For a given handler, the primary data may be one of the referenced items when
it is desired that it be stored elsewhere, or divided into extents; or the
primary metadata may be contained in the meta-box (e.g. in an XML box).
Either this box must occur, or there must be a box within the meta-box (e.g.
an XML box) containing the primary information in the format required by the
Fields inherited from class net.sourceforge.jaad.mp4.boxes.FullBox