PipeWire

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Warning
As of mid 2022, PipeWire is still in active development. Some things may still not be fully integrated, tested, or implemented, and there may be large changes. It can work well for some, though the experience is not guaranteed to be perfect, free of issues, or bugs.
Important
This article currently describes the state-of-affairs in the testing branch (~arch), rather than stable. This will change in future, once the pace of development slows down a bit.

PipeWire is a low-latency, graph-based, processing engine and server, for interfacing with audio and video devices. It can be used to support use-cases currently handled by ALSA, PulseAudio, and/or JACK, and aims to improve handling of audio and video under Linux.

Some key features of PipeWire include:

  • Minimal latency capture/playback of audio and video.
  • Real-time multimedia processing.
  • Multi-process architecture allowing multimedia content sharing between applications.
  • Seamless support for PulseAudio, JACK, ALSA, and GStreamer.
  • Applications sandboxing support with Flatpak, with a security model that facilitates interacting containerized applications.


PipeWire currently ships a PipeWire daemon, an example session manager, tools to introspect and use the PipeWire Daemon, a library to develop PipeWire applications and plugins, and the SPA (Simple Plugin API) used by both the PipeWire daemon and the PipeWire library.

Installation

Kernel

CONFIG_SND_PROC_FS and CONFIG_SND_VERBOSE_PROCFS are needed for newer versions of media-video/wireplumber to work.

KERNEL
Device Drivers  --->
    <*> Sound card support  --->
        <*> Advanced Linux Sound Architecture  --->
            [*]   Sound Proc FS Support
            [*]     Verbose procfs contents

USE flags

To use PipeWire as a sound server, specify the sound-server USE flag on media-video/pipewire.

When using PipeWire as a replacement for the PulseAudio sound server:

  • Ensure media-libs/libpulse is installed, which will allow PipeWire to emulate a PulseAudio sound server. Not many applications currently support PipeWire's native API.
  • Ensure the pulseaudio USE flag is still set in make.conf.

PipeWire requires the presence of a D-Bus session bus and an XDG-compliant environment. Both requirements should be met by a desktop profile; on such systems, starting PipeWire is as simple as running the pipewire binary. On other profiles, if using OpenRC, permissions requirements might also need the elogind USE flag on the media-video/wireplumber package, together with sys-auth/elogind itself.

To enable direct screencasting support on applications offering it, specify the screencast USE flag on the relevant packages. Otherwise, screencasting support may also be provided through the PulseAudio or JACK compatibility layers.

USE flags for media-video/pipewire Multimedia processing graphs

X Enable audible bell for X11
bluetooth Enable Bluetooth Support
dbus Enable dbus support for anything that needs it (gpsd, gnomemeeting, etc)
doc Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
echo-cancel Enable WebRTC-based echo canceller via media-libs/webrtc-audio-processing
extra Build pw-cat/pw-play/pw-record
flatpak Enable Flatpak support
gstreamer Add support for media-libs/gstreamer (Streaming media)
jack-client Install a plugin for running PipeWire as a JACK client
jack-sdk Use PipeWire as JACK replacement
lv2 Allow loading LV2 plugins via media-libs/lv2
modemmanager Combined with USE=bluetooth, allows PipeWire to perform telephony on mobile devices.
pipewire-alsa Replace PulseAudio's ALSA plugin with PipeWire's plugin
readline Enable support for libreadline, a GNU line-editing library that almost everyone wants
sound-server Provide sound server using ALSA and bluetooth devices
ssl Enable raop-sink support (needs dev-libs/openssl)
system-service Install systemd unit files for running as a system service. Not recommended.
systemd Enable use of systemd-specific libraries and features like socket activation or session tracking
test Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)
udev Enable virtual/udev integration (device discovery, power and storage device support, etc)
v4l Enable support for video4linux (using linux-headers or userspace libv4l libraries)
zeroconf Support for DNS Service Discovery (DNS-SD)

