Encoding apparatus and method, recording apparatus and method, and decoding apparatus and method

An encoding method for converting m-bit data words into n-bit code words, where m and n are both integers and satisfy an expression 2n≧2m×2, the encoding method comprising the step of:

• executing encoding for an m-bit data word that has been input, where an n-bit code word in a first conversion table in which 2m m-bit data words are associated with 2m n-bit code words selected from 2n n-bit code words or an n-bit code word in a second conversion table in which the 2m m-bit data words are associated with 2m n-bit code words that have been selected from the 2n n-bit code words and that do not overlap with the 2m n-bit code words in the first conversion table is selected and output, the selected and output n-bit code word having a smaller number of symbols “1”.

A recording method for converting m-bit data words into n-bit code words, where m and n are both integers and satisfy an expression 2n≧2m×2, and performing recording on an optical recording medium, the recording method comprising the steps of:

• executing encoding for an m-bit data word that has been input, where an n-bit code word in a first conversion table in which 2m m-bit data words are associated with 2m n-bit code words selected from 2n n-bit code words or an n-bit code word in a second conversion table in which the 2m m-bit data words are associated with 2m n-bit code words that have been selected from the 2n n-bit code words and that do not overlap with the 2m n-bit code words in the first conversion table is selected and output, the selected and output n-bit code word having a smaller number of symbols “1”;
• and
• performing recording on the optical recording medium on the basis of the n-bit code word output in the step of executing the encoding.

A decoding apparatus that decodes a code string obtained by executing encoding for converting m-bit data words into n-bit code words, where m and n are both integers and satisfy an expression 2n≧2m×2 and where n-bit code words obtained from a first conversion table in which 2m m-bit data words are associated with 2m n-bit code words selected from 2n n-bit code words or n-bit code words obtained from a second conversion table in which the 2m m-bit data words are associated with 2m n-bit code words that have been selected from the 2n n-bit code words and that do not overlap with the 2m n-bit code words in the first conversion table are sequentially output, the decoding apparatus comprising:

• a first decoding table that is the first conversion table or that is a table in which the 2m m-bit data words are associated with the 2m n-bit code words in the same manner as the first conversion table;
• a second decoding table that is the second conversion table or that is a table in which the 2m m-bit data words are associated with the 2m n-bit code words in the same manner as the second conversion table;
• a decoder configured to search both the first decoding table and the second decoding table for an m-bit data word associated with an n-bit code word that has been input, in order to output the m-bit data word.

A decoding method for decoding a code string obtained by executing encoding for converting m-bit data words into n-bit code words, where m and n are both integers and satisfy an expression 2n≧2m×2 and where n-bit code words obtained from a first conversion table in which 2m m-bit data words are associated with 2m n-bit code words selected from 2n n-bit code words or n-bit code words obtained from a second conversion table in which the 2m m-bit data words are associated with 2m n-bit code words that have been selected from the 2n n-bit code words and that do not overlap with the 2m n-bit code words in the first conversion table are sequentially output, the decoding method comprising the step of:

• searching, for an m-bit data word associated with an n-bit code word that has been input, both a first decoding table that is the first conversion table or that is a table in which the 2m m-bit data words are associated with the 2m n-bit code words in the same manner as the first conversion table and a second decoding table that is the second conversion table or that is a table in which the 2m m-bit data words are associated with the 2m n-bit code words in the same manner as the second conversion table, in order to output the m-bit data word.