def closest_point(time)
      segment = segments.select { |s| s.contains_time?(time) }
      segment.first
    end
def closest_point(time)
      segment = segments.select { |s| s.contains_time?(time) }
      segment.first
    end
Finds the closest point (to "time") within this track.  Useful for
 correlating things like pictures, video, and other events, if you are
 working with a timestamp.