Patent ID: 7042667

Claim:
A method of reading data written on a data-holding medium using a data reader, said data being arranged into a plurality of data items, each including user data and non-user data, said non-user data including one or more synchronisation fields, said method comprising: reading data from said data-holding medium; and detecting at least one synchronisation field by processing said data, said processing including qualifying die detection of said synchronisation field to tolerate one or more errors therein, detection of said synchronisation field (sync) being qualified by determining a sync pattern formed by a part of said sync to be detected, wherein detection of said sync pattern is qualified by determining that said sync pattern must be preceded by a predetermined pattern of data, and enabling sync detection only in response to said predetermined pattern being detected, each data item including first and second codeword pairs forming two user data items, and a forward sync field positioned before said first codeword pair, a resync field positioned between said first and second codeword pairs, and a back sync field positioned after said second codeword pair, and detection of one of said forward sync fields or one of said back sync fields being qualified by determining that the forward or backward synchronization field must be preceded by a predetermined pattern of data.