Title of Invention

"AN APPARATUS FOR ALLOCATING CODE WORDS"

Abstract

A method for generating and allocating codewords is provided. The method if dudes allocating one of two selectable codewords b1 and b2 as codeword b w ion a preceding codeword a and a following codeword b form a code stream , in which codewords b1 and b2 have opposite INVs which are Parameters irw icating whether the number of '1 s' contained in a codeword is an odd number o an even number and when the code stream of a and b1 is X1, and the code i tream of a and b2 is X2, allocating codewords such that the iNVs of X1 and X2 are maintained to be opposite when a or b1(b2) should be replaced by ai other codewords in compliance with a predetermined boundary condition giver between codewords. According to the method, by using a short codeword hav ig less bits as a main conversion codeword, high efficiency is achieved in re< ording density. Also, when codewords which do not satisfy the run length co ditions are replaced by other codewords, the codewords are allocated so tl at the DC suppression capability of the code stream can be maintained, an i therefore higher DC capability of the code stream is provided.

Full Text

BACKGROUND OF THE INVENTION Field of the Invention The Present invention relates to an apparatus for allocating codewords. The present invention relates to generation and allocation of modulation codes of source codes to be recorded on a recording medium, and more particularly, to a method for generating and allocating codewords in which codewords having a restricted run length are generated and the generated codewords are allocated so that the DC control characteristic of a code stream is maintained. In a Run Length Limited (RLL) code represented by (d, k, m, n), the performance of a code is evaluated mainly based on the recording density and the capability to suppress the DC component of the code. Here, m denotes the number of data bits (the number of so-called source data bits, which is also referred to as the number of information word bits), n denotes the number of codeword bits after modulation (the number of so-called channel bits), d denotes the minimum number of a series of 'Os' that can exist between T and T in a codeword, and k denotes the maximum number of a series of 'Os' that can exist between T and T in a codeword. The interval between bits in a codeword is represented by T. In a modulation method, to improve recording density it is used to reduce the number of codeword bits n while regarding d and m as given conditions. In the RLL code, however, d which is the minimum number of a series of 'Os' that can exist between T and T in a codeword, and k which is the maximum number of a series of'Os' that can exist between T and T in a codeword, should be satisfied. If, with this (d, k) condition satisfied, the number of data bits is m, the number of codewords satisfying RLL(d, k) should be equal to or greater than 2. Moreover, in order to actually use this code, run length constraints, that is, RLL(d, k) conditions, should be satisfied in a part where a codeword is linked to another codeword. In addition, when the DC component of a code affects the system performance, it is desirable to use a code which has a DC suppression capability. The ffijwatit,n mason for suppressing the DC component in the RLL modulated eo* e stream is to minimize a reproducing signal's affect on a servo band. Herein, ifter, methods for suppressing the DC component will be referred to as Digital $ mi Vatue (DSV) control methods. DSV i^ol metres can Deoroadlyc^ssified into two types. One is a method having a OSV control code itself, where the DSV control code is capable of corjtrotiing a OSV. The other is a method of inserting a merge bit at each OSV control time. An Eight to Fourteen Modulation plus (EFM+) code performs DSV control using a separate code table, while An EFM code or a (1, 7) code per The OSV control and satisfying] each of a ph DSV control by inserting a merge bit ?, the shape of the prior art modulation code group having the itself capable of controlling suppression tftrw DC conditions described above is as shown in FIG. 1, in which (mined number of main conversion code groups has a corresponding, code group for controlling suppression of the DC component Each main cor version code group and its corresponding code group form a pair so that the D there are som* characteristics that distinguish codewords of the predetermined main conversion code groups. That is, there are no identical codewords between the n ain conversion code groups A and B. If duplicated codes are used, there mtiht be the conversion code groups C and D for demodulating the duplicated codes, where there are no identical codewords between the conversion code groups C and D, but codewords in the code group A or B may C or D for demodulating duplicated codes. The number of main conversion code groups A and B and the conversion be in the code codewords in1 code groups 0 bits in the toun If code and D for demodulating duplicated codes is 2m if the number of » word before conversion is m. groups E through H are OC suppression control code groups used for suppr issing DC components together with code groups A through D, respectively, tf 9 characteristics of codewords in each of the code groups E through H are'the same as the characteristics of codewords in the main code orouos A throuloh D respectively. That is. the same conditions for aeneratina duplicated codewords or the same conditions for determining the number of lead zeros in ja codeword are applied to each of the