Emerge

Once the USE flags have been specified, rebuild the affected packages:

root #emerge --ask --verbose --changed-use --update --deep @world

Alternatively, PipeWire may be emerged independently, though the previous method is usually what is required:

root #emerge --ask media-video/pipewire

Typically, the WirePlumber session manager should also be installed. WirePlumber is a replacement for pipewire-media-session; refer to this article for an introduction and the details. The media-video/wireplumber package provides the wireplumber.service systemd service and the wireplumber binary used by gentoo-pipewire-launcher.

root #emerge --ask media-video/wireplumber

Configuration

Note
PipeWire is still in heavy development - configuration paths, options and defaults can change from one minor release to another - if things on the system do not align with documentation, double check or at least make a backup before making changes.
Tip
Detailed, non Gentoo-specific, configuration documentation can be found at the project's official wiki.

Typically, things work reasonably well out of the box, and PipeWire's global configuration is usually best left unmodified.

Global PipeWire configuration can be changed by editing the /etc/pipewire/pipewire.conf file, and ~/.config/pipewire/pipewire.conf may be used for per-user configuration. /etc/pipewire/pipewire.conf is not installed by default, but can be created by copying /usr/share/pipewire/pipewire.conf:

root #cp /usr/share/pipewire/pipewire.conf /etc/pipewire/pipewire.conf

Note that this configuration tries to use realtime scheduling to increase audio thread priorities. If the user doesn't have the necessary permissions for this, the configuration will try to use RTKit instead, so the sys-auth/rtkit package will need to be installed.

PipeWire also recognizes multiple environment variables that allow these settings to be changed, per-user, or for individual commands.

No additional configuration is required to use PipeWire as video server; this functionality is enabled by default.

The following sections describe configuration of PipeWire as a sound server.

systemd

PipeWire provides socket and service files when built with the systemd USE flag.

If the PulseAudio user service is enabled, disable it; this is safe to do even if the user service was not in use.

user $systemctl --user disable --now pulseaudio.socket pulseaudio.service

While PipeWire does not appear to utilize the ~/.config/pulse/ directory beyond the cookie file, it may be a good idea to rename or delete it.

user $systemctl --user enable --now pipewire.socket pipewire-pulse.socket wireplumber.service

Socket activation means the service will only be started when required, which is usually sufficient. However, the user service can be always started when the user logs in by replacing pipewire.socket with pipewire.service:

user $systemctl --user enable --now pipewire.service

In these cases, the --now flag is optional, but probably safe to use, as starting PipeWire with default configuration merely allows using new interfaces and doesn't change the existing ones, i.e. non-PipeWire clients continue using the same libraries and services they were using previously.

OpenRC

There is no truly standardized way (outside of systemd) to load PipeWire when starting a graphical shell, and users need to choose the correct approach based on how their graphical environment is started.

Important
In all cases where systemd user services are not being used, PipeWire must be started before anything that might try to connect to any sound input or output, such as a volume monitoring applet.
Note
Older versions of PipeWire (<0.3.39) worked by calling pipewire directly, but this is no longer recommended/correct.

Prerequisites

  • XDG_RUNTIME_DIR

This variable is usually set automatically by systemd-logind, elogind or seatd. Systems that don't use any of these seat management daemons will need to set XDG_RUNTIME_DIR manually, e.g. in ~/.bash_profile, ~/.zprofile, etc.:

# Ensure XDG_RUNTIME_DIR is set
unset XDG_RUNTIME_DIR
export XDG_RUNTIME_DIR=$(mktemp -d /tmp/$(id -u)-runtime-dir.XXX)
  • DBUS_SESSION_BUS_ADDRESS

This variable is usually set automatically by desktop environments such as GNOME or KDE. Note that a D-Bus session bus is not what is typically being provided by the system D-Bus service, which is instead providing a system bus for things like hardware events, etc.

When running a window manager, such as i3, bspwm or Sway, the WM needs to be started with dbus-launch, which will set DBUS_SESSION_BUS_ADDRESS for the session. For example, if starting X via startx, the final line of ~/.xinitrc could be:

FILE ~/.xinitrc
exec dbus-launch --exit-with-session bspwm

Note that the exec means that no subsequent commands in that file will be executed until the session ends. Any commands needing to be run from within the new session should be added to the WM's configuration/setup file, e.g. ~/.config/bspwm/bspwmrc.

