HD videomplayer2 is a fork of mplayer and is available in the Software Manager.
The mplayer2 configuration file is now under /home/"USER"/.mplayer and named config. Add:
vo=vdpauMake mplayer your default video player.
Surround soundSwitch in your Sound Preferences from Analog Stereo to Digital Surround 5.1 (HDMI) Output.
Testing your surround channels with a test file (e.g. chain-id.wav) everything sounds right. Using the build-in audio check the channel order is wrong.
I did not open the chain-id.wav with mplayer! If you do so the order is still wrong. Add in addition to the previous entries this to the mplayer config file:
# 5.1 surround soundNow my videos look and sound great again!
# Using correct sound device
# For both AC-3 and DTS passthrough