A timeline track associated to a region by ID. Normally, each region will
have zero or one timeline track, but not more than one. The track also
contains a list of elements, which are intended to be played one after the
other, taking into account their durations and offsets.
A timeline track associated to a region by ID. Normally, each region will have zero or one timeline track, but not more than one. The track also contains a list of elements, which are intended to be played one after the other, taking into account their durations and offsets.