/usr/share/mplayer/skins/Blue/symbolsg.fnt is in mplayer-skin-blue 1.11-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | ;image=file
image=symbols2
;"character"=x,y,width,height
"n"=185,0,9,8 ; no sound symbol
"m"=150,0,9,8 ; mono symbol
"t"=160,0,15,8 ; stereo symbol
"r"=240,0,12,8 ; surround symbol
|