VITERBI DECODER AND VITERBI DECODING METHOD

摘要

PROBLEM TO BE SOLVED: To solve a problem of a conventional Viterbi decoder that it cannot maintain excellent recording performance on the occurrence of unarranged shapes of recording marks due to a medium characteristic and nonlinear distortion in a reproduced waveform when data recorded on a recording medium are reproduced by using a Viterbi algorithm. SOLUTION: A data estimate circuit 14 outputs estimated data resulting from estimating input data at a point of time before a prescribed bit period from present input data on the basis of a decoded data sequence outputted from a path memory 12. An object value arithmetic circuit 15 corrects the object value by using a difference between the estimated data and the present input data for an object error and outputs 1st object values that are obtained to a branch metric arithmetic circuit 11 as a plurality of object values. Since the branch metric arithmetic circuit 11 can execute the branch metric arithmetic operation on the basis of a plurality of the 1st object values close to a plurality of mean values with the highest incidence frequency (a peak in a histogram), the decoding performance can be enhanced more than the use of a fixed object value.