Patent ID: 7012873

Claim:
A reproducing method comprising: reproducing a corded pre-pit area recorded beforehand on an optical disk via a first reproducing circuit; and reproducing recorded recording data written on the optical disk based on the recorded pre-pit data via a second reproducing circuit, said reproducing recorded recording data including decoding the recorded recording data via a PRML decoder, said PRML decoder including: an equalizer; an ML decoder; an RILL demodulator; and a PILL circuit, said equalizer being a linear equalizer which is formed of an FIR filter (transversal filter) and which performs an equalizing process for a waveform (reproduced waveform) of a reproduction signal into a waveform of PR( 1 , 1 ) characteristic, said ML decoder being a Viterbi decoder which decodes an equalized waveform from the equalizer, detects the equalized waveform as binary data, and outputs the binary data to the RILL demodulator, said RILL demodulator demodulating decoded binary data from the ML decoder based on an RILL code, and said PILL circuit generating a channel clock based on a signal from the equalizer such that the channel clock is recovered by converting a difference between an amplitude of a PR equalized waveform and an ideal amplitude value into a phase difference.