libavcodec : If you want to use this DivX3/DivX4/DivX5/MP42/etc codec, check the 2.2.1.2 section before compiling. Features :
 
you can gain DivX/DivX4/DivX5/MP42 playing on non-x86 machines  
RealVideo 1.0/VIVO/MJPEG/h263/others playing and encoding  
this codec has the greatest decoding speed for DivX and DivX4/DivX5 movies (even faster than the original DivX4 library itself) ! Recommended!  
Win32 codecs : If you plan to use MPlayer on x86 architecture, you will possibly need them. Download and unzip w32codecs.zip to /usr/lib/win32 BEFORE compiling MPlayer, otherwise no Win32 support will be compiled!
Note: the avifile project has similar codecs package, but it differs from ours, so if you want to use all supported codecs, then use our package! However, you can use our codecs package with avifile. Features:
 
you need this if you want to play or encode for example movies recorded with various hardware compressors, like tuner cards, digital cameras (example: DV, ATI VCR, MJPEG)  
needed if you want to play WMV movies or older (MP42) ASF's  
DivX4/DivX5 : information about this codec is available in the 2.2.1.1 section. If you don't want to encode with it, you possibly don't want this codec as libavcodec (see above) is much faster than this.
Features :
1 pass or 2 pass encoding with MEncoder  
can play old DivX3 movies much faster than the Win32 DLL but slower than libavcodec !  
it's closed-source, and only an x86 version is available.  
XviD : Opensource encoding alternative to Divx4Linux
Features :
1 pass or 2 pass encoding with MEncoder  
it's open-source, so not only an x86 version is available.  
it's about 2 times faster than divx4 when encoding - about the same quality  
The XAnim codecs are the best (full screen, hardware YUV zoom) for decoding 3ivx and Indeo 3/4/5 movies, and some old formats. And they are multiplatform, so this is the only way to play Indeo on non-x86 platforms (well, apart from using XAnim. But for example Cinepak movies are best played with MPlayer's own Cinepak decoder !  
For Ogg Vorbis audio decoding you need to install libvorbis properly. Use deb/rpm packages if available, or compile from source (this is a nightly updated tarball of vorbis CVS).  

 
##
## Use GUI mode by default
##
 
gui = no
 

##
## MPlayer config file
##
## This file can be copied to /etc/mplayer.conf and/or ~/.mplayer/config .
## If both exist, the ~/.mplayer/config's settings override the
## /etc/mplayer.conf ones. And, of course command line overrides all.
## The options are the same as in the command line, but they can be specified
## more flexibly here. See below.
##
 
vo=xv   # To specify default video driver (see -vo help for
   # list)
 
ao=oss   # To specify default audio driver (see -ao help for
   # list)
 
fs=no   # Enlarges movie window to your desktop's size.
   # Used by drivers: all
 
# fsmode=0  # This option workarounds some problems when using
   # specific windowmanagers and fullscreen mode. If you
   # experience fullscreen problems, try changing this
   # value between 0 and 7. Hint: either 0 or 1 should
   # be sufficient.
   # 0 = new method (since 0.18pre3)
   # 1 = ICCCWM patch (for KDE2/icewm)
   # 2 = old method (0.17a)
   # 3 = ICCCWM patch + Motif method
 
# vm=no   # Tries to change to a different videomode
   # Used by drivers: dga2, x11, sdl
 
# bpp=0   # Force changing display depth.
   # Valid settings are: 0, 15, 16, 24, 32
   # may need 'vm=yes' too.
   # Used by drivers: fbdev, dga2, svga
 
# zoom=no  # Enable software scaling (powerful CPU needed)
   # Used by drivers: svga, aalib
 
double=yes  # use double-buffering (recommended for xv with
   # SUB/OSD usage)
 
# x=800   # scale movie to <x> pixels width
# y=600   # scale movie to <y> pixels height
 
##
## Use GUI mode by default
##
 
gui = yes
 
##
## Specify your preferred default skin here
## (skins are searched in /usr/local/share/mplayer/Skin/yourskin
##  and ~/.mplayer/Skin/yourskin)
##
 
skin = proton
##
## Multiple languages are available
##
## Hungarian igen nem
## English yes no
## German ja nein
## Spanish si no
## Binary 1 0
 
## French oui non
##
## You can also use spaces and/or tabs.
##
 
# sound  = 1
# nosound = nein
# mixer  = /dev/mixer
# master = no  # no : set PCM volume   yes : set MASTER volume
 
##
## resample the fonts' alphamap
## 0 plain white fonts
## 0.75 very narrow black outline (default)
## 1 narrow black outline
## 10 bold black outline
##
 
# ffactor = 0.75
 
##
## FBdev driver: specify your monitor's timings, so resolutions
## can be autodetected.
## (see for example /etc/X11/XF86Config for timings!)
## ** CAUTION! IF YOUR DISPLAY DOESN'T SUPPORT AUTOMATICALLY TURNING OFF WHEN
##    OVERDRIVED (AND EVEN IF IT DOES), THIS MAY CAUSE DAMAGE TO YOUR DISPLAY!
##    WE AREN'T RESPONSIBLE, IT'S YOUR DECISION! **
##
## k, K : means multiply by 1000
## m, M : means multiply by 1.000.000
##
 
# fb = /dev/fb0    # framebuffer device to use
# fbmode = 640x480-120   # use this mode (read from fb.modes!)
# fbmodeconfig = /etc/fb.modes  # the fb.modes file
# monitor_hfreq = 31.5k-50k,70k  # horizontal frequency range
# monitor_vfreq = 50-90   # vertical frequency range
# monitor_dotclock = 30M-300M  # dotclock (or pixelclock) range
 
##
## SDL driver
##
 
# vo = sdl:aalib # use SDL video driver by default
   # use "vo = sdl:aalib" or "vo sdl:dga" and so on,
   # for specifying SDL subdrivers
# ao = sdl:esd  # use SDL audio driver by default
   # use "ao = sdl:esd" to use SDL's ESD driver
# noxv = no  # whether to use XVideo hardware acceleration or not
# forcexv = yes  # force XVideo even if not detected
 
 
# nodshow  # disable usage of DirectShow video codecs
 
 
##
## Other (preferred to be default from configfile) switches
##
 
framedrop  = yes # drop frames, when not in sync (slow CPU, videocard,
   # etc)
 
# vfm  = 5 # use libavcodec video codec family (you know,
   # opensource DivX for example.. So preferred default on
   # non-x86 boxes)
 
##
## You can also include other configfiles
## Specify full path!
##
## Delete this default
##
 
# include =  
# /home/gabucino/.mplayer/i_did_not_RTFM_carefully_enough...

Tu as alors un dossier plastic, que tu dois renommer en default pour mplayer utilise ce skin.