CN1889185A - Method for coding high density optical disk modulating code - Google Patents

Abstract

A coding method for modulation codes for high-density optical discs, characterized in that: run length RLL (1, 10) is used, and the code rate is 4/6; DC control bits are added to the source data to improve the ability to control the DC component ; Among the 6-bit codewords, there are 21 kinds of codewords that meet the requirement of d-k, and 16 kinds of codewords are selected as the basic codewords to form the basic coding table. Among the remaining 5 codewords, the codewords whose beginning and end are 0 are used as connectors , the replacement table is the combination of basic codewords and connectors, and the length of the replacement table is 56; the lookahead encoding is used to solve the cascading conflict problem of codewords, and the source data of 4 bits is looked ahead at each modulation. If the current data is modulated If there is a conflict between the codewords and the concatenated codewords modulated by the forward-looking data, the codewords in the replacement table are used to replace the two groups of conflicting codewords; otherwise, the current data is modulated. It has higher capacity and encoding efficiency than DVD, and the single-sided and double-layer capacity can reach 13G, meeting the requirements of high-definition video programs. At the same time, its DC component is within an acceptable range, the maximum DSV is twice that of DVD, the code rate is 33.3% higher than DVD, and the coding efficiency is 1% higher than DVD.

Description

Coding method for modulation code used in high-density optical disk

Technical field

The invention belongs to the technical field of optical disc storage, and in particular relates to the design of optical disc modulation codes, which can be applied in high-density optical storage devices.

technical background

At present, the capacity of traditional DVD discs can no longer meet the high-capacity requirements for watching high-definition video programs. Although Blu-ray discs have been produced abroad (the capacity of which can reach 25G on a single side and a single layer), its expensive cost makes it in the current market. Can not promote in the market, therefore, it is imperative to develop a kind of high-capacity disc based on red light technology. At the same time, the survival of the manufacturers of DVD players in my country is greatly threatened because of the problem of DVD copyright patents. In order to get rid of the burden of expensive patent fees, it is urgent to design a new modulation code for multimedia discs with its own intellectual property rights, so that the production of multimedia disc players in our country has strong market competitiveness.

The modulation and coding characteristics of DVD discs are as follows:

1. Coding principle

DVD uses EFM-Plus modulation code, the run length is RLL (2, 10), and the code rate is 8/16. When d=2, k=10, the maximum capacity of the code is 0.5418, so the code rate can only be about 1/2.

EFM-Plus uses state-dependent fixed-length block codes. In state-dependent codes, the fixed-length encoded codeword associated with a fixed-length source codeword is designed to depend on the previous encoded codeword. The EFM-Plus code has 4 states, and each state is divided by the type of codeword entering and leaving a given state. After specifying the division conditions, t _{i, j} can be introduced to represent the number of codewords in the 4*4 state transition matrix T that leave state i and enter state j.

$\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\left[\begin{array}{cccc}\mathrm{<span\; class="notranslate">\; 138</span>}& \mathrm{<span\; class="notranslate">\; 96</span>}& \mathrm{<span\; class="notranslate">\; 96</span>}& \mathrm{<span\; class="notranslate">\; twenty\; two</span>}\\ \mathrm{<span\; class="notranslate">\; 145</span>}& \mathrm{<span\; class="notranslate">\; 90</span>}& \mathrm{<span\; class="notranslate">\; 90</span>}& \mathrm{<span\; class="notranslate">\; 27</span>}\\ \mathrm{<span\; class="notranslate">\; 132</span>}& \mathrm{<span\; class="notranslate">\; 102</span>}& \mathrm{<span\; class="notranslate">\; 102</span>}& \mathrm{<span\; class="notranslate">\; 15</span>}\\ \mathrm{<span\; class="notranslate">\; 164</span>}& \mathrm{<span\; class="notranslate">\; 113</span>}& \mathrm{<span\; class="notranslate">\; 113</span>}& \mathrm{<span\; class="notranslate">\; 25</span>}\end{array}\right]$

From each row of T, there are at least 351 codewords output from each state. The encoder assigns the input source codewords to the corresponding 351 output codewords in each state, and the excess codewords are deleted. After the corresponding relationship is established, given the source codeword and the given encoder state, the encoder can output the corresponding channel codeword, and at the same time give the information of the next state. Since the input only needs to accommodate 256 source code words, EFM-Plus has 2 coding tables, one is a main table with 256 items (see Figure 1), and the other is an alternative table with 87 items (see Figure 2). In this way, there are 2 tables for the first 87 source code words to choose during encoding, so as to achieve the effect of controlling and reducing low-frequency components.

