Patent ID: 7813256
Filing Date: 2010-10-12
Classification: G11B

Abstract:
1. An optical disc playing apparatus for playing a read-only optical disc in which recording is made in units of a cluster including a row of recording-information bits and an error-correcting code, lands and pits are formed contiguously to each other along a recording track and the sequence of lands and pits complies with a predetermined variable-length modulation rule, a specific one of the clusters having a disc-unique identifier additionally recorded thereon after having a land/pit pattern formed therein by modulating an arbitrary row of information bits and error-correcting code for the information bit row, the specific cluster having set therein two continuous areas, first and second, for each bit in the identifier, each of the continuous areas having additionally formed therein lands (specific lands) in positions where the entire bit row complies with the variable-length modulation rule even if the lands are replaced with pits by transition of them to the pits correspondingly to the values of corresponding bits in the identifier, and in case the number of the specific lands transited to the pits is larger in the first one of the continuous areas, the bit value of a corresponding identifier being zero (0), while in case the number of the specific lands transited to the pits is larger in the second continuous area, the bit value is one (1), the apparatus comprising: a demodulating means for demodulating the bit row read from the optical disc with the variable-length modulation technique; an error-correcting means for making error correction of the bit row demodulated by the demodulating means; and an identifier detecting means for detecting the identifier in the cluster having the identifier additionally recorded thereon, the identifier detecting means making a comparison in number of errors between the first and second continuous areas to determine each bit value of the identifier.