US Patent 11765393 Syntax for signaling video subpictures

Methods, devices and systems for signaling the use of subpictures in coded video pictures are described. One example method of video processing includes performing a conversion between a video and a bitstream of a video, wherein the bitstream conforms to a format rule, wherein the format rule specifies that a first syntax element signaled in a sequence parameter set (SPS) of the bitstream is indicative of a length of identifiers of subpictures in the SPS, and wherein the signaling of the first syntax element is independent of a value of a second syntax element that is indicative of explicit signaling of the identifiers of the subpictures in the SPS or a picture parameter set (PPS).