Abstract: A recording and reproducing device including a Viterbi decoder which improves address reading rate but has some amount of delay in decoding process, starts ALPC (Automatic Laser Power Control) operation by opening a write gate at the record start position of a sector, re-appraises recording suitability for the sector in question when the result of reading the last address of the sector comes out during the ALPC area, and terminates ALPC operation by closing the write gate at any point by the start of data recording area of the sector when the sector is not suitable for recording so as not to perform recording operation subsequently.

Abstract: A two-layer optical disk has a first layer of a disk shaped recording medium for storing data and a second layer of a disk shaped recording medium placed over the first layer for storing data. Data blocks A, B, C are stored in the first layer in said order. Similarly, data blocks X, Y, Z are stored in the second layer in said order. When reading the data from the two-layer optical disk, the data blocks are read in the order of A, X, B, Y, C, Z.

Abstract: An optical disk is provided which includes a rewritable first recording area and a read-only second recording area. The first recording area includes groove tracks and land tracks divided into first sectors. Each first sector has a header region with identification data and a data region for recording user data. The second recording area includes tracks formed with physical bit rows, the tracks being divided into second sectors. Each second sector includes a header region and a data region having read-only data recorded as the bit rows. The header regions in the first sectors include pits the width of groove tracks and wobbled from a center line of the groove track. The header regions in the second sectors include pits having a width smaller than the groove tracks and formed along the center line of a track.

Abstract: A two-layer optical disk has a first layer of a disk shaped recording medium for storing data and a second layer of a disk shaped recording medium placed over the first layer for storing data. Data blocks A, B, C are stored in the first layer in said order. Similarly, data blocks X, Y, Z are stored in the second layer in said order. When reading the data from the two-layer optical disk, the data blocks are read in the order of A, X, B, Y, C, Z.

Abstract: A data detection apparatus retrieved binary data modulated in conformity with the (d, k) constraint from an analog signal includes a timing extracting unit for generating a timing signal representing the timing at which the analog signal crosses the threshold value, a clock generating unit for generating a clock signal having a cycle corresponding to one bit of the binary data from the timing signal, a timing position detector for detecting the position in the cycle of the timing, and an error correcting unit for correcting an error in the binary data in accordance with the detected position.