A multi-beam optical disc system is disclosed for recording on DVD or CD
optical discs. Recorded data includes inner and outer error protection
codes applied to data blocks having a predetermined size. Each block
comprises several sectors. Multi-channel read-out provides in parallel a
set of N sub-sequences, without restriction to the block or sub-block
boundaries. Sector ID codes are detected within each channel to identify a
series of sub-blocks forming a part of a data block and, even in the
absence of data from the start of the block, outer error protection
circuitry processes the sub-blocks to accumulate a partial error
protection syndrome for the block. Upon reaching the end of the block, a
syndrome for a next block within the subsequence is accumulated.
