In a method of decoding data that contains payload data, start codes and stuffing data that prevents emulation of start codes within the data, and correspondingly in a method of encoding data that contains payload data and start codes, data is read or written. Substantially simultaneously with reading or writing the data, the data is checked for the presence of stuffing data which are to be discarded or the need to insert stuffing data as the case may be. In preferred embodiments, one or more state machines are used to track the need to discard/insert stuffing data.