence data of (1), and a digital signal modulating device.

10) The operation of converting the source data having the bit number p (p is a positive integer) into the code word data having the bit number q (q is an integer larger than p) is repeated a plurality of times to generate the code word data. A group of code words is generated at a predetermined bit interval, a code word data group is arranged following the code word generated, and the code word data group is obtained as a coded sequence signal. NRZI (Non Retur
A digital signal recording medium in which a signal obtained by performing n to Zero Inverse) conversion is recorded, the first sync word and the second sync word being obtained by the NRZI conversion in which different numbers of inversions of polarities depending on the sync word are obtained. Each of the synchronization words is generated at the same time, and the codeword data group is generated based on a run length encoding method in which the run length is limited to a predetermined range, and the generated codeword data group is generated by the first synchronization. The first coded sequence data is generated by arranging the code word data group following the word, and the second coded data group is generated by arranging the code word data group after the second synchronization word by the second coded word sequence. The first DC component data relating to the DC component generated when the first coded sequence data is NRZI converted, and the second DC component related to the DC component generated when the second coded sequence data is NRZI converted Ingredient de Data and compares the first DC component data with the second DC component data to obtain the smaller one of the first encoded sequence data or the second encoded data. A digital signal recording medium characterized in that any one of series data is selected and the coded series data obtained by the selection is recorded.

11) The operation of converting the source data having the bit number p (p is a positive integer) into the code word data having the bit number q (q is an integer larger than p) is repeated a plurality of times to generate the code word data. When generating the group, when the specific source data capable of generating the first code word data and the second code word data having different values with respect to one source data is supplied, the specific source data is supplied after the specific source data. The code word data group is generated from the source data, and the generated code word data group is obtained as a coded sequence signal that is arranged following the first code word or the second code word. NRZI (Non Return to Zer)
o Inverse) conversion, which is a digital signal recording medium in which a signal obtained by converting the first codeword and the second codeword, each of which is obtained by the NRZI conversion, has a number of inversions of different polarities. The codeword data group is generated based on a run length encoding method in which the run length is limited to a predetermined range, and the generated codeword data group is arranged following the first codeword. To generate first coded sequence data, and to arrange the codeword data group following the second codeword to generate second coded sequence data, and to generate the first coded sequence data. NRZI
The first DC component data relating to the DC component generated when the conversion is performed is obtained, and the second encoded sequence data is NRZI.
The second direct current component data relating to the direct current component generated upon conversion is obtained, the first direct current component data is compared with the second direct current component data, and the smaller one of the direct current component data is obtained. A digital signal recording medium characterized in that either the first coded sequence data or the second coded sequence data is selected and the coded sequence data obtained by the selection is recorded.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a digital signal modulating method, a digital signal modulating device, and a digital signal recording medium according to the present invention will be described below with reference to preferred embodiments. FIG. 1 shows a schematic configuration of a digital signal modulation apparatus equipped with a digital signal modulation method according to the embodiment.

The digital signal modulator 1 shown in the figure has a format unit 11, a pq modulator 12, coding tables 13a, 13b, ..., 13n, NRZI (Non Retur).
n to Zero Inverse) conversion unit 14 and a recording drive unit 15, and the signal of the digital signal modulation device having such a configuration is supplied to the recording device for recording on the recording medium 2 or the transmission encoding device 31. Is supplied to the transmission medium through the following. Next, the operation of the digital signal modulator 1 will be outlined.

First, MPEG (moving picture experts)
group) -2 or the like, the digital information signal such as an image or a sound compressed and encoded is formatted by the format unit 11
Where the error correction code is added to the supplied digital information signal, the supplied data is scrambled, interleaved, etc., and the processed information signal is p bits (p is For example, the source data is divided into source data for every 4) such as 4, and the divided source data for every p bits is p−q.
It is supplied to the modulator 12.

The p-q modulator 12 converts the source data signal, which is an information signal supplied by p bits, into q-bit (q is an integer larger than p, such as 6) coded data. Is a circuit for generating a block-converted signal, and the pq modulation unit 12 uses a predetermined number of source data as a unit, and inserts a preset synchronization word for each unit number of source data. To work.

.., 13n are incorporated in the p-q modulator 12, and the supplied source data is supplied to the encoding tables 13a, 13b ,. , 13n, DSV (Digital Sum Valiation) control is performed by the method described later while being supplied as a coded sequence signal that is block-converted into a q-bit codeword.

The block-converted coded sequence signal is supplied to the NRZI conversion unit 14, where the supplied coded bit sequence signal is NRZI-converted, and the digital modulation signal obtained by the conversion is the recording drive unit. The digital modulation signal supplied to the recording drive section 15 is supplied as a signal in which the intensity of the laser beam for recording the signal on the optical disc is converted into the intensity,
The intensity-converted laser beam is applied to the recording medium 2, and a digital modulation signal corresponding to the intensity is recorded.

Further, the digitally modulated signal is supplied to the transmission encoding unit 31, and the second digital modulation is performed as necessary so that the signal becomes a signal suitable for transmission through the transmission medium 3. Then, the modulated signal is supplied to the transmission medium 3 and is transmitted through the transmission medium.

