Abstract: An information recording medium on which a data signal having a variable frequency oscillator (VFO) signal part and a data signal part are recorded, wherein an indicator having a pattern distinguishable from a pattern used in the VFO signal part is included at a predetermined position within the VFO signal part, a method of recording and/or reproducing the information recording medium having the indicator in the VFO signal part, and an apparatus to record and/or reproduce the information recording medium having the indicator in the VFO signal part.

Abstract: A method, medium, and system for identifying a frame number for a data decoding system requiring less frame sync identification data (ID) than frame numbers, including detecting a sync ID of a current frame and/or sync IDs of previous frames from input data, and identifying a current frame number according to whether a number of matching sync IDs in a combination, considering sequence, of a detected sync ID of the current frame and/or sync IDs of previous frames is equal to or greater than a predetermined number. Even when, in a stable state, an error-free current frame sync ID does not exist, or even when sync IDs of frames being compared are not continuously detected, a frame number can be recognized if the number of matching sync IDs, among sync IDs of frames being compared, is equal to or greater than a predetermined number, by using uniqueness of a combination, considering sequence, of the current frame sync ID and sync IDs of previous frames.