DC suppression control code groups E through H for controlling suppression of DC components and the conversion CCH current Oigitaj le groups A through D. For a) ample, the characteristics of the EFM+ code, which is used in Versatile Discs (DVD), has a run tength condition of RLL(2, 10) and a codewtrd length (n) of 16 bits, is as shown in FIG. 2. The main conversion code groups are MCG1 ("A* in FIG. 1) and MCG2 ("B" in FIG. 1) and the conversion code groups for demodulating duplicated codes are DCG1 ("C" in FIG. 1) andt>CG2 ("D* in FIG. 2). There are four DSV code groups FIG. 1) which make pairs with respective conversion code groups to control suppression of group, MCG2 Thati? from the duplicated manner. In suppression together with sequence of DC components. There are no identical codewords between the four conversis 'i code groups and the four DSV code groups which are code groups for con rolling DC components. Atso, code groups s, -e the same, and the characteristics of codewords in each code group pair thi t can control DC components (MCG1 and the first DSV code and the second DSV code group, DCG1 and the third DSV code group, or DCQ 2 and the fourth DSV code group) are the same. a codeword having a continuous sequence of from 2 to 5 zeros Significant Bit (LSB) of the codeword is generated using •ds. This rule is applied to each code group in the same of the codewords of the first DSV code group for controlling DC components, which controls suppression of DC components main conversion code group MCG1, there is a continuous 2 and 9 'Os' from the Most Significant Bit (MSB). In each of the codewq ds of the second DSV code group for controlling suppression of DC componen s, which controls suppression of DC components together with the main cony rsion code group MCG2, there is either 0 or 1 '0' continuing from the MSB. Son te bits (here, b15(MSB) or b3) in the codewords of the third DSV code group ft r controlling suppression of DC components, which controls suppression on DC components together with the conversion code group DCG1 Of DwC icAo/mii ponents for demodulating duplicate eodss are 'Ob', *tiiie scras bits (hers, &15(MSS) or b3) in the codewords of the fourth DSV code group for controlling supprsesten. i, wfitefi corrirois suppression of DC components together with code group OCG2 for demodulating dupitcaiea codes, some bits b15(M$B) and b3) are 'ib", in developing 8 to 15 nxsduSatior, code advantage in the recording density aspect compared to the prior which us«» the modulation code group shown in the original characteristics of a cods sirssra change when a change codeword because of a boundary rule applied to the locations iich connects a codeword to another codeword. an' the (here, which art modulaticr1 method FIG. 1or2: occurs in a iO ."* SUMMARY OF THE INVENTION To soi^e the above problems, it is an objective of the present invention nsthod for generating and allocating codewords in which a codeword havi TO a njn length restriction is generated sntt tnd codeword is allocated so th£t the originaf charactehstics of a code stream are maintained even when a codeword is replaced according to the boundary nils when a coite stream is aHssated. To aca mplish the objective of the pra««nt inytntign, there is provided a method for ger eraitng and allocating codewords of source words which are to be rdccrdsd »n a recording meciium, ihd ffminod inauaing generating codewords »«i«fying nmdetermined njn tength condit'ons and grouping codewords acwding to each run length condition; and allocating the codewords su$ i thai a c6de\word) for the source word is capable of controlling suppression of 3G oomponents. It is pn iferable that when a predetermined boundary condition is not satisfied in the [code stream, aiiocating codewords such that codewords which sa»Jsfy the bourtter/ eondflon and maintain the DC contra! characteristics which are considered when the initial codeword* are allocated replace the init-a! codewords. ; !t is ppfarsbie that the step far ganeratiny couewurus inciudes generating codewords satisfying !h* length of a predetermined first codeword, and predetermined run length conditions, grouping the codewords according to each predetermined run length condition to generate a main conversion codeword tat te; generating DC control codewords satisfying the length of a predetermine: I second codeword, and predetermined run length conditions in order to cent ol DC components in the codeword) stream, grouping the DC control coda* ords, and to generate a code conversion table for cor4rc4ling DC components; codewords wt iich satisfy the predetermined run length conditions and are not needed in the control codew Also, provided ano and generating additional DC control codewords by taking main conversion codeword table, and grouping the additional DC rds. accomplish tite objective of the present invention, there is her method an allocation method for allocating codewords generated for fcource words to be recording on a recording medium, the method including wrwm a preceding codeword a and a following codeword b form a code stream k allocating one of two selectable codewords b1 and b2 as codeword b, In which codewords b1 and b2 have opposite INVs which are parameters indicating whether the number of 'Is' contained in a codeword is an odd number oa an even number and when the code stream of a and bl is X1, and the code stream of a and b2 is X2, allocating codewords such that the INVs of X1 and X3 are maintained to be opposite when a or b1(b2) should be replaced by another codewords in compliance with a predetermined