[CentOS] sound problems... alsa & systemd?

Wed Mar 29 13:43:03 UTC 2017
ken <gebser at mousecar.com>

On 03/28/2017 08:53 PM, ken wrote:
> The www has failed me with this, so I'm trying you guys.  Sound worked 
> great out of the box when I installed 7.2... Yay!  I could watch all 
> kinds of videos, like on facebook and youtube.  And I could listen to 
> most podcasts too.  But then something happened. It was either a 
> kernel upgrade or that I installed vlc (for watching videos on DVD) 
> and the whole stack of codecs for it... I don't know exactly when, but 
> at some point I no longer had sound with youtube  and other web 
> videos.  The videos played fine, just no sound.  Note that using vlc, 
> both video and the audio with it play just fine.  I need to select the 
> audio driver (from a list in a vlc menu), however, else the sound 
> won't work in vlc either.
> If I go into the Applications menu, then System Tools -> Settings -> 
> Sound, under "Choose a device for sound output:" there are no devices 
> listed.  There used to be.
> If I run "aplayer file.wav", nothing plays (no sound at all) and I get 
> the error "main:786: audio open error: No such file or directory".  
> If, on the other hand, I run "aplay file.wav -D plughw:0" (i.e., 
> specify the/a device), I do get sound, the file does play.
> I ran alsa-info.sh and it posted tons of info from it on my setup at 
> http://www.alsa-project.org/db/?f=1dba91886be054df4816000768a0f5b109947a48. 
> Yet it still doesn't tell me what's missing.
> Anyone here have an idea...? or thoughts about where to look next?
> tia,
> ken 

Still poking around my system for a solution, I found this comment at 
the top of /usr/lib/systemd/system/alsa-state.service and two other 
files in the same directory:

> # Note that two different ALSA card state management schemes exist and 
> they
> # can be switched using a file exist check - /etc/alsa/state-daemon.conf .

The /etc/alsa/state-daemon.conf file consists of one line:

> # Remove this file to disable the alsactl daemon mode

I understand that a daemon continually runs, waiting for an event and 
then acts in some way in response, but it has to mean something more in 
this context.  Anyone familiar with the internals of this?