[LAU] Alsa setup question

[Len Ovens]

On Wed, 29 Apr 2015, hollundertee at gmx.net wrote:

> On Tue, 28 Apr 2015 14:45:02 -0700 (PDT)
> Len Ovens <len at ovenwerks.net> wrote:
>
>> Just to be clear:
>> if exists USB use USB
>> else use internal
>>
>> Is that about it?
>
> Yes, this is exactly what I want.

OK

> I have configured the internal interface so that it only outputs to the
> headphone jacks, because I don't want my laptop to make any unexpected
> sounds in the library, office, etc. (one reason why I don't use pulse:
> it messes with the alsa mixer).

OK

> In the very rare occasion that I do need to use pulse, I also start it
> manually. I have taken all kinds of measures to prevent pulse from
> starting itself. This question is solely about alsa.

Or to put it another way, desktop audio. The tool that does what you want 
is (you probably won't like this) pulseaudio. PA is the only tool I know 
that can switch an application from one output/input to another on the fly 
without stopping the application streaming that audio. Learning about 
Pulse enough to find a way of stopping it from playing with IF levels 
seems to be the solution to the problem.

Almost any other solution would require the restarting of the application 
streaming audio to pick up the new device. PA can move the stream to a new 
device in mid stream. It would still take some script I think... probably 
run by udev, but I am not sure as I have my system setup to never do sleep 
mode... In fact my swap partitions are not big enough as they were setup 
when I had less memory :)

PA does not always play with alsa volume levels. It seems to depend on the 
AI itself. For example the ice1712 based cards do not have this problem. 
This says to me that there is probably a profile set up for the intel HDA 
cards that tells PA how to set the volume levels and changing the profile 
could make it so PA was no longer able to do so.


--
Len Ovens
www.ovenwerks.net