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MPlayer's comprehensive documentation covers many topics like
output devices, video encoding, repairing broken files etc.
It is auto-generated daily and can be found on the project
homepage in the documentation section:

http://www.mplayerhq.hu/design7/documentation.html
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MPlayer's system-wide configuration dir is

%%PREFIX%%/etc/mplayer

If you want to install configuration files into this location
in order to change mplayer's default settings for all users on
your system, you find some examples in

%%DATADIR%%/examples/etc
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