A method or system for supporting dynamic construction of a user selected sub-region (e.g., viewport or region of interest) from other sub-regions of a reference media presentation encodes reference media presentation as component tracks. A streaming decoder receives a streaming media file of the reference media presentation and displays an arbitrarily selected sub-region of the reference media presentation. The streaming media file has a derived track that (i) references one or more of the plurality of component tracks and (ii) specifies a set of operations for constructing media samples based on the media samples of the referenced component tracks. The streaming decoder provides media samples for the selected sub-region by retrieving the referenced component tracks and performing the set of operations specified by the derived track.