CN1155349A - Method for converting a sequence of m-bit information words into a modulated signal, method for manufacturing a record carrier, encoding device, decoding device, recording device, reading device, signal and record carrier - Google Patents

Abstract

Method of converting a sequence of m-bit information words (1) into a modulated signal (7). For each information word of the sequence, a codeword (4) of n-bits is passed. The transmitted code words (4) are converted into modulated signals (7). The code words (4) are distributed over at least one group (G11, G12) of a first type and one group (G2) of a second type. For the delivery of each codeword of a group (G11, G12) of a first type, the associated group establishes a coding state of the first type (S1, S4). When each codeword (4) belonging to a group (G2) of a second type is delivered, a coding state (S2, S3) of a second type determined by an information word belonging to the delivered codeword is established. When one of the code words (4) is assigned to the received information word (1), this code word is selected from a set of code words (V1, V2, V3, V4) that depends on the coding state (S1, S2, S3, S4). The set of code words (V2, V3) belonging to the second class of coding states (S1, S2) is an inverse set. In this coding method, the number of unique bit combinations that can be established by the code words in the sequence is enlarged. The modulated signal (7) thus obtained can be reconverted into an information word (4) by first converting the modulated signal (7) into a sequence of code words (4) and then assigning an information word (1) to each code word from the sequence in dependence on the code word to be converted and in dependence on the logical values of the bits of the bit string located at predetermined positions relative to the code word. A recording apparatus and a reading apparatus are also disclosed.

Description

Method of converting a sequence of m-bit information words into a modulated signal, method of manufacturing a record carrier, encoding device, decoding device, recording device, reading device, signal, and record carrier

The invention relates to a method for converting m-bit (bit) information word sequences into modulated signals, where m is an integer. In this method, an n-bit codeword is transmitted for each received information word, where n is an integer exceeding m, and the transmitted codeword is converted into a modulated signal, and the information word sequence is according to the conversion rule It is converted into a codeword sequence so that the corresponding modulated signal meets a predetermined standard.

The invention also relates to a method of manufacturing a record carrier on which a signal is recorded.

The invention also relates to an encoding device for implementing a method as claimed, the device comprising an m-bit to n-bit converter for converting an m-bit information word into an n-bit code word, and for converting an n-bit code word word to the device of the modulated signal.

The invention also relates to a recording device in which an encoding device of this type is used.

The invention also relates to signals.

The invention also relates to the record carrier on which the signal is recorded.

The invention also relates to a decoding device for converting this signal into a sequence of m-bit information words, the device comprising conversion means for converting the signal into a bit string of bits having a first or second logical value, the bits The string contains n-bit codewords corresponding to the part of the information signal, and the device also includes a device for converting the sequence of codewords into a sequence of information words, and at the same time assigning an information word related to the codeword to each codeword to be converted device.

Finally, the invention also relates to a readout device in which a decoding device of this type is used.

Such methods, such devices, such record carriers and such signals were published by K.A. Schouhamer Immink in the book "Coding Techniques for Digital Recorders" (ISBN 0-13-140047-9). In said title, a modulation system called EFM is described, for example, which is used for recording information on so-called Compact Discs. The EFM modulated signal is obtained by converting the 8-bit information word sequence into a 14-bit code word sequence, and three merging bits are inserted into the code word. The codeword is selected such that the minimum number of "0" bits between the "1" bits is d(2) and the maximum number is k(10). This restriction is called the dk-restriction. By modulo 2 quadrature operation, the codeword sequence is converted into a corresponding signal formed by bits with high or low signal values. In the modulated signal, a "1"-bit represents Changes to low signal values or vice versa. A "0"-bit indicates that no change in signal value occurs when transitioning between two bit elements. The merging bits are chosen such that the dk-constraint is satisfied even in the transition region between two codewords and the value of the so-called running digital sum remains essentially constant in the corresponding signal. The running digital sum value at a given instant is considered to be the average of the difference between the number of bit elements with a high signal value and the number of bit elements with a low signal value, calculated from the modulated signal at the instant preceding that instant. A substantially constant running number and value means that the spectrum of the signal does not contain frequency components in the low frequency region. This signal is also referred to as a DC-free signal. The absence of low frequency components in the signal is advantageous when the signal is to be read from a record carrier on which the signal is recorded in the track, since a continuous tracking control independent of the recorded signal is then possible. Information recording has a constant need to increase the information density on the record carrier.

A possible solution to this problem is to reduce the number of bits per information word in the modulated signal. However, the problem that arises at this time is that, as a result of reducing the number of bits per information word, the number of unique bit combinations that can represent an information word will decrease, due to which less strict restrictions can be imposed on the modulated signal , for example, regarding the limitation of the low-frequency content of the modulated signal.

It is an object of the invention to provide a measure for reducing the number of bit elements per information word while preventing a reduction in the number of unique bit combinations.

According to a first aspect of the invention, this object is achieved with the method described in the opening paragraph, characterized in that the codewords are distributed at least over a group of the first type and a group of the second type, and at the same time, belong to the first type The transfer of each codeword of the group establishes the coding state of the first type determined by the associated group, and the transfer of each codeword belonging to the second type of group establishes the encoding state determined by the information word associated with the transferred codeword. The second type of encoding status. And, when one of the codewords is assigned to the received information word, this codeword is selected from a set of codewords, which depends on the coding state established when the previous codeword was passed, and codes belonging to the second type of coding state The word set does not contain any common codewords.

According to a second aspect of the invention, an encoding apparatus is characterized in that the apparatus comprises: state establishing means for establishing encoding states when the converter delivers codewords, the state establishing means being arranged for each The transmitted codewords belonging to a group of the first type establish the coded state of the first type, the state of the group of the first type being determined by the associated group, and for each transmitted codeword belonging to a group of the second type The codewords establish a second type of coded state, the state of this second type of group is determined by the information word associated with the codeword being delivered, and also includes an m-bit to n-bit converter, which contains means for selecting the codeword, For selecting a codeword corresponding to an information word from a selection of coding state-dependent codewords, the set of codewords belonging to the second type of coding state does not contain any common codewords.

In the method and the encoding device according to the invention, the combination of the same codeword with a codeword from its antimeaning set (=the set without common codewords) creates various unique bit combinations, so that many More than one information word can be uniquely represented by a combination of the same codeword and successive codewords. Codewords in groups of the second type are, as such, always followed by a codeword, to which set this codeword belongs can always be unambiguously established. Thus, it is always possible to use the codewords from each antisense set to create a sufficient number of unique bit combinations to represent all information words.

These measures then give the possibility of creating a large number of unique bit combinations with codewords having a relatively small number of bits per codeword. Where codewords are chosen to be distributed over sets and groups such that the number of unique bit combinations exceeds the number of distinct information words, it is possible to use the remaining bit combinations to affect predetermined characteristics of the modulated signal.

Alternatively, it is also possible to use only the same number of bit combinations as the information word. The remaining bit combinations at this point allow for specific additional requirements to be made on the codeword.