boundary condition given between codewords. It Is preferable that when the predetermined boundary condition is that i ] the number of (continuous 'Os' between codewords should be at least 2, and of continuous 'Os1 from the Least Significant Bit (LSB) of the Most Significant Bit (MSB) direction is 0, and the number of the MSB of the codewords b1 or b2 in the LSB direction is of either the codeword a or b1(b2) occur to satisfy the on. when the codeword a in continuous "Os* 1, code boundary It is preferable that when the number of continuous 'Os' between the codewords a and b is 1 or 0, the codeword a or b is changed such that the number of Os forming the boundary is greater than 2 and less than 10. It is preferable that the codeword "a" of the code stream XI and the codeword "a" of the code stream X2 are changed to other codewords such that the resulting codewords "a" of code streams XI and X2 have the same INV value, and as a result, by the INVs of codewords bl and b2 following the codewords "a" respectively, the INVs of the XI and X2 become different. Also, to accomplish the objective of the present invention, there is provided an allocation method of allocating codewords of source words to be recorded on a recording medium, the method including when a preceding codeword "b" and a following codeword "c" from a code stream Y, allocating one of two selectable codewords bl and b2 as the codeword "b", wherein codewords bl and b2 have opposite INVs which are parameters indicating whether the number of 'Is' contained in a codeword is an odd number or an even number and when the code stream of bl and "c" is Yl, and the code stream of b2 and "c" is Y2, allocating codewords such that INVs of Yl and Y2 are maintained to be opposite when the codeword bl, b2, or "c" should be replaced by another codeword in compliance with a predetermined boundary condition between codewords. It is preferable that when the predetermined boundary condition is that the number of continuous 'Os' between codewords should be at least 2, and when the number of continuous 'Os' from the Least Significant Bit (LSB) of the codeword "c" towards the Most Significant Bit (MSB) is 1, codeword "b" which does not satisfy the boundary condition and is xxxxxxxxxxx 1001 or xxxxxxxxxx 10001 appears in both bl and b2. According to an embodiment of the present invention, an apparatus for allocating codewords generated for source data to be recorded on a recording medium, characterized in that, the said apparatus comprising: a memory device containing one or more code tables arranged to include codewords corresponding to source data; a first checking means for determining whether a preceeding code word "a" and following code word "b" are connected to form a code stream "X"; a first allocator being in operational communication with the first checking means and being arranged to allocate one of two selectable codewords "bl" and "b2" as codeword "b", wherein codewords "bl" and "b2" have opposite INV values which indicate whether the number of "Is" contained in a codeword is an odd number or an even number; a second checking means for determining whether the code stream of "a" and "bl" is "XI", and the code stream of "a" and "b2" is "X2"; and a second allocator in operational communication with second checking means and being arranged to allocate code words such that the INV values of "XI" and "X2" are maintained to be opposite when "a" or "bl(b2)" should be replaced by another codewords in compliance with a predetermined boundary condition given between codewords. In yet another embodiment of the present invention, wherein when the predetermined boundary condition is that the number of continuous "Os" between codewords should be at least 2, and when the number of continuous "Os" from the Least Significant Bit (LSB) of the codeword "a" in the Most Significant Bit (MSB) direction is 0, and the number of continuous "Os" from the MSB of the codewords "bl" or "b2" in the LSB direction is 1, code changes of either the codeword "a" or "bl(b2)" occur to satisfy the boundary condition. In another embodiment of the present invention, wherein when the number of continuous "Os" between the codewords "a" and "b" is smaller than a predetermined number, the number of continuous "Os" between the codewords "a" and "b" becomes greater than or equal to the predetermined number. In further embodiment of the present invention, wherein the codeword "a" of the code stream "XI" and the codeword "a" of the code stream "X2" are changed to other codewords such that the resulting codewords "a" of code streams "XI" and "X2" have the same INV value, and as a result, by the INV values of codewords "bl" and "b2" following the codeword "a", respectively, the INV values of the code stream "XI" and "X2" become different. In another embodiment of the present invention, wherein the predetermined number is "1". In yet another embodiment of the present invention, wherein the first and second checking means comprise a comparator. In another embodiment of the present invention, wherein the first and second allocator is a processor. BRIEF DESCRIPTION OF THE DRAWINGS The above objects and advantageous of the present invention will become more apparent and by describing in detail preferred embodiments thereof with reference to the attached drawings in which: FIG. 1 is a diagram of an example of the shape of a prior art modulation code group; FIG. 2 is a table showing prior art code group and characteristics of codewords included in the code group; FIG.' 3 is a flowchart showing a method for generating and