OpenSolaris comes with several basic multimedia players, however they miss important codecs, so after installation you can't really use OpenSolaris to play many types of videos (avi, mpeg, wmv, rm, etc.). Until recently you could get multimedia packages from lifewithsolaris.jp, but the site doesn't provide these packages anymore. The other solution that exists is to use Fluendo codecs (the mp3 codec is available for free but video codes are not free) which provide decoding functionality for media players distributed with OpenSolaris. For more details see this blog entry.
For those who prefer a free solution for playing video and audio files, this blog provides instructions on how to build and install MPlayer on OpenSolaris 2008.11. In case you don't know MPlayer, it's a great open source multimedia player that can play basically any video or audio files.
\* First of all, you need the source code. Get it from here. Unzip the source in your home directory and switch to the MPlayer directory: cd MPlayer-1.0rc2
\* Install GCC and gmake by running: pfexec pkg install SUNWgcc SUNWgmake
\* Replace the configure script with an updated script (two small changes were necessary for OpenSolaris - the original configure script won't work). The new configure script can be downloaded from here.
\* Run configure: ./configure --prefix=/opt/mplayer
\* Run gmake: gmake
\* Run install (as root): gmake install
Supposing everything went well (it should), mplayer is now available and can be ran from /opt/mplayer/bin/mplayer [video_file].
You can right click on video files and define associations to provide an easy playback for different video types. It may be also useful to add MPlayer to your PATH using the .profile script in your home directory. It is also possible to compile MPlayer with a GUI, but I prefer the command line version, so these steps just describe the non-GUI version. In case of the GUI version you need to get various additional header files from the IPS repository, otherwise MPlayer won't build.