Embodiments of the present disclosure provide a solution for video processing. A method for video processing is proposed. The method comprises: performing a conversion between a bitstream of a video and a media file of the video, wherein a first data structure in the media file comprises a first indication and at least one second data structure describing a preselection in the media file, and the first indication is signaled before the set of second data structures and specifies the number of non-alternative tracks grouped by a preselection track group for the preselection.