Patent ID: 8040769

Claim:
An optical disc reproducing apparatus comprising: a decode processing circuit configured to generate decoded data by decoding encoded data read out from an optical disc such that the decoded data is written into a buffer memory, and to output a write signal to indicate a data rate when the decoded data is written in said buffer memory; a data processing circuit configured to convert the decoded data read out from said buffer memory into output data, and to output a read signal to indicate a data rate when the decoded data is read out from said buffer memory; and an optical disc rotation control circuit configured to control a number of rotations of said optical disc based at least in part on the write signal and the read signal, wherein said optical disc rotation control circuit comprises: a first counter configured to output a first counter value based on the write signal; a second counter configured to output a second counter value based on the read signal; a phase difference data calculating circuit configured to multiply predetermined fixed values with the first counter value and the second counter value, respectively, and to calculate a difference between the multiplication results; an UP-DOWN counter configured to output a third counter value based on a number of cycles of said first counter and a number of cycles of said second counter; a cycle difference data calculating circuit configured to calculate a difference of the number of cycles of said first counter and the number of cycles of said second counter based on the third counter value; and an adding circuit configured to add an output of said phase difference data calculating circuit and an output of said cycle difference data calculating circuit for calculation of a summation, wherein the number of rotations of said optical disc is controlled based at least in part on the summation.