CD: Correction of physical position information during reading In a recording medium having a large influence of mechanical elements such as thermal expansion, distortion, eccentricity and vibration Since it is impossible to move the header to the correct position with a single shot, After moving to the position it is estimated that you will wait for the target position to be encountered while leading. Then, for specifying the position, the Q channel of the subcode, that is, the physical position information It is inferred that it will be obtained in advance. Therefore, the physical position information during reading is 2 to 3 sectors It is considered to precede.