An embodiment method includes: performing balancing processing on a data stream that includes a plurality of sub-data stream segments, and performing segment de-interleaving on a data stream obtained after the balancing processing. The method further includes separately performing forward error correction (FEC) decoding on each sub-data stream segment in a data stream obtained after the segment de-interleaving. The method further includes performing, according to a balancing termination state of each sub-data stream segment obtained after previous balancing processing, balancing processing on each sub-data stream segment obtained after the FEC decoding, and performing FEC decoding on the data stream obtained after balancing processing is performed on each sub-data stream segment. When it is determined that a preset iteration termination condition is met, the method includes outputting the data stream obtained after the FEC decoding.