             }
         }
         
-        // update
+        // update   jump frame
         if (index != frameIndex && !miss) || (index == frameIndex && miss) {
             time = nextTime
             frameIndex = index

    public func moveToFrameAtIndex(index: Int) {
        frameIndex = index % frameCount
        self.time = durations[0...frameIndex].reduce(0) { $0 + $1 }
        miss = false
    }
    
    public func moveToTime(var time: NSTimeInterval) {

        }
        self.frameIndex = index
        self.time = time
        miss = true
    }

}
