OPTICAL DISC AUTHENTICATION USING ALTERNATE DATA MODULATION ENCODING SCHEMES

摘要

Apparatus and method for writing data to an optical disc (112), and subsequently reading the data therefrom. An encoder (126) usesa first modulation encoding scheme (MES1) to encode input data (128) as data symbols having nominal symbol lengths over a first range. The encoder further uses a second modulation encoding scheme (MES2) different from the MES1 to encode input data as data symbols having nominal symbol lengths over a second range coexistent with the first range. The MES1 is used to encode primary data written to the disc while the MES2 is used to encode secondary data (138) inserted at selected locations for disc authentication purposes. A readback system (160) includes a primary decoder (164) which decodes and outputs the primary data, and a secondary decoder(172) which searches for a leading synchronization pattern which, when detected, allows remaining portions of the secondary data to be decoded.