Hierarchical tiles

A device for decoding a coded video sequence, the device comprising:

• at least one memory configured to store program code;
• and
• at least one processor configured to read the program code and operate as instructed by the program code, the program code including:
• decoding code configured to cause the at least one processor to decode a tile which comprises a first tile boundary defined by a first tile layout and a second tile boundary defined by a second tile layout,
• wherein the coded video sequence indicates that at least one first prediction mechanism is available across the first tile boundary, and that the at least one first prediction mechanism is not available across the second tile boundary,
• wherein the first tile layout divides an image included in the coded video sequence into a plurality of tiles including a first tile and a second tile, and
• wherein the second tile layout divides the first tile into a third tile and a fourth tile, and does not divide the second tile.

A non-transitory computer-readable medium storing instructions, the instructions comprising:

• one or more instructions that, when executed by one or more processors of a device for decoding a coded video sequence, cause the one or more processors to:
• decode a tile which comprises a first tile boundary defined by a first tile layout and a second tile boundary defined by a second tile layout,
• wherein the coded video sequence indicates that at least one first prediction mechanism is available across the first tile boundary, and that the at least one first prediction mechanism is not available across the second tile boundary,
• wherein the first tile layout divides an image included in the coded video sequence into a plurality of tiles including a first tile and a second tile, and
• wherein the second tile layout divides the first tile into a third tile and a fourth tile, and does not divide the second tile.