The digital modulation signal transmitted here is
For example, in the case where the signal of the digital signal modulator is supplied to another peripheral device as a baseband signal as a digital modulated signal, even if the ground potential between the devices is different and they are coupled by a high frequency transformer, etc. Since there is almost no DC component contained in the digital modulation signal, stable signal transmission can be achieved.

In this way, the digital information signal supplied from the digital signal modulator 1 is output as laser beam output light which is optically modulated by the pq modulation in which the DC component is suppressed and the NRZI modulated signal. , Or as a baseband signal output for supplying signals to other transmission media.

Next, the configuration and operation of the pq modulator 12 which is the main part of the digital signal modulator 1 will be described in detail. FIG. 2 shows the configuration of the pq modulator 12 in detail.

The pq modulation unit 12 in the figure includes a codeword option presence / absence detection circuit 121, coding tables 13a, 1
, 13n and the encoding table address generation unit 122 including the synchronization word generation unit 123, the code word memory “0” 124, the code word memory “1” 125, the DSV operation peak value memory “0” 126, the DSV. It is composed of a calculation peak value memory "1" 127, a memory control coding unit 128, and a peak value comparison unit 129, and also has a DSV calculation peak value memory "0" 126, a DSV calculation peak value memory "1" 127, and a peak. The value comparison unit 129 constitutes the peak value calculation unit 16.

Next, the operation of the pq modulator 12 having such a configuration will be described. First, the synchronization word generation unit 123
Then, the state S is calculated for each predetermined number of p-bit source data.
Two types of sync words for (k) are generated. That is, these two types of sync words are code words that are preset so that the DSV polarities are opposite to each other and the number of 1s included in a code bit is different from each other, and one sync word is C
(K) 0 is supplied to the code word memory “0” 124, the other synchronization word is set to C (k) 1 and supplied to the code word memory “1” 125, and the two types of synchronization words are DSV operation peak values. It is supplied to each of the memory “0” 126 and the DSV calculation peak value memory “1” 127, and the DSV calculation peak value memories calculate the respective DSVs to obtain the absolute peak values. Each of the obtained peak values is updated to the memory contents of the peak values stored in advance. At the same time, the sync words are stored in the respective code word memories, and after the operations are performed, the supply of the source data is started.

The source data D (k) supplied from the format unit 11 is supplied to the address generation unit 122, and the source data is also supplied to the code word option presence / absence detection circuit 121, in which the source data sequence is set. It is detected whether or not a code word, which will be described later, can be exchanged is included.

The detection result concerning the presence / absence of an option obtained by the detection is supplied to the encoding table address generation unit 122, and the encoding table address generation unit 122 detects whether an option is detected or not. Different actions are performed.

First, the operation when no option is detected will be described. When the code word relating to the option that meets the condition described later is not detected in the source data, the source data supplied in p bits is uniquely code-converted into q-bit coded data. In the conversion, the address value of the encoding table corresponding to the data value stored in the encoding tables 13a, 13b, ..., 13n is designated to obtain the codeword in which the code conversion is performed.

Since the number of code words thus obtained is one, the obtained one code word is designated as C (k) 0 and C (k) 1, and the code word memory "0" 124 and the code It is supplied to the word memory “1” 125, and C (k)
The respective code words of 0 and C (k) 1 are supplied to the DSV calculation peak value memory “0” 126 and the DSV calculation peak value memory “1” 127, respectively, and each DSV is calculated by them. Absolute peak values are obtained, and each of the obtained peak values updates the memory contents of the previously stored peak values.

In this way, the peak values stored in the respective DSV calculation peak value memory “0” 126 and the DSV calculation peak value memory “1” 127 are supplied following each of the two types of sync words. The pq modulation is performed while the peak value generated by the code word is sequentially updated.

Then, the operation in the case where an option is detected in the next supplied codeword will be described. It means that two codewords can be obtained for one supplied p-bit source data. For those two codewords, two coded sequences based on the two codewords can be created in the same manner as two coded sequences can be created for the two sync words described above. Is something that can be created.

Therefore, when an option is detected in the supplied codeword, the coded sequence that gives the smaller DSV peak value can be obtained from the coded sequences for the two sync words described above. The operation for that is performed.

That is, in the operation, the peak value of the absolute value accumulated in each of the DSV calculation peak value memory “0” 126 and the DSV calculation peak value memory “1” 127 is the peak value comparison unit 129. And the peak value comparison unit 129 compares the peak values of the two.
The comparison result obtained by the comparison is used as the memory control code output unit 12
Supply to 8.

In the memory control code output unit 128, the code word having the smaller peak value of the DSV absolute value is selected as the code word memory “0” 124 or the code word memory “1” 125 based on the supplied comparison result. Thus, a code word sequence including a code word supplied after the synchronization word is obtained, and the obtained coded sequence is supplied from the memory control code output unit 128 as a pq-modulated digital modulation output.

At the end of such a series of operations, the contents of the DSV operation peak value memory accumulated in the code word memory "0" 124 and the code word memory "1" 125 are cleared and detected by the above options. Similar DSs for two coded sequences for two different codewords obtained
The generation of a code word having a small DSV peak value by the V value management is restarted.

