CN1219294C - Data coding and decoding method modulated by adopting limited run length - Google Patents

Abstract

The present invention relates to a data coding and decoding method which adopts limited run length to modulate, which belongs to the field of optical disk memory. The present invention discloses a coding method which carries out RLL (4, 18) modulation on data by using an encoder, the aim of which is to effectively raise memory size of the optical disk and solve the defects of the existing modulation technology by adopting the limited run length in an optical disk system. The method comprises that original serial binary sequence data is processed by serial-parallel conversion, each of 4 bits as a group of code word enters the encoder as input data which is coded to generate 12 bits as a group of code words as output data. Meanwhile, the present invention discloses a decoding method of data which is coded, which uses the decoder to carry out the RLL (4, 18) modulation and decoding on the data, and converts the 12-bit code words to 4-bit code words to obtain end users' data. Compared with a modulation method of a DVD, the method of the present invention can increase 11% optical disk capacity, and has an important function on development of optical disk industry.

Description

Adopt the digital coding and the coding/decoding method of limited run length modulation

Technical field

The present invention relates to a kind of Code And Decode method that can be used in record high density compact disc data, belong to the optical disc storage field.

Background technology

CD has obtained increasingly extensive application as a kind of storage medium, and since nineteen eighty-two was released CD, CD developed into erasablely from read-only, develops into DVD from CD, in the middle of the standard of blue-ray DVD of future generation is also being formulated.CD storage technique is except self original some advantage, beyond, life-span length big as capacity, disc change, reproduction speed are fast etc., the kind of CD player and function are also quite perfect, therefore except peripherals as various computing machines, in each field of national economy important use is arranged all, and CD can be used for recording voice, literal, figure and dynamic and static image simultaneously, is the indispensable instrument of multimedia technology, also occupies critical positions in household electrical appliance and national education.

At present, the most gordian techniquies in the CD are grasped in foreign vendor and research institution's hand, and the core technology that has autonomous property right is significant to China's CD industrialization.In optical disc storage system, modulation technique is being played the part of important role, and it improves capacity of optical storage and have vital role for overcoming intersymbol interference.Data are that mode with pits exists on the disc in optical disc storage, and pits is burnt to carve by laser instrument and formed.Utilize pits and bank to reading the different of hot spot reflectivity, can recover the digital signal of ' 0 ' and ' 1 ' expression when reading.Information source data through Error Correction of Coding are recorded in the structure that often will pass through modulated process change code word on the disc before, thereby make the requirement of the suitable system of characteristic of modulation back code word.

The size of focal beam spot is by the digital aperture NA decision of laser wavelength and focusing objective len in the optical disk system, under the certain situation of spot size as can be known, the narrow more then quality of channel of width of short message hole/bank is poor more, when spot diameter during greater than the width of short message hole/bank system show as low-pass characteristic, read output signal can produce distortion, therefore cause intersymbol interference, require the width of short message hole/bank to get and proportional certain definite value of spot diameter when designing optical disk system.Obviously, the data before the modulation of the pits of equal length/bank representative are many more, and then the storage density of CD is high more.Read-out system circuit requirement sense data can provide stable clock information, does not promptly allow to occur for a long time continuously ' 0 ' or ' 1 ', and unmodulated data do not satisfy this requirement, need modulate to make it satisfy the requirement of extracting clock.In addition, the low-frequency component of CD read-out signal can impact servo-drive system, reduces servo precision, and the signal after therefore requiring to modulate has low low-frequency component.

In order to reach above-mentioned requirement to modulation, in optical disk system, adopt limited run length modulation technique, be also referred to as RLL (d, k) modulation.(d, k) Tiao Zhi basic parameter is RLL: d and k, wherein T _Min=d+1 is a minimum run length, T _Max=k+1 is a maximum run length.(d, k) sign indicating number just is meant in the code stream after the modulation that two have d ' 0 ' continuously at least between ' 1 ' to RLL, and k ' 0 ' is arranged at most.(d, k) the NRZI conversion is carried out to code stream in the modulation back to RLL, gets record data to the end.The NRZI conversion is meant when occurring ' 1 ' in the code stream carries out level conversion, does not change when occurring ' 0 '.

