Modulation apparatus and method

A modulation method for a modulation apparatus for converting data having a basic data length of m bits into variable-length code (d, k;

• m, n;
• r) having a basic code length of n bits, said modulation method comprising:
• a conversion step of converting input data into codewords in accordance with a conversion table containing conversion codes having a coding rule that the remainder of the number of “1's” in each element of the data sequence divided by two and the remainder of the number of “1's” in each element of the converted codeword string divided by two are equally 1 or 0;
• a minimum-run-length limitation code detection step of detecting a minimum-run-length limitation code from the input data, the minimum-run-length limitation code being contained in the conversion codes of the conversion table and limiting the minimum run length to a predetermined number or less;
• a consecutive-minimum-run replacement step of replacing the codeword string converted by performing the conversion step so that the minimum run length is limited to the predetermined number or less based on the minimum-run-length limitation code detected by performing the minimum-run-length limitation code detection step;
• and
• a modulation information storage step of counting the number of conversions performed in the conversion step based on a specified conversion code of the conversion codes contained in the conversion table and controlling storage of information indicating the conversion count,
• wherein, in the minimum-run-length limitation code detection step, detection of the minimum-run-length limitation code from the input data is controlled based on the information stored by performing the modulation information storage step.

A recording medium having a computer-readable program recorded therein, the program being adapted for a modulation apparatus for converting data having a basic data length of m bits into variable-length code (d, k;

• m, n;
• r) having a basic code length of n bits, the program including:
• a conversion step of converting input data into codewords in accordance with a conversion table containing conversion codes having a coding rule that the remainder of the number of “1's” in each element of the data sequence divided by two and the remainder of the number of “1's” in each element of the converted codeword string divided by two are equally 1 or 0;
• a minimum-run-length limitation code detection step of detecting a minimum-run-length limitation code from the input data, the minimum-run-length limitation code being contained in the conversion codes of the conversion table and limiting the minimum run length to a predetermined number or less;
• wherein said minimum-run-length limitation code detection step further comprises detecting the minimum-run-length limitation code from the input data based on the information stored by performing the modulation information storage step;
• a consecutive-minimum-run replacement step of replacing the codeword string converted by performing the conversion step so that the minimum run length is limited to the predetermined number or less based on the minimum-run-length limitation code detected by performing the minimum-run-length limitation code detection step;
• and
• a modulation information storage step of counting the number of conversions performed in the conversion step based on a specified conversion code of the conversion codes contained in the conversion table and for storing information indicating the conversion count.