ISO IEC 23001-16:2021 pdf download – Information technology — MPEG systems technologies — Part 16: Derived visual tracks in the ISO base media file format. If a referenced track is a member of an alternate group or switch group, or if the reference is to a track group, then the reader should pick a track from the group as the input to the derived visual track. NOTE 2 The TrackSelectionBox can be used to provide guidance on the selection between members of an alternate group or switch group. Similarly, if a referenced image item is a member of an alternate...