For different parameter d and k, the RLL modulation has different structures, even for identical d and k, (d, k) modulation also has different implementation methods to RLL.In the CD optical disk system, modulation system is the EFM modulation, and it is a kind of of RLL (2,10) modulation; In the DVD optical disk system, modulation system is the EFMPlus modulation, and it also is a kind of realization of RLL (2,10) modulation.For different modulation, use modulation efficiency R and density rate DR to estimate.Modulation efficiency R is meant the ratio of preceding code word figure place of modulation and modulation back code word figure place, and R is big more, and modulation efficiency is high more.Density rate DR=(d+1) * R, it is an overall target of estimating modulation system, and the factor of modulation efficiency R has been included among the density rate DR, and DR has represented that modulation system improves the ability of memory capacity, and DR is big more, and the memory capacity of the CD of same size is big more.D=0 when unmodulated, R=1, DR=1.

Summary of the invention

In order effectively to improve the memory capacity of CD, solution has the deficiency of the limited run length modulation technique that adopts now in optical disk system, the invention provides a kind of data-encoding scheme that adopts limited run length modulation, it is characterized in that this method is to utilize scrambler that data are carried out RLL (d, k) modulating-coding, parameter d=4 wherein, k=18; Described RLL (4,18) modulating-coding adopts the block encoding mode, and original serial binary sequence data is through string and after changing, per 4 bit data are that a set of code words enters scrambler, as the input data, 12 of coding back generations are one group code word, as output data;

This method comprises the steps:

1) input 4 bit word and its next 4 bit word in scrambler;

2) the basic coding table according to RLL (4,18) modulation carries out code conversion to current 4 enter code words and next code word, obtains two 12 code word P and S;

3) judge whether code word P and S the situation of d=4 restriction occurs running counter to, if, then respectively code word P and S are carried out conversion according to additional coding schedule at the d=4 restriction, enter step 4) then; If not, then directly enter step 5);

4) at present clock output code word P, wait for,, get back to step 1) circulation above-mentioned steps then, finish up to coding at next clock output code word S;

5) at present clock output code word P, then S is composed corresponding code word P to new current enter code word, and obtain new 4 bit word input as next enter code word, and according to RLL (4,18) Tiao Zhi basic coding table carries out code conversion and obtains new S, get back to step 3) circulation above-mentioned steps then, finish up to coding.

Above-mentioned steps 2) and the basic coding table described in the step 5) constitute by 16 kinds of 4 enter code words and 16 12 corresponding bit word thereof; Described 16 12 bit word from reciprocal at least back 4 for all code words of ' 0 ' and reciprocal back 3 for ' 0 ' and the 4th codeword set B that forms for ' 1 ' part code word reciprocal choose, except the all-zero code word; Corresponding relation between described 16 code words choosing out and 16 kinds of 4 enter code words is arbitrarily.

Above-mentioned steps 3) described in be at the mapping mode to current code word P and next code word S in the additional coding schedule of d=4 restriction: choose two not by 12 bit word of using in the described basic coding table as special code word, with current code word P and next code word S be transformed into can unique decoding special code word.

Above-mentioned steps 2) and 3) in, no matter be to adopt the basic coding table or adopt additional coding schedule at the d=4 restriction, the data behind the coding all can satisfy the requirement of k=18 restriction automatically.

Adopt the coding/decoding method of the data of limited run length modulating-coding, it is characterized in that this method be utilize demoder that data are carried out RLL (d, k) decode-regulating convert 12 bit word to 4 bit word, obtain end user data, parameter d=4 wherein, k=18;

This method comprises the steps:

1) input 12 bit word P and its next 12 bit word S in demoder;

2) judge that whether current code word P is the special code word of to run counter to the d=4 restriction and producing in order to eliminate, if according to next code word S, the additional coding schedule at the d=4 restriction that adopts during according to coding carries out conversion to code word P and S, enters step 3) then; If not, then directly enter step 4).

The RLL (4 that adopts when 3) searching coding by current code word P, 18) 4 bit word of correspondence in Tiao Zhi the basic coding table as the output of present clock, are waited for, search 4 corresponding in described basic coding table bit word by current code word S, as the output of next clock.Get back to step 1) circulation above-mentioned steps then, finish up to decoding.

