TerraTec-SoundSystem Aureon PCI

I bought this TerraTec SoundSystem Aureon 7.1 PCI, Dolby Digital Live soundcard [1] because I wanted AC3 (Raw Digital audio stream) Output using the S/PDIF adapter to my Sony digital-audio capable amplifier when I watched DVD. All the AC3 or DTS decoding is done on the amplifier. This soundcard are also on the list of ALSA preferred soundcard [2]. I have not managed to do this with the Asus A8N-SLI Premium motherboard my pc has, which has a integrated Realtek ALC850 7.1 soundchip.

Fedora Core 6 installation

For installation of Fedora Core 6 I followed Jarod Wilson howto [3]. The soundcard was auto-configured during firstboot because ALSA is the default sound system in the 2.6 kernel. These should be automatic, but if not, this is what my /etc/modprobe.conf has in it

alias snd-card-0 snd-cmipci
options snd-card-0 index=0
options snd-cmipci index=0
remove snd-cmipci { /usr/sbin/alsactl store 0 >/dev/null 2>&1 || : ; }; /sbin/modprobe -r --ignore-remove snd-cmipci

ALSA configuration

For the ALSA and Mythtv configuration I followed the howto "Configuring Digital Sound with AC3 and SPDIF" [4].

[mythtv@mythpc etc]$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: CMI8738MC8 [C-Media PCI CMI8738-MC8], device 0: CMI8738-MC8 [C-Media PCI DAC/ADC]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: CMI8738MC8 [C-Media PCI CMI8738-MC8], device 1: CMI8738-MC8 [C-Media PCI 2nd DAC]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: CMI8738MC8 [C-Media PCI CMI8738-MC8], device 2: CMI8738-MC8 [C-Media PCI IEC958]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

This was a bit unexpected dump of the command aplay -L, but this is what I got from my Fedora pc.

[mythtv@mythpc ~]$ aplay -L
front:CARD=CMI8738MC8,DEV=0
    C-Media PCI CMI8738-MC8, C-Media PCI DAC/ADC
    Front speakers
iec958:CARD=CMI8738MC8,DEV=0
    C-Media PCI CMI8738-MC8, C-Media PCI DAC/ADC
    IEC958 (S/PDIF) Digital Audio Output
null
    Discard all samples (playback) or generate zero samples (capture)

After boot I disabled the aRts (the KDE sound server). To do so, while logged in as your mythtv user, choose "Control Center" off the Fedora (Red Hat) menu. Navigate through "Sound & Multimedia" to "Sound System" and deselect "Start aRts soundserver on KDE startup" ("Enable the sound system" on KDE 3.3 or later) and then click "Apply". On subsequent logins, aRts will not launch.

Remember to unmute the "iec958" device!!!

To do this bring up alsamixer and, using the arrow keys, move over to the "iec958" device and un-mute it by hitting the "m" key. Hit "esc" to exit and save the settings. With the S/PDIF interface unmuted, we are free to start sending audio down the line. You should now check if you have some light on the S/PDIF adapter.

asound.conf

I use the same asound.conf the howto "Configuring Digital Sound with AC3 and SPDIF" use

Create the following /etc/asound.conf:

pcm.!default {
type plug
slave {
pcm "spdif"
rate 48000
format S16_LE
}
}

Digital sound

By referencing the ALSA-plugin ALSA:spdif with aplay or mplayer command you can test the AC3 output. You can get a Dolby Digital Surround wav file from here [5]. If you test with aplay with this SURROUNDTEST_DD_640.wav file will give you sound in all the 5.1 speakers. Follow the howto "Configuring Digital Sound with AC3 and SPDIF" [6].

Another howto I followed for testing digital sound was this Alsa wiki howto [7]. Tell your program to send sound to 'hw:x,y' or 'plughw:x,y', where x is the card number and y is the device number shown by 'aplay -l'. For this card, this is hw:0,2

Try:

aplay -D hw:0,2 SURROUNDTEST_DD_640.wav
aplay -D ALSA:spdif SURROUNDTEST_DD_640.wav

and with mplayer:

mplayer SURROUNDTEST_DD_640.wav -ao alsa:device=hw=0,2
mplayer -ao alsa:device=spdif -ac hwac3 SURROUNDTEST_DD_640.wav

If you get error when you try using the ALSA:spdif plugin you can try to rename the /etc/asound.state file and then take a reboot of your Fedora pc. Alsa will make a new /etc/asound.state file which wil make a proper statement of the ALSA:spdifplugin. This happens sometime because you have upgraded alsa with yum.

Configure MythTV for Digital Sound

In mythfrontend->Setup

This part is the easy part. Fire up mythfrontend and navigate to: Utilities/Setup->Setup->General On Page 3, change the default audio device to "ALSA:default" and change the passthrough device to "ALSA:default". Finally, check the box next to "AC3 to SPDIF passthrough".