Types of content handled by a track. If the content is not one of
GES_TRACK_TYPE_AUDIO,GES_TRACK_TYPE_VIDEO or GES_TRACK_TYPE_TEXT,
the user of the #GESTrack must set the type to GES_TRACK_TYPE_CUSTOM.
GES_TRACK_TYPE_UNKNOWN is for internal purposes and should not be used
by users
Types of content handled by a track. If the content is not one of
GES_TRACK_TYPE_AUDIO,GES_TRACK_TYPE_VIDEOorGES_TRACK_TYPE_TEXT,the user of the #GESTrack must set the type toGES_TRACK_TYPE_CUSTOM.GES_TRACK_TYPE_UNKNOWNis for internal purposes and should not be used by users