Patent ID: 6879269

Claim:
An allocation method for allocating codewords of source words to be recording on a recording medium, the method comprising: when a preceding codeword b and a following codeword c form a code stream Y, allocating one of two selectable codewords b 1 and b 2 as the codeword b, wherein the codewords b 1 and b 2 have opposite INVs which are parameters indicating whether the number of ‘1s’ contained in a codeword is an odd number or an even number and when the code stream of b 1 and c is Y 1 , and the code stream of b 2 and c is Y 2 , allocating codewords such that INVs of Y 1 and Y 2 are maintained to be opposite when the codeword b 1 , b 2 or c should be replaced by another codeword in compliance with a predetermined boundary condition between codewords.