computer program code configured to  with the at least one processor  cause the apparatus at least to: receive a picture; encode the picture as one or more slices; encode  into a slice header of a slice of the one or more slices  one or more tile identifiers indicative of one or more tile positions for one or more tiles in the slice; and encode one or more assignments of one or more tile identifier values for the one or more tile identifiers indicative of tile positions in a parameter set file. 7. An apparatus according to Claim 6  wherein the at least one memory and the computer program code are further configured to  with the at least one processor  cause the apparatus at least to: encode  into the slice header  a block index relative to a tile of the one or more tiles  wherein the block index comprises a syntax element indicative of a block position for a block within the tile. 8. An apparatus according to Claim 7 wherein one tile identifier of the one or more tile identifiers is indicative of a tile that comprises a pre-defined block of the slice. 9. An apparatus according to any of Claims 6 to 8  wherein the at least one memory and the computer program code are further configured to  with the at least one processor  cause the apparatus at least to: construct one or more motion vectors associated with one or more prediction units in one or more coding units in the one or more tiles  wherein the one or more motion vectors apply in one or more anchor locations derived from one or more anchor location identifiers defining a position relative to the one or more tiles indicated by the one or more tile identifiers. 10. An apparatus according to any of Claims 6 to 9  wherein the at least one memory and the computer program code are further configured to  with the at least one processor  cause the apparatus at least to: construct a decoding order constraint file associated with the picture  wherein the decoding order constraint file includes a reorder indication indicating whether the one or more tiles are able to be reordered without affecting decodability for the one or more tiles.