An example device for accessing media data includes a memory configured to store media data; and one or more processors implemented in circuitry and configured to: receive a scene description of a GL Transmission Format 2.0 (glTF2) bitstream including a timed media object; determine a position of the timed media object in a presentation environment using the scene description; retrieve current timed media data for the timed media object for a current presentation time; and present the current timed media data according to the position of the timed media object at the current presentation time.