snd_hda: how to configure line-in passthrough to line-out?

[Brandon Kuczenski]

On Wed, 5 Oct 2011, Polytropon wrote:

> On Tue, 4 Oct 2011 20:58:14 -0700 (PDT), Brandon Kuczenski wrote:
>> I'm working on the sound on my system running 8.2-RELEASE.  Currently I
>> have sound input and output working using snd_hda (i.e. I can record on
>> line in, and play it back on line out).
>>
>> What I would like to do is take the audio coming in on line-in and send it
>> back out the line-out "live" without recording it.
>>
>> Is this easy to do?  I'd appreciate any hints.
>
> I think it is easy to do. If I remember terminology
> correctly, the thing you're searching for is MONITOR.
> Instead of setting rec source to mic, set it to line,
> and increase monitor level.

Thanks for your assistance.. unfortunately, setting the mixer
levels has not been enough to get a passthrough.  Here is my mixer output:

Mixer vol      is currently set to   1:1
Mixer pcm      is currently set to  45:45
Mixer line     is currently set to  75:75
Mixer mic      is currently set to   0:0
Mixer cd       is currently set to  75:75
Mixer rec      is currently set to  75:75
Mixer igain    is currently set to 100:100
Mixer ogain    is currently set to  50:50
Mixer monitor  is currently set to 100:100
Recording source: line

I'm using wavplay(1) from the ports collection to record on line-in, and 
then I can play it back.  On playback I can hear it just fine-- it mixes 
with other outputs on the PCM channel as I would expect.  but when the 
line is "live" it is not being mixed into the output.



> The line level should be possible to set independently
> of the rec channel setting, so you should be able to
> pass through line anyway - at least, that has been the
> default ability of sound cards when they became available
> for PC. But well... this has been 10... 20... years ago,
> and nobody expects simple things to work as simple today
> as they did in the past. :-)

Indeed, I wonder if it is a hardware capability problem, but I don't know 
how to try to answer that question.