System using timing information contained in data read from reproduction unit controlled by first oscillator to vary frequency of independent system clock signal

摘要

The present invention relates to a digital data processing apparatus for transferring digital data which is output from a disc reproduction section (151) to a buffer memory (18)-equipped host processing section (13) and for making processing. By detecting a shift in frequency of an operation clock on the basis of an output of the disc reproduction section (151) and varying the frequency of the operation clock of the host processing section (13) in accordance with a result of that detection, it is possible to prevent the memory (18) from being placed in an over- or an underflowed state and to perform a normal data reproduction.