When encoding an array of data elements, or a stream of such arrays, using an encoder comprising encoding circuitry operable to encode the array(s) of data elements as a plurality of independent segments, wherein each independent segment can be decoded independently; a header is generated for output with an encoded data stream including the plurality of independent segments wherein the header contains information indicative of the location of each of the plurality of independent segments within the encoded data stream. When an encoded data stream associated with such a header is to be decoded, a decoder may thus read the header to identify the location of the independent segment within the data stream and then read and decode the identified segments from the identified location(s) in the data stream.