How do I use two sound cards at once?

vxc69 · 01-05-2005, 08:12 AM

Long time since I posted here.

Anyway, I have two sound cards on my system. I want to use both at once for output so that I can fix more speakers.

Is this possible? If it is how do I go about configuring?

I currently have ALSA, OSS and I think aRTS.

Thanks,
vxc

p.s: I've got a Sound Blaster Live and an onboard AC' 97, both have been detected and both work fine. Default according to Kmix is the AC' 97 and I believe this is /dev/dsp0 whereas the Sound Blaster is /dev/dsp1

p.s.s: BTW my system is running Yoper. Thanks again!

vxc69 · 01-06-2005, 03:03 AM

After some sleep and some more googling' I found this:

http://www.linuxdj.com/audio/quality/#multi

According to this you cannot use two sound cards at the same time for synchronized output.

Quote:

The trouble is that each sound card derives its sampling rate from a crystal oscillator clock. The clocks in the two sound cards will inevitably not be synchronized. You might think that 44,100 Hz is always exactly 44,100 Hz, but sadly, it's not. Your software doesn't know this - it thinks 44,100 samples from one card represents the same amount of time as 44,100 samples from the other. As a result, the sound from one sound card will gradually lag farther and farther behind the sound from the other sound card. If there's any sound common to both cards, you may even get weird phasing effects.

Makes a lot of sense and I should have thought about it before posting. You learn something new everyday (almost)!

Thanks anyway guys,
vxc