2. Decoding principle

The current channel code plus X ₃ bits and X ₁₅ bits of the next channel code can solve the source code word.

B(t)=H ^-1 {X(t), X ₁₅ (t+1), X ₃ (t+1)}

3. DC control

The low-frequency component suppression or DC control method of EFM-Plus is to control the RDS (Running digital sum) of the codeword. The extra 88 channel codes are used as the source code word 0-87 candidate channel codes, and the principle of selecting the candidate channel codes is to minimize the RDS of the overall channel codes.

At the same time, the choice of synchronization code can also help to control RDS. EFM-Plus has designed 7 sets of synchronization codes (see Figure 3). The synchronization codes in a certain state can be selected from the main synchronization code and the alternative synchronization code, so as to obtain a smaller DSV (Digital Sum Value).

In addition, when encoding source codewords from 88 to 255, if the state is 1 or 4, you can select an encoding codeword in 1 state or 4 state. Under the premise of satisfying the run length limit, the selection standard is that the smaller the DSV the better. The main disadvantages of this modulation code are:

The capacity is small, the RLL parameter d=2 is taken by the modulation code of DVD, and the maximum capacity of the code is 0.5418, so the code rate can only be about 1/2, which is not enough for the standard of 15 GB per side of a new generation of high-density red-ray disc Yes, the coding efficiency needs to be improved.

Contents of Invention

The purpose of this invention is to design a kind of coding method for the modulation code of high-density optical disk, the modulation coding that is suitable for NVD (next generation universal optical disk) channel characteristic, this modulation code has higher coding efficiency, so that the optical disk has larger The effective storage capacity, its DC component control ability does not drop too much.

The technical scheme of the present invention is: a kind of coding method for the modulation code of high-density optical disk, it is characterized in that: adopt run-length length RLL (1,10), code rate is taken 4/6; Add DC control bit in source data , improve the ability to control the DC component;

Among the 6-bit codewords, there are 21 kinds of codewords that meet the requirements of d-k, and 16 kinds of them are selected as the basic coding codewords to form the basic coding table. Among the remaining 5 kinds of codewords, the codewords with 0 at the beginning and the end are used as connectors, and the replacement table It is the combination of basic codewords and connectors, and the replacement table length is 56;

Use look-ahead coding to solve the problem of cascading conflicts of codewords. For each modulation, look forward to 4 bits of source data. The code words in the replacement table replace the two groups of conflicting code words; otherwise, the current data is modulated.

The method for encoding modulation codes for high-density optical discs as described above is characterized in that a P control bit is added every 288 bytes in the source data, and after modulation, P with a smaller DSV is selected to control the DSV.

The method for encoding modulation codes for high-density optical discs as described above is characterized in that a synchronization code is added to the modulated data every 108 bytes, and there are 2 groups of synchronization codes, which are added according to the state of the current code word.

Basic principle of the present invention is:

1. Longer channel bit length and higher code rate

The constraint of (d=1, k=10) indicates that the run length of the actual recording spot is between 2T and 11T, where T is the channel bit length. Theoretically the code capacity of (d=1, k=10) is 0.6909, and the code fetching rate is 4/6 in the design; In contrast, the code capacity of (d=2, k=10) is 0.5418, while the EFM code The code rate is 8/17, and the code rate of EFM+ is 8/16=1/2. Therefore, the modulation code has higher efficiency and increases the recording capacity.

RLL modulation codes have two important performance indicators: modulation rate and density rate. The modulation rate R=m/n, the larger the R is, the higher the encoding efficiency is; the density rate DR=R(1+d), DR represents the ability of the modulation method to improve the storage density. Table 4 compares the main performance parameter indexes of RLL (1, 10) codes and several popular RLL modulation codes at present.

2. Add DC control bits to the bitstream of the source data

Unlike EFM and EFM+, where the DC control bits are added to the channel bit stream, the DC control bits of the (1, 10) modulation code are added to the source data bit stream. Examples are as follows:

Consider the source data bit stream "P010 0110", where 'P' is the added DC control bit (or merging bit). If 'P'='1', after modulation (refer to Table 3), "100010 010010" is obtained, and then NRZI conversion is performed to obtain "000011 100011", and its digital run length and DSV=+1; if 'P'=' 0', then "001001 010010" is obtained after modulation, and "110001 100011" is obtained through NRZI conversion again, and its digital run length and DSV=0. In this way, by selecting an appropriate value of 'P', the polarity of the DSV can be controlled, thereby controlling the DC component and low frequency component of the recording signal. Moreover, the overhead of adding DC control bits in the source data is relatively small, about 0.1494%. In contrast, the EFMPlus code adds DC control bits in the codeword stream, and the overhead is about 58%.

