Can't configure 5.1 audio with 12.04

I have an Intel ALC892 and a Nvidia GT 520m connected to speakers via HDMI.

On lspci, I see

00:1b.0 Audio device: Intel Corporation N10/ICH 7 Family High Definition Audio Controller (rev 02)
    Subsystem: ZOTAC International (MCO) Ltd. Device a218
    Flags: bus master, fast devsel, latency 0, IRQ 47
    Memory at db400000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: [50] Power Management version 2
    Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+
    Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
    Capabilities: [100] Virtual Channel


02:00.1 Audio device: NVIDIA Corporation HDMI Audio stub (rev a1)
    Subsystem: ZOTAC International (MCO) Ltd. Device 2180
    Flags: bus master, fast devsel, latency 0, IRQ 18
    Memory at db080000 (32-bit, non-prefetchable) [size=16K]
    Capabilities: [60] Power Management version 3
    Capabilities: [68] MSI: Enable- Count=1/1 Maskable- 64bit+
    Capabilities: [78] Express Endpoint, MSI 00
    Kernel driver in use: snd_hda_intel

My alsamixer looks like

I enabled pulseaudio configuration file to have 6 channels. My sound setting looks like

When I use the test dialog, only front left and right have sounds. If I use alsa in XBMC on a 5.1 video, there's no sound. If I use pulseaudio, only front right and left have sound. I can barely hear any speech since I'm guessing it's mapped to front center. Any clues?

Update: on what I'm hearing on Ubuntu's IRC, I can't do 5.1 over HDMI and my best bet is to encode AC3 live over S/PDIF using A52 but I can't compile alsa-plugins... it gives an error somewhere while building oss. Any second opinions?

I solved this by changing a couple of lines in /etc/pulse/daemon.conf First, open the file for editing:

sudo gedit /etc/pulse/daemon.conf

Then make sure the following line is uncommented and set to 6

default-sample-channels = 6 

also uncomment and edit the following line to yes

enable-lfe-remixing = yes

This enabled 5.1 audio on my Intel soundcard in 12.04

Although I don't have 5.1 audio, I noticed that your alsamixer screen is showing settings for your Intel ALC892 audio and your second screenshot is trying to configure the sound through your HDMI port (Nvidia GT 520m). In order to switch the controls in alsamixer to your NVidia HDMI audio you have to press F6 (as it's written in the top right corner of alsamixer).

If everything is ok with the alsamixer settings and you still can't get any sound, I would try installing the paman package- Pulse Audio Manager. After you install it, open your console and write paman as the package is not installed with an menu entry. After you start the program you'll see 5 tabs - Server Information, Devices, Clients, Modules, Sample Cache. Go to the Devices tab. You'll see a list of Sinks and Sources. You should have 2 sinks by the way, one for your analog Intel output and one for the NVidia HDMI. At this point you should start your audio/video application that uses Pulse Audio for the output and that is configured to output 5.1 volume. Play a file that has a surround sound and you'll notice that new entry appears below one of your sinks in the form of #some_number (eg. #6) . If everything is configured properly in your audio/video application, the entry will appear below your HDMI sink entry. Click on the entry and press the properties button. A new panel appears. What you are trying to do whit all this is make sure that the volume is not set at 0%. Adjust the volume manually with the slider or press reset so that it's set at 100%. Also click on properties for the HDMI sink itself and check that the volume is also set at 100%.

I don't know if this will help you, but it's worth trying it. I discovered Pulse Audio Manager 2 days ago while trying to solve a problem with a muted test sound in Skype- the test call was producing audio, while the test sound was completely silent.