Abstract: The present invention provides a method and an apparatus to accurately and consistently distinguish blank sectors from written sectors on optical media despite drive and media variations. A readback envelope threshold is established each time optical media is mounted into an optical drive. In one embodiment, the gain of readback amplifiers are set to a first level, the optical head seeks to and reads a sector or set of sectors on the optical disk known to have information recorded thereon and a first readback envelope generated. The gain of the readback preamplifier is then set to a second level, the optical head seeks to and reads another sector or set of sectors known to have information recorded thereon and a second readback envelope generated. The readback threshold is calculated from the amplitudes of the first and second envelopes.

Abstract: The present invention provides a method and an apparatus to accurately and consistently distinguish blank sectors from written sectors on optical media despite drive and media variations. A readback envelope threshold is established each time optical media is mounted into an optical drive. In one embodiment, the gain of readback amplifiers are set to a first level, the optical head seeks to and reads a sector or set of sectors on the optical disk known to have information recorded thereon and a first readback envelope generated. The gain off the readback preamplifier is then set to a second level, the optical head seeks to and reads another sector or set of sectors known to have information recorded thereon and a second readback envelope generated. The readback threshold is calculated from the amplitudes of the first and second envelopes.

Abstract: The present invention locates spare sectors for replacing secondary defects found during disk use. A sorted defective sector list is maintained for tracking the spare sectors that have been previously used for replacements of other secondary defects. When a secondary defect address is found, a secondary defect list is updated both on the disk and in the drive's memory. A spare sector, for replacing the secondary defect is located by first calculating a group number to determine which group the secondary defect is located in. Next, the boundaries for a plurality of spare sectors allocated for that group is determined. After searching the replacement sector list, the first available spare sector of the plurality of spare sectors is identified as the replacement sector. If all of the plurality of spare sectors have been previously assigned as replacement sectors, a spare sector is instead located from a plurality of spare sectors allocated to a neighboring group.

Abstract: An optical disk has four copies or sets of its control data structures. The control data structure includes a disk definition structure DDS, a primary defect list PDL, and a secondary defect list SDL. Procedures are described for checking to whether or not all copies of the data structures have congruence. If not, all the tables are then made congruent and re-recorded on a disk. In the procedure, the copy having the greatest number of entries is first examined for determining whether or not congruence is possible. If congruence is not possible from the longest copy, then the next longest copy is used.