| 摘要 |
PROBLEM TO BE SOLVED: To solve the following problem; conventionally, when reproducing the data recorded on a recording medium by a Viterbi algorithm, a favorable reproducing cannot be maintained if there are non-uniformity of recording mark shapes caused by medium characteristics and non-linear distortion of a reproduced waveform. SOLUTION: Based on a decoded data sequence outputted from a path memory 12, a data estimation circuit 14 outputs an estimated data estimating the input data at a point in time before a predetermined bit period earlier than the input data. A target value calculation circuit 15 corrects a target value adopting a difference between the estimated data and the input data as a target value error, and outputs a plurality of 1st target values obtained to a branch metric operation circuit 11 as a plurality of target values. Since the branch metric operation circuit 11 is able to perform branch metric operation based on the plurality of 1st target values approaching to a plurality of average values with the highest appearance frequency (having a peak in a histogram), the decoding performance can be improved rather than using a fixed target value. COPYRIGHT: (C)2005,JPO&NCIPI
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