METHOD AND APPARATUS FOR ENCODING INFORMATION SYMBOL, AND METHOD AND APPARATUS FOR DECODING INFORMATION SYMBOL

PROBLEM TO BE SOLVED: To prevent data inserted in the form of an electronic watermark, from being wrongly detected. SOLUTION: The encoding method includes: a first parity adding step of dividing a plurality of information symbols into a plurality of groups and adding a parity to each of the groups; and an error-correcting codeword generating step of generating an error-correcting codeword including the plurality of information symbols on the basis of the plurality of information symbols. A predetermined number of frequency components each representing an information symbol, has a non-zero amplitude and are disposed on the same circle in a two-dimensional frequency space. Each parity is represented as a pair of a frequency component having a zero-amplitude and a frequency component having a non-zero amplitude, which is disposed on the same circle in the two-dimensional frequency space. Each check symbol included in the error-correcting codeword is represented as a pair of a frequency component having a zero-amplitude, and a frequency component having a non-zero amplitude, and the pair is disposed on the same circle in the two-dimensional frequency space. COPYRIGHT: (C)2011,JPO&INPIT