Digital Surround 5.1 via S/PDIF is only possible after *disabling* digital output

How to reproduce:
1. $ gnome-control-center sound
2. Go to Hardware tab.
3. Set Internal Audio profile to "Digital Stereo (IEC958) Output" (digital surround output is *not* available)
4. $ vlc --spdif http://www.lynnepublishing.com/surround/www_lynnemusic_com_surround_test.ac3

At this point, vlc outputs only stereo. Other applications such as Youtube videos in Firefox can also output stereo.

5. Set Internal Audio profile to "Analog Stereo Output".
6 $ vlc --spdif http://www.lynnepublishing.com/surround/www_lynnemusic_com_surround_test.ac3

This time, vlc outputs 5.1 surround sound (shown as DTS on my receiver). But now, there's no sound from the Test Speakers applet, Firefox or (it seems) any other applications which use PulseAudio.

So if you want to watch DVDs with 5.1 surround sound and YouTube videos, you'll have to change the audio settings when going from one to the other.

Hardware:
$ sudo lshw
*-multimedia
     description: Audio device
     product: ATI Technologies Inc
     vendor: ATI Technologies Inc
     physical id: 0.1
     bus info: pci@0000:03:00.1
     version: 00
     width: 64 bits
     clock: 33MHz
     capabilities: pm pciexpress msi bus_master cap_list
     configuration: driver=HDA Intel latency=0
     resources: irq:77 memory:fbcfc000-fbcfffff
*-multimedia
     description: Audio device
     product: 82801JI (ICH10 Family) HD Audio Controller
     vendor: Intel Corporation
     physical id: 1b
     bus info: pci@0000:00:1b.0
     version: 00
     width: 64 bits
     clock: 33MHz
     capabilities: pm msi pciexpress bus_master cap_list
     configuration: driver=HDA Intel latency=0
     resources: irq:76 memory:fb9f8000-fb9fbfff

$ mintwelcome
Release: 12 (lisa)
Edition: Gnome 64-bit