That is, once the DSV calculation peak value memory “0” 126 and the DSV calculation peak value memory “1” 1
After the peak value of DSV accumulated in 27 is cleared, of the two types of code words obtained from the source data,
One code word is C (k) 0, and the code word memory is "0" 1
24, the other codeword is supplied as C (k) 1 to the codeword memory "1" 125, and each of these two types of codewords is stored and these codewords are C (k).
The peak value of the DSV given by each of 0 and C (k) 1 is the DSV calculation peak value memory “0” 126, and the DSV.
The calculated peak value memory “1” 127 is supplied and temporarily stored.

As described above, every two kinds of sync words generated at a predetermined interval, or every time two kinds of code words are obtained, with respect to the two code word sequences supplied so far. While generating codeword sequences having different DSV peak values, each of the codeword sequences having two types of DSV polarities is temporarily stored in the codeword memory.

Then, when the sync word is generated or when two types of selectable code words are obtained, the DSV
Since the code word sequence having the smaller peak value is determined and supplied as the digital modulation signal output, the output signal becomes a code word sequence which is intermittent in time,
Actually, the memory control codeword output unit 128 has a built-in temporary storage circuit, and the codeword sequence signal once buffer-recorded therein is p-as a continuous codeword sequence signal.
It is supplied from the q modulator 12.

Next, the coding tables 13a, 13b, ..., 13n for performing the pq code conversion will be described. In FIG. 3, p = 4, q = 6, and RLL
An example of the encoding table in the (1,9) restriction is shown.

The encoding table shown in the figure is (1, 9)
The number of “0” existing between “1” and “1” is 1
9 is a table showing codewords in RLL (Run Length Limited) coding, which is limited to ~ 9.

That is, S (k) = in the encoding table.
An encoding table having four states 0 to 3 (here, encoding tables 13a, 13b, 13c, 13d
, A, b, c, and d are each composed of 1, 2, 3, and 4), in which S (k) is the state of the coding table and D (k) is 4 (p). ) Bit source data, C (k) is a 6 (q) bit codeword, and
(K) is expressed by both a decimal value and a binary value.

Then, S (k + 1) shows the state information related to C (k + 1) selected after C (k), and C (k + 1) for the next supplied D (k + 1).
Of the four states from S (k) = 0 to 3 in the table,
It is obtained from the table corresponding to the number given by S (k + 1).

Next, C (k) thus obtained
In, the conditions in the case of being detected as having the above options will be described. FIG. 4 shows a table of conditions when the condition determination with the option is made.

In the figure, D (k) is 4-bit source data, C (k) is a 6-bit code word, S (k) is the state of the table at time k, and L (k-1) is C
It is the lower zero run length of (k-1).

In this table, for example, the condition with options shown as condition 1 is when S (k) = 3 and the lower zero run length L (k-1) of the preceding codeword is 4 or 5. And D (k) is 6 or less, or L (k-1) is 6 and D
It shows that exchange with a code word of S (k) = 1 is possible if the condition that (k) is 1, 3, or 5 is satisfied.

Therefore, when a condition corresponding to one of the above-mentioned six conditions occurs, there exists a codeword that can be exchanged, so that the presence / absence of codeword option detection shown in FIG. 2 is detected. A signal with an option is supplied from the circuit 121 as the option detection result, and the option detection result signal is supplied to the peak value comparison unit 129, and D of two code sequences is supplied.
Comparison of SV peak values is started.

The comparison processing of the DSV peak value is performed at the time when the sync signal is generated. Next, the sync signal will be described. FIG. 5 shows an example of four synchronization signals used corresponding to the value of S (k).

In the figure, a 24-bit synchronization code given for each state of S (k) 0 to 3 is shown, and X indicates that the least significant bit can be inverted. Then, after those synchronization signals, S (k) =
It is assumed that the transition to 1.

The signal of the code word sequence having the smaller peak value of DSV is generated by the pq modulator 12 based on the synchronization code inserted every predetermined period or based on the condition shown in FIG. Is supplied as an output signal of
Next, the operation will be described with reference to a flowchart.

FIG. 6 is a flowchart showing the operation of the pq modulator, and its operation will be described. First, the initial state is set to take an arbitrary S (k) (step 1
01), it is then determined whether or not a word other than the sync word is supplied, and if it is a sync word (N at step 102).
o) The DSV peak values stored in the respective peak memories in the DSV calculation peak value memories 126 and 127 are referred to.

Then, D given by each coded sequence
The code word memory 12 which is the smaller of the SV peak values
The coded sequence signal stored in 4 or 125 is selected and supplied as an output signal (step 111).

After the output signal is supplied, the stored contents of the unselected codeword memory are set to the contents of the same codeword as the selected codeword memory, and the DS of the unselected one is used.
The contents of the V memory are rewritten to the contents of the selected DSV memory, and the peak values stored in the selected and unselected peak value memories are cleared (step 112).

After the peak value is cleared, the sync word shown in FIG. 5 is selected according to the value of S (k). For example, the sync word whose LSB is 0 is the code word memory “0” 124.
And the sync word whose LSB is 1 is the code word memory "1".
It is supplied to 125 (step 108).

However, since the memory contents are supplied as output signals here, the code words are not replaced when the code words are not temporarily stored in the memory.

