Arch Linux

tuomas

Member

From: Europe

Registered: 2008-10-27

Posts: 17

[solved] No subwoofer output when converting from stereo to 5.1

I have set up my onboard Intel soundcard to be used solely for playing music using a 5.1 setup.

I plug everything in to the right ports, and tested under Windows, and found that everything was working perfectly, however under linux I get no subwoofer/center output under the regular orange port (well, weirdly enough center seems to play front left and front right in speaker-test) and have to plug my subwoofer/center lead into the gray rear speaker out port to have sound.

It's getting a little annoying to crawl under my desk to mess around with ports whenever I boot into a different OS, so I'd like to try fixing it I'm just not sure where I would begin.

from .asoundrc

pcm.ch51dup {
    type route
#    slave.pcm surround51
    slave.pcm surround51:Intel
    slave.channels 6
    ttable.0.0 1
    ttable.1.1 1
    ttable.0.2 1
    ttable.1.3 1
    ttable.0.4 0.5
    ttable.1.4 0.5
}

Any ideas?

Last edited by tuomas (2009-06-18 16:30:08)

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arch@thinkpad t61

whoops

Member

Registered: 2009-03-19

Posts: 891

Re: [solved] No subwoofer output when converting from stereo to 5.1

First of all, I think you might be mixing up to 5.0...? 5.1 should be 6 channels, right? So you could try adding

# mix channel 0 to channel 5, 50% volume; 
    ttable.0.5 0.5
# same for channel 1, if I understood those two right.
    ttable.1.5 0.5

Also: Are you sure, your apps are using the right pcm device? If not, you could first try telling speakertest -D ch51up to use surround51 and/or ch51up to try... or maybe just try:

pcm.!default {
    type route
#    slave.pcm surround51
    slave.pcm surround51:Intel
    slave.channels 6
    ttable.0.0 1
    ttable.1.1 1
    ttable.0.2 1
    ttable.1.3 1
    ttable.0.4 0.5
    ttable.1.4 0.5
}

(just leaving that as default might be an ugly solution, even if it works though - don't have much of an idea what I'm doing )

Last edited by whoops (2009-06-17 21:29:49)

tuomas

Member

From: Europe

Registered: 2008-10-27

Posts: 17

Re: [solved] No subwoofer output when converting from stereo to 5.1

First of all, I think you might be mixing up to 5.0...? 5.1 should be 6 channels, right? So you could try adding

# mix channel 0 to channel 5, 50% volume; 
    ttable.0.5 0.5
# same for channel 1, if I understood those two right.
    ttable.1.5 0.5

This worked, thanks! It also made me understand this ttable business much more. I realise now I was just having the two rear channels feed through my subwoofer/center which is a very wrong way of doing things

And yeah it's definitely the right pcm device, I only have MPD configured to use this device. Still, many thanks.

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arch@thinkpad t61