Patent ID: 6965329

Claim:
A digital sum value (DSV) control bit generating method for generating a DSV control bit that is used for modulation in which a channel-bit sequence from an input bit sequence and generating code sequence from the channel-bit sequence generated, the DSV-control-bit generating method comprising: a first post-insertion-bit-sequence-candidate generating step of inserting a first candidate bit for the DSV control bit at a predetermined position of the input bit sequence to generate a first post-insertion-bit-sequence candidate from the input bit sequence; a second post-insertion-bit-sequence-candidate generating step of inserting a second candidate bit for the DSV control bit at the predetermined position of the input bit sequence to generate a second post-insertion-bit-sequence candidate from the input bit sequence; a modulating step of modulating the first and second post-insertion-bit-sequence candidates based on a conversion rule of a variable-length code (d, k; m, n; r); a synchronization-signal inserting step of inserting a synchronization signal including a unique pattern at a predetermined position into each of the modulated first and second post-insertion-bit-sequence candidates supplied from the modulating step, a modulation-delimiter detecting step of detecting a modulation delimiter that serves as a delimiter for conversion of the variable-length code in the modulating step; a valid-delimiter detecting step of detecting a valid delimiter for controlling timing for determining a value of the DSV control bit, based on the modulation delimiter detected in the modulation-delimiter detecting step; a DSV calculating step of calculating DSV values based on first and second channel-bit-sequence candidates generated respectively in the modulating step; and a DSV-control-bit determining step of determining either the first or the second candidate bit as the DSV control bit based on the DSV values calculated in the DSV calculating step, at the timing based on the valid delimiter detected in the valid-delimiter detecting step.