A method and apparatus are provided for encapsulating a plurality of data substreams encoded in a bit stream, wherein the encoded data substream is obtained by entropy encoding of a symbol subsequence representing an image or a series of images. The method includes grouping data substreams into substream pairs according to an iterative traversal order predetermined from the plurality of substreams, and on the basis of a pair of the substreams, obtaining a symmetrical pair by reversing a data order making up the second substream of the pair. The obtained pairs are then concatenated within a sequence. The binary stream is created by encapsulating the sequence and information related to a number of substreams and related to the sizes of pairs of symmetrical substreams.