allocating codes accor (ing to the present invention. According to the method for generating a id allocating codewords of source words to be recorded on a recording m$ jium, codewords satisfying predetermined run length conditions are generate? and the generated codewords are grouped according to each run length condH on in step 300. The codewords are allocated so that the codeword) s| earns for source words are capable of controlling DC components in step 310. j are satisfied H the codeword while me DC codewords an Code control characteristics which are considered when the original allocated can be kept. abies of the codewords for source code conversion are roughly divided into tt ree types: 1) main conversion tables, 2} conversion tables for controlling DC components, and 3} auxiliary conversion tables for controlling DC components. FIG. End Zero (EZ LSB of acod codeword in codewords the s determined whether or not predetermined boundary conditions the code stream in step 320. If the conditions are not satisfied, are replaced by codewords satisfying the boundary conditions is a table showing a variety of codeword groups of main conversion tal; es and the characteristics of codewords in each code group. It is assumed tf at d denotes the minimum run length limit of a codeword, k denotes the ro, ixtmum run length limit of a codeword, m denotes the number of bits of source data, n denotes the number of bite of a codeword after modulation, denotes the number of 'Os' in a continuous sequence from the word in a direction toward the MSB of the codeword, and LZ denotes the number of 'Os' in a continuous sequence from the MSB of a direction toward the USB of the codeword. For example, satisfy d=0, k*10, m=8, n-15, OS EZ* 8 are divided according to die following tZ conditions: 1) nurrj m of codewords satisfying 2$ US 10:177 2) num «r of codewords satisfying 1£ LZS 9. 257 3) numl >er of codewords satisfying 05 LZS 6: 360 4} numl ler of codewords satisfying OS LZS 2: 262 If the codewords for number of codewords in condttton from to group 1), 4) are 260, 25 number of of FIG. 4, codewords codewords codewords lumber of bits of source data satisfies m=8, the number of jorwersion shoutd be 256 or more. However, in condition 1), the codewords the codewords Tiien, salsfytng satisfying codewords sat] rfytng In aacn of the can be used FIG. 5 table for OC group. For conversion cod 4 groups (con; respective! 1) numl Each group have at teast therefore shout Since the numbjw is less than 51 does not amount to 256. Therefore, the number of (jondition 1) can amount to 256 by taking some codewords from a surplus number of codewords, in this case, 83 codewords satisfying group 3)'s LZ condition may be taken and added i, the numbers of codewords included in conditions 1} through 277(~360-83), and 262, respectively, and satisfy the minimum modplation codewords, that is, 256 for B-btt source data. In the table Mai* Code Group 1 (MCG1) is the name of a code group containing satjsfying condition 1) and some (63) codewords are taken from condition 3). MCG2 and MCG4 are the names of condition 2), and 4), respectively. MCG3 is the name of condition 3), excluding the 63 codewords taken by MCG1. Train code groups MCG1 through MCG4, only 256 codewords asjconvarsion codes for source codes. a table showing a variety of codeword groups of a conversion control and the characteristics of codewords in each codeword , assuming that d=2, k=10, m=8, n=17, and tables for controlling OC components may indude the following wponding to DCG1, DCG2, DCG3, and DCG4 of FIG. 5, ity) a« wording to the LZ conditions: example, of codewords satisfying 2£ LZS 10: 375 2} number of codewords satisfying 1£ IZS 9 546 1} number of codewords satisfying 0£ LZ£ 6: 763 er of codewords satisfying Q£ LZ£ 2: 556 fonjning a conversion table for controlling DC components should 2 codewords that seiecfively correspond to one source data, and have at least 512 (= 28 +28) codewords for 8-oU source data, of codewords in the code group satisfying the LZ condition 1) , code group 1) can take surplus codewords from other code groups satisfy ng other 12 conditions to amount to the number of 512. For example, in ft e above embodiment, code group 1) may take 177 codewords from th« coctelgroup satisfying the condition 3} so as to have 552 (=375 +177} codewords. FIG. of is a table showing a variety of codeword groups of an auxiliary conversion tel code group. n=15, codewo te for DC control ami the characteristics of codewords in each :or example, among codewords satisfying d=2, JtstQ, m=»S, and tls satisfying 9£ EZS 10, the remaining codewords of the main code conversion groups (MCGs), and codewords satisfying LZ=7, 8 or LZ=4, 5 are used as codewords of ouxiHary code groups (ACGs) for controlling suppression of DC components. The conditions for generating these codewords wiff now be explained in detail. The following conditions correspond to ACG1 th ugh ACG4, respectively, which are names of the auxiliary conversion tab as for controlling suppression of DC components: 1) 5 e KJewords (satisfying 9S iZ£ 10 and LZ* 0) + the remaining 4 codewords (in [he MCG1) = 9 codewords, codewords (in 2} 5 he MCG1} » 6 codewords, 15 3) 5 cbdawords (satisfying & EZ* 10 and LZ* 1) codewords (satisfying 75 J2£ BandOi E2S 8 )=41 codewords, the remaining • codewords in the MCG1 = 9 codewords, 4) 7 ct dewords (satisfying 9£ E2^ 10 + the remaining 6 codewords in the MCG4) 4 85 codewords (satisfying 3^LZ^5andO^EZ^8) = 98 codewords. When xxJeword a and codeword b are connected, the junction where the two codewords are