how to merge the mp4 videos using mp4parser which are taken from both front and back camera alternatively

Question

i am developing an app to merge the n number of videos using mp4parser.The videos which are to be merged are taken in both front camera and back camera. if i merge these videos into single , it is merging all videos fine, but the alternative videos which are taken via front camera are merged as inverted. what can i do. please any one help me.

this is my code to merge videos:

try {


String f1,f2,f3;


f1 = Environment.getExternalStorageDirectory() + "/DCIM/testvideo1.mp4";// video took via back camera


f2 = Environment.getExternalStorageDirectory() + "/DCIM/testvideo2.mp4";// video took via front camera


f3 = Environment.getExternalStorageDirectory() + "/DCIM/testvideo3.mp4";// video took via front camera


        Movie[] inMovies = new Movie[] {
          MovieCreator.build(f1),
          MovieCreator.build(f2),
          MovieCreator.build(f3) 
         };
            List<Track> videoTracks = new LinkedList<Track>();
            List<Track> audioTracks = new LinkedList<Track>();
            for (Movie m : inMovies) {
                for (Track t : m.getTracks()) {
                    if (t.getHandler().equals("soun")) {
                        audioTracks.add(t);
                    }
                    if (t.getHandler().equals("vide")) {
                        videoTracks.add(t);
                    }
                }
            }
            Movie result = new Movie();
            if (audioTracks.size() > 0) {
                result.addTrack(new AppendTrack(audioTracks
                        .toArray(new Track[audioTracks.size()])));
            }
            if (videoTracks.size() > 0) {
                result.addTrack(new AppendTrack(videoTracks
                        .toArray(new Track[videoTracks.size()])));
            }
            BasicContainer out =  (BasicContainer) new DefaultMp4Builder().build(result);
            WritableByteChannel fc = new RandomAccessFile(
            String.format(Environment.getExternalStorageDirectory()+ "/DCIM/CombinedVideo.mp4"), "rw").getChannel();
            out.writeContainer(fc);                  
            fc.close();

        } catch (Exception e) {
            Log.d("Rvg", "exeption" + e);
            Toast.makeText(getApplicationContext(), "" + e, Toast.LENGTH_LONG)
                    .show();
        }