Abstract: A method generates a stream of data, wherein the stream comprises a plurality of encoded data blocks. The encoded data blocks comprise a plurality of self-contained blocks including all information for decoding the block and a plurality of blocks including only partial information for decoding. The distance of the self-contained blocks in the stream is varied dependent on the content encoded in the stream. The stream is a main stream, and wherein tuning into the main stream is effected via a secondary stream comprising at least a subset of the data blocks of the main stream encoded at a quality different from a quality of the data blocks of the main stream. The self-contained blocks are inserted at positions in the main stream where differences in the quality of the data encoded in the main stream and in the secondary stream are less detectable.