connected should satisfy a run length (d, k) condition. FIG. 7 is a diagram snowing what should be considered for the run length conditions whan codewords a and b are connected. Satisfying the run length condition mear s that in FIG. 7 a value obtained by adding the end zero (EZ_a) of codeword q and the toad zero (IZjb) of codeword b is equat to or greater than the minin urn run length d and equal to or less than the maximum run length k. FIG. meaning will conversion wfjen the Codeword b codeword, not have other code the EZ of referred to is a table showing an example of changes in INV (whose be described below) before code conversion and after code run length conditions described in FIG. 7 are not satisfied, determined in a group indicated by the EZ of the preceding a. When a or b is included tn a code group which does codewords to meet the condition and takes codewords from groups, the (d, k) condition may not be satisfied. In this example, ca eword a changes to satisfy the run length condition, which is as) the codeword number of'1s' change from according to paid to allocator) FIG. to selective the code conversion have to the bounded two code problem, be maintained considering th First, ii the codeword selected as which are separating different INVs, then codeword boundary rule. Variable INV which indicates whether the in a codeword stream is an even number or an odd number may previous 1NV while the codeword a didn't change (unclear), boundary rule Due to this characteristic, attention should be of a codeword between code conversion tables capable of controlling suppression of DC components. a diagram showing an example of code stream branching due codewords b1 and b2 for OC control. One of the major features of conversion of the present invention is that the codewords of two code that can be selected for DC control are allocated so that they opposttejlNV characteristics. When the previous INV changes according conversion ^\At-J * vjtntKwise rule as described above, if the INVs of both codewords in the tables that can be selected change, then there will be no , characteristics of codewords having opposite INV cannot For this reason, a code conversion table is designed A of FIG. 9, that is, at the junction where the codeword a and |b are connected to each other, if b1 and b2, which can be codeword b, are codewords in DCG11 and DCG12, respectively, regnbuped in the code conversion table DCG1 shown in FIG. 5 after codewords which correspond to the same source code but have )f if t>1 and b2 are codewords of MCG1 and MCG2, respectively, in which LZ_b1 (the number of 12s of codeword b1) and LZJ>2 (the number ofLZs of codeword b2) is 1 are allocated on the location. By doing so, when the EZ of the codeword a is '0', according to the boundary rule, the JMV of codeword a changes in both the code stream containing the codeword bl and the code stream containing the codeword b2, or the INV of codeword a does not chan je in either the code steam containing the codeword b1 or the code stream c intaintng the codeword b2, such that the 4NVs of the two code streams are m, rintained to be opposite. An example is as follows: code code 000001000001 1NV1 code source data 250 streaml (before 00000100000' 001(MCG1) 010010010000000(MCG1) 224 27 ccfwersion)000001 streaml (after 000 010010010000000 conversion)000001000010001 00000100000' 001(MCB1) code 00000100000' INV2 ; Next, codeword c respectively ir an MCG2 and (xx) the boundary i j codewords b1 source data maintained to source data 1 strsam2(before 1 0 corwereion)()000()tO()OX)10001(MGG3} stream2(after conversion)00000t000010001 000 010010000000000 1 1 8 of FIG. 9, that is, at the Junction where codeword b and connected to each other, if codewords b1 and b2 are in code conversion tables DCG11 and DCG12, OCG21 5G31 and DCG32, OCG41 and OCG42, MCG1 and ACG1, MCG3 and ACG3, or MCG4 and ACG4, and due to the IZ of the following codeword a Therefore, these b2 are allocated to the location for corresponding same each table such that the INVs of the two code streams are i opposite. An example is as follows: 250 152 210 code streamj (before conversion) 000001000010001 (MCG3) Of000000010G01001(DCG11) 000000100000001(MCG1) code streaml (fcfter conversion) 000001000010000 01000000010001001 000000100000001 INV1 I 0 0 0 code stream! codes trearf INV2 [(before conversion) 010010000100 3100t((DCG12}010000001001001^MCG1> 000001000010001 (MCG3) 2(after conversion) 0000010000100000 010000001001001 1 for thej junctions A and B of FIG. 9, the codewords are first allocated to the location corresponding same source data in each code conversion table (DCG11 and Oi JG12 or MCG1 and ACG1) considering above, deferring to the following exam lie, in point B, according to the boundary rule, the INVs of code streaml and c streams and code stream* are maintained to be opposite. Also, at point B, according to the boundary rule, the INVs of code streaml and code streams are maintained to be opposite and the INVs of code stream2 and code streanvt are maintained to bp opposite. source data code streaml 0100000001 eodestream1( 01000001001 250 152 7 before conversion) 000001000010001 (MCG3) 100l(DCGtt> D1O100010010001{MCG1> conversion) 000001000010000 OIOXWOOOOIOOOTOOO code 010000000H code 0100000001C INV2 code 010010000K code stream 010000010011 INV3 code 01001OOOOK code strear 01001 OOOOK INV4 0 1 1 conversion) 000001000010001 (MCG3) ^OOt(OCG11) Q1QQ1001QQ1Q001{ACG1) {after conversion) 0000010000100000 MOOO 010010010010001 0 1 0 [before conversion) 000001000010001(MCG3) tOOl(DCGl2)010000010010001(MCGl) tor conversion) 