apulse can't open playback device when alsaequal is used

[worldowner]

I use alsaequal (https://aur.archlinux.org/packages/alsaequal/) to have system-wide alsa equalizer.

Configuration is simple:

$ cat .asoundrc ctl.equal { type equal; }

pcm.plugequal { type equal; slave.pcm "plug:dmix";
}

pcm.!default { type plug; slave.pcm plugequal; }

It doesn't work with apulse:

$ apulse firefox [apulse] [error] do_connect_pcm: can't open playback device "default". Error code -1 (Permission deined) [apulse] [error] do_connect_pcm: failed to open ALSA device. Apulse does no resampling or format conversion, leaving that task to ALSA plugins. Ensure that selected device is capable of playing a particular sample format at a particular rate. They have to be supported by either hardware directly, or by "plug" and "dmix" ALSA plugins which will perform required conversions on CPU.

I think that sample rate of a signal sent to equalizer doesn't matter. After equalizer does its job signal is sent further to dmix which handles conversion.

[SoniEx2]

$ APULSE_PLAYBACK_DEVICE=plugequal apulse firefox

Worked for me until I did a system upgrade.*

[i-rinat]

until I did a system upgrade

Hmm.

@worldowner, @SoniEx2, have you tried to set "security.sandbox.content.write_path_whitelist" parameter (on about:config page) to "/dev/snd/"?

[SoniEx2]

I did.

Right after the system upgrade, I was getting EACCES (-13 I think), then I set that, now I'm getting EPERM (-1) [apulse] [error] do_connect_pcm: can't open playback device "plugequal". Error code -1 (Operation not permitted)...

[SoniEx2]

This seems to only happen with firefox...

[SoniEx2]

Added all these to security.sandbox.content.write_path_whitelist:

/dev/snd/,/usr/share/alsa/alsa.conf,/usr/share/alsa/cards/,/usr/share/alsa/pcm/,/etc/asound.conf,/usr/share/alsa/alsa.conf.d/,/usr/lib/alsa-lib/libasound_module_pcm_equal.so,/home/soniex2/.alsaequal.bin,/home/soniex2/.asoundrc

And it worked. Sadly no way to filter write path whitelist and read-only path whitelist so this risks my asoundrc...

[worldowner]

Before sandbox Firefox had rw access to all the files that your user has. So it's still better. If your're concerned about your files just run Firefox in container. I run it in LXC and works fine.

[i-rinat]

Sadly no way to filter write path whitelist and read-only path whitelist so this risks my asoundrc...

@SoniEx2, as far as I understand, that particular sandbox in Firefox allows accesses to all files for reading. And you only need add paths which need to be writable to the exception list. So, maybe "/dev/snd/,/home/soniex2/.alsaequal.bin" would be enough?

[SoniEx2]

Nope. I had to add my asoundrc or else it wouldn't work.

[memeplex]

I would like to say that I'm in (very up-to-date) arch using dmix+alsaequal+plug and apulse works out of the box with latest firefox, no need to tweak any settings. Has anything changed since you last discussed about this?

[memeplex]

Also notice alsa is not enabled https://git.archlinux.org/svntogit/packages.git/tree/trunk/PKGBUILD?h=packages/firefox.

[SoniEx2]

@memeplex Please visit about:support and tell me what you see under Application Basics -> Multiprocess Windows.

Edit: Also tell me what you see under Sandbox.

[memeplex]

Sure @SoniEx2

Multiprocess Windows    0/1 (Disabled by add-ons)

Sandbox
---
Seccomp-BPF (System Call Filtering) true
Seccomp Thread Synchronization  true
User Namespaces false
Content Process Sandboxing  true
Media Plugin Sandboxing true
Content Process Sandbox Level   2

[SoniEx2]

@memeplex sandbox doesn't work if multiprocess windows is disabled.

[memeplex]

You're right @SoniEx2. It was an autoreload addon that was disabling multiprocess windows. Now that I have paused that addon I get not sound anymore. I have set the sandbox whitelist to

• /dev/snd
• /usr/share/alsa
• /usr/lib/alsa-lib
• /etc/asound.conf (not in my system anyway)
• /home/carlos/.alsaequal.bin
• /home/carlos/.asoundrc

but to no avail...

[SoniEx2]

needs to be /dev/snd/, /usr/share/alsa/ and same for alsa-lib.

[memeplex]

Ahh, ok, shame on me. By trial and error I concluded that I just need to add

• /dev/snd/
• /home/carlos/.alsaequal.bin

to get it working. In particular, there was no need of adding ~/.asoundrc.

[worldowner]

Today I tried on Ubuntu Xenial:

ALSA lib dlmisc.c:254:(snd1_dlobj_cache_get) Cannot open shared library /usr/lib/x86_64-linux-gnu/alsa-lib/libasound_module_pcm_equal.so [apulse] [error] do_connect_pcm: can't open playback device "default". Error code -6 (No such device or address)

The library exists: $ ls /usr/lib/x86_64-linux-gnu/alsa-lib/libasound_module_pcm_equal.so /usr/lib/x86_64-linux-gnu/alsa-lib/libasound_module_pcm_equal.so

Any ideas?

[eisnerd]

I currently get exactly the same two pulseaudio log lines when trying to load module-alsa-sink for an alsaequal device on 18.04.3. The library exists, ldd shows no missing libs and arch matches, so I have no idea why it doesn't load. It works from other alsa programs, like aplay and mpd.