However, for one or more sets, it is preferable to assign a pair of codewords from the relevant set to each of the plurality of information words, so that when switching, any one of the available pairs is selected according to specified criteria. codewords in order to affect specified characteristics of the modulated signal. An implementable method is characterized in that the information word sequence is converted into a code word sequence according to a conversion rule, so that the corresponding modulated signal exhibits substantially no frequency components in the low frequency region of the frequency spectrum, and the modulated signal wherein The number of consecutive bits with the same signal value in each has a minimum of d+1 and a maximum of k+1. For each information word in at least a certain number of information words, the code word set contains a code word pair, and when the information word is converted, the low frequency component of the modulated signal is selected by code word selection from the code word pair. avoid.

The advantage of this embodiment is that, despite the reduced number of bits per information word, the presence of low frequency components in the modulated signal can be largely avoided.

Another embodiment is characterized in that a synchronization word (sync) is inserted in the codeword sequence, this synchronization word exhibits a bit pattern that cannot occur in the bit string formed by the codeword, and a synchronization word with a different bit pattern is used, so The sync word used depends on the encoding state, after a sync word has been inserted, a predetermined encoding state is established for switching the next information word. At the same time, these synchronization words are made distinguishable from each other on the basis of bit logic values at predetermined bit positions in such a manner that sets of codewords belonging to the second type of encoding state are distinguishable from each other.

The advantage of this embodiment is that when a codeword of the second type group is tracked by a synchronization word, the information word is established by the combination of bits formed by the codeword and the synchronization word, similarly to the codeword of the second type group by a codeword The case of word tracking.

The latter embodiment also has the advantage that the coding state is established each time a sync word has been delivered, so that the constraints imposed on the bit string are always satisfied when transitioning from the sync word to the next code word.

The signal obtained by the encoding device according to the invention has the advantage that it can be decoded in a particularly simple manner.

An embodiment of the implemented decoding device is characterized in that the conversion means are arranged for converting the information word also according to the logical value of a bit in the bit string at a predetermined position relative to the code word.

Referring to the accompanying drawings 1 to 17, the present invention will be further described. in:

Fig. 1 shows an information word sequence, a corresponding code word sequence and a modulated signal;

Figures 2 and 3 show tables establishing the relationship between information words and code words;

Figure 4 shows the values of different parameters when a sequence of information words is converted into a sequence of codewords;

Figures 5a and 5b show the low-frequency part of the spectrum for different signals;

Figures 6 and 8 show various embodiments of encoding devices;

Figure 7 shows an embodiment of a selection circuit used by the encoding device of Figure 6;

Figure 9 shows possible bit patterns for a suitable sync word;

Figure 10 shows the adaptation of the encoding device of Figure 6 for inserting sync words;

Figure 11 shows a decoding device;

Figure 12 shows a record carrier;

Figure 13 shows a high magnification view of a part of the record carrier of Figure 12;

Figure 14 shows the recording device;

Figure 15 shows the readout device;

Figure 16 shows part of the modulated signal and its corresponding codeword, and

Figure 17 gives a graphical representation of the distribution of codewords over groups and sets.

Figure 1 shows three consecutive m-bit information words, where the 8-bit information word is marked as 1, and the three information words 1 have word values "24", "121" and "34", respectively. The sequence of three information words 1 is converted into three consecutive n-bit code words, where the 16-bit code word is marked as 4. The codeword 4 forms a bit string having bits with the value of logic "0" and bits with the value of logic "1". The conversion of the information word is such that, in the bit string, the minimum number of bits with a logical "0" value lying between two with a logical "1" value is d, and the maximum number is k, where d is equal to 2 and k equals 10. Such bit strings are usually designated as RLL strings with dk limits (RLL=Run Length Limited). The individual bits of the codeword are further denoted as x1,...,x16, where x1 denotes the first bit of the codeword (counting from the left) and x16 denotes the last bit of the codeword.

The bit string formed by the codeword 4 is converted into a modulated signal 7 by means of a modulo-2 quadrature operation. This modulated signal comprises three information signals 8 representing codewords 4 . The information signal part comprises bit elements 11, which may have a high signal value H or a low signal value L. The number of bits per information signal part is equal to the number of bits of the associated codeword. Each codeword bit with a logic "1" value represents a transition in the modulated signal 7 from a bit element with a high signal value to a bit element with a low signal value, or vice versa. Each codeword bit having a logic "0" value indicates that there is no change in signal value upon a bit transition in the modulated signal 7 .

In addition, the frequency spectrum of the modulated signal 7 is required to contain substantially no low frequency components. In other words, the modulated signal 7 is DC free.

Embodiments of the method for obtaining a modulated signal according to the present invention will be described in detail below.

First, there are certain requirements for codewords satisfying the dk-constraint. FIG. 17 illustratively shows the set of all possible codewords satisfying the dk-constraint in the area enclosed by the line box 170 . The codewords are divided into at least one first type group and at least one second type group. When a codeword is delivered from one of the first type groups, an encoding state is established exclusively which depends on the first type group to which the delivered codeword belongs. When one of the codewords of the first type group is delivered, an encoding state is established which depends both on the first type group and on the information word represented by the delivered codeword. In the present embodiment described here two groups of the first type can be distinguished, namely: the first group G11 containing codewords ending in a bits with logical "0" value, where a is equal to 0 or 1 and a second group G12 of codewords ending with b bits with logical "0", where b is an integer less than or equal to 9 and greater than or equal to 6.

In FIG. 17 , codewords belonging to group G11 are boxed in 171 , and codewords belonging to group G12 are boxed in 172 .

The coded state established by the first group G11 of the first type is hereafter denoted S1 and the coded state established by the second group G12 of the first type is hereafter denoted S4. The embodiment described here knows only one group of the second type. This group contains codewords ending with c bits having a logical "0" value, where c is an integer greater than or equal to 2 and less than or equal to 5. This group will henceforth be denoted as group G2. The codewords of group G2 in FIG. 17 are boxed in 173. In the example described here, two coding states, namely S2 and S3, can be established by combining codewords and associated information words.

When an information word is converted into a codeword, a codeword belonging to a set of codewords depending on the coding state is assigned to the information word to be converted. The sets of codewords belonging to coding states S1, S2, S3 and S4 will henceforth be labeled V1, V2, V3 and V4, respectively. Codewords for sets V1, V2, V3 and V4 are boxed in 174, 175, 176 and 177. The codewords in these sets are chosen such that each bit string can be formed from a codeword in the group that establishes the encoding state and from an arbitrary codeword in the set determined by the encoding state, will satisfy the dk-limit. In the case where the coding state S4 is established by the passing of the previously passed codeword, and this coding state represents that the previous codeword is with a logic "0" value greater than or equal to 6 and less than or equal to 9 In the case of the end of the bit string, the codeword set V4 established by the coding state S4 is only allowed to contain codewords starting with at most 1 bit with a logical "0" value. For this reason, codewords starting with a greater number of bits with logical "0" values will have regions of transition between the preceding codeword and the codeword to be delivered, in which consecutive bits with logical The number of bits of "0" value will not always be less than or equal to 10, so the dk-constraint is not satisfied. For the same reason, set V1 contains only codewords starting with the number of bits having a logical "0" value greater than, equal to 2 and less than, equal to 9.

