Optical disc apparatus and adip decoder

Abstract

An ADIP decoder for decoding address in pre-groove (ADIP) of a wobble of an optical disc, has: a band pass filter that filters a wobble signal having a period corresponding to the wobble; a wobble PLL circuit that divides a frequency of a phase-locked clock signal in response to an input of the filtered wobble signal, and outputs a locked wobble signal; a timing generating circuit that generates a sampling timing signal based on the clock signal; an analog to digital converter that converts the filtered wobble signal into a digital signal in synchronization with the sampling timing signal; and an ADIP decoding circuit that counts a clock of the locked wobble signal with a counter, holds an address and one of a minimum amplitude value and a maximum amplitude value of the digital signal for each counter period, the address corresponding to a wobble clock count value where the digital signal has one of the minimum amplitude value and the maximum amplitude value, and that decodes the ADIP based on a distribution of the held address.