Multichannel audio is broken

[Rudd-O]

This bug is really odd. I have a SBLive! on another machine which uses PulseAudio to turn the machine into an audio server.

This machine of course is capable of 4-channel multichannel audio. But, being the cheap bastard that I am, the machine only has one stereo system connected, to which my stereo headset is attached. Therefore, I took the liberty of creating the following ALSA sound card definitions in /etc/asound.conf:

pcm.simulatedsurround {
    type softvol
    slave {
        pcm "downmix51"
    }
    control {
        name "Virtual surround volume"
        card 0
    }
}

pcm.downmix51 {
    type route
    slave.pcm "default"
    slave.channels 2
    ttable {
        0.0 0.25
        1.1 0.25
        2.0 0.25
        3.1 0.25
        4.0 0.25
        4.1 0.25
        5.0 0.25
        5.1 0.25
    }
}

So far, so good. Speaker-test with channels set to six reports both center and LFE are mapped stereo, and the rear channels are mapped to the front. Basically, all sound from all "channels" reaches my ears. So far so good.

The problem arises because I don't watch DVDs on that machine. I watch my DVDs on my PowerEdge (another machine yet holds the CD-ROM drive, long story, 1U servers can't hold full-size DVDs, so I'm using GNBD to export the drive through the network).

Now, here's the relevant snippet of my /etc/pulse/default.pa:

load-module module-alsa-sink device=hw:0 sink_name=stereo
load-module module-alsa-sink device=simulatedsurround channels=6 sink_name=simulatedsurround
set-default-sink stereo

I have verified using paplay that the stereo sink works fine with stereo files. Moreover, I have also verified using paplay's device and --channel-map arguments, that mono,, stereo and multichannel sound files play correctly on my "simulatedsurround" output. This *works*.

But Xine doesn't. Thus, Kaffeine doesn't. Both refuse to use the pulseaudio ALSA output plugin on my PowerEdge (strangely, because all other alsa apps work OK). Both autochoose the pulseaudio output plugin. And the pulseaudio output plugin in Xine/Kaffeine actually *outputs sound* when playing 5.1 DVDs -- just not the dialogs. When watching the PulseAudio volume meter on the monitor output, I can see that the front channels are being fed what appears to sound like ambient music, and the LFE/center channels are also being fed similar signal.

What's it gonna take for me to have surround sound working properly with my DVDs?

Kaffeine does work correctly with stereo sound DVDs.

The a/52 downmix toggle does not have any effect in Xine.

Please help. GMPlayer is also refusing to play the DVDs (for altogether different reasons, might I add).

[Rudd-O (rudd-o)]

I should add that I have no way of verifying directly with *kaffeine* on the machine with the sound card, since it's headless and it runs a minimal set of server software. I have, however, verified that the multichannel audio works correctly with paplay (through the network) and speaker-test (locally).

[Rudd-O (rudd-o)]

VLC works. It apparently downmixes and chooses the "stereo" pulseaudio output sink, therefore, letting me watch DVDs.

[Daniel T Chen (crimsun)]

Is this symptom still reproducible in 8.10 RC or later?

[Rudd-O (rudd-o)]

I cannot know. I moved to Fedora 9 (got tired of apt and I also needed multilib 64 bit) then installed KDE 4. I now use Dragon Player for all my movie viewing. It still uses libxine, but there is nothing to configure, and I don't have multichannel audio files to test it with, at the moment.

[Harald Sitter (apachelogger)]

Closing.