[lug] Forcing a Sound Device

[Davide Del Vento]

I have no clues about the issue at hand, but you can relatively easily
find out which file a program alters using strace: run the program
with it, redirecting the stdout/err to a file, and do the "thing" that
triggers the change you want to find out. Try to minimize everything
else you do, because the output is huge.

Open the file, look at the format, and do lots of grepping... You'll
learn a lot about what that program does (even answers to questions
you did not have).

Best of luck.
Davide

On Sun, Nov 12, 2017 at 11:46 AM,  <stimits at comcast.net> wrote:
> Thanks for the reply! Unfortunately I think your control has more in it than
> this one. I can set a device to muted, but not to disabled by this method.
> When I set the USB headphones as default, any removal of them results in a
> permanent switch to analog motherboard output and never goes back to
> headphones when the headphones are reconnected. It probably does not matter
> because no device is getting audio now unless I use a pulse audio control.
>
> If I run the "pavucontrol" application, this too has a default device list,
> but no matter which device I select, each song forces it back to built in
> analog audio...the device setting works for one song, then reverts. Wish I
> knew what file pavucontrol alters...I'd use SElinux and make it immutable to
> everything. Or if I knew what it is that tells pavucontrol to change, I'd
> bzip2 the binary so it can't be used (at this point I don't care if it
> brings down the system...I just want to know debugging information).
>
> In the pavucontrol output device tab I have no ability to remove built-in
> analog audio, all I can do is uncheck it as a fallback device. HDMI never
> has output unless I turn the monitor off and back on and then use
> pavucontrol to set the individual firefox playback device to HDMI...and
> after the song is done firefox reverts to analog integrated audio.
>
> Anyone know why pulse audio is used? I'm not sure if I could remove it and
> have things work...it seems using purely alsa would be best.
>
> ----- Original Message -----
> From: Alan Robertson <alanr at unix.sh>
> To: lug at lug.boulder.co.us
> Sent: Sun, 12 Nov 2017 15:12:20 -0000 (UTC)
> Subject: Re: [lug] Forcing a Sound Device
> I use KDE on Ubuntu (Kubuntu) and always use a non-default audio device.
> Here's how I make that happen on Kubuntu:
> right click the speaker icon, and bring up Audio Volume Settings.
> Click on the configuration tab (far right tab).
> For all your unwanted audio devices, click on Profile and select "off".
> Click OK.
> It works for Kubuntu - don't know about Fedora.
> --
>   Alan Robertson
>   alanr at unix.sh
> On Sat, Nov 11, 2017, at 03:51 PM, stimits at comcast.net wrote:
>
> I've tried a number of things to get a change in the default audio on my
> Fedora/KDE system. For whatever reason, no matter what I do, every playback
> device wants to start with the built in analog audio of the motherboard. I
> can change this to use the HDMI or USB audio...as soon as a song or video
> ends, it reverts. If I watch a video and go to full screen...it reverts. I
> don't have the analog audio on the motherboard connected.
>
> Various mixers have allowed me to change default audio device. Until the
> song or video ends...then it reverts to being default.
>
> One of the things I tried was to blacklist the motherboard's kernel module
> for the device...but apparently other things depend on this despite no other
> module depending on this. I can remove the module, and no other module
> reports needing it, but no mixer or audio application works after that. The
> USB headset has its own digital audio, and the video card for HDMI has its
> audio...I do not believe the integrated audio should have any effect unless
> other programs mistakenly demand to open integrated audio.
>
> I've also tried settings in pulse audio's default.pa, but these seem to fail
> as well.
>
> Does anyone have any idea how I can summarily ban the motherboard's
> integrated audio? I'm about to try disabling it in the BIOS, but this is a
> multi-boot system and I suspect this will cause other issues which I won't
> be able to set right again once it happens (short of a full system restore).
> I'd love to find a file I can remove write permission to and set SElinux
> permissions to deny write to anyone or anything...ever...but I don't know
> where this default setting is coming from if the mixer GUI's set a value and
> then it reverts. I cannot find the file. I suspect it is in udev.
>
> There are too many mechanisms for audio...pulse, alsa, KDE, gnome, systemd,
> udev. I really wish there were just one mechanism and it worked.
>
> Thanks!
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