here is how to use this app many of newbie don't understand live focus!!

open camera app and start video rec. and now tap screen(anywhere if it is not full screen) >now on the top left corner (yes the status bar where the battery indicator etc. is shown) tap there and you will see a new menu or you may call icon(this is live focus icon) tap the icon and here you will see all functions of live focus(touch arrow button for more functions)