4 corresponding bit word in the basic coding table of RLL (4, the 18) modulation of adopting when 4) searching coding by current code word P are as the output of present clock, S is composed to new current code word P, and obtain next new code word S, and get back to step 2 then) the circulation above-mentioned steps, finish up to decoding.

The modulation efficiency R=1/3 of RLL (4, the 18) modulation that the present invention proposes, density rate DR=(d+1) * R=1.67.In the prior art, the density rate DR=1.41 of the EFM modulation that CD adopts, the density rate DR=1.5 of the EFMPlus modulation that DVD adopts.As seen, if other conditions of optical disk system are constant, change modulation system merely, then from EFM to EFMPlus, capacity of optical storage can increase by 6%, and this is the contribution that modulation technique is increased from CD to the DVD evolution process.And if RLL (4, the 18) modulation that modulation technique adopts the present invention to propose, the EFMPlus modulation of comparing DVD can improve 11% CD capacity again.In addition, compare EFMPlus and have 8 inputs, 16 outputs, RLL (4,18) modulation only needs 4 inputs, 12 outputs, and needed hardware resource significantly reduces, and the complexity of coding and decoding has substantial degradation.This shows that RLL disclosed by the invention (4,18) modulation technique has vital role for the development of CD industry, can further improve the memory capacity of CD.

Description of drawings

Fig. 1 is the coding method process flow diagram according to the preferred embodiments of the present invention.

Fig. 2 is the coding/decoding method process flow diagram according to the preferred embodiments of the present invention.

Fig. 3 is a kind of encoder hardware structured flowchart of realizing coding method of the present invention.

Fig. 4 is a kind of decoder hardware structured flowchart of realizing coding/decoding method of the present invention.

Embodiment

RLL (4,18) coding adopts the block encoding mode.Raw data is the serial binary sequence, and after string and conversion, per 4 bit data are one group and enter scrambler, as the input data, it is one group code word that coding back produces 12, as output data, and then through and string be converted to and can be used for the serial data stream of imprinting on CD.For 4 bit parallels input data, have 16 kinds of possibilities, with I _j, 0≤j≤15, expression, input data I _jAppearance be at random.Corresponding 12 outputs of each input are with C _j, 0≤j≤15, expression.12 outputs corresponding 2 ¹²=4096 kinds of possibility code words, therefore, therefrom the selected part code word is to meet the requirement of RLL (4,18) coding.RLL (4,18) requires in the continuous bit stream that a plurality of code words form, and ' 0 ' number is at least 4 between adjacent two ' 1 ', mostly is 18 most.In order to satisfy above-mentioned requirements, principle and the method for choosing code word have hereinafter been analyzed.

By the restriction of d=4 as can be known, ' 1 ' number of times that occurs mostly is 2 times most in the middle of the code word, otherwise code word itself or two same code words will vary from a rule when occurring continuously.In addition, in the middle of same code word, need 4 ' 0 ' between two ' 1 ' at least.By the restriction of k=18 as can be known, the all-zero code word does not meet rule.Satisfy the above code word that requires and constitute a set A, the code word that meets the demands must be among the A.Yet for Basic Encoding Rules: 4 directly corresponding 16 kinds of output code words of input can not find 16 code words and can directly satisfy the requirement of RLL (4,18) in A.Therefore, seek a subclass B in A, set up coding to replenish rule simultaneously, the two cooperates to satisfy the requirement of RLL (4,18).Code word among the subclass B also need satisfy except the requirement of satisfying A: back 3 of code word is 0 entirely at least.Therefore, can be divided into two orthogonal subsets D1 and D2 to B, two subclass sums are B, and wherein D1 is that zero code word is formed by back four reciprocal at least entirely, and D2 is 1 by the 4th reciprocal, and back three is that zero code word is formed entirely.As can be known, include only 14 code words among the D1.Remove the code word ' 000000001000 ' and ' 100000001000 ' among the D2, constitute new subset D 3.Can form the output code word of basic coding table, i.e. C by any two code words among D1 and the D3 _j, 0≤j≤15, wherein C _jAny with the corresponding order of 16 code words.In the following description, current code word is called P, next code word is called S.

