         return (videoComposition, mix)
     }
     
-    func getTransitionInstuctions(srcTrack:AVMutableCompositionTrack, dstTrack:AVMutableCompositionTrack, range:CMTimeRange, transition:VideoTransition)->[AVMutableVideoCompositionLayerInstruction]
+    private func getTransitionInstuctions(srcTrack:AVMutableCompositionTrack, dstTrack:AVMutableCompositionTrack, range:CMTimeRange, transition:VideoTransition)->[AVMutableVideoCompositionLayerInstruction]
     {
         switch transition
         {


class MovieEditor
{
    var asset:AVAsset!
    var insertClips:[CMTimeRange]!
    
    private var assetComposition:AVMutableComposition!
    private var transitionClips:[CMTimeRange]!

    }
    
    //MARK: push transition effect
    private func push(srcTrack:AVMutableCompositionTrack, dstTrack:AVMutableCompositionTrack, range:CMTimeRange, direction:VideoTransitionDirection)->[AVMutableVideoCompositionLayerInstruction]
    {
        let size = srcTrack.naturalSize
        let center = CGAffineTransform.identity