The operation when the sync word is generated has been described above. Next, the operation when the sync word is not generated will be described. That is, when the supplied modulation target data is other than the synchronization word (step 102
Yes), the 4-bit source data D (k) is supplied to the code word option presence / absence detection circuit 121 (step 10).
3).

The code word supplied to the code word option presence / absence detection circuit 121 is detected whether or not there is a code word that meets the above-described conditions shown in FIG. 4, and if it is detected (step In the case of Yes in 104), the peak memory 126 and 127 are referred to, the code word memory having the smaller peak value is selected, and the signal of the code word sequence stored in the code word memory is supplied as the output signal. (Step 105).

After the code word sequence signal is supplied, the stored contents of the unselected code word memory are replaced with the contents of the selected code word memory, and the DSV memory of the unselected one is replaced. DS of the person who selected the content
The value of the peak value stored in both peak value memories is cleared by replacing it with the contents of the V memory (step 10).
6).

Next to the clearing of the peak value, the above-mentioned FIG.
The first and second codewords are selected from the encoding table shown in FIG. 1, and the first codeword is the codeword memory “0” 124.
, And the second codeword is supplied to the codeword memory “1” 125 and stored in the respective memory (step 1
08).

After the storage, a CDS (Code Word Digital Sum) is performed for each of the code words C (k) 0 and C (k) 1 supplied to the first and second code word memories.
Value is calculated, DSV value is calculated based on that value,
The peak value is updated so that the value of the calculated peak value is stored in each peak memory (step 109).

After such a series of operations, it is judged whether or not the encoding is completed (step 110). If the encoding is completed (Yes in step 110), the encoding is completed, and if not completed (step 110). No in step 110) step 10
Returned to 2.

In this way, a coded sequence signal having a small DSV peak value is obtained, and the obtained signal is NR.
An NRZI-modulated signal having a small DC component when ZI-modulated is obtained, and the operation therefor will be described next.

FIG. 7 shows C for the generated codeword signal.
The values of DS and DSV will be illustrated. In the figure,
Two code words a) and b) are shown, and C (k-1)
And C (k + 1) are the same codeword as each other, but C
(K) is an exchangeable code word that meets the condition shown in the condition 1 of FIG. 4 described above, and is “101001” on the side of a).
Codeword is selected, and "001001" is selected on the b) side.
This is the case where the code word of is selected.

Then, in a), the CDS of each codeword is −
Since DSVs up to C (k + 1) are 0, and CDS is also -4, 0, +4 in b), since DS is 4, 0, and +4 and modulation is performed from level 1, DS
V becomes -8. This is because the number of "1" s in C (k) differs between a) and b), and thus DSV inversion is performed.

In this way, when the code words that meet the above-mentioned conditions shown in FIG. 4 are supplied, the code words having different DSV polarities are used as shown by a) and b). As a result, it is possible to obtain digital modulation signals having different DSV characteristics between a) and b).

Of the two codeword sequences thus obtained, it is necessary to select and obtain the codeword sequence having the smaller DC component of the digital modulation signal generated after NRZI modulation. The method of determining the codeword sequence according to the DSV level up to a plurality of DSV conversion points ahead will be described.

FIG. 8 shows an example of the relationship between the code word and the DSV level for explaining the operation of the peak value calculator 16 in FIG. In the figure, the horizontal axis represents the time axis and the vertical axis represents the DSV value. And time k, k + 1,
It is the time at which a code word that meets the above-described DSV conversion enabling condition appears or a sync word is inserted at k + 2 and k + 3.

At the time point k, the code word sequence has already been selected and determined, and the code word sequence before the time point k has been supplied as the output code word.
4 and 125 show the state in which no code word is left.

Further, P0 is the peak value of DSV when C (k) 0 is the head in the section from k to k + 1, and P1 is the D value when C (k) 1 is the head.
It is the peak value of SV. Hereinafter, in the section from k + 1 to k + 2, four peak values of P00 to P11 are k + 2.
There are eight peak values of P000 to P111 in the section from to k + 3.

In this way, 8 is provided in the section from k to k + 3.
Although the data of the peak values are obtained, the codeword memory “0” 124 or the codeword memory “1” 1 at the time point k + 1 is performed based on the obtained data.
A method of determining a codeword relating to which of the codeword sequences temporarily stored in 25 is selected will be described.

That is, the time point k + 1 is the time point at which the above-mentioned selectable codeword or synchronization signal appears, and C (k) 0 is stored in the codeword memory “0” 124 and the codeword memory “1” 125, respectively. Leading codeword and C (k) 1
The code word starting with is stored.

The code word memory is selected at the time point k + 1 depending on whether C (k) 0 has a smaller peak level until time point k + 3 or C (k) 1 is selected. Whether or not the peak level is low is calculated and obtained.

The calculation of the peak level therefor is performed by the peak value calculation unit 16, in which the peak level up to k + 3 when C (k) 0 is selected and C (k).
The peak level up to k + 3 when 1 is selected may be calculated. Then, it is not necessary to store the codeword in the section from the time points k + 1 to k + 3 in the codeword memory, and it is sufficient to obtain only the DSV level and the peak level of the codeword.

