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

i developing app merge n number of videos using mp4parser.the videos merged taken in both front camera , camera. if merge these videos single , merging videos fine, alternative videos taken via front camera merged inverted. can do. please 1 me.

this code merge videos:

try {   string f1,f2,f3;   f1 = environment.getexternalstoragedirectory() + "/dcim/testvideo1.mp4";// video took via 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>();             (movie m : inmovies) {                 (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();         }