Can find, work as C _jIn two code words can have the situation of running counter to d=4 when linking to each other, its rule is: if current code word P is from D3, and next code word S is a most significant digit is ' 1 ' code word, ' 10001 ' situation then can occur, then must use this moment the coding at the d=4 restriction to replenish rule: when occurring ' 10001 ', current code word P becomes a special code word, and next code word S carried out conversion, make its requirement of satisfying RLL (4,18), and will have unique decodability.Special code word can not be selected by C _jThe code word that comprises.Obviously, only use basic coding table code word can not run counter to the requirement of k=18 restriction, also will guarantee P and S requirement when selecting special code word without prejudice to the k=18 restriction.By said method, can select RLL (4,18) to modulate needed code word, and determine coding method.

Need benly be, with 16 kinds of corresponding Codeword Sets C of enter code word _jBe not unique, wherein the part code word can replace with other code words shown in above-mentioned method, as selecting other code words among the D3.In addition, C _jMiddle code word and 16 kinds of corresponding relations of importing between the data are arbitrarily.Because each code word can obtain new code word by lowest order to the mutual displacement of most significant digit head and the tail, as can be known subclass B, D1, D2, D3, C in the said method _jThe subclass that all has a correspondence, wherein the concentrated element of each element and atom has mirror.Corresponding subclass has the character identical with former subclass, to RLL (4,18) run counter to and to satisfy situation identical, therefore, the new C that adopts corresponding subclass to form _j, also should belong to the scope of protection.

The step of determining also just to have determined coding and decoding of code word selection and coding method.Can be described in detail this in the middle of preferred embodiment, the aid illustration by embodiment can have clearer understanding to code word selection and coding method simultaneously.

The preferred embodiments of the present invention have been selected a set of code words as C _j, and selected special code word, provided basic coding table and additional coding schedule simultaneously.Describe cataloged procedure and decode procedure in detail at this embodiment, the method that this process adopts has versatility, applicable to RLL (4,18) modulation, and is not limited only to this embodiment.At last, the scrambler realized at this embodiment and the concrete device of code translator hardware configuration and employing have been provided.

For the code word of clearly representing to select, employing table 1 comes aid illustration.Table 1 is the basic coding table of RLL (4,18) modulation, and per 4 of information data forms a code word before the coding, represents with I0, I1...I15 respectively, and per 12 of the data behind the coding form a code word, represent with C0, C1...C15 respectively.

The basic coding table of table 1 RLL (4,18) modulation

Information data before the modulation	Modulation back code word
		0000 I0	001000001000 C0
0001 I1	000001000000 C1
		0010 I2	000100000000 C2
0011 I3	000100001000 C3
		0100 I4	001000000000 C4
0101 I5	100001000000 C5
		0110 I6	100000100000 C6
0111 I7	010000000000 C7
		1000 I8	100000000000 C8
1001 I9	100000010000 C9
		1010 I10	010000100000 C10
1011 I11	000000010000 C11
		1100 I12	001000010000 C12
1101 I13	000010000000 C13
		1110 I14	000000100000 C14
1111 I15	010000010000 C15

Obviously, use table 1 is worked as the situation that the d=4 rule can appear running counter in two code word consecutive hourss merely, therefore needs to adopt to replenish rule treatments, and the code word of feasible final output satisfies the requirement of RLL (4,18).Call P in this current code word, next code word is called S.Have the situation of running counter to d=4 rule among the RLL (4,18), ' 10001 ' pattern can occur, specifically if current code word is C0 or C3, and next code word is among C5, C6, C8 or the C9 any one, will produce above-mentioned pattern.Need to adopt additional coding rule for this reason, eliminate ' 10001 ', make it meet the requirement of RLL (4,18) at the d=4 restriction.Adopt two special code words ' 010000000100 ' and ' 010000001000 ', these two code words are not the code words in the basic coding table, and what just mean employing when occurring is the additional rule that limits at d=4.Correspond respectively to C0 and C3 for two special code words of this embodiment.Work as P=C0/C3, during S=C5/C6/C8/C9, use this and replenish rule, P is become corresponding special code word respectively, and S is carried out conversion, eliminated ' 10001 ' situation after the conversion, simultaneously owing to form different code words respectively after the different conversion of S according to C5, C6, C8 and C9, therefore has uniqueness, correct in the time of can guaranteeing to decipher.Table 2 has provided this and has replenished the concrete variation of rule, and left column is the code word before the conversion, and code word P and the S after the conversion classified on the right side as, and as seen, P becomes special code word, satisfied the requirement of d=4 after the S conversion, and for identical P, S has uniqueness.

