a) This ONLY applies if you have an NVIDIA card that supports GPU hardware accelerated decoding (VDPAU)
b) You are going to need a video player with VDPAU support, so install gnome-mplayer (or mplayer) and/or vlc
sudo apt-get install gnome-mplayer vlc
c) You will need to install the official NVIDIA drivers for your graphics card:
or from the Ubuntu repositories (synaptic ect.)
d) Install the libvdpau1 and vdpau-va-driver packages:
sudo apt-get install libvdpau1 vdpau-va-driver
e) Set up your player to use the VDPAU support -
In GNOME MPlayer, go to -
Edit>Preferences>Player (tab)>Video Output:
and select vdpau from the drop-down menu.
In VLC, go to
Tools>Preferences>Video
and make sure ther is a tick in Accelerated video output (Overlay)
1080p playback should now be much smoother 