000001000010000 01001000010001000 J1 0 0 0 {before conversion) 000001000010001 (MCG3) |1001(DCG12) 010010010010001 (ACG1) (after conversion) 0000010000100000 MOOO 010010010010001 0 0 1 As desc ribed above, considering changes in the INV of a codeword due conversion components, than the prior rule in a codeword stream, codewords are allocated so that the a codeword pair after modulation is always be maintained to be 10 is a graph showing the relationship of (NV values of this code codewords are allocated such that the INV values of a code always opposite, a codeword can be selected so that a code DC components between the code stream pair is formed to the rule that INV values are maintained to be opposite at 9 may occur when source data is from 251 to 255 in the code . In such exceptional cases, the codewords are made to be opposite so that the difference values in the code stream pair is made. 11 a through 11e are main conversion code tables in which described above. 2a through 12j are code conversion tables for DC control in are generated and allocated considering conditions described to the bounds INV polarities opposite. FKJ stream pair, stream pair a stream which Exceptions point A of FIC conversion tat to for controlling DC components. CSV signs between DSV FIGS, codewords arej generated and allocated considering conditions FIGS. which codewords above. FIGS. in which described abo FIG. 1 spectrum according to trj the frequency The graph modulated as the frequen the present components a 3a and 13b are auxiliary code conversion tables for DC control are generated and allocated considering cod words conditions wta i sho vs ooc i I is a graph showing the difference between the frequency codewords of the code conversion table for DC control present invention are used in 25% of all of the codewords, and pectrum when prior art EFM+ modulation codewords are used, that in a low frequency band, the frequency spectrum of the stream according to the present invention is almost the same y spectrum of the EFM+, which indicates that the code stream of inrention has almost the same capability of suppressing DC that of the EFM+ method. Accord! igly, since the present invention uses 15-bit codes as the main code and selectively uses 17-bit DC control codes for controlling DC i present invention has better efficiency in recording density t EFM+ code and has the same DC suppression capability as the EFM+ code. Accoraing to the present invention, by using a short codeword having less bits as'e main conversion codeword, high efficiency is achieved in recording density. Also, When codewords which do not satisfy the run length conditions are replaced by other codewords, the codewords are allocated so that the DC suppression capability of the code stream can be maintained, and therefore higher DC suppression capability of the code stream is provided, We Claim; 1. An apparatus for allocating codewords generated for source data to be recorded on a recording medium, characterized in that, the said apparatus comprising: a memory device containing one or more code tables arranged to include codewords corresponding to source data; a first checking means for determining whether a proceeding code word "a" and following code word "b" are connected to form a code stream "X"; a first allocator being in operational communication with the first checking means and being arranged to allocate one of two selectable codewords "bl" and "b2" as codeword "b", wherein codewords "bl" and "b2" have opposite INV values which indicate whether the number of "Is" contained in a codeword is an odd number or an even number; a second checking means for determining whether the code stream of "a" and "bl" is "XI", and the code stream of "a" and "b2" is "X2"; and a second allocator in operational communication with second checking means and being arranged to allocate code words such that the INV values of "XI" and "X2" are maintained to be opposite when "a" or "bl(b2)" should be replaced by another codewords in compliance with a predetermined boundary condition given between codewords. 2. The apparatus as claimed in claim 1, wherein, when the predetermined boundary condition is that the number of continuous "Os" between codewords should be at least 2, and when the number of continuous "Os" from the Least Significant Bit (LSB) of the codeword "a" in the Most Significant Bit (MSB) direction is 0, and the number of continuous "Os" from the MSB of the codewords "bl" or "b2" in the LSB direction is 1, code changes of either the codeword "a" or "bl(b2)" occur to satisfy the boundary condition. 3. The apparatus as claimed in claim 1, wherein, when the number of continuous "Os" between the codewords "a" and "b" is smaller than a predetermined number, the number of continuous "Os" between the codewords "a" and "b" becomes greater than or equal to the predetermined number. 4. The apparatus as claimed in claim 1, wherein the codeword "a" of the code stream "XI" and the codeword "a" of the code stream "X2" are changed to other codewords such that the resulting codewords "a" of code streams "XI" and "X2" have the same INV value, and as a result, by the INV values of codewords "bl" and "b2" following the codeword "a", respectively, the INV values of the code stream "XI" and "X2" become different. 5. The apparatus as claimed in claim 1, wherein the predetermined number is Ml " 6. The apparatus as claimed in claim 1, wherein the first and second checking means comprise a comparator. 7. The apparatus as claimed in claim 1, wherein the first and second allocator is a processor.

