Patent ID: 6487155
Filing Date: 2002-11-26
Classification: G11B

Abstract:
A method for writing data to an optical disc in which input data are encoded to provide a corresponding series of data symbols having nominal symbol lengths, the method comprising steps of:(a) defining a first modulation encoding scheme for the encoding of input data as data symbols having nominal symbol lengths over a first range of symbol lengths; (b) defining a second modulation encoding scheme different from the first modulation encoding scheme for the encoding of input data as data symbols having nominal symbol lengths over a second range of symbol lengths so that, for a given set of input data, the second modulation encoding scheme provides a different set of data symbols as compared to the first modulation encoding scheme, wherein each symbol length of the second range of symbol lengths appears in the first range of symbol lengths; (c) using the first modulation encoding scheme to encode and write primary data to the optical disc, the primary data having an informational content used by a user of the optical disc; and (d) using the second modulation encoding scheme to encode and write secondary data to the optical disc at a location adjacent a portion of the primary data, the secondary data having an informational content used to authenticate the optical disc as an authorized copy, wherein the secondary data include a leading synchronization pattern which, when detected, allows remaining portions of the secondary data to be decoded using the second modulation encoding scheme.