Code allocation method

摘要

A method for generating and allocating codewords is provided. The method includes allocating one of two selectable codewords b1 and b2 as codeword b when a preceding codeword a and a following codeword b form a code stream X, in which codewords b1 and b2 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 a and b1 is X1, and the code stream of a and b2 is X2, allocating codewords such that the INVs of X1 and X2 are maintained to be opposite when a or b1(b2) should be replaced by another codewords in compliance with a predetermined boundary condition given between codewords. According to the method, by using a short codeword having less bits as a main conversion codeword, high efficiency is achieved in recording density. Also, when codewords which do not satisfy the run length conditions are replaced by other codewords, the codewords are allocated so that the DC suppression capability of the code stream can be maintained, and therefore higher DC suppression capability of the code stream is provided.