Embodiments for video processing, including video coding, video decoding and video transcoding are described. One example method includes performing a conversion between a video having one or more layers having one or more video pictures having one or more subpictures and a bitstream of the video according to a rule, wherein the rule defines network abstraction layer (NAL) units to be extracted from a bitstream during a sub-bitstream extraction process to output a sub-bitstream, wherein the rule further specifies that one or more inputs to the sub-bitstream extraction process include a target output layer set (OLS) index (targetOlsIdx) that identifies an OLS index of a target OLS and is equal to an index to a list of OLSs specified by a video parameter set, and wherein the one or more inputs satisfy a set of conditions.