How to check if the Sonos Playbar is playing Dolby Digital?

I have paired a Sonos Playbar with Sonos Connect:AMP running a pair of SpeakerCraft AIM8 Three High Ceiling Speakers which are connected via HDMI to my Intel NUC D54250WYK home theatre PC (HTPC).

Using Media Player Classic, Windows 8 Media Player (Windows 8 added native Dolby Support) and XBOX Media Center (XBMC) 5.1 works great.

I have not yet worked out how to play Dolby Digital 5.1 content using VLC player. The Windows sound control panel only shows two channels of audio with Dolby Digital bitstream support and you don't get the speaker configuration wizard which I have seen in the past on some sound cards.

Testing individual speakers was quite difficult using the movies I had available, however the following short VOB video goes through each speaker at a time making testing each channel easy.

http://www.wooferbasstest.com/download/test-tool-ac3-dolby-digital-5-1ch-sound-test

Dolby test video

Another way of testing to make sure that the playbar is receiving the bitstream source is by visiting the support infoweb pages on the playbar. To check this you can connect to the IP address of any Sonos device on the network at the following URL - http://:1400/support/review

Under the Playbar device there is a TOSLINK Status section which will show other Stereo or Dolby Digital 5.1 letting you know the format being played.

Sonos support page showing TOSLINK Status.

Something else I've observed is that if the Playbar is playing bistream audio, the volume controls in Windows no longer have any affect and you need to control the volume from your remote/Sonos desktop controller.

The new beta of XBMC Gotham also supports "upmixing" stereo to the rear spears as well which I'm looking forward to testing next weekend.