Table 2 is at the additional coding schedule of d=4 restriction

Before the conversion	After the conversion
		P S	P S
C0 C5	010000000100 000000010000
		C0 C6	010000000100 000000100000
C0 C8	010000000100 000001000000
		C0 C9	010000000100 001000010000
C3 C5	010000001000 000000010000
		C3 C6	010000001000 000000100000
C3 C8	010000001000 000001000000
		C3 C9	010000001000 001000010000

According to basic coding table and additional coding schedule, carry out conversion according to above-mentioned method, can obtain the final output code word that RLL (4,18) requires that meets.And decoding is the inverse process of coding, and it is based on identical coding rule, according to this rule, can obtain well-determined raw data.

The coding method of the preferred embodiment of the present invention is described with reference to Fig. 1.RLL (4,18) coded system reads in the incoming bit stream 4 input data and exists among the register R0, reads next 4 input data subsequently and has (step 10) among the register R1.Carry out code conversion according to the basic coding table to having current enter code word and next enter code word among R0 and the R1 then, obtain 12 code word P and S respectively, and have (step 11) among register R2 and the R3.Then, scrambler judges whether P and S run counter to the requirement (step 12) of d=4 coding rule.If, then P and S are carried out conversion respectively according to additional coding schedule at the d=4 restriction, make it satisfy the requirement (step 13) of d=4.Then,, and wait, get back to step 10 at last to circulate, up to end-of-encode (step 14) by the time next clock is exported code word S at present clock output code word P.If not, then, then S is composed to P at present clock output code word P, exist among the register R0, and obtain new 4 enter code words and be converted to new code word S, and exist among the register R1 according to the basic coding table, get back to step 12 at last and circulate, up to end-of-encode (step 15).

The coding/decoding method of the preferred embodiment of the present invention is described with reference to Fig. 2.At first, RLL (4,18) decode system reads in the incoming bit stream 12 input data P and deposits among the register R4, reads next 12 input data S subsequently and deposits among the register R5 (step 20).Then, judge whether P is at the special code word (step 21) shown in the additional coding schedule of d=4 restriction.If then P and S are carried out conversion (step 22) respectively according to additional coding schedule at the d=4 restriction.Then, in the basic coding table, search 4 bit word of P correspondence,, search 4 bit word of S correspondence,, get back to step 20 circulation decoding at last, finish (step 23) up to decoding in next clock output as the output of present clock.If not, then in the basic coding table, search 4 bit word of P correspondence, as the output of present clock, then S is composed to P, exist among the register R4, obtain 12 new input data S then, exist among the register R5, get back to step 21 circulation decoding at last, finish (step 24) up to decoding.

According to the description of above-mentioned RLL (4,18) modulating-coding and decoding, developed the encoder of a kind of realization RLL (4,18) modulation, but the method for the invention and being limited to this kind hardware circuit realizes.In Fig. 3 and Fig. 4, provided the structured flowchart of encoder in the hardware circuit of realizing the embodiment of the invention respectively.Encoder is made up of input-buffer circuit, ROM look-up table, logic judging circuit, control circuit and output buffers circuit 5 modules respectively.That the realization of hardware circuit and logic function is adopted is the programmable logic device (PLD) EPF1K50 of altera corp, carries out logical design by utilizing this chip, writes the program that realizes logic function, can realize encoder on a slice chip simultaneously.The program that realizes logic function is that the hardware description language AHDL that adopts altera corp to propose writes.

CD drive is made up of optical system, precision mechanical system, electric-control system and data handling system, and its normal operation is the result of above-mentioned four systems co-ordination.Optical system is the basis of realizing CD read and write, precision mechanical system is the assurance of driver normal operation, electric-control system is the key that guarantees read-write and data reliability, and the data processing and the information transmission system then are further to reduce the bit error rate and improve the indispensable ingredient of system works efficient.By data handling system, user data has experienced and has write and read two processes.In ablation process, user data utilizes scrambler to carry out RLL (4,18) modulating-coding through after the Error Correction of Coding, is burnt on the CD then.In readout, photodetector detects the data of imprinting on CD of reading, and after amplification, equilibrium and judgement, utilizes demoder to carry out RLL (4,18) decode-regulating, carries out error correction decoding at last, obtains end user data.