Sets V2 and V3 of codewords belonging to coding states S2 and S3 contain only codewords starting with a number of bits having a logical "0" value greater than, equal to 0 and less than, equal to 5. The codewords satisfying this condition are distributed on the two sets V2 and V3, so that the sets V2 and V3 do not contain any common codewords at all. In the following, sets V2 and V3 will be marked as antisense sets. The distribution of the codewords over sets V2 and V3 is preferably such that it can be determined which set a codeword belongs to based on a limited number of logical values of P bits. In the example described above, the bit combination x1.x13 was used for this purpose. The codewords of set V2 can be identified according to the bit combination x1.x13=0.0. Then the codewords of set V3 can be recognized from the combination x1.x3 not equal to 0.0. The distinction between codewords that, when delivered, establish encoding state S1 (group G11), codewords that, when delivered, establish encoding state S2 or S3 (group G2), and codewords that, when delivered, establish encoding state S4 (group G12) are drawn out. Set V1 includes 138 codewords of group G11, 96 codewords of group G2, and 22 codewords of group G12. Obviously, the number of different codewords in set V1 is less than the number of different 8-bit information words.

Since a codeword of group G2 is always followed by a codeword of set V2 or a codeword of set V3, and also since it is possible to determine which set this codeword belongs to from a codeword following a codeword of group G2, Thus a G2 group codeword followed by a V2 set codeword can be unambiguously distinguished from a G2 group of the same codewords unless followed by a V3 set codeword. In other words, each codeword of the G2 group can be used twice when the codeword is assigned to an information word. Each codeword of the G2 group forms a unique bit combination with any codeword of the V2 set, which cannot be separated from the bit combination formed by the same codeword and any codeword of the same V3 set. This means that 138 unique bit combinations (codewords) of G11 group can be used in V1 set, 22 unique bit combinations (codewords) of G12 group and 2×96 unique bit combinations (G2 The combination of the codeword of the group and the subsequent codeword), a total of 352 useful unique bit combinations are obtained, and the unique bit combination numbers formed by the codewords of the V2 set, the V3 set and the V4 set are 352, 351 and 415 respectively .

Figure 17 shows diagrammatically the codewords 178 belonging to the G2 group. This means that the next codeword belongs to V2 set or V3 set. Codeword 178 and the next codeword can then unambiguously determine two different information words. In Fig. 17, the information word determined by the codeword 178 followed by the codeword of the V2 set (such as the codeword 179) is different from the information word determined by the codeword 178 followed by the V3 set codeword (such as the codeword 180) . Codeword 179 belongs to group G11, with the result that regardless of the next information word to be coded, codeword 179 is always followed by codewords of set V1, so that codeword 179 determines no more than a single information word. The same is true for codeword 180. The conversion of the message word proceeds as follows:

We assume that the last delivered codeword is the codeword 178 of the G2 group, and the next codeword belongs to either the V2 set or the V3 set, depending on the information word to be converted. Assuming that this information word defines codeword 179, this means that the next codeword will belong to set V1. Which codeword of the V1 set is used is determined by the information word to be converted. This is codeword 181 in this example. Codeword 181 belongs to group G12, so the next codeword will belong to set V4. Which codeword this will be will then also be determined by the information word to be converted. This is codeword 182 in this example. Codeword 182 belongs to group G2, which means that, depending on the information word corresponding to codeword 182, the next codeword is from either set V2 or set V3. Which codeword of the V2 set or the V3 set is used depends on the information word to be converted. In this example, codeword 182 is followed by codeword 183 . The code word 183 also belongs to the G2 group, so, according to the information word corresponding to the code word 183, the next code word will come from the V2 set or the V3 set, which code word is used in this set still depends on the information word to be converted . At this time, it is code word 184. In the manner explained above, any random sequence of information words can be uniquely converted into a sequence of code words.

It has been explained before that the number of codewords available is extended by subdividing the codewords into groups of first and second types, the types determining the coding states which themselves create a set of codewords from which A codeword is selected for conversion of the next information word. Thus, in the case where the coding states are formulated by codewords of the second type group, it is necessary that the set of codewords from which to choose have no codewords in common. As a result, the same codeword of a set of codewords can be assigned to different information words, as long as due care is taken that the codewords following the same codeword belong to different sets with no common codeword. It is obvious to a person skilled in the art that the method of subdividing said codewords into sets and groups in order to obtain codewords that can be assigned to more than one information word can also be applied to any number of bit codeword. Each codeword sequence does not have to satisfy a specific dk-constraint. Other limitations are possible, for example, as described in EP-A-0,319,101 (PHN 12,339).

As explained before, the presence of a greater number of unique bit combinations available is based on the fact that more than one unique bit combination can be created with codewords of the second type group (G2). Typically, the subdivision of codewords into groups and sets will be chosen such that the number of unique bit combinations available is greater than the number of different information words. This surplus of unique bit combinations offers the possibility of imposing additional restrictions on switching.

One possibility is to use only as many unique bit combinations available as there are different information words, in which case the remainder of unique bit combinations allows certain additional restrictions to be imposed on the codewords.

However, for one or more sets it is preferable to assign a codeword pair formed by two codewords from the associated set to each of the plurality of information words, and then, according to some conversion criteria, select from the codeword pair Any codeword that may be used in order to affect a specified characteristic of the modulated signal.

An attractive possibility is to influence the low frequency components in the modulated signal. This effect preferably includes a minimization of the DC component. This is accomplished by determining the sum of numbers at the end of each information signal part and choosing such codewords when the information is converted so that the sum of numbers determined at the end of each information part will last around some reference value . This can be implemented by assigning to some information words pairs of codewords that cause different changes in number and value. Preferably, each codeword pair contains no more than two codewords for which the change of number and value has an opposite sign. At the end of the last information signal portion, for a given signal level, once a codeword has been delivered, the codeword may be chosen such that its numerical sum value is closest to the reference value.

Another possibility to choose the codewords is to choose the codewords such that for a given signal level at the end of the last delivered codeword the sign of the number and value changes caused by the associated codeword will be delivered with the codeword The sign of the difference between the preceding number and the value and the reference value is reversed. When it is possible to choose from two codewords that have opposite effects on the number and value, then the choice of the codeword to be delivered can be based on the signal value at the end of each information signal part, and The numbers associated with this end and the sign of the difference between the value and the reference value are simply made.

Figure 2 shows graphically for each V1, V2, V3 and V4 set the codewords assigned to each possible information word. In this figure, the first column (left) shows the word values of all possible information words. The second, fourth, sixth and eighth columns show the codewords assigned to the information words of sets V1, V2, V3 and V4, respectively. The third, fifth, seventh and ninth columns show the coding states S1, S2, S3 and S4 determined by the associated codeword with reference numerals 1, 2, 3 and 4, respectively. In Figure 2 no more than 256 available codewords are used for each of sets V1, V2, V3 and V4. Similar to Figure 2, Figure 3 shows the set of codewords not shown in the table of Figure 2 for the 88 information words to which a pair of two codewords are assigned. Indicates that the codeword in Figure 3 is marked as a replacement codeword from now on. The codewords are assigned to the information words such that the changes in numbers and values caused by the replaced codewords are opposite to the changes in numbers and values caused by the codewords of Figure 2, which are assigned to the information words comprising the entire A word value from "0" to "87".

