| 摘要 |
PROBLEM TO BE SOLVED: To solve such a problem that, when data recorded in a recording medium by using viterbi algorithm is reproduced, good reproduction performance cannot be kept in the prior art in the case that unevenness of shapes of recorded marks caused by media characteristics and non-linear distortion of a reproduced waveform are caused. SOLUTION: A data estimating circuit 14 outputs estimation data in which input data at the point of time before the prescribed bit period is estimated rather than input data on the basis of a decoding data system outputted from a path memory 12. A target value arithmetic circuit 15 performs target value correction making the difference between the estimation data and the input data as a target value error, and outputs a plurality of obtained first target values to a branch metric arithmetic circuit 11 as a plurality of target values. Since the branch metric arithmetic circuit 11 can perform a branch metric arithmetic operation on the basis of the plurality of first target values approaching to a plurality of average values having the highest appearance frequency (have a peak in histogram), decoding performance can be improved more than in the case where a fixed target value is used. COPYRIGHT: (C)2005,JPO&NCIPI
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