Patent ID: 7024617

Claim:
A data decoding method for converting a first decoded code data sequence resulting from decoding of a signal sequence of non-code information by a maximum likelihood data sequence decoding method, comprising: a first step of providing a data decoding circuit for carrying out the data decoding method; a second step of inputting to said circuit the signal sequence and inputting to said circuit the first decoded code data sequence decoded from said signal sequence by using said maximum likelihood data sequence decoding method, and calculating, based on said signal sequence, likelihood values representing probabilities that error events having preset predetermined code error patterns occur at each code position on said first decoded code data sequence, the likelihood values being calculated for respective codes of the first decoded data sequence in a one-to-one relation; a third step of verifying contents of decoded code values on the first decoded data sequence corresponding to a position of a relevant decoded code, for which each likelihood value is calculated at said second step, and positions before and after the relevant decoded code over a predetermined code length, and adding a predetermined compensation value corresponding to the verified decoded code values to the likelihood value calculated at said second step; a fourth step of comparing each likelihood value compensated at said third step with a predetermined reference value; and a fifth step of inverting code values of a decoded code position of said first decoded code data sequence if the decoded code position corresponds to the preset predetermined code error pattern, based on a result of said fourth step, thereby generating a second decoded code data sequence, and outputting from said circuit the second decoded code data sequence as a resulting decoded code data sequence.