The conditions for selecting the code word memory will be described below. That is, P0 + P00 + P000, P0 + P
00 + P001, P0 + P01 + P010, and P0 +
Let min (P0) be the minimum value of P01 + P011,
P1 + P10 + P100, P1 + P10 + P101, P
1 + P11 + P110, and P1 + P11 + P111,
Let min (P1) be the minimum value of min (P1)
0) is less than min (P1), select codeword memory "0", otherwise, codeword memory "1"
Make sure to select.

As a matter of course, the operation for comparing the levels of the DSV values to obtain such a result and selecting the code word that gives the minimum value of the DC component of the modulated signal after NRZI modulation is performed as described above. Other calculation method may be used.

The case where the CDS calculation is performed for each code word bit has been described above. However, the CDS value can be obtained in advance as a table for each code word, and the CDS value can be obtained using the table.

FIG. 9 shows a table of CDS values obtained for codewords. In the figure, the CDS value of each codeword when the input level is 1 is calculated, and is calculated from the value of the source data D (k) and the value of S (k), and the CDS shown in the table is obtained. The value of corresponds to each code word in the encoding table in FIG.

In this way, the value of CDS is obtained based on the value of the source data. Based on the value of CDS thus obtained, the code word of the digital signal with less DC component is obtained. The series can be selected in advance.

In the above description of the operation in FIG. 1, an example in which the code word supplied from the code word memory is NRZI converted has been described, but the code word memory stores the recorded code word string after NRZI conversion. Of course, you may keep it.

Further, an example of the sync signal is shown in FIG. 5 described above. The sync word is a sync pattern that is easily distinguished from the code word, and the two sync words are set so that their DSV values are different from each other. The same operation can be performed even when another synchronization pattern is used.

Furthermore, in the above-mentioned example, the 4-state coding table for converting 4 bits into 6 bits has been described as an example, but of course other modulation is performed using a coding table for converting p bits into q bits. It is also possible to configure the method of carrying out the above, and to configure a modulator equipped with it. By changing the values of p and q, for example, the number of conditions with options shown in FIG. The appropriate p and q values may be selected according to the characteristics of the digital modulation signal to be obtained, such as by selecting the code sequence.

As described above, according to this embodiment, the DSV control can be performed by the peak value of the DSV of the recording code sequence, and the peak level can be effectively reduced as compared with the control using the conventional DSV. It is possible to effectively reduce the dispersion of the word DSV.

The method of generating the digital modulation signal for keeping the peak level value of the DSV value small has been mainly described. That is, when reproducing the signal recording medium generated in this way, for example, one portion having a large peak level is detected. This is because even in some cases, there are many cases in which there is a bad influence on tracking performance and the like.

However, in the case where the circuit for controlling them is not required to have a fast response performance, for example, the average level of the control signal is used to perform the reproduction control of the optical disk reproducing apparatus or the reproduction control for the special reproduction. In such a case, it is necessary that the peak value of the DSV value is limited to a small value and the level of the average value is also limited to a small value. Further, in the control for keeping the average value of the DC component of the modulated signal after the NRZI modulation small, the peak value control described above is read as the average value control,
It can be done in the same way.

[0100]

According to the invention of claim 1, NRZI
Based on the run-length coding method in which the first sync word and the second sync word, which can obtain the number of inversions of different polarities depending on the sync word by conversion, are simultaneously generated, and the run length is limited to a predetermined range. To generate a codeword data group, arrange the generated codeword data group following the first synchronization word to generate the first coded sequence data, and generate the codeword data group into the second codeword data group. Second after the sync word
When the second encoded sequence data is NRZI-converted while the first encoded component data relating to the DC component generated when the first encoded sequence data is generated and the first encoded sequence data is NRZI-converted is generated. The second direct current component data relating to the generated direct current component is obtained, the obtained first direct current component data and the second direct current component data are compared, and encoding of the smaller direct current component data is performed. Since the sequence data is selected and supplied, for example, a digital modulation having a DC component suppressing characteristic suitable for recording while performing predetermined run-length limited encoding on a disk-type high-density recording medium such as an optical disk. There is an effect that a digital signal modulation method capable of generating a signal can be provided.

According to the invention of claim 2, NR
The ZI conversion generates a plurality of codewords that can obtain the number of inversions of polarities different from each other, and also generates a codeword data group based on the run length encoding method in which the run length is limited to a predetermined range, and the generated codeword data group is generated. To generate first coded sequence data in which the codeword data group is arranged after the first codeword, and second coded sequence data in which the codeword data group is arranged after the second codeword Then, the first DC component data relating to the DC component generated when the first coded sequence data is NRZI converted, and the second DC component related to the DC component generated when the second coded sequence data is NRZI converted. So as to obtain the component data, compare the obtained first DC component data and the obtained second DC component data, and select and supply the coded sequence data of the one giving the smaller DC component data. I have to Thus, for example, a digital signal modulation method capable of generating a digital modulation signal having a DC component suppressing characteristic suitable for recording while performing predetermined run-length limited encoding on a disk-type high-density recording medium such as an optical disk. There is an effect that can be provided.

According to the third aspect of the present invention, since the DC component data is used as the DC component data, the DC component data relating to the DC component generated when the NRZI conversion is performed in advance can be obtained. In addition to the effect of item 1 or 2, there is an effect that it is possible to provide a digital signal modulation method that can more easily generate a digital modulated signal having a preferable DC component suppression characteristic.

