GNOME Mplayer: "Failed to open VDPAU backend libvdpau_nvidia.so" error

I'm using the proprietary NVIDIA driver and I fixed this by creating a symlink to the VDPAU lib:

ln -s /usr/lib/vdpau/libvdpau_nvidia.so.1 /usr/lib/libvdpau_nvidia.so

This has the benefit of actually enabling VDPAU rather than falling back to XV or X11. Of course you need a video card that supports VDPAU acceleration.

You can suppress all dialogues like this in mplayer variants by editing ~/.mplayer/config in the editor of your choice and somewhere in the file including really-quiet="1". I use plain mplayer (no GUI at all) but that shouldn't change things, this worked for me in GMplayer too. Here's my config:

[default]
vo=vdpau,xv,
vc=ffh264vdpau,ffmpeg12vdpau,

ao=pulse
really-quiet="1"
fs=1
xineramascreen=1
msglevel=all=0
showsubtitles=0

You probably don't want the vo and vc lines (I'm a Nvidia user) and you might not want any of the other settings. If I were you, I would just use this:

[default]
ao=pulse
really-quiet="1"

For Intel VGA, and x64 I have solved it with

sudo apt-get install i965-va-driver
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install libvdpau-va-gl1
cd /usr/lib/x86_64-linux-gnu/vdpau/
sudo ln -s libvdpau_va_gl.so.1 libvdpau_i965.so.1

For Nvidia the package are

sudo apt-get install libvdpau1 vdpau-va-driver