Belive you, I choose U, than 2, reboot, tested and the sound is there. Anyway, is not posible to make a button in the screen, how it is for open the flash light on the video-screen to use to mute/unmute the sound? I think is more practical with that button instead to run N9QTweak and to reboot the phone just for a mute/unmute on a video. Another variant is to make the button with +/- volume not only with mute/unmute, something similar with what you did it already for zoom. If you try and succeed will be extraordinary!