3. Use look-ahead coding

It is determined whether the current codeword should be replaced with another codeword according to the situation of the codeword to come.

There are 21 codewords that meet the requirements of d-k in the 6-bit codeword. The concatenation of codewords ending with '1' and starting with '1' will cause d conflicts. Therefore, according to minimize conflicts but reserve enough connections According to the principle of symbols, 16 kinds are selected as the basic coding codewords.

In the basic coding table, each codeword itself conforms to the limit of the run length, and some codewords in them will violate the limit of the run length when they are concatenated. For example, the concatenation of A and I will violate the limit of d. Therefore, when such codewords are concatenated, they are replaced with the codewords in the substitution table. The substitution table consists of the combination of basic codewords and connectors.

And when replacing, if the original codeword starts with 0, then the replaced codeword must also start with 0, otherwise new conflicts will occur.

4. Design of synchronization code

There are 2 sets of synchronization codes: "100000000000" and "000000000001".

Add a synchronization code to the encoded data every 108 bytes. If the current channel code word status is 0 (that is, start with '0'), add the synchronization code "000000000001"; if the current channel code word status is 1 (that is, start with '1' ) then add the synchronization code "100000000000".

Advantage and beneficial effect of the present invention are:

The run length RLL (1, 10) is used, which has a longer channel bit length and a larger code capacity; the code rate is 4/6, which has a higher coding efficiency; the look-ahead (look-ahead) coding is used to solve the code Word cascading conflicts; add DC control bits to the source data to improve the ability to control the DC component. Using the modulation and coding method proposed in the application of the present invention, the source data is modulated by 4/6, and the coding efficiency is increased by 1% compared with EFM-Plus, and by adding DC control bits, the DC component is greatly reduced, which is about 90% lower than that without adding %.

It has higher capacity and encoding efficiency than DVD, and the single-sided and double-layer capacity can reach 13G, meeting the requirements of high-definition video programs. At the same time, its DC component is within an acceptable range, the maximum DSV is twice that of DVD, the code rate is 33.3% higher than DVD, and the coding efficiency is 1% higher than DVD.

Description of drawings

Figure 1 is the main table of the EFM-Plus coding table in Table 1.

Figure 2 is the EFM-Plus coding table alternative table in Table 2.

Figure 3 is the synchronization code of Table 3 EFM-Plus.

Fig. 4 is a comparison of main performance parameters of the RLL modulation modes in Table 4.

FIG. 5 is a table 5 of the RLL (1, 10) modulation basic coding table of the embodiment of the present invention.

Fig. 6 is a replacement table for the restriction of d=1 in Table 6.

FIG. 7 is a flow chart 1 of multimedia data modulation and encoding according to an embodiment of the present invention.

FIG. 8 is a flow chart 2 of multimedia data modulation and encoding according to an embodiment of the present invention.

Fig. 9 is a decoding flowchart of the embodiment of the present invention.

Specific implementation methods

Embodiments of the present invention are represented by FIG. 5 (Table 5), FIG. 6 (Table 6), FIG. 8 and FIG. 9 . Below in conjunction with accompanying drawing (table), do further description.

1. Basic coding table design

The basic coding table is shown in Fig. 5, and there are 16 kinds of code words. There are altogether 21 kinds of 6-bit long codewords satisfying d=1, k=10, and 16 kinds are selected as basic coding codewords.

Firstly, it is coded according to the basic coding table. When there is no conflict between the current code word and the code word modulated by the look-ahead code word, the code word in the basic coding table is used.

Generally speaking, the method of DC control is to allow as many input codewords as possible to have two optional codewords after modulation, and the polarities of "1" in these two codewords are different. Since the DC control method considered in this design is to add DC control bits to the source code, when designing the code table, the polarity of the code word "1" corresponding to the source code word with a Hamming distance of 1 in the source code must be reversed. For example, the polarity of the encoded codeword "1" corresponding to "0000" is odd, and the polarity of the encoded codeword "1" corresponding to "0001", "0010", "0100" and "1000" is even.

2. Replacement code table design

The current 4-bit codeword is called P, and the next 4-bit codeword is called S. See Figure 6 for a substitution table for the d=1 constraint.

Among the 16 codewords in the basic coding table, some codewords can be concatenated with any other codewords without violating the restriction of d, such as 000010, and such codewords are used as "connectors".