Further, according to the invention described in claim 4, since the DC component data value which gives a smaller average value level is used as the DC component data, in addition to the effect of claim 1 or 2, it is more preferable. There is an effect that a digital signal modulation method capable of generating a digital modulation signal having various DC component suppression characteristics can be provided more easily.

According to the invention described in claim 5, since the direct current component data uses the value of the direct current component data which gives a small peak level, in addition to the effect of the first or second aspect, it is more preferable. There is an effect that a digital signal modulation method capable of generating a digital modulation signal having a DC component suppression characteristic can be provided more easily.

According to the invention described in claim 6, particularly, the selection of the coded sequence data is performed at the time when the synchronization word is generated,
Alternatively, in addition to the effect of claim 1, further preferable direct current component suppression characteristics are obtained when the source data capable of generating a plurality of code word data having different values is supplied to one source data. There is an effect that it is possible to more easily provide a digital signal modulation method capable of generating a digital modulation signal having.

According to the invention described in claim 7, particularly, the selection of the coded sequence data is performed at the time when the synchronization word is generated,
Alternatively, since the processing is performed at the time when the source data capable of generating a plurality of codeword data having different values is supplied to one source data, in addition to the effect of claim 2,
There is an effect that a digital signal modulation method capable of generating a digital modulation signal having a more preferable DC component suppression characteristic can be provided more easily.

According to the invention of claim 8, NR
A run-length coding method in which the first sync word and the second sync word, which can obtain the number of inversions of different polarities depending on the sync word by the ZI conversion, are simultaneously generated and the run length is limited to a predetermined range. A codeword data group is generated based on the generated codeword data group, the generated codeword data group is arranged following the first synchronization word to generate the first coded sequence data, and the codeword data group is generated as the second codeword data group. No. 1 related to a DC component generated when NRZI conversion is performed on the first coded sequence data by generating the second coded sequence data after the synchronization word
Second direct current component data and second direct current component generated when NRZI conversion of the second coded sequence data is performed.
Of the DC component data, compares the first DC component data with the second DC component data, and selects and supplies one of the encoded series data obtained as the smaller DC component data. Therefore, for example, a configuration of a digital signal modulator for generating a digital modulation signal having a DC component suppressing characteristic suitable for recording while performing predetermined run-length limited encoding on a disk-type high-density recording medium such as an optical disk. There is an effect that can be provided.

According to the invention of claim 9, NR
The ZI conversion generates a plurality of codewords that can obtain the number of inversions of polarities different from each other, and also generates a codeword data group based on the run length encoding method in which the run length is limited to a predetermined range, and the generated codeword data group is generated. To generate first coded sequence data in which the codeword data group is arranged after the first codeword, and second coded sequence data in which the codeword data group is arranged after the second codeword Then, the first DC component data relating to the DC component generated when the first coded sequence data is NRZI converted, and the second DC component related to the DC component generated when the second coded sequence data is NRZI converted. So as to obtain the component data, compare the obtained first DC component data and the obtained second DC component data, and select and supply the coded sequence data of the one giving the smaller DC component data. I have to Thus, for example, a digital signal modulation device capable of generating a digital modulation signal having a DC component suppressing characteristic suitable for recording while performing predetermined run-length limited encoding on a disk-type high-density recording medium such as an optical disc. The effect is that the configuration can be provided.

According to the invention of claim 10, N
A run-length coding method in which the first sync word and the second sync word, which can obtain the number of inversions of different polarities depending on the sync word by the RZI conversion, are simultaneously generated and the run length is limited to a predetermined range. A codeword data group is generated based on the generated codeword data group, the generated codeword data group is arranged following the first synchronization word to generate the first coded sequence data, and the codeword data group is generated as the second codeword data group. And the second direct current component data relating to the direct current component generated when the first coded sequence data is NRZI converted, and the second direct current component data is obtained. Second DC component data relating to a DC component generated when the encoded sequence data of NRZI conversion is performed, and the obtained first DC component data and second DC component data are compared, and the smaller one DC component day Since the coded sequence data of the one obtained as is selected and supplied, a digital signal recording medium in which a digital modulated signal having a suitable DC component suppressing characteristic is recorded while performing predetermined run length limited encoding There is an effect that can be provided.

Further, according to the invention of claim 11, N
The RZI conversion generates a plurality of codewords that can obtain the number of inversions of polarities different from each other, and also generates a codeword data group based on the run length encoding method in which the run length is limited to a predetermined range, and the generated codeword data group is generated. First codeword data group
Of the first coded sequence data and the code word data group arranged after the second code word
NRZI of the first DC component data relating to the DC component generated when the first encoded sequence data is generated and the first encoded sequence data is NRZI converted.
The second direct current component data relating to the direct current component generated upon conversion is obtained, and the obtained first direct current component data and second direct current component data are compared, and the smaller direct current component data is given. Since one of the coded sequence data is selected and supplied, it is possible to provide the digital signal recording medium in which the digital modulated signal having the preferable DC component suppressing characteristic is recorded while performing the predetermined run length limited coding. There is.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a digital signal modulator according to an embodiment of the present invention.

