A method comprising: encoding a first input picture into a coded constituent picture, wherein the coded constituent picture comprises a base quality encoded representation of an entire field of view of content of the input picture; reconstructing, as a part of said encoding, a decoded constituent picture corresponding to the coded constituent picture; and encoding a spatial region of the first input picture or a second input picture into a coded tile comprising a higher quality encoded representation of at least a part of the field of view of the content of the input picture, the encoding comprising: determining a horizontal offset and a vertical offset indicative of a region-wise anchor position of the spatial region within the decoded constituent picture; encoding the horizontal offset and the vertical offset; determining that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to the region-wise anchor position, wherein the first horizontal coordinate and the first vertical coordinate are horizontal and vertical coordinates, respectively, within the spatial region; indicating that the prediction unit is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset; deriving the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively; determining a motion vector for the prediction unit; and applying the motion vector relative to the prediction-unit anchor position to obtain a prediction block. encoding a first input picture into a coded constituent picture, wherein the coded constituent picture comprises a base quality encoded representation of an entire field of view of content of the input picture; reconstructing, as a part of said encoding, a decoded constituent picture corresponding to the coded constituent picture; and encoding a spatial region of the first input picture or a second input picture into a coded tile comprising a higher quality encoded representation of at least a part of the field of view of the content of the input picture, the encoding comprising: determining a horizontal offset and a vertical offset indicative of a region-wise anchor position of the spatial region within the decoded constituent picture; encoding the horizontal offset and the vertical offset; determining that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to the region-wise anchor position, wherein the first horizontal coordinate and the first vertical coordinate are horizontal and vertical coordinates, respectively, within the spatial region; indicating that the prediction unit is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset; deriving the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively; determining a motion vector for the prediction unit; and applying the motion vector relative to the prediction-unit anchor position to obtain a prediction block. determining a horizontal offset and a vertical offset indicative of a region-wise anchor position of the spatial region within the decoded constituent picture; encoding the horizontal offset and the vertical offset; determining that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to the region-wise anchor position, wherein the first horizontal coordinate and the first vertical coordinate are horizontal and vertical coordinates, respectively, within the spatial region; indicating that the prediction unit is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset; deriving the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively; determining a motion vector for the prediction unit; and applying the motion vector relative to the prediction-unit anchor position to obtain a prediction block.