Patent ID: 6898166

Claim:
A synchronous signal generating method in which a plurality of coding tables is used to subject input data words of p-bits to modulation and to thereby obtain words of q-bits (q>p), said plurality of coding tables storing the code words corresponding to respective input data words, and to state information indicating the coding table for use in modulating a next input data word to obtain a next code word satisfying a predetermined run length restriction rule even with the next code word coupled directly with the code word, the method comprising: generating a synchronous signal for decoding reproducing data, that is separable from a string of code words satisfying said predetermined run length restriction rule, and comprises a specific code for identifying a position in one sector and a synchronous pattern comprising a first bit pattern of a run length longer than a maximum run length in said predetermined run length restriction rule by 1T or more (T is a period of channel bit of the string of code words) and a following second bit pattern of a run length longer than a minimum run length, and said synchronous pattern including part of a following code word; and inserting said synchronous signal into every predetermined number of code words in said string of code words satisfying said predetermined run length restriction rule to generate a synchronous frame.