42. An apparatus according to any of Claims 37 to 4 1 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: decode the one or more tiles according to 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. 43. A computer program product comprises at least one non-transitory computer- readable storage medium having computer executable program code instructions stored therein, the computer executable program code instructions comprising program code instructions configured, upon execution, to: receiving a coded picture comprising one or more slices; decoding, from 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 decoding slice data of the slice into a decoded picture starting from one or more tile positions for one or more tiles in the slice. 44. A computer program product according to Claim 43 wherein the computer executable program code instructions further comprise program code instructions configured, upon execution, to: decoding, from 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. 45. A computer program product any of Claims 43 to 44 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. 46. A computer program product according to any of Claims 43 to 45 wherein the computer executable program code instructions further comprise program code instructions configured, upon execution, to: decoding 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