All righty, I have managed to get the latest (and that means the VERY LATEST) version of mplayer to work under Gentoo. Other Linux distros untested, your mileage may vary, and this probably will not run on non x86 machines.
Right.
Under Gentoo, emerge sync or emerge rsync. Non-Gentoo people: this updates the package repository to have the latest files. One of these files is the 'ebuild' that is needed: mplayer-1.0_pre4.ebuild . for the rest of you, you may need an rpm or the source tarball from mplayerhq.hu - I reccomend the source tarball.
Now, gentoo people: go to your portage directory - on my system it's /usr/portage - and probably is on your system unless you tweaked that. now go into the media-video/mplayer dir. That's where the mplayer-1.0_pre4.ebuild file is.
do: emerge -up ./mplayer-1.0_pre4.ebuild
That will tell you what it needs to add. More than likely it will only need to update itself, but if you haven't updated in a while, you might have some other files.
Anyway, it will install itself nicely.
Other distros: Do whatever it is that your distro does to get files onto the system, or (preferably:) untar the source tarball into a temporary directory, and build and install it.
Now, everything is set up, except you are missing the codec. ):
IF you don't have the following programs installed, emerge them: unshield (unarchives installshield archives) cabextract (unarchives microsoft CAB files.)
If you don't run gentoo, these should be available for your distro, or if not, check freshmeat or sourceforge for the source tarballs. Again, I reccomend building from source.
Now you'll need to actually get the codec package,which is located here: http://www.on2.com/downloads/vp6-decoder/
Download this somewhere nice and safe, like a temp directory. (I suggest /var/tmp )
Now use cabextract on it, similarly to this:
cd /var/tmp mkdir vp6thing cd vp6thing cabextract /var/tmp/vp6_vfw_codec.exe
This should give you a subdirectory (Disk1) which contains various setup files. There's another file in there, data1.cab, which contains the files you need. So:
cd Disk1 unshield data1.cab
This will give you a bunch more files. You're interested in the vp6* files, and you want to put them in the directory you have your win32 codecs for mplayer. On the default gentoo setup, these are in /usr/lib/win32 - IF you installed from the ebuild.
If you built from the source tarball - you specified where you wanted these codecs in the /.configure stage. Put them in that directory.
On my system I did:
cp vp6* /usr/lib/win32
And then I executed this commandline (as a normal user, not as root:) mplayer http://nectarine.oulu.fi:8000/ -vo sdl
Which will launch mplayer, stream from the tv source, and