mplayer: Error opening/initializing the selected video_out (-vo) device

That was indeed the error message that mplayer was presenting me:

Error opening/initializing the selected video_out (-vo) device

Now, I had not chose one. I even deleted my ~/.mplayer folder but nothing, it got stucked there. It's strange, because mplayer should have chosen automatically a video_out device on startup and I swear I never had this problem before on my Debian/testing.

In fact, I had just reinstalled a Debian/testing distribution on Sun xVM VirtualBox on a Solaris Express Community Edition host, because I'm using it as a platform for video transcoding. I'd like to do that on Solaris but I haven't found the time to recompile at least ffmpeg, if not mplayer and all of its dependencies. Blastwave's ffmpeg, indeed, is way too old and I found some bugs that prevented it doing its job. Until then, and thanks to VirtualBox, I'll use Debian/testing instead.

Now, the solution's pretty easy but I'd like to rely on autoprobing... Anyway:

enrico@debian:~$ gmplayer -vo help
MPlayer dev-SVN-r29241Available video output drivers:
xmga Matrox G200/G4x0/G550 overlay in X11 window (using /dev/mga_vid)
mga Matrox G200/G4x0/G550 overlay (/dev/mga_vid)
tdfxfb 3Dfx Banshee/Voodoo3/Voodoo5
s3fb S3 Virge over fbdev
xv X11/Xv
x11 X11 ( XImage/Shm )
xover General X11 driver for overlay capable video output drivers
gl X11 (OpenGL)
gl2 X11 (OpenGL) - multiple textures version
dga DGA ( Direct Graphic Access V2.0 )
sdl SDL YUV/RGB/BGR renderer (SDL v1.1.7+ only!)
ggi General Graphics Interface (GGI) output
fbdev Framebuffer Device
fbdev2 Framebuffer Device
svga SVGAlib
aa AAlib
caca libcaca
dxr3 DXR3/H+ video out
v4l2 V4L2 MPEG Video Decoder Output
directfb Direct Framebuffer Device
dfbmga DirectFB / Matrox G200/G400/G450/G550
xvidix X11 (VIDIX)
cvidix console VIDIX
null Null video output
xvmc XVideo Motion Compensation
mpegpes MPEG-PES to DVB card
yuv4mpeg yuv4mpeg output for mjpegtools
png PNG file
jpeg JPEG file
gif89a animated GIF output
tga Targa output
pnm PPM/PGM/PGMYUV file
md5sum md5sum of each frame

If you're using gmplayer or another mplayer front-end you can probably access some video preferences menu, such as the following, and set your preference there. It will be remembered the next time you launch mplayer.

In my case I'm using VirtualBox 3D Acceleration so I chose gl:

mplayer -vo gl [my-movie]

By the way: KDE 4.2 just got its way into Debian/testing, but I'll tell you another day. Amazing experience! I wish I could use it on Solaris as well.