| 摘要 |
PURPOSE:To improve the reliability of an alternate destined address by adding a CRC only to the alternate destined address data when adding said address data in a data part, and inserting plural number of the added addresses to the data part. CONSTITUTION:Two alternate areas 1, 2 are arranged to the inner and outer circumferences of an optical disk and a user area 3 is arranged at the middle, and an error caused in the user area 3 is processed by using the nearby alternate area 1 or 2 so as to reduce the time of alternate processing. The alternate destined address data 12, 13 are added at two positions in the data part 11. The effectiveness of the alternate destired address is confirmed by using CRCs 14, 15 added thereto. Thus, at the occurrence of alternate processing of an optical disk or a magneto-optical disk having a high error rate, since the alternate processing is applied while checking whether or not the alternate destination is correct, the alternate data is extracted accurately at high speed.
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