Documents:

469-del-2002-abstract.pdf

469-del-2002-assignment-23-05-2008.pdf

469-DEL-2002-Claims-19-05-2008.pdf

469-del-2002-claims-23-05-2008.pdf

469-del-2002-claims.pdf

469-DEL-2002-Correspondence-Others-19-05-2008.pdf

469-del-2002-correspondence-others-23-05-2008.pdf

469-del-2002-correspondence-others.pdf

469-del-2002-description (complete)-19-05-2008.pdf

469-del-2002-description (complete)-23-05-2008.pdf

469-del-2002-description (complete).pdf

469-DEL-2002-Drawings-19-05-2008.pdf

469-del-2002-drawings.pdf

469-DEL-2002-Form-1-19-05-2008.pdf

469-DEL-2002-Form-1-31-07-2002.pdf

469-del-2002-form-1.pdf

469-del-2002-form-13.pdf

469-del-2002-form-18.pdf

469-DEL-2002-Form-2-19-05-2008.pdf

469-del-2002-form-2.pdf

469-del-2002-form-26.pdf

469-DEL-2002-Form-3-19-05-2008.pdf

469-del-2002-form-5.pdf

469-DEL-2002-Others Document-19-05-2008.pdf

469-del-2002-others document-23-05-2008.pdf

469-DEL-2002-Petition-137-19-05-2008.pdf

469-del-2002-petition-138-23-05-2008.pdf