Examples of video encoding methods and apparatus and video decoding methods and apparatus are described. An example method of video processing includes performing a conversion between a video and a bitstream of the video according to a rule. At least one of the one or more parameter sets of the bitstream includes a general syntax structure including timing and hypothetical reference decoder (HRD) parameters. The rule specifies that a first syntax flag is not included in the general syntax structure in response to (1) a second syntax flag specifying that network abstraction layer (NAL) HRD parameters are not present in the general syntax structure, and (2) a third syntax flag specifying that video coding layer (VCL) HRD parameters are not present in the general syntax structure, where the first syntax flag specifies that same picture-level timing information applies to all output layer sets in the bitstream.