Linux SB Audigy2 Support

• AC3 Passthrough (Dolby Digital Passthrough Mode)
• Configuration Files (Sample Configs)
• Mixer Channels (Mixer Channel Matrix)

This page is for Audigy2 (emu10k2) chipset cards. They can do 24bit 192Khz with 106dB SNR. The Platinum ed adds a "Audigy2Drive", 5 1/4" bay used to hook up digital in/out and also includes a IR remote. Look at Creative Labs website for more information. This newer and more advanced DSP (Digital Signal Processor) has lots of neat features with the good support under Linux. This how-to covers ALSA since at this time (05/03/2003) the OSS (emu10k1) driver doesn't seem to fully support Audigy2 cards.

My setup includes:

• SB Audigy2 Platinum (Audigy2Drive Digital Out)
• Logitech Z680 Dolby Digital 5.1 THX Speaker System
• Linux Kernel 2.6.0-gentoo-r1
• Alsa 1.0.0-rc2 (Kernel modules)

AC3 Passthrough

I have tested both Xine (Xine-libs 1.0.0-rc3a) and mplayer version 1.0pre3-3.3.2 and found AC3 to work. AC3 worked using Coax out on my Audigy2Drive. (5 1/4" Bay Connector) For Xine, you just need to check the a52_pass_through on the Audio tab.

And for mplayer using the following command:

mplayer -ao alsa9 -ac hwac3 dvd://1

Configuration Files

~/.xine/config

audio.a52_pass_through:1
audio.five_lfe_channel:1

Mixer Channels

As of ALSA 0.9.7 the following matrix gives you an idea of what all those mixer channels actually do on my Audigy2. Please noticed that the AC97 Channels show up in Alsamixergui as "AC97", "AC97", and "AC97 Master." However, the first AC97 is actually AC97 Playback Volume. The reason this is important is if you wanted to record from your TV card that passes sound through line-in, you can do so without having it come across the rest of the card. I record TV broadcasts for viewing later without having to watch/listen to the live show. This way you can skip commericals later and not have to shut down xmms! *grin*

Alsa 0.9.x

Versions <= 0.9.8 have a problem with mixer channels doing what you'd expect. For example, if you trun down PCM channel to 0%, you would expect no sound from xmms. However, if you have Wave Center/Wave Surround/etc turned up then sound is still played.

UPDATE: The developers have fixed the mixer controls in 1.0.0-rc2 so that PCM now controls PCM output for all channels. And Master controls all output volume. They also change AC97 to Analog Mix for my Audigy2. This does not apply to AC3 passthrough levels.

Alsa 1.0.0-rc2