Data encoding method and device, data decoding method and device, and data supply medium

An encoding device for encoding m-bit data to an n-bit code, characterized by comprising:

• encoding means for converting an input m-bit data word to an n-bit code word having as a start point a predetermined state contained in a state assembly set as start points of the code;
• code word converting means for converting an n-bit code word having as a start point a predetermined state contained in a state assembly set as start points by the code supplied from said encoding means to an n-bit code word having as a start point another state contained in a state assembly set as start points of the code;
• code word examining means for examining the state of the end point (end-state) of a code word and the type of the code word on the basis of the code word supplied from said encoding means;
• end point state converting means for converting the state of the end point supplied from said code word examining means to the state of the end point output from said code word converting means;
• and
• storing means for storing the end-point state output from said end-point state converting means by the amount corresponding to one code word, and outputting the state of the start point of a code word which will be next output from said code word converting means.

A decoding method for decoding an n-bit code to m-bit data, characterized in that:

• the n-bit code is generated according to a finite state transition diagram representing the restriction of ADS and RDS received by a code sequence;
• two states contained in a state assembly set as start points of the n-bit code in the finite state transition diagram exist at symmetrical positions with respect to the center point of the finite state transition diagram, at symmetrical positions with respect to the ADS axis passing through the center point of the finite state transition diagram or at the symmetrical positions with respect to the RDS axis passing the center point of the finite state transition diagram;
• an n-bit code having as a start point any state contained in a state assembly set as start points of the code is converted to another n-bit code having as a start point a predetermined state contained in a state assembly set as start points of the code;
• and the m-bit data is obtained by decoding the converted code word.

A decoding device for decoding an n-bit code to m-bit data, characterized by comprising:

• code word examining means for examining the state of a start point of an input n-bit code word and the type thereof;
• code word converting means for converting an n-bit code word having as a start point any state contained in a state assembly set as start points of the input code to another n-bit code word having as a start point a predetermined state contained in a state assembly set as start points of the code;
• and
• decoding means for decoding a code word converted by said code word converting means to the m-bit data word.