The X axis value of the position of the mute/unmute button
in a video playback popup.
Using RELATIVE
as the value will make the mute/unmute button placement relative to the
pause/play button.
Child of: <popup>
Parent of: Nothing
See also: <muteunmute_y>,
<pauseplay_x>, <pauseplay_y>
Example:
<muteunmute_x>RELATIVE</muteunmute_x>