[00191] An example embodiment has been described above in relation to slice headers. It needs to be understood that other embodiments apply equally to any other types of headers for picture partitioning units, such as slice segment headers or tile headers. 

[00192] Certain example embodiments have been described above in relation to tiles. It needs to be understood that other embodiments apply equally to any other types of picture partitioning units or spatiotemporal units, such as slices or slice groups. Tiles and slices have been described above to comprise an integer number of entire coding tree units. It needs to be understood that tile and slices may be more fine-grained in their boundaries. For example, tile width and height could be specified in terms of coding units of certain width and height, such as 8x8 coding units. In another example, a slice could be allowed to comprise an integer number of coding unit but not required to have an integer number of entire coding tree units. 

[00193] Certain example embodiments have been described above in relation to tile grids and tile identifiers indicating a tile position in a tile grid. It needs to be understood that other embodiments apply equally to identifier grids described in certain example embodiments and grids of other picture partitioning units (e.g. MCTS grids). Similarly, embodiments apply to any identifiers, from which an assignment of the position within the grid in use can be derived. 

[00194] Embodiments also apply to other types of picture partitioning means than grids. For example, in an embodiment, it may be indicated which adjacent grid cells in raster scan order are merged to form one cell in the identifier assignment. Such merging may be beneficial e.g. to reach shorter tile identifier codewords in slice headers. 

[00195] In the above, where the example embodiments have been described with reference to an encoder, it needs to be understood that the resulting bitstream and the decoder may have corresponding elements in them. For example, as illustrated in Figure 6, at block 60, a decoder may comprise means for receiving a picture, wherein the picture comprises one or more slices. As illustrated in block 62, the decoder may further comprise means for decoding, from a slice header of a slice, tile identifiers indicative of tile positions, the tile identifiers may be used for indicating slice location, for determining an anchor position for a motion vector, and/or for determining an anchor position for obtaining a motion vector candidate. As illustrated in block 64, the decoder may further comprise means for decoding an assignment of tile identifier value to tile positions in a parameter set file. 

[00196] Similarly, as illustrated in Figure 7, at block 70, a decoder may comprise means for receiving a bitstream comprising a coded picture, the coded picture comprising one or more tiles. As illustrated in block 72, the decoder may further include means for receiving an indication of an in-picture-prediction-enabled tile set, wherein the in-picture-prediction- 