Note that the entire set of Fig. 3 contains equally many codewords. Obviously, this is not necessary for an ordinary skilled person to know. It is also possible that the sets are not equally large.

In addition, it can be seen that the assignment of codewords to information words is chosen such that, on the one hand, the combination of bits x1 and x13 of one codeword and the next codeword, and on the other hand, the relationship between the information words is unique , thus decoding can be uniquely achieved according to the x1 and x13 bits of the received codeword and the next codeword. For the assignment of codewords, this means that if a codeword occurs in different sets, then these same codewords represent the same information word in different sets. For example, an information word having a word value of "2" is represented by "0010000000100100" in sets V0 and V2 shown in FIG. 2, and by "1000000000010010" in sets V2 and V3.

There is no need to pay attention: it is not necessary that codewords of different sets represent the same information word. However, this does mean that when decoding to reconstruct the original information word, the decoding state needs to be restored.

The conversion from information word sequence to code word sequence will be further explained with reference to FIG. 4 .

Column IW shows the word values of the sequence of m-bit information words consecutive from top to bottom. For each information word whose word value is included in column IW, a plurality of data is displayed. Column SW indicates the proposed coding state when the codeword is delivered as a result of the transformation of the previous information word. This codeword is hereafter referred to as the previous codeword. The coding state in the SW column indicates which of the V1, V2, V3 and V4 codeword sets will be used for the conversion of the information word. Column LB shows the signal value of the modulated signal at the end part of the information signal corresponding to the codeword obtained when the previous information word was converted. This signal value is hereafter referred to as the operating information signal value. In the column DSV is shown the number sum value, which belongs to the running signal value of the modulated signal, ie the running modulated signal value (running modulated signal value).

Column CW shows the codewords assigned to the information words of column IW according to the columns of FIGS. 2 and 3 . In the case where a codeword pair is assigned to an information word, the two codewords of the pair are shown, namely the upper codeword of the pair corresponding to the table of FIG. The following codeword of the pair. The column dDSV shows the digital sum value change caused by the codeword, assuming the running modulated signal value has "H" value.

Column DSVN shows the new number sum value for the associated codeword as it was when it was delivered for the associated codeword. The column LBN indicates by a logic "1" that the signal values at the beginning and at the end of the information signal part belonging to the codeword are different. Logical "0" indicates that the signal values at the beginning and the end of the relevant information signal are the same. If the associated codeword contains an odd number of "1" bits, ie corresponds to an odd number of signal level changes of the information signal part, then the signal values at the beginning and end of the information signal part are different. When there is an even number of "1" bits in the codeword, the signal values at the beginning and end of the information signal portion are the same. In the column SWN, the coding state that will be established if the relevant codeword is delivered is shown.

Here, column CS is indicated by an asterisk "*" which codeword is actually delivered for the associated information word.

The first (top) word of the sequence of codewords shown in column IW has a word value of "2". We assume that the coding state (column SW) is S1 when the information word sequence transition starts, and that the modulated signal starts with signal level H, and that the digital sum value DSV is equal to zero. In this case, for the upper codeword, the associated DSVN value is equal to -6, while for the lower codeword of the pair of codewords, its DSVN value is +10. When applying the criterion that the codeword whose DSVN value is closest to the possible reference value of 0 is delivered, for an information word with a word value of "2", the upper codeword of the two codewords of the word pair is passed transfer. This means that the encoding state becomes S2 for the next information word (word value "8"). At the end of the information signal portion corresponding to the transmitted codeword, the signal value is L, thus at the beginning of the next information portion, the signal value is L, as shown in column LB. For the upper codeword belonging to the codeword pair having the information word with word value "8", its dDSV value is equal to -6. This -6 value applies to the case where the signal value at the beginning of the relevant information signal part is H. Since the signal value is L in the case shown, the change in the digital sum value caused by the codeword is not equal to -6 but +6. This means that DSVN becomes equal to 0. The lower codeword DSVN for this codeword pair is equal to -18. For the upper codeword, the value of DSVN is the value closest to 0, so the upper codeword is passed. Next, the message word with the word value "100" will be converted. No more than one codeword is assigned to this information word, so selection according to DSVN is not possible for this information word. In a manner similar to that described above, information words having word values "230", "0", "61" and "255" are converted. Each time a conversion of an information word assigned to a codeword pair is performed, the particular codeword is selected from the codeword pair such that its DSVN is closest to zero. In this way, the DC voltage level of the modulated signal remains substantially constant, and the frequency spectrum of the modulated signal will not exhibit any low frequency components. Although codeword sets are not available for every information word, on average, for 88/256 of all information words to be converted, numbers and values will still be possible. In fact these appear to be sufficient so that low frequency components do not appear in the modulated signal. It is preferable to include in a codeword pair the codeword which causes the greatest change in number and value. On the one hand, it has the advantage that the sum of numbers can be brought to its maximum value. On the other hand, this means that the changes to the numbers and values caused by codewords not belonging to the codeword pair are relatively small, and the influence of such codewords on the numbers and values is relatively small.

Fig. 5a shows diagrammatically the low-frequency part of the frequency spectrum of the modulated signal obtained by implementing the method according to the invention. In Fig. 5b, the corresponding low frequency part of the spectrum of the EFM-modulated signal is plotted. It can be seen from Figures 5a and 5b that the frequency spectra of these two signals are basically the same. The EFM-modulated signal and the dk-limit of the modulated signal obtained by carrying out the method according to the invention are also substantially identical. The number of bits per information word is equal to 17 in the EFM-modulated signal, while it is equal to 16 in the modulated signal according to the invention. This means that if the method according to the invention is implemented, an increase in information density of approximately 7% can be obtained relative to the EFM-modulated signal without compromising the increase in low-frequency content and compromising the dk-limitation.

FIG. 6 shows an embodiment of an encoding device 140 according to the present invention capable of implementing the above method. The encoding device is arranged to convert an m-bit information word 1 into an n-bit code word 4, and the number of different encoding states can be represented by s bits. The encoding device comprises a converter 60 for converting an (m+s+1) binary input signal into an (n+s+t) binary output signal. From the input of the converter, m inputs are connected to bus 62 to receive m-bit information words. From the output of the converter, n outputs are connected to bus 62 to convey n-bit codewords. Additionally, the s inputs are connected to the s-bit bus 63 to receive a status word representing the current encoding status. The status word is delivered by the buffer memory 64 (for example in the form of s flip-flops). Buffer memory 64 has s inputs connected to bus 58 for receiving status words to be stored in the buffer memory. In order to transfer the status word to be stored in the buffer, the s outputs of the converter 60 connected to the bus 58 are used.

The bus 62 is connected to the parallel input of a parallel-to-serial converter 66, which converts the codeword 4 received via the bus 62 into a serial bit string which is supplied via signal line 67 to the modulator circuit 68, which converts the bit string into a modulated signal 7, which is transmitted through the signal line 70. The modulator circuit 68 may be of a conventional type, such as a so-called modulo-2 integrator.

