Information recording method, format changing method, and information reproduction method

For recording AV data in accordance with the DVD-VR format on a DVD medium which already has AV data recorded thereon in accordance with the DVD-Video format, it was conventionally necessary to perform logical formatting of the DVD medium. The DVD-Video format and the DVD-VR format are compared regarding the sum of data sizes of a volume structure, a file structure and management information, and an area having a size corresponding to a larger sum is saved on a disc. While a program is being recorded in accordance with the DVD-Video format, VOBU information and real time data information are recorded. During the format change, the volume structure, the file structure and the management information of the DVD-VR format are recorded in the saved area. Navigation data information of each VOBU is rewritten with the real time data information.