More generally, dbus-launch can be run directly from the command line:

user $dbus-launch --exit-with-session sway

Display manager environments (SDDM, LightDM, GDM, etc)

Gentoo's PipeWire package now installs the needed autostart files to /etc/xdg/autostart/pipewire.desktop, so no action should be required.

However, it is also possible to start PipeWire via the ~/.xprofile file, by adding:

FILE ~/.xprofile
gentoo-pipewire-launcher &

Wayland / Sway / Window Managers

The XDG autostart approach should work for Wayland as well as X, but it is not clear whether .xprofile is necessarily sourced when starting a Wayland session.

For Sway in particular, edit ~/.config/sway/config to add:

FILE ~/.config/sway/config
gentoo-pipewire-launcher &

More generally, when using a window manager, a call to gentoo-pipewire-launcher needs to be added to the WM's configuration/setup file, e.g.:

FILE ~/.config/i3/config
gentoo-pipewire-launcher &

Verifying PulseAudio server emulation

user $LANG=C pactl info | grep "Server Name"
Server Name: PulseAudio (on PipeWire 0.3.39)

Setting sample rates

PipeWire uses a global sample rate in the audio processing pipeline. All signals are converted to this sample rate and then converted to the sample rate of the device.

To change the sample rate, uncomment and change this line:

FILE pipewire.conf
default.clock.rate = 48000

It is also possible to dynamically force a sample rate at runtime see here

Avoid resampling

Since 0.3.33, it is possible to specify up to 16 alternative sample rates. Use the following config option to specify the sample rates:

FILE pipewire.conf
default.clock.allowed-rates = [48000 44100 96000]

Note that this not enabled by default because of kernel driver bugs.

According to the PipeWire developer, with the above configuration, no resampling is done when the graph is at a rate which both the client and the device can support.

Screensharing with Chrome

Change "WebRTC PipeWire support" to "Enabled" from chrome://flags

Adding multi user support

The default configuration only allows the current user (who started pipewire-pulse) to play audio.

For multi-user support, the TCP interface is needed:

user $cp -r /usr/share/pipewire/ /etc/
user $$EDITOR /etc/pipewire/pipewire-pulse.conf

Locate server.address = [ section and uncomment one of the available TCP options.

Replacing JACK

To have JACK clients routed through PipeWire, currently the only method supported by Gentoo is to run them via pw-jack which uses LD_PRELOAD to redirect clients from JACK's original libraries to PipeWire's alternatives:

user $pw-jack qsynth
Important
Existing JACK users are likely to have realtime capability set up but new users are advised to raise the RLIMIT_MEMLOCK value from Gentoo's default of 64 kilobytes to 256 kilobytes on all PipeWire users that want to use its JACK emulation. For instructions on how to achieve that please see the subsection on that below (also listed in the table of contents for this page). Failure to do this will likely cause at least occasional buffer underuns (xruns) as a single page fault is likely to spend half to the entire length of a buffer just in kernel time to resolve.

It should be noted that either due to PipeWire incompleteness or Gentoo configuration shortcomings, not every client will work. Some may even ungracefully exit due to missing symbols. It will likely also require re-configuration of JACK clients, because they will attempt to use their old configuration files, if such exist.

Alternatively it should be possible to have PipeWire connect to a real jackd and act as a gateway for non-JACK applications but, unless there already is a working JACK setup, this is not recommended for the overall worse user experience with JACK.

Troubleshooting

CS:GO (and other games using the Valve's Source engine)

Note
It appears that this issue has been resolved by a patch by Valve in early 2021. If the issue is no longer present without any fixes applied, then please delete this subsection entirely.

The default sound buffer length is 0.025. This can sometimes be too low causing cracking audio; for now the workaround is to increase the size of the application's audio buffer from within CS:GO[1][2]:

snd_mixahead is the length of the sound buffer in seconds, so 0.05 is 50ms (0.10, edited: 25ms is the default). This is essentially the audio delay, so reducing it gives better synchronization. Not all hardware can handle a buffer setting this low though, so if there are any crackling or pops at