A media container file (1) is generated by organizing media data (2; 3) defined by a media track (12) in the file (1). Sub-track information (72, 74) identifying media data portions (4, 5; 6, 7, 8) of the media data (2; 3) is organized for each sub-track of multiple sub-tracks defined in the media track (12). At least one of the sub-tracks is assigned selection information (62, 64) defining a selective processing of the media data portion (4, 5; 6, 7, 8) defined by the sub-track in relation to other media data organized in the media container file (1). The media data (2, 3) advantageously relate to layered media or media defining multiple camera views which are organized into sub-tracks (12). The selection information (62, 64) allows selection among tracks (12) and sub-tracks when setting up a media session and switching between tracks (12) and sub-tracks during such a media session.