Special declaration, embodiment described herein are a specific implementation of the present invention, and claim of the present invention is as described in claims, and are described in detail in instructions, and not only are confined to the foregoing description.

Claims (2)

1. adopt the data-encoding scheme of limited run length modulation, it is characterized in that this method is to utilize scrambler that data are carried out RLL (d, k) modulating-coding, parameter d=4 wherein, k=18; Described RLL (4,18) modulating-coding adopts the block encoding mode, and original serial binary sequence data is through string and after changing, per 4 bit data are that a set of code words enters scrambler, as the input data, 12 of coding back generations are one group code word, as output data;

This method comprises the steps:

1) input 4 bit word and its next 4 bit word in scrambler;

2) the basic coding table according to RLL (4,18) modulation carries out code conversion to current 4 enter code words and next code word, obtains two 12 code word P and S;

3) scrambler judges whether code word P and S the situation of d=4 restriction occurs running counter to, if, then respectively code word P and S are carried out conversion according to additional coding schedule at the d=4 restriction, enter step 4) then; If not, then directly enter step 5);

4) at present clock output code word P, wait for,, get back to step 1) circulation above-mentioned steps then, finish up to coding at next clock output code word S;

5) at present clock output code word P, then S is composed corresponding code word P to new current enter code word, and obtain new 4 bit word input as next enter code word, and according to RLL (4,18) Tiao Zhi basic coding table carries out code conversion and obtains new S, get back to step 3) circulation above-mentioned steps then, finish up to coding;

Wherein, described basic coding table is made of 16 kinds of 4 enter code words and 16 12 corresponding bit word thereof; Described 16 12 bit word from reciprocal at least back 4 for all code words of ' 0 ' and reciprocal back 3 for ' 0 ' and the 4th codeword set B that forms for ' 1 ' part code word reciprocal choose, except the all-zero code word; Corresponding relation between described 16 code words choosing out and 16 kinds of 4 enter code words is arbitrarily;

Describedly be at the mapping mode to current code word P and next code word S in the additional coding schedule of d=4 restriction: choose two not by 12 bit word of using in the described basic coding table as special code word, with current code word P and next code word S be transformed into can unique decoding special code word.

2. adopt the coding/decoding method of the data of limited run length modulating-coding, it is characterized in that this method is to utilize demoder that data are carried out RLL (d, k) decode-regulating, convert 12 bit word to 4 bit word, obtain end user data, parameter d=4 wherein, k=18;

This method comprises the steps:

1) input 12 bit word P and its next 12 bit word S in demoder;

2) demoder judges that whether current code word P is the special code word of to run counter to the d=4 restriction and producing in order to eliminate, if according to next code word S, the additional coding schedule at the d=4 restriction that adopts during according to coding carries out conversion to code word P and S, enters step 3) then; If not, then directly enter step 4);

The RLL (4 that adopts when 3) searching coding by current code word P, 18) 4 bit word of correspondence in Tiao Zhi the basic coding table as the output of present clock, are waited for, search 4 corresponding in described basic coding table bit word by current code word S, as the output of next clock.Get back to step 1) circulation above-mentioned steps then, finish up to decoding;

4 corresponding bit word in the basic coding table of RLL (4, the 18) modulation of adopting when 4) searching coding by current code word P are as the output of present clock, S is composed to new current code word P, and obtain next new code word S, and get back to step 2 then) the circulation above-mentioned steps, finish up to decoding;

Wherein, described basic coding table is made of 16 kinds of 4 enter code words and 16 12 corresponding bit word thereof; Described 16 12 bit word from reciprocal at least back 4 for all code words of ' 0 ' and reciprocal back 3 for ' 0 ' and the 4th codeword set B that forms for ' 1 ' part code word reciprocal choose, except the all-zero code word; Corresponding relation between described 16 code words choosing out and 16 kinds of 4 enter code words is arbitrarily;

Describedly be at the mapping mode to current code word P and next code word S in the additional coding schedule of d=4 restriction: choose two not by 12 bit word of using in the described basic coding table as special code word, with current code word P and next code word S be transformed into can unique decoding special code word.

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