for protecting the recording from shifting in the position , by conducting sync detection , correctly , from land pre pits , in an optical type recording disc , even if sync pattern errors , in more detail , synchronization is conducted on a recording circuit , with certainty , even if an even sync pattern erroneously changes into an odd sync pattern . when the even sync pattern is detected from an odd sync pattern detection window , a sync lock flag is turned into a condition of unlock . when the sync lock flag continues a lock condition for 16 sectors , the synchronization is carried out on a detection cycle counter and a recording cycle counter .