The following content is captured from web.archive.org because the original domain no longer exists. I copy the content here for reference as I found this useful when setting up my own Via EPIA EN12000 S/PDIF 5.1 system with Gentoo linux.
The content below is provided as-is, and is unchanged from the original text. If it doesn't work for you, then your guess is as good as mine as to why.
3.1 Setting up Alsa
Make sure your /usr/src/linux link points to the correct kernel, as Alsa and other packages use this to get the correct headers and modversions. Run emerge alsa-utils to get required alsa tools and the init script. If you are using the 2.4 kernel, you will need to run "ALSA_CARDS=via82xx ACCEPT_KEYWORDS=~x86 emerge alsa-driver" to get the drivers (2.6 includes the drivers). It is helpful to add ALSA_CARDS="via82xx" to your /etc/make.conf and "media-sound/alsa-driver ~x86", etc to your /etc/portage/package.keywords so you don't have to specify them every time.
Please refer to the official Gentoo ALSA guide (cache) if you have any questions.
3.1.2 Configuring AlsaNow we need to configure it to auto start.
Here are some relavent via82xx module options:
ac97_clock - AC'97 codec clock base (default 48000Hz)
dxs_support - support DXS channels,
0 = auto (defalut), 1 = enable, 2 = disable,
3 = 48k only, 4 = no VRA
The default of dxs_support=0 usually results in wierd sounding non-48Khz files so try one of the other options. Now we need to edit /etc/modules.d/alsa it should look something like this:
# ALSA portion
alias char-major-116 snd
alias snd-card-0 snd-via82xx
options snd-via82xx dxs_support=3
# OSS/Free portion
alias char-major-14 soundcore
alias sound-slot-0 snd-card-0
alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-oss
alias /dev/mixer snd-mixer-oss
alias /dev/dsp snd-pcm-oss
alias /dev/midi snd-seq-oss
options snd cards_limit=1
Then run modules-update after which, you can type /etc/init.d/alsasound start to insert the alsa modules. rc-update add alsasound boot will load that every time you reboot.
3.1.3 Unmuting Alsa
Alsa is muted by default. Run alsamixer to view the mixer levels. Move left and right with the arrow keys, and press 'M' to unmute Master and PCM channels. Up and Down will adjust the volume levels. Press 'Esc' to exit. The alsasound boot script will restore mixer settings on reboot.
3.1.4 6 Channel Output (5.1)
Now how to switch to 5.1 out...
Once you switch the sound card to output 5.1, the functions of the jacks change.
Jack : Mode 1/Mode 2
Blue : Line-In/Rear-Out
Green : Line-Out/Front-Out
Pink : Mic-In/Center&Subwoofer-Out
3.1.5 Using the S/PDIF out
The EPIA-M can output S/PDIF through the RCA jack on the back. First you need to change a jumper on the motherboard before you can use this, it is near the RCA port, see your manual for details.
The S/PDIF output is controled through the IEC958 Playback AC97-SPSA mixer channel you can set the different options with the command amixer set 'IEC958 Playback AC97-SPSA' 0. The S/PDIF always outputs at maximum volume, the main and pcm mixers have no affect on it. Here are the different output options for IEC598 Playback:
1. PCM2,PCM1 (rear)
2. Center and LFE
3. PCM3,Modem,Dedicated S/PDIF
Most people want to use 0.
To get AC3 passthrough with mplayer, use mplayer -ao alsa -ac hwac3
Also, if you haven't set the above mixer setting, then you should be able to use mplayer -ao alsa9:iec958 to get s/pdif output still.
3.2 OSS Kernel Module
The OSS sound driver is included in the kernel. Enable "VIA 82C686 Audio Codec" under sound in the menuconfig. The module will be called via82cxxx_audio.
3.3 VIA Combo Audio Driver
http://www.viaarena.com/?PageID=294 (cache) offers a oss driver that supports all of VIA's sound chips. It supports six channel audio and spdif out.
You can get viaaudiocombo for 2.6.1 here: