In the same or another embodiment, when a subpicture is independently encoded without any reference to another subpicture, the value of subpicture identifier of a region may be changed within a coded video sequence.
The samples are processed in units of CTBs. The array size for each luma CTB in both width and height is CtbSizeY in units of samples. The width and height of the array for each chroma CTB are CtbWidthC and CtbHeightC, respectively, in units of samples. Each CTB is assigned a partition signalling to identify the block sizes for intra or inter prediction and for transform coding. The partitioning is a recursive quadtree partitioning. The root of the quadtree is associated with the CTB. The quadtree is split until a leaf is reached, which is referred to as the quadtree leaf. When the component width is not an integer number of the CTB size, the CTBs at the right component boundary are incomplete. When the component height is not an integer multiple of the CTB size, the CTBs at the bottom component boundary are incomplete.