Patent ID: 8095844

Claim:
A method of reproducing digital information having a set of information bits of a length L and a set of parity check bits of a length P that are alternately arranged, both the information bits and the parity check bits conforming to rules for run-length limited coding, and the parity check bits representing check information obtained by a predetermined arithmetic operation conducted on the corresponding information bits, the method comprising the steps of: checking up the matching between results obtained by the arithmetic operation conducted on the information bits and the check information represented by the parity check bits, the checking-up being conducted at the time of reproducing the information; and extracting a bit pattern with the highest probability of error from the information bits and then correcting the extracted bit pattern when the checking-up results in the mismatching between the two, wherein the bit pattern to be corrected is an edge portion in the information bit, that is, a portion where a switching between “1” and “0” occurs, the extraction of a bit pattern with the highest probability of error is carried out by the steps of: extracting edge portions from the information bits; identifying the bit pattern on the basis of the number of consecutive “0s” and the number of consecutive “1s” that precede and follow the edge portion, measuring the edge shift amount for each of the edge portions, checking-up the matching between the bit pattern and predetermined, registered bit patterns, determining whether each of the edge shift amounts has a sign that is identical to the sign of one of registered edge shifts defined for the respective registered bit patterns when the checking-up results in the matching between the bit pattern and the registered bit patterns, and extracting, from the information bits, a position of a bit pattern having the largest absolute value of the edge shift amount, from the bit patterns that are identical to the registered bit patterns and have the signs identical to the signs of the registered edge shifts, by holding the positions of bit patterns and the absolute values of the edge shift amounts of the information bits, when the signs of the edge shift amounts of the information bits are determined as identical to the signs of the registered edge shifts.