Possible issues with using MPlayer on OpenBSD:

all arches:
  MPlayer might fail due to lack of shared memory, e.g. when using gui
  mode under KDE.  Starting with OpenBSD 3.3, sysctl(8) can modify the
  shared memory parameters. In particular kern.shminfo.shmall might need
  to be raised, e.g. 

  # sysctl kern.shminfo.shmall=32768

  The GUI is deprecated so we stripped it from the build. You can use
  x11/gnome-mplayer instead.

i386:
  win32 codecs were disabled in OpenBSD's build, as the open-source codecs
  are now of decent quality.

arm:
  You may encounter slow video output.  In this case you can disable
  the X.Org screen rotation in /etc/X11/xorg.conf. Depending on the
  video you are playing you may want to pass the -framedrop or the
  -hardframedrop option to mplayer.

  The internal mp3lib (mpg123) is disabled because it relies on the
  FPU. Instead of using mp3lib the mad flavor is enabled by default.
  If you want to use libmad as an audio decoder please pass the
  '-ac mad' option to mplayer.

See the package description for a list of FLAVORs and their meaning.