When the codewords in the basic coding table produce cascading conflicts, a basic codeword plus a connector is used to replace the original two conflicting basic codewords to resolve the cascading conflicts. For example: when 0000 and 1000 are cascaded, look up the codeword of the basic code table (see Figure 5) to get 100001.100000, which produces a conflict of d, so check the replacement table (see Figure 6), and get the replacement codeword: 000001.001010 to replace the original basic The codeword resolves the conflict of d.

Since there are 7 codewords ending with "1" and 8 codewords starting with "1" in the basic coding table, there are 56 kinds of cascading conflicts in total, so the replacement table length is 56 (see Figure 6).

3. Synchronous code design

2 sets of synchronization codes: 000000000001 and 100000000000.

If the current state is 0 (the first digit of the code word after the synchronization code is '0'), select the synchronization code 000000000001; if the current state is 1 (the first digit of the code word after the synchronization code is '1'), select the synchronization code 100000000000. This can ensure that the connection of the synchronization code and the data code word does not violate the regulation of d. Since k=10, when a signal exceeding 11T is detected, it can be determined that a synchronization code has appeared.

4. Coding process

The encoding process is shown in Figure 7 and Figure 8. Among them, the process of encode() is as follows:

1) Input the 4-bit codeword and the next 4-bit codeword into the encoder;

2) According to the basic coding table modulated by RLL (1, 10), the current 4-bit input codeword and the next 4-bit codeword are converted into code patterns to obtain two 6-bit codewords P and S;

3) judge whether codeword P and S violate the restriction of d=1, if so, then replace P and S according to the substitution table for d=1 restriction, obtain legal new P and new S, then enter step 4); If not, go directly to step 5);

4) Output the code word P at the current clock, wait, output the code word S at the next clock, then get back to step 1), and cycle the above steps until the encoding is completed;

5) Output codeword P at the current clock, assign S to P as a new current codeword; read in the next 4-bit codeword, and perform a new 4-bit code according to the basic code table modulated by RLL (1, 10) Word is carried out code pattern conversion to obtain new S, then returns to step 3); If no code word can be read in at the end of the file, then directly output code word P at the next clock; cycle above-mentioned steps, until coding finishes.

5. Decoding process

The encoding process is shown in Figure 9. Among them, the process of decode() is as follows:

1) Input 6-bit codeword P and next codeword 6-bit S in the decoder;

2) judge whether P and Q are special codewords used for replacement in order to eliminate violations of the d=1 restriction, if so, transform the codewords P and S according to the substitution table for the d=1 restriction adopted during encoding, and then Enter step 3); if not, then directly enter step 4);

3) output the conversion of the codeword P at the current clock, and output the conversion of the codeword S at the next clock, then get back to step 1), until the end of decoding;

4) Transform P according to the RLL (1, 10) modulation basic coding table adopted during encoding, and output the transformation of codeword P at the current clock, assign S to P, and read in a new 6-bit codeword S, Then go back to step 2 until the decoding ends.

In the embodiment of the present invention, the evaluation of modulation coding is as follows:

According to the characteristics of high-density optical disc multimedia applications, the source data is modulated and coded by RLL (1, 10; 4, 6).

Its capacity is 33.3% higher than the modulation code of DVD, and the coding efficiency is increased by one percentage point.

The maximum DSV is reduced by 1 to 2 orders of magnitude than without the DC control bit, but the maximum value is about 2 times that of DVD.

Therefore, the modulation code has the feasibility of being applied to a high-density optical disc to improve the effective storage capacity of the optical disc.

Claims (3)

1, a kind of coding method that is used for the modulation code of high-density optical disk, it is characterized in that: adopt run length RLL (1,10), code rate gets 4/6; Add DC control bit in source data, improve control DC component Ability; Among the 6-bit codewords, there are 21 kinds of codewords that meet the requirements of d-k, and 16 kinds of them are selected as the basic coding codewords to form the basic coding table. Among the remaining 5 kinds of codewords, the codewords with 0 at the beginning and the end are used as connectors, and the replacement table It is the combination of basic codewords and connectors, and the replacement table length is 56; Use look-ahead coding to solve the problem of cascading conflicts of codewords. For each modulation, look forward to 4 bits of source data. The code words in the replacement table replace the two groups of conflicting code words; otherwise, the current data is modulated. 2. The encoding method for modulation codes for high-density optical discs as claimed in claim 1, characterized in that: a P control bit is added every 288 bytes in the source data, and after modulation, a P with a smaller DSV is selected to realize Control over DSVs. 3. The encoding method for modulation codes used in high-density optical discs as claimed in claim 1 or 2, characterized in that: a synchronization code is added to the modulated data every 108 bytes, there are 2 groups of synchronization codes, according to the current codeword status is added.

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