A method includes detecting different data patterns in data read from a portion of a non-transitory data storage medium. Bit errors in the different data patterns are then determined. Further, bits in error for a total number of bits in each of the different data patterns are calculated from the determined bit errors in the different data patterns.

A method includes detecting different data patterns in data read from a portion of a non-transitory data storage medium. Bit errors in the different data patterns are then determined. Further, bits in error for a total number of bits in each of the different data patterns are calculated from the determined bit errors in the different data patterns.

An optical disc apparatus is disclosed. The optical disc apparatus includes: a driver configured to rotate an optical disc having a recording surface for data; an optical pick-up configured to emit a light beam to the optical disc rotated by the driver; and at least one processor configured to operate the optical pick-up to focus the light beam emitted from the pick-up unit to perform one of recording and reproducing the data on the recording surface and track curvature of the recording surface within a preset allowable range, and to process the light beam reflected from the recording surface, the at least one the processor further configured to increase the allowable range if it is determined that the focus of the light beam cannot track the curvature of the recording surface in a section of the recording surface.