A method of processing video data, the method comprising: receiving, by a computing device, a bitstream comprising a stream of Network Abstraction Layer units, the stream of NAL units comprising a plurality of coded slice NAL units, each respective coded slice NAL unit of the plurality of coded slice NAL units encapsulating a respective Raw Byte Sequence Payload (RBSP) for a respective slice segment of a plurality of slice segments of a slice of a picture of the video data, each respective slice segment of the plurality of slice segments of the slice comprising an integer number of Coding Tree Units (CTUs) of the picture, the plurality of slice segments of the slice including an independent slice segment and one or more dependent slice segments, wherein: no values of syntax elements in a slice segment header of the independent slice segment are inferable from values for any preceding slice segment, for each respective dependent slice segment of the one or more dependent slice segments, the respective dependent slice segment has values of one or more syntax elements of a slice segment header of the respective dependent slice segment inferable from values for the independent slice segment, the picture is partitioned into a plurality of tiles, the plurality of tiles including a first tile and a second tile, and the plurality of slice segments of the slice includes one or more slice segments that contain CTUs of the first tile and the plurality of slice segments of the slice includes one or more slice segments that contain CTUs of the second tile; and generating, by the computing device, a file storing the bitstream, wherein generating the file comprises: generating, by the computing device, in the file, a sample-to-group box and a sample group description box, the sample group description box containing a tile region sample entry associated with the sample-to-group box, an entry in the sample-to-group box mapping a sample to the tile region sample entry, the tile region sample entry in the sample group description box defining a tile region, the tile region being a rectangular tile region that comprises an integer number of tiles of the plurality of tiles forming a rectangular region encoded in one or more of the slice segments, the rectangular tile region including the first tile, the rectangular tile region not including the second tile. receiving, by a computing device, a bitstream comprising a stream of Network Abstraction Layer units, the stream of NAL units comprising a plurality of coded slice NAL units, each respective coded slice NAL unit of the plurality of coded slice NAL units encapsulating a respective Raw Byte Sequence Payload (RBSP) for a respective slice segment of a plurality of slice segments of a slice of a picture of the video data, each respective slice segment of the plurality of slice segments of the slice comprising an integer number of Coding Tree Units (CTUs) of the picture, the plurality of slice segments of the slice including an independent slice segment and one or more dependent slice segments, wherein: no values of syntax elements in a slice segment header of the independent slice segment are inferable from values for any preceding slice segment, for each respective dependent slice segment of the one or more dependent slice segments, the respective dependent slice segment has values of one or more syntax elements of a slice segment header of the respective dependent slice segment inferable from values for the independent slice segment, the picture is partitioned into a plurality of tiles, the plurality of tiles including a first tile and a second tile, and the plurality of slice segments of the slice includes one or more slice segments that contain CTUs of the first tile and the plurality of slice segments of the slice includes one or more slice segments that contain CTUs of the second tile; and no values of syntax elements in a slice segment header of the independent slice segment are inferable from values for any preceding slice segment, for each respective dependent slice segment of the one or more dependent slice segments, the respective dependent slice segment has values of one or more syntax elements of a slice segment header of the respective dependent slice segment inferable from values for the independent slice segment, the picture is partitioned into a plurality of tiles, the plurality of tiles including a first tile and a second tile, and the plurality of slice segments of the slice includes one or more slice segments that contain CTUs of the first tile and the plurality of slice segments of the slice includes one or more slice segments that contain CTUs of the second tile; and generating, by the computing device, a file storing the bitstream, wherein generating the file comprises: generating, by the computing device, in the file, a sample-to-group box and a sample group description box, the sample group description box containing a tile region sample entry associated with the sample-to-group box, an entry in the sample-to-group box mapping a sample to the tile region sample entry, the tile region sample entry in the sample group description box defining a tile region, the tile region being a rectangular tile region that comprises an integer number of tiles of the plurality of tiles forming a rectangular region encoded in one or more of the slice segments, the rectangular tile region including the first tile, the rectangular tile region not including the second tile.