An example method of video processing includes performing a conversion between a picture of a video that comprises one or more sub-pictures and a bitstream representation of the video. The bitstream representation conforms to a format rule that specifies that information about a sub-picture is included in the bitstream representation based on at least one of: (1) one or more corner positions of the sub-picture, or (2) a dimension of the sub-picture. The format rule further specifies that the information about the sub-picture is positioned after information about a coding tree block in the bitstream representation.