In addition to the code word and the status word, the converter asks the bus 75 for each received combination of the information word and the status word information, which represents:

- for the relevant status word, whether the relevant information word is assigned a codeword or a pair of codewords;

- for each codeword so allocated, the dDSV change of the digital sum value caused by this codeword which should occur at a high signal value at the beginning of the information signal part corresponding to this codeword;

- Whether the number of "1" bits in the codeword is odd or even.

To transfer information to the selection circuit 76 , the bus 75 is connected to an input of the selection circuit 76 .

Based on this information, selection circuit 76 delivers a selection signal indicating whether the conversion of the code word fed to bus 62 and the information word presented is based on the relationship established in the table of FIG. 2 or in the table of FIG. 3 carried out in relationship. This selection signal is applied to converter 60 via signal line 77 .

Converter 60 may include a ROM memory in which the codewords shown in the tables of Figures 2 and 3 are stored at addresses specified by combinations of the status word and the information word applied to the converter input. Depending on the detection signal, an address of a memory cell is selected with a code word corresponding to the table shown in FIG. 2, or a memory cell address is selected with a code word corresponding to the table shown in FIG.

In the embodiment shown in FIG. 6 , the status word is stored in memory 60 . In addition, it is also possible to derive only the status word from the code word passed to the bus 62 by means of the gate.

Instead of a ROM, the converter may include combinational logic circuits made up of gate circuits. Synchronization of the operations performed in the device is achieved in the usual manner using a synchronous clock signal, which is derived from a conventional (not shown) clock generating circuit. FIG. 7 shows a possible implementation of selection circuit 76 . The signal lines forming the bus 75 are divided into a sub bus 80 and a sub bus 81 . Via the sub-bus 80, the values of dDSV for the code words of the table shown in Fig. 2 are transmitted, which code words are assigned according to the received combination of the status word and the information word. In case the table shown in FIG. 3 contains codewords for the associated combination of status word and information word, the value of dDSV for the codeword in the table is transmitted via sub-bus 81 . The sub-bus 80 is connected to a first input of an arithmetic circuit 82 whose second input receives a DSV value stored in a buffer memory 83 via a bus 85 . Also, the control input of the arithmetic circuit receives a control signal via signal line 84 indicating whether the signal value has a high value H or a low value L at the beginning of the portion of the information signal corresponding to the relevant codeword. The signal on signal line 84 is obtained by means of, for example, a flip-flop. The state of the flip-flop is always adapted to the state when the codeword was delivered, and this adaptation occurs according to whether the number of bits having logic value "1" in the delivered codeword indicated by the signal is odd or even. This signal is passed by converter 60 and provided on one of the signal lines making up bus 75 . Arithmetic circuit 82 is of a conventional type that subtracts or adds the dDSV value (received via bus 80) from or adds to the DSV value (received via bus 85), respectively, in accordance with a control signal.

Selection circuit 76 also includes arithmetic circuit 86, which, similar to arithmetic circuit 82, adds the dDSV value received via bus 81 to the DSV value received via bus 85, or subtracts dDSV from DSV, in accordance with a control signal on signal line 84. The results of operations performed by the arithmetic circuits 82 and 86 are supplied to a decision circuit 89 and a multiplexing circuit 90 via buses 87 and 88, respectively. These results show that if a codeword pair has been assigned to the current status word, the new number and value change DSVN will be obtained when two different codewords of the codeword pair are passed. The decision circuit 89 is of the usual type, and according to the DSVN value received via the buses 87 and 88, it decides which of the two received values is closer to the reference value, and this circuit 89 sends a decision signal to the signal line 91 according to the result . When a selection is made from two codewords of a codeword pair, this decision signal indicates which of the two codewords is to be passed on. This decision signal is applied to the signal line 77 through the AND gate 92 . In the event that no codeword pair is available but only one codeword is available, the signal on signal line 77 indicates that the information word delivered according to the table shown in FIG. 2 is to be converted. To accomplish this, the second input of AND gate 92 is provided with a signal from bus 75 indicating whether a single codeword or a codeword pair is available for the combination of status and information words presented .

Signal line 77 is also connected to a control input of multiplex circuit 90 . Depending on the signal on its control input, the multiplexer circuit 90 passes the DSVN value received from the buses 87 and 88 to an output belonging to the transmitted codeword. The output of the demultiplexing circuit 90 is coupled to the buffer memory 83 . The loading of the buffer memory is controlled in the usual manner so that the DSVN value delivered by the multiplexing circuit is stored in the buffer memory 83 when the selected codeword is delivered.

In an embodiment of the encoding device described, in case a set of codewords is available for the presented information word, the codeword is selected from a pair of codewords, when the relevant codeword is delivered, the codeword of this codeword The numbers and values are closest to the predetermined reference value. Another possibility to select a codeword from a pair of codewords is to choose a codeword whose numerical sum value changes as a result of the passing of the codeword, with the same number and sum at the beginning of the codeword passing The sign of the value is reversed.

Figure 8 shows an embodiment of a coding device according to the invention, in which the codewords are selected according to said criteria. The encoding device is again arranged to convert the m-bit information word 1 into an n-bit code word 4, while the number of different encoding states can be represented by s bits. The encoding device comprises a converter 50 for converting an (m+s+1) binary input signal into an (n+s) binary output signal. From the converter inputs, m inputs are connected to a bus 51 for receiving m-bit information words. From the converter output, n outputs are connected to a bus 52 for conveying n-bit codewords. Also, s inputs are connected to an s-bit bus 53 for receiving a status word, which indicates the momentary encoding status. The status word is transferred by means of a buffer memory consisting of, for example, s flip-flops. The buffer memory 54 has s inputs connected to the bus to receive status words to be loaded into the buffer memory. To deliver the status word to be loaded into the buffer memory, s outputs of the converter 50 are used.

The bus 52 is connected to the parallel input of a parallel/serial converter 56, which converts the codeword supplied via the bus 52 into a bit string to be applied via a signal line 57 to a modulator circuit 58, which converts the bit string Converted into a modulated signal 7 to be delivered via the signal line 40 . Modulator circuit 58 may be of a conventional type, such as a modulo-2 integrator. The modulated signal 7 is applied to a circuit of usual type to obtain a running digital sum value of the modulated signal 7 . Circuit 59 delivers a signal Sdsv depending on the determined number and value, indicating whether the codeword is to be converted according to the relationship determined in FIG. 2 or the presented information word is converted according to the relationship determined in FIG. 3 . Converter 50 may be of a similar type to converter 60 except that in converter 50 only the codeword and the associated status word need be stored. In the embodiment of FIG. 8, the information supplied to the decision circuit 76 via the bus 75 using the converter is redundant.

In order for operations to be performed synchronously, the device includes a clock generating circuit 41 of the usual type to generate a clock signal for controlling the parallel/serial converter 58 and for controlling the loading of the buffer memory 54 .

