MPlayer runs on all known BSD flavors. There are ports/pkgsrc/fink/etc versions of MPlayer available that are probably easier to use than our raw sources.
If MPlayer complains about not finding /dev/cdrom or /dev/dvd, create an appropriate symbolic link:
ln -s /dev/your_cdrom_device /dev/cdrom
To use Win32 DLLs with MPlayer you will need to
re-compile the kernel with "option USER_LDT"
(unless you run FreeBSD-CURRENT,
where this is the default).
If your CPU has SSE, recompile your kernel with
"options CPU_ENABLE_SSE" (FreeBSD-STABLE or kernel
patches required).
Due to limitations in different versions of gas (relocation vs MMX), you
will need to compile in two steps: First make sure that the non-native as
is first in your $PATH and do a gmake -k, then
make sure that the native version is used and do gmake.
As of OpenBSD 3.4 the hack above is no longer needed.
See the Mac OS section.