Method and apparatus for error processing in optical disk memories

The present invention more efficiently retrieves and processes data stored on an optical disk in a DVD-ROM format. Generally, the retrieval and processing of data includes inner and outer code error correction for a Reed-Solomon product like code and an error detection process for evaluating an extent of errors in a sector of data. For this device, the sector of is encoded within a plurality of inner codes and parts of plural sectors encoded within each outer code. The device calculates an initial and an intermediate error detection values for data within the sector. The target for the error detection value is non-zero because the data within the sector are scrambled. If there is a match between the initial or intermediate error detection value, the sector can be presumed to be free of errors. Decisions as to whether error correction operations are to be made or how error correction operations are to be performed are then made on the basis of the knowledge that some or all of the sectors within a block of DVD-ROM are free of errors.