FIG. 2 is a block diagram of a pq modulation section related to the main part of the digital signal modulation apparatus according to the embodiment of the present invention.

FIG. 3 is p = 4 and q = 6 according to an embodiment of the present invention,
It is a figure which shows an example of the encoding table in RLL (1, 9) restrictions.

FIG. 4 is a diagram showing a condition when a condition determination with an option is made according to an embodiment of the present invention.

FIG. 5 is a diagram showing an example of a synchronization signal used corresponding to a value of S (k) according to the embodiment of the present invention.

FIG. 6 is a flowchart showing the operation of the pq modulation unit according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating values of CDS and DSV for a generated codeword according to an embodiment of the present invention.

FIG. 8 is a diagram showing how the code word and the DSV level change with time according to the embodiment of the present invention.

FIG. 9 is a diagram illustrating a CDS for a codeword according to an embodiment of the present invention.
The values of are shown in a table.

[Explanation of symbols]

1 Digital signal modulator 2 recording media 11 format section 12 p-q modulator 13a, 13b, ..., 13n encoding table 14 NRZI converter 15 Recording drive 16 Peak value calculator 31 transmission coding device 121 Code Word Choice Presence / Absence Detection Circuit 122 address generator 123 Synchronous word generator 124 Code word memory “0” 125 code word memory "1" 126 DSV calculation peak value memory “0” 127 DSV calculation peak value memory “1” 128 memory control code part 129 Peak value comparison unit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshio Kuroiwa             3-12 Moriya-cho, Kanagawa-ku, Yokohama-shi, Kanagawa             Local Victor Company of Japan, Ltd. F-term (reference) 5D044 GL01 GL20 GL21 GL22 GL26                 5J064 AA02 BA08 BC01 BD03

Claims (11)

