| 摘要 |
PROBLEM TO BE SOLVED: To make dealable with even a high density disk and to make keepable the compatibility with a standard disk by using two bits of the most significant bit of second information in a sub-code and the most significant bit of frame information and expressing recording density information and address expansion information. SOLUTION: The recording density information and the address expansion information on the disk recording medium are obtained from detection values of two bits of the most significant bit of the second information and the most significant bit of the frame information in the sub-code read out from the disk recording medium, and the setting processing according to the recording density information and the address detection processing using the address expansion information are performed. For instance, quaternary by these two bits is discriminated, and the setting processing and the address detection processing are performed based on the result detecting whether it is of a first recording density, or is of a second recording density and of an address expansion value zero part, or is of the second density and of an address expansion value (a) part, or is of the second density and of an address expansion value (b) part.
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