Method of modulating and/or demodulating RLL code having enhanced direct current suppression capability

A method of modulating m-bit input data into a run length limited (RLL) code which is expressed as (d,k,m,n), where d denotes a minimum run length, k denotes the maximum run length, m denotes the bit length of data, and n denotes the bit length of a codeword, the method comprising:

• searching for a codeword for the m-bit input data in a data modulation code group designated as a code group having a codeword to come next to a previously modulated codeword;
• determining whether the run length condition (d,k) between a found codeword and the previous codeword/next codeword is violated;
• modulating the m-bit input data into the found codeword and determining a code group having a codeword to come next to the modulated codeword, if the run length condition is violated;
• modulating the m-bit input data into a codeword searched in a code group, which is favorable for DC suppression, among a data modulation code group designated as a code group having a codeword to come next to the previous codeword and a corresponding DC suppression control code group, if the run length condition is not violated;
• and
• determining a code group having a codeword to come next to the modulated codeword.

A method of demodulating a codeword stream received by an optical recording/reproduction apparatus using a run length limited (RLL) code (d,k,m,n), where d denotes a minimum run length, k denotes a maximum run length, m denotes a bit length of data, and n denotes a bit length of a codeword, in which input data has been modulated into a codeword in a code group, which is favorable for DC suppression, from a predetermined number of first code groups for data modulation and a predetermined number of second code groups for DC suppression control, the first and second code groups having duplicate codewords and being produced so that the codewords within the first code group have a first parameter CSV (codeword sum value) which represents the direct current (DC) value of a codeword, the sign of which is opposite to that of corresponding codewords within the second code group, and a second parameter INV which predicts the digital sum value (DSV) transition direction of the next codeword, the characteristic of which is opposite to that of corresponding codewords within the second code group, and the first and second code groups have different duplicate codeword generation conditions, the method comprising:

• updating a parameter NCG (next code group) designating a code group having a current codeword to be currently demodulated, depending on the characteristics of a previous codeword;
• determining whether two identical current codewords in a code group designated by the updated parameter NCG;
• and
• demodulating the current codeword into the original data for a codeword in a code group designated by the third updated parameter NCG, if the current codeword does not have a duplicate, and demodulating the current codeword into original data for one of the two identical codewords selected depending on the LZ of the next codeword, if the current codeword has a duplicate.

A method of producing run length limited (RLL) code groups for an RLL code having the form (d,k,m,n) where d is a minimum run length, k is a maximum run length, m is a data bit length, and n is a codeword bit length, the method comprising:

• producing 2n codewords;
• selecting produced codewords which meet the minimum run length d and the maximum run length k;
• extracting parameters LZ, EZ, CSV and INV from each selected codeword, wherein LZ is a number of lead zeros, EZ is a number of end zeros, CSV is a codeword sum value determined by summing the bits in the codeword bitstream by counting a 0 as −1 and a 1 as +1 and the parameter INV has a characteristic of 0 where an even number of 1s are included within the codeword or a characteristic of 1 where an odd number of 1s are included in the codeword;
• comparing the EZ of each selected codeword with the minimum run length d and a codeword duplication parameter y and determining a next code group (NCG) based on the comparison;
• and
• storing each selected codeword relationally with the corresponding determined NCG in at least one of a plurality of codeword tables based on a comparison of the LZ of the codeword with a factor.

A method of grouping codewords meeting a (d,k) condition of an RLL code having the form (d,k,m,n), where d is a minimum run length, k is a maximum run length, m is a data bit length, and n is a codeword bit length, the method comprising:

• extracting parameters LZ, EZ , CSV and INV from each selected codeword, wherein LZ is a number of lead zeros, EZ is a number of end zeros, CSV is a codeword sum value determined by summing the bits in the codeword bitstream by counting a 0 as −1 and a 1 as +1 and the parameter INV has a characteristic of 0 where an even number of 1s are included within the codeword or a characteristic of 1 where an odd number of 1s are included in the codeword;
• comparing the EZ of each selected codeword with the minimum run length d and a codeword duplication parameter y and determining a next code group (NCG) based on the comparison;
• and
• storing each selected codeword relationally with the corresponding determined NCG in at least one of a plurality of codeword tables based on a comparison of the LZ of the codeword with a factor.