ALSA, pulseaudio and 5.1 surround

alarm9k · #1 11th March 2008, 06:07 PM

I have an Audigy2 sound card. I managed to create a pulseaudio sink with ALSA 'surround51'. Both PA volume control and PA manager indicate that I have a sink with 6 channels. But all applications still produce a stereo upmix and not a real 5.1 sound. For example Mplayer produces a stereo from 5.1 movie and copies the sound to the rear speakers. Stereo mp3s in Amarok are also played in all speakers, being duplicated from front to rear. Playback streams appear with only 'front left' and 'front right' volume sliders, no matter how many channels the sound file has.

How do I force the applications to produce a real 5.1 sound -- if it's stereo, then being played only in front left and front right? If it's a 5.1 movie than having each track in its respective speaker.

Here is what I have.
/etc/alsa/pulse-default.conf:

Code:

pcm.pulse {
    type pulse
}

ctl.pulse {
    type pulse
}

# Let's make it the default!

pcm.!default {
    type pulse
}

ctl.!default {
    type pulse
}

/etc/pulse/default.pa

Code:

load-module module-alsa-sink device=surround51
load-module module-alsa-source device=hw:0

Just to mention that ALSA surround51 is a perfectly working device. I can successfully run speaker-test and I have a working 5.1 surround in Doom3 (after a bit of channel rerouting).

Amarok and Mplayer are configured to use 'pulseaudio' output plugin rather than ALSA.

EDIT: Here's an update. I found how to disable upmixing in /etc/pulse/daemon.conf but applications still produce only 2 channels of sound

alarm9k · #2 12th March 2008, 04:29 PM

Update: guys from #pulseaudio irc channel told me that this is a problem with the application, not the sound server.

For those who want to know. The proper way to start mplayer to produce true 5.1 audio thru pulseaudio is:

Code:

gmplayer -ao pulse -channels 6

Sort of solved.