Preferably, the modulated signal 7 comprises a synchronization signal portion having a signal pattern which does not occur in a random sequence of information signal portions. The addition can be realized by inserting the sync word into the n-bit code word sequence. FIG. 9 shows two 26-bit synchronization words 100 and 101 which are excellently suited for use in combination with the codewords shown in FIGS. 2 and 3 . These synchronization words each contain two sequences of 10 bits having the value of logic "0" separated by a bit having the value of logic "1". For the two synchronization words 100 and 101, only the logical value of the bit at the first position (x1) of the codeword is different. Which of the two codewords is inserted depends on the encoding state determined by the codeword immediately preceding the inserted syncword. In case the coding state S1 is determined, a synchronization word 101 starting with 3 bits with the value of logic "0" is inserted. Since the codeword determining the coding state S1 ends with at most one bit with a logical "0" value, the dk-constraints with d=2 and k=10 are fulfilled when making the transition from codeword to syncword.

In case the encoding state S4 is established, a sync word 100 is inserted. Since the codeword establishing the coding state S4 ends with a minimum of 6 bits and a maximum of 9 bits with a logical "0" value, the dk-limit with d=2 and k=10 when converting from a codeword to a syncword to be satisfied again.

In case the encoding state S2 is established, a sync word 101 is inserted. The bit combination x1.x13 in this sync word is equal to 0.0. In case the coding state s3 is determined, a synchronization word 100 is inserted. The bit combination x1.x13 in this sync word is equal to 1.0. In a synchronization word following a codeword establishing coding state S2, the bit pattern x1.x13 is always 0.0, while for a synchronization word following a codeword establishing state S3, the bit pattern x1.x3 is always 1.0 , thus a correlation information word is always unambiguously established from this codeword and the next codeword.

Both syncwords 100 and 101 end with a bit having a logic "1" value, which indicates that the codeword following either of the two syncwords is to be selected from the V1 set so that the codeword from the syncword to the next The dk-constraints with d=2 and k=10 can always be satisfied at the transition of the codeword. This means that with each pass of the codeword, the codeword state S1 is established.

Figure 10 shows a modification of the encoding device shown in Figure 6, with which synchronization words can be inserted in the manner described above. In FIG. 10, the same components as those of FIG. 6 are denoted by the same reference characters. The modification involves the memory 103 having two memory cells for storing the two synchronization words 100 and 101 respectively. Memory 103 includes addressing circuitry for addressing either of the two memory locations based on a status word applied via bus 63 to the address input of memory 103 . The synchronization word in the addressed storage unit is sent to the parallel/serial converter 105 through the bus 104 , and the serial output of the converter 105 is sent to the first input terminal of the electronically controlled switching unit 106 . The signal line 67 is connected to a second input of the switching unit 106 . The encoding device is controlled by a control circuit 107 of usual type, which alternately brings the encoding device into the first or second state. In the first state a predetermined number of information words are converted into code words which are sent to the modulo-2 integrator 68 via the switching unit 106 in a serial fashion. When transitioning from the first to the second state, the conversion of the information word is interrupted, and the synchronization word determined by the state word is transferred by the memory 103, and is added to the modulo 2 integrator 68 through the parallel/serial converter 104 and the exchange unit superior. In addition, when transitioning from the second to the first state, under the control of the control circuit 107, the buffer memory is loaded with the state word corresponding to the encoding state S1, and then the conversion of the information word to the code word is restarted until the encoding device is restarted. Once brought into the second state by the control circuit 107 .

For inserting sync words, the encoding device shown in FIG. 8 can be adapted in a manner similar to the adaptation shown in FIG. 10 .

FIG. 11 shows an embodiment of a decoding device 150 according to the invention for reconverting a modulated signal obtained by one of the methods described above into a sequence of information words. The decoding circuit includes a modulo-2 differentiator 110 for converting the modulated signal into a string of bits, wherein a bit having a logic "1" value represents a transition from a bit element having a signal value L to a bit element having a signal value H or Conversely, and wherein each bit element having a logic "0" value represents two consecutive bit elements having the same signal value. The bit string thus obtained is sent to two serially connected shift registers, each having a length corresponding to the length of an n-bit codeword. The contents of shift registers 111 and 112 are provided to respective buses 113 and 114 via parallel outputs. The decoding device includes an (n+p) to m-bit converter 115 . All n bits present on shift register 112 are applied via bus 114 to the input of converter 115 . From the n bits present on the shift register 111, p bits are applied to the converter 115 which, together with the n bits on the shift register 114, uniquely define an information word. Converter 115 may include a memory with a look-up table containing an m-bit information word for each allowed bit combination consisting of n bits of an n-bit codeword and the bit string following the codeword The part is composed of predetermined P bits. However, converters can also be realized by gates.

The conversion performed by the converter 115 can be synchronized in the usual manner by means of the synchronization circuit 117, so that every time a complete code word is loaded in the shift register 112, an information word appears at the output of the converter, this information word corresponding to The bit combination applied to the converter 115 input.

Preferably, a sync word detector 116 connected to the buses 113 and 114 is used to detect a bit pattern corresponding to a sync word and is used for synchronization.

Figure 16 shows diagrammatically a signal obtainable according to the method of the invention described above. The signal comprises a sequence of q consecutive information signal portions 160, where q is an integer, representing q information words. Between the information signal portions are inserted synchronization signal portions, one of which is referenced 161 in FIG. 16 . A number of information signals are shown in detail. Each information signal portion 160 contains n bits, in this example 16, which have a first (low) signal value L or a second (high) signal value H. Since the bit string formed by the codeword and represented by the modulated signal satisfies the dk-constraint, the number of consecutive bits with the same signal value is at least equal to d+1 and at most equal to k+1. Due to the choice of codewords depending on the number and value, at any point in the signal, the running value of the difference between the number of bits with the first signal value and the number of bits with the second signal value, for the The signal part is basically constant. Each information signal portion corresponding to a codeword of the first type group uniquely establishes an information word. In FIG. 16, this is, for example, the information signal portion 160c corresponding to the code word "0100000001000010". This codeword uniquely establishes an information word with word value "121". Each information signal portion representing a code word of the second type group, together with adjacent signal portions, uniquely represents an information word.

The information signal portion 160a shown in FIG. 16 corresponds to the code word "00010000000100100". This code word can establish two information words with word value "24" and with word value "34". Which information is actually determined from this codeword then depends on the logic values at the first and thirteenth bit positions of the immediately following part of the bit string. If the logic values of these bits are all equal to 0, then the information word with word value "24" is asserted. If these bits are not equal to 0, an information word with word value "34" is asserted. Following the codeword established by the information signal portion 160a in FIG. 16, the bit values at the first and thirteenth bit positions are both equal to 0, so an information word having a word value "24" is established. The codeword established by information signal portion 160b is the same as the codeword established by information signal portion 160a. However, the code word represented by information signal portion 160b is immediately followed by a sync word whose first bit has a logic "1" value, so that an information word having a word value of "34" is now established.