[Claims] 1. A codeword data in which an operation of converting source data having a bit number p (p is a positive integer) into codeword data having a bit number q (q is an integer larger than p) is repeated a plurality of times. A group of code words is generated at a predetermined bit interval, a code word data group is arranged following the code word generated, and the code word data group is obtained as a coded sequence signal. Is a method of modulating a digital signal for NRZI conversion to obtain a signal to be supplied to a recording medium or a transmission medium, wherein the NRZI conversion obtains the number of inversions of polarities different from each other depending on the synchronization word. A first step of simultaneously generating each of the word and the second synchronization word, and generating the code word data group based on a run length coding method in which the run length is limited to a predetermined range, and generating the raw word data group. The generated codeword data group is arranged subsequent to the first synchronization word to generate first encoded sequence data, and the codeword data group is arranged following the second synchronization word to generate the first encoded sequence data. A second step of generating coded sequence data of No. 2, obtaining first DC component data relating to a DC component generated when the first coded sequence data is NRZI converted, and performing the second coding. A third step of obtaining second DC component data relating to a DC component generated when NRZI conversion of the series data is compared with the first DC component data and the second DC component data, and the smaller one is compared. A fourth step of selecting and supplying either the first coded sequence data or the second coded sequence data, which is obtained as the DC component data, Dizzy Modulation method of digital signal. 2. Code word data by repeating a plurality of operations of converting source data having a bit number p (p is a positive integer) into code word data having a bit number q (q is an integer larger than p). When generating the group, when the specific source data capable of generating the first code word data and the second code word data having different values with respect to one source data is supplied, the specific source data is supplied after the specific source data. The code word data group is generated from the source data, and the generated code word data group is obtained as a coded sequence signal that is arranged following the first code word or the second code word. A method of modulating a digital signal for NRZI-converting a coded sequence signal to obtain a signal to be supplied to a recording medium or a transmission medium, the number of times of inversion having mutually different polarities by the NRZI conversion. A first step of generating each of the first code word and the second code word, which is obtained by the following, and the code word data group based on a run length encoding method in which a run length is limited to a predetermined range. Generated and arranged the generated codeword data group following the first codeword to generate first coded sequence data, and continuing the codeword data group after the second codeword. A second step of arranging the first coded sequence data to generate second coded sequence data, and obtaining first DC component data relating to a DC component generated when the first coded sequence data is NRZI converted, and A third step of obtaining second DC component data relating to a DC component generated when the second coded sequence data is NRZI-converted, and the first DC component data and the second DC component data are compared. The smaller one A fourth step of selecting and supplying either the first coded sequence data or the second coded sequence data that is obtained as stream component data. Method for modulating digital signals. 3. The method of modulating a digital signal according to claim 1, wherein the DC component data in the third step is CDS data. 4. The method of modulating a digital signal according to claim 1, wherein the DC component data in the fourth step is the DC component data having a smaller average value level. 5. The method of modulating a digital signal according to claim 1, wherein the DC component data in the fourth step is the DC component data whose peak value has a smaller level. 6. The selection of coded sequence data in the fourth step is performed at the time when the synchronization word is generated, or source data capable of generating a plurality of codeword data having different values with respect to one source data. The method for modulating a digital signal according to claim 1, wherein the method is performed at the time when is supplied. 7. The selection of the coded sequence data in the fourth step is performed at the time when a sync word is supplied, or when source data capable of generating a plurality of code word data having different values with respect to the one source data. 3. The method of modulating a digital signal according to claim 2, wherein the method is performed at the time of supplying the signal. 8. Code word data is obtained by repeating a plurality of operations of converting source data having a bit number p (p is a positive integer) into code word data having a bit number q (q is an integer larger than p). A group of code words is generated at a predetermined bit interval, a code word data group is arranged following the code word generated, and the code word data group is obtained as a coded sequence signal. Is a digital signal modulating device for obtaining as a signal to be supplied to a recording medium or a transmission medium by performing NRZI conversion, wherein the NRZI conversion obtains the number of inversions of polarities different from each other depending on the synchronization word, A code word data group is generated based on a code word generation means for simultaneously generating each of the two code words and a run length coding method in which the run length is limited to a predetermined range, and the code word data group is generated. A code word data group is arranged following the first synchronization word to generate first coded sequence data, and a code word data group is arranged following the second synchronization word to form a second coded data group. Coded sequence data generation means for generating coded sequence data, first DC component data relating to a DC component generated when the first coded sequence data is NRZI converted, and the second encoding DSV operation memory means for obtaining second DC component data relating to the DC component generated when NRZI conversion of the series data is compared with the first DC component data and the second DC component data, and the smaller one is compared. A code word output means for selecting and supplying either the first coded sequence data or the second coded sequence data, which is obtained as the DC component data, Digital signal modulator to be used. 9. Code word data by repeating the operation of converting source data having a bit number p (p is a positive integer) into code word data having a bit number q (q is an integer larger than p) a plurality of times. When generating the group, when the specific source data capable of generating the first code word data and the second code word data having different values with respect to one source data is supplied, the specific source data is supplied after the specific source data. The code word data group is generated from the source data, and the generated code word data group is obtained as a coded sequence signal that is arranged following the first code word or the second code word. A digital signal modulator for NRZI converting the coded sequence signal to obtain a signal to be supplied to a recording medium or a transmission medium, wherein the NRZI conversion can obtain the number of inversions of mutually different polarities. Codeword generating means for generating each of the first codeword and the second codeword, and the codeword data group is generated based on a run length encoding method in which a run length is limited to a predetermined range. , Arranging the generated codeword data group following the first codeword to generate first coded sequence data, and arranging the codeword data group following the second codeword. Coded sequence data generation means for generating second coded sequence data, and first DC component data relating to a DC component generated when the first coded sequence data is NRZI converted, and Comparing the first DC component data and the second DC component data with DSV operation memory means for obtaining second DC component data relating to the DC component generated when the second encoded sequence data is NRZI converted Then small And a code word output means for selecting and supplying either the first coded sequence data or the second coded sequence data that is obtained as the other DC component data. A digital signal modulation device characterized by the above. 10. Code word data is obtained by repeating a plurality of operations of converting source data having a bit number p (p is a positive integer) into code word data having a bit number q (q is an integer larger than p). A group of code words is generated at a predetermined bit interval, a code word data group is arranged following the code word generated, and the code word data group is obtained as a coded sequence signal. Is a digital signal recording medium recording a signal obtained by NRZI conversion of the first synchronization word and the second synchronization word, the NRZI conversion being capable of obtaining the number of inversions of polarities different from each other depending on the synchronization word. Each of them is generated at the same time, and the code word data group is generated based on a run length encoding method in which the run length is limited to a predetermined range, and the generated code word data group is generated by the first synchronization. To generate first coded sequence data, and to arrange the codeword data group following the second synchronization word to generate second coded sequence data, Second DC component relating to a DC component generated when NRZI conversion is performed on the second encoded sequence data, and first DC component data relating to a DC component generated when NRZI conversion is performed on the encoded sequence data Data is obtained, the first DC component data is compared with the second DC component data, and the first coded sequence data or the second encoded data that is obtained as the smaller DC component data is obtained. A digital signal recording medium characterized by selecting any one of series data and recording the coded series data obtained by the selection. 11. Code word data by repeating a plurality of operations for converting source data having a bit number p (p is a positive integer) into code word data having a bit number q (q is an integer larger than p). When generating the group, when the specific source data capable of generating the first code word data and the second code word data having different values with respect to one source data is supplied, the specific source data is supplied after the specific source data. The code word data group is generated from the source data, and the generated code word data group is obtained as a coded sequence signal that is arranged following the first code word or the second code word. A digital signal recording medium for recording a signal obtained by NRZI conversion of a coded sequence signal, wherein the first code word and the first code word which can obtain the number of inversions of different polarities by the NRZI conversion. And the second codeword, the codeword data group is generated based on a run length encoding method in which the run length is limited to a predetermined range, and the generated codeword data group is generated. Generates first coded sequence data by arranging after the first codeword, and arranges the codeword data group by arranging after the second codeword to generate second coded sequence data. Then, the first DC component data related to the DC component generated when the first coded sequence data is NRZI converted is obtained, and the DC component generated when the second coded sequence data is NRZI converted is calculated. The second DC component data is obtained, the first DC component data is compared with the second DC component data, and the smaller one of the first encoded sequence data or the one obtained as the smaller DC component data is obtained. Second coded sequence Digital signal recording medium and select one of the over data, characterized by recording the encoded sequence data obtained in this selection.