Digital adaptive equalizer for different quality signals

An adaptive equalizer for adaptively equalizing discrete sampled data of a first signal and a second signal reproduced from an optical disk, the first and second signals having different signal qualities multiplexed in time basis, wherein the optical disk has a periodically wobbling sector format which includes a first region on which the first signal is recorded and a second region on which the second signal is recorded, said adaptive equalizer comprising:

• a learning portion operable to adaptively equalize each of the multiplexed first and second signals according to a respective signal format of the first and second signals, said learning portion comprising a FIR filter portion operable to equalize the sampled data of each of the first and second signals, and a coefficient calculating portion operable to recursively renew coefficients of said FIR filter portion based on output data of said FIR filter portion,
• wherein said coefficient calculating portion includes a holding portion operable to temporarily hold the renewed coefficients as learned results of at least one of the first and second signals learned by said learning portion, and
• wherein said learning portion is operable to perform adaptive equalization using last learned results temporarily held in said holding portion, and an equalization operation duration of said learning portion is determined in accordance with a formatted data length of each of the first and second signals.