Abstract: DVD data is read from an optical disc. Double buffering (230A/230B) is used for outer error correction syndromes, the syndrome for one ECC frame being accumulated in one syndrome buffer (230A), while error correction calculations for preceding data block are performed using a syndrome accumulated previously in another syndrome buffer (230B). The syndrome buffers are used in alternating fashion as further blocks of data are received, while the flow of data to a main buffer (208) is uninterrupted. This reduces buffering requirements in the decoder, and relaxes time constraints on the error correction calculations. A multi-beam implementation is disclosed, providing higher throughput.