An apparatus includes at least one processor; and at least one non-transitory memory including computer program code; wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform: provide signal information to identify an atlas identifier on a sample of a volumetric media track, or on the volumetric media track in a multi-track container; wherein the signal information allows a file parser to link volumetric media tracks with different atlas identifiers that originate from a volumetric media elementary stream; and wherein the file parser is able to reconstruct the volumetric media elementary stream based on the signal information and data encapsulated in the multi-track container.