[alsa-devel] Help With Getting Line-in monitoring working

Kevin Atkinson kevina at gnu.org
Mon Sep 5 09:28:15 CEST 2011


I need some help getting my cards line-in monitoring working.  That is 
analog pass-through from line-in to headphone out.

I am using Ubuntu 10.04 with Linux kernel Linux Intel 2.6.38-10 (Ubuntu 
package).  I am using on-board audio with HDA-Intel with the Realtek ALC892 

With the stock Ubuntu kernel (lets call this setup "stable") I can't get 
line-in monitoring working (note however I can record from line in, I just 
can't get the analog pass-through working).  However, when I install the 
latest ALSA drivers (lets call this setup "soso") (recompiled a source 
package from the Ubuntu-audio-dev ppa, head 7c48f32b). I can get Line-in 
monitoring but the mixer controls are all mixed up.  The Line-in control 
controls the Line-in volume, but the master control has no effect.  Also,
the PCM control has no effect on PCM volume and the front control 
controls the output to the headphone but in order to mute the headphone
I still need to use the headphone mute.  The mixer work correctly with the 
stable setup.

Thus I am lead to the conclusion that the latest ALSA drivers are doing 
something right with line-in but getting a lot of other things wrong.

Attached is the alsa-info output of both setups.

Please give me some guidance on how to debug this problem.  For example 
what is the newer code doing that the old code is not that gets line-in 
monitoring working but gets a lot of the other mixer setups wrong.   I 
assume it is just a matter of "hooking up" the line in to the headphone 
out, and all that is needed is the right verb, but I am at a complete lost 
to what verb that is.

If there is some specific version of the ALSA drivers I should try please 
let me know.  If the Ubuntu kernel is causing a problem I am willing to 
install a stock kernel, but I rather not unless absolutely necessary.
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