This app was mentioned in 2 comments, with an average of 1.00 upvote
Does it have any benefits over this version?
https://play.google.com/store/apps/details?id=phuc.entertainment.dualnbackpremium&hl=en
Not free, but you can get it for free, like many things. You should try it if you haven't already, implement features it has and use it to improve your version.
This one,
https://play.google.com/store/apps/details?id=phuc.entertainment.dualnbackpremium
Is th best and highest quality