| 摘要 |
PROBLEM TO BE SOLVED: To turbo-decode a reproduction signal reproduced from a recording medium. SOLUTION: At the preceding stage of an APP decoder 43 in the PR channel of two APP decoders constituting a turbo-decoder, a logarithmic likelihood arithmetic circuit 42 is placed to calculate the logarithmic likelihood L(y'i|yi ) of a reproduction signal y'i being not-binary information. At a post-stage, a likelihood conversion RLL demodulator 44 and a likelihood conversion RLL modulator 51 which can deal with logarithmic likelihood ratios being not-binary information, are placed before the APP decoder 47 of a fold-in code. Thereby, both RLL demodulation and turbo-decoding are carried out and turbo-decoding with high error correction performance can be used when reproducing channel data ai recorded on a recording medium. Accordingly, a recording density on the recording medium can be improved.
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