Patent ID: 7003046
Filing Date: 2006-02-21
Classification: G11B,H03M

Abstract:
1. A modulation method comprising the steps of: generating a final 15-bit output code word in response to every 8-bit input code word by referring to a set of encoding tables, wherein the encoding tables contain output code words assigned to input code words, and contain state information accompanying each output code word, wherein the state information designates an encoding table among the encoding tables which is used next to generate an output code word immediately following the output code word accompanied with the state information in a manner such that a resultant succession of the output code words follows predetermined run length limiting rules, and wherein NRZI conversion results of output code words in first specified one of the encoding tables which are assigned to prescribed input code words are opposite in polarity to NRZI conversion results of output code words in second specified one of the encoding tables which are assigned to the prescribed input code words; generating a first candidate current output code word in response to a current input code word equal to one of the prescribed input code words by referring to the first specified one of the encoding tables; generating a second candidate current output code word in response to the current input code word equal to said one of the prescribed input code words by referring to the second specified one of the encoding tables; calculating a first DSV from the first candidate current output code word and previous final output code words; calculating a second DSV from the second candidate current output code word and previous final output code words; determining which of an absolute value of the first DSV and an absolute value of the second DSV is smaller; selecting one from the first and second candidate current output code words which corresponds to the smaller DSV absolute value as a final current output code word: and superimposing auxiliary information on a sequence of final output code words; wherein the predetermined run length limiting rules causes a minimum run length in a result of NRZI conversion of the sequence of the final output code words except a sync signal to be equal to 3T, and causes a maximum run length therein to be equal to 14T or less, where T denotes a channel bit period related to the final output code words.