[alsa-devel] Capturing from Line and Mic simultaneously

Tobin Davis tdavis at dsl-only.net
Mon Dec 10 18:28:01 CET 2007

This really depends on the driver, I would think.  Some drivers are
setup for single input at a time, as the most common usage model is for
voice conferencing.   But i can see where this would be useful from a
recording studio perspective.  The trick would be to have the recording
program enable the correct capture pathways, which can be driver
independent.  It also can be a hardware limitation, like with some sound
chips on the HDA-Intel bus.  Some of them may have multiple paths for
input through pin reassignment, but only 1-2 ADC's. for actual capture.

If you let us know exactly what hardware you have, the developer(s) for
that system may be able to better answer.


On Mon, 2007-12-10 at 17:20 +0100, Christophe Osuna wrote:

> Hi,
> I would like to capture sound from the Line and Mic inputs
> simultaneously. The sound chip seems capable to do so: inside
> alsamixer, in the "Capture" tab I can select up to three subdevices,
> and from the "Playback" tab I can set the input source one to "Mic"
> and the input source two to "Line" (and three to whatever).
> When trying to use several output ports at the same time I use four,
> six or eight channels. I tried the same thing for input (i.e. use four
> channels) but that failed. I guess I have to use subdevices but I have
> no idea on how to start working with them.
> Could anyone:
>  * tell me if ALSA is limited to two capture channels, and in that
> case what should be done;
>  * point me to some documentation showing what to do, or give me some
> general hints
> Thanks.
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Tobin Davis  

Win98 is called Win98 because 98 bugs have been added since the last version

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