Figure 12 shows by way of example a record carrier 120 according to the invention. The record carrier shown is of an optically detectable type. The record carrier may also be of another type, eg magnetically readable. The record carrier contains an information pattern arranged in tracks 121 . Shown in FIG. 13 is a high magnification of portion 122 of track 121 . The information pattern shown in the track portion 121 of Figure 13 comprises a first area 123, eg in the form of optically detectable marks, and a second area 124, eg an intermediate zone between two marks. The first areas and the second areas are arranged alternately along the recording track 125 direction. The first region 123 exhibits a first detectable characteristic and the second region 124 exhibits a second characteristic distinguishable from the first detectable characteristic. The first field 123 represents the bit cells 12 of the modulated binary signal 7 having a signal level, eg low signal level L. The second field 124 represents bit cells 11 with another signal level (eg high signal level H). The record carrier 12 may be obtained by first generating a modulated signal and then supplying the record carrier with an information pattern. If the record carrier is of the optically detectable type, the record carrier can be obtained from the modulated signal 7 using per se known mastering and replicating techniques.

FIG. 14 shows a recording device for recording information, in which an encoding device according to the invention is used, for example, the encoding device 140 shown in FIG. 6 . The signal lines for conveying the modulated signal in the recording device are connected to a control circuit 141 for a write head 142 along which a writable record carrier 143 is moved. The write head 142 is of a conventional type capable of introducing marks on the record carrier 143 with detectable changes. The control circuit 141 may also be of the usual type for generating control signals for the write head from the modulated signal applied to the control circuit 141 so that the write head introduces a mark pattern corresponding to the modulated signal.

Fig. 15 shows a reading device in which a decoding device according to the invention, for example, the decoding device 153 shown in Fig. 11, is used. The reading device comprises a reading head of the usual type for reading a record carrier according to the invention carrying an information pattern corresponding to the modulated signal. The read head 150 then generates a modulated analog read signal based on the information pattern read by the read head 150 . The detection circuit 152 converts the read signal to a binary signal and applies it to a decoding circuit 153 in the usual manner.

Claims (38)

1. change the method that the m-bit series of m-bit information words becomes modulated signals for one kind, here m is an integer, in the method, each information word that receives is transmitted the code word of a n-bit, here n is the integer that surpasses m, and the code word of transmitting is converted into modulated signals, and wherein series of m-bit information words is to convert codeword sequence to according to transformation rule simultaneously, makes corresponding modulated signals satisfy predetermined standard, it is characterized in that

Code word distributes on one group of the first kind and second type one group at least, simultaneously, the first kind encoding state that is determined by relevant group has been set up in the transmission that belongs to each code word of first kind group, the second class encoding state by the information word decision of the code word that is relevant to transmission has been set up in the transmission that belongs to each code word of second type group, and, when one of code word is assigned to the information word that receives, this code word is selected from a code word set, it depends on the encoding state of setting up when previous code word is transmitted, and the code word set that belongs to the second class encoding state does not comprise any common code word.

2. the method for claim 1, it is characterized in that, it is according to such transformation rule that series of m-bit information words is converted into codeword sequence, basically the frequency component that does not occur low frequency region in the frequency spectrum of the modulated signals that it is corresponding, and in modulated signals, each successive bits number with same signal value is at least d+1, be at most k+1, for each information word at least one determined number information word, it is right that code word set comprises a code word at least, when information word was converted, the low frequency component in the modulated signals was by selecting code word from this code word centering and being avoided.

3. the method for claim 2, it is characterized in that, the operation digital sum value is as measuring of current flip-flop is established, its value is to be determined in the first forward part scope of modulated signals, and the currency that its expression has the bit-cell number of first value and has difference between the bit-cell number of second value for this part, and the code word that comprises two code words is right, for digital sum value opposite effect is arranged, and code word is selecteed from code word centering according to certain digital sum value, so that digital sum value continues to be restricted.

4. claim 2 or 3 method, it is characterized in that, information word is converted into codeword sequence, this codeword sequence is set up bit with first logical value and the Bit String with bit of second logical value, the number of successive bits that has first logical value and be in the middle of the bit with second logical value is at least d, be at most k, and this Bit String is converted into modulated signals, otherwise wherein the transformation from bit-cell to bit-cell with secondary signal value with first signal value or, be corresponding to the bit that has second logical value in the Bit String.

5. aforesaid right one of requires the method that requires, it is characterized in that, the code word set that belongs to the second class encoding state can be distinguished mutually according to the logical value of the bit of the bit locations of being scheduled in the code word, and P is the integer less than n here.

6. the method for claim 5, it is characterized in that, synchronization character (sync) is inserted in the codeword sequence, this synchronization character manifests the bit pattern in the Bit String that can not appear at code word formation, and used synchronization character with different bit patterns, employed synchronization character depends on encoding state, after a synchronization character has been inserted into, for changing next information word, one predetermined encoding state is established, simultaneously, the mode of distinguishing with a kind of code word set phase mutual energy that belongs to the second class encoding state, logical value according to the bit of predetermined bit position can be distinguished these synchronization characters mutually.

7. aforesaid right one of requires the method that requires, it is characterized in that d equals 2, and k equals 10, and n is 2: 1 to the ratio of m.

8. the method for claim 7 is characterized in that, m equals 8 and n equals 16.

9. the method for one of aforesaid right requirement 4,5,6,7 or 8 requirement is characterized in that P equals 2.

10. in claim 6,7, the method that requires in 8 or 9, it is characterized in that, the code word that second type is first group is made of the code word of a with first logical value bit ending, wherein a equals 0 or 1, and the code word of second group of second type is made of the code word of the b with first logical value successive bits ending, wherein b be greater than, equal 6 and less than, equal 9 integer, the group of second type is made of the code word of the c with first logical value bit ending, wherein c be greater than, equal 2 and smaller or equal to 5 integer, and from the code word set relevant, select the code word that is assigned to information word with encoding state, this code word set is made of the code word that begins with a plurality of bits with first logical value, number of bits depends on the relevant encoding state of this collection, thereby in this Bit String that is made of two continuous code words, the number with successive bits of first logical value equals d at least, and equals k at the most.

11. a method of making record carrier, wherein modulated signals is produced by the method for one of aforesaid right requirement, and will represent the information pattern of this signal to offer this record carrier.

12. encoding device that is used to realize desired method, this equipment comprises that the m bit is to the n bit converter, be used for the m-bit information words is converted to the code word of n-bit, and comprise the device that is used for the n-bit codewords is converted to modulated signals, it is characterized in that, this equipment comprises the state apparatus for establishing that is used for setting up encoding state when converter transmits code word, this state apparatus for establishing is arranged to and is used to the code word of being transmitted of each group that belongs to the first kind to set up first kind encoding state, the state of the group of this first kind is determined by relevant group, and be used to the code word of being transmitted of each group that belongs to second type to set up the second class encoding state, the state of this second type group is determined by the information word relevant with the code word of being transmitted, comprise that also the m bit is to the n-bit converter, it comprises the device of selecting code word, be used for selecting code word, belong in the code word set of the second class encoding state and do not contain any common code word corresponding to information word from the code word selected works that depend on encoding state.

13. the equipment that transitional information word sequence becomes modulated signals that is used for as claim 12, this modulated signals presents the frequency component that does not have low frequency region in frequency spectrum basically, and wherein each minimum number with successive bits unit of same signal value is d+1, and its each maximum number is k+1, converter comprises that the information word that is used for each at least one determined number produces the device that code word is right, and this equipment comprises selecting arrangement, is used to the code word transmission and chooses any one code word according to the predetermined criteria of the low-frequency component that relates to modulated signals from code word centering.

14. the equipment that claim 13 requires, it is characterized in that, equipment comprises the device of determining the operation digital sum value, this value representation has the bit-cell number of first value and the runtime value of the difference of the bit-cell number with second value for the previous section of modulated signals, every pair that code word is right comprises at least two code words that digital sum value had adverse effect, and this selecting arrangement includes a kind of like this device, this device is used for according to the criterion that depends on digital sum value, concentrate those code words of selection from this, make for the digital sum value of these code words and continue to be limited according to this criterion.

15. the equipment of claim 13 or 14, it is characterized in that, this equipment is arranged for information word is converted to codeword sequence, it sets up the Bit String that has the first logical value bit and have the second logical value bit, the minimum number that has first logical value and be in the successive bits between the bit with second logical value is d, and maximum number is k, and equipment also comprises mould 2 multiplicators, is used for Bit String is converted into modulated signals.

16. the equipment that one of claim 12,14 or 15 requires is characterized in that, the code word set that belongs to the second class encoding state can be distinguished mutually according to the logical value at the bit of P predetermined bit position in the code word, here P be less than, equal the integer of n.

17. claim 15 or 16 equipment that require, it is characterized in that, this equipment comprises and is used to insert the device of synchronization character to Bit String, synchronization character manifests the bit pattern in the Bit String that can not appear at the code word formation, this equipment comprises the device that is used to select the synchronization character that will be inserted into, synchronization character has the different bit patterns that depend on definite encoding state, with corresponding to so a kind of mode, promptly belong to mode that the code word energy collecting of the second class encoding state distinguished mutually, according to the logical value of the bit of predetermined bit position synchronization character is distinguished mutually.

18. the equipment of claim 17 is characterized in that, in case this equipment comprises that being used for synchronization character is inserted into the device of promptly realizing predetermined encoding state.

19. the equipment that one of claim 12 to 18 requires is characterized in that d equals 2, k equals 10, and n is 2: 1 to the ratio of m.

20. the equipment of claim 19 is characterized in that, m equals 8 and n equals 16.

21. the equipment that one of claim 16 to 20 requires is characterized in that P equals 2.

22. in claim 19, desired equipment one of in 20 or 21, it is characterized in that, the code word that second type is first group, code word by a with first logical value bit ending constitutes, wherein a equals 0 or 1, and the code word of second group of second type, code word by the b with first logical value successive bits ending constitutes, wherein b be greater than, equal 6 and less than, equal 9 integer, the group of second type is made of the code word of the c with first logical value bit ending, wherein c be greater than, equal 2 and less than, equal 5 integer, and from the code word set relevant, select the code word that is assigned to information word with encoding state, this code word set is formed by the code word that begins with a plurality of bits that have first logical value, and the number of bit depends on the relevant encoding state of this collection, so that in this Bit String that is formed by two continuation code words, number with successive bits of first logical value equals d at least, and equals k at the most.

23. equipment that is used for recorded information, this equipment comprises as the desired encoding device of one of claim 10 to 12, series of m-bit information words in order to conversion expression information becomes modulated signals, also comprises the device that is used for the information pattern that record is corresponding with signal on record carrier.

24. signal that comprises the sequence of q continuous information signal section, it has represented q information word, here q is an integer, in this signal, each information signal part comprises the n bit cell with first or second logical value, predetermined group each message part that belongs to message part has been established an information word uniquely, it is characterized in that, each information signal part that belongs to second group of information signal part combines with the neighbor information signal section to establish a unique information word.

25. the signal of claim 24, it is characterized in that, each successive bits unit number minimum with same signal value is d+1, maximum is k+1, and in the arbitrfary point of signal, it is confined having the bit-cell of first logical value and the runtime value of the difference of the bit-cell number with second logical value in the signal section before this point.

26. the signal of claim 25 is characterized in that n equals 16, d equal 2 and k equal 10.

27. claim 24,25 or 26 signal, it is characterized in that, this signal comprises the synchronizing signal part, it has the bit-cell pattern in the sequence that can not appear at continuous information signal part, simultaneously, the unique information word is established by the combination of each second group of information signal part and one of adjacent synchronization character or neighbor information signal.

28. claim 24,25,26 or 27 signal, it is characterized in that, each adjacent signal section, the continuous bit-cell of predetermined bit-cell transformation place of p between the appearance that changes of logical value or do not occur, combine with the related information section of second group of information signal part, established the relevant information word, P is the integer less than n here.

29. the signal of claim 28 is characterized in that P equals 2.

30. the signal that one of claim 24 to 29 requires, it is characterized in that, s the bit-cell ending of information signal part to have identical logical values, and t the bit-cell ending of second group information signal part to have identical logical values, wherein, s can be assumed to a plurality of different values and wherein t can be assumed to a plurality of different values, and wherein s is different with t.

31. the signal of claim 30 is characterized in that, s greater than, equal 2 and less than, equal 5.

32. record carrier, be recorded on the road above it as the desired signal of one of claim 24 to 31, information pattern on the road has been represented signal section, its information pattern comprises first and second parts that replace along the road direction, first presents detectable character, and second portion presents second kind of character can distinguishing with first kind of character, and, part representative with first kind of character has the bit-cell of first logical value, and the part representative with second kind of character has the bit-cell of second logical value.

33. one kind is used to change the decoding equipment that becomes the m-bit series of m-bit information words as the desired signal of one of claim 24 to 31, this equipment comprises and is used to change the device that this signal becomes the Bit String of the bit with first or second logical value, this Bit String comprises the n-bit code word corresponding to information signal part, and this equipment comprises conversion equipment, be used to change codeword sequence to series of m-bit information words, information word is assigned to each code word that will be converted and depends on these code words, it is characterized in that conversion equipment is arranged to also according to being positioned in the Bit String with respect to the logical value of the bit in P precalculated position of code word and the transitional information word.

34. the decoding equipment of claim 33 is characterized in that n equals 16, m equals 8, and wherein P equals 2.

35. the decoding equipment of claim 34 is characterized in that, P predetermined bit position is the first and the 13 bit position of crossing ending place of relevant code word.

36. the decoding equipment of one of claim 33 to 35, it is characterized in that equipment comprises pick-up unit, be used to detect synchronization character with bit pattern, this bit pattern can not be made of code word continuous in the sequence, and perhaps can not be combined with an adjacent code word by a part of synchronization character constitutes.

37. the decoding equipment of claim 36, it is characterized in that, pick-up unit is arranged to detect the 26-bit sync word corresponding to bit pattern " 10010000000000100000000001 " or bit pattern " 00010000000000100000000001 ", wherein " 0 " expression first logical value reaches wherein " 1 " expression second logical value.

38. readout equipment, be used for the read record carrier, information is recorded with the information pattern form on record carrier, this equipment comprises and is used for the conversion equipment that the transitional information pattern is corresponding scale-of-two read output signal, readout equipment comprise as one of claim 34 to 39 decoding equipment that require, that be used for the scale-of-two read output signal is converted to the series of m-bit information words of m-bit.

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