US Patent 11778200 Constraints on reference picture information

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 comprising a video picture comprising a slice and a bitstream of the video according to a rule. The rule specifies that a default value of a syntax element specifying a number of entries in a reference picture list syntax structure associated with a reference picture list (RPL) index is equal to 0 due to a condition being satisfied. The condition is satisfied in case (1) the video picture is an instantaneous decoding refresh picture, (2) a first syntax flag specifies that RPL syntax elements are not present in a slice header of the slice, and (3) a second syntax flag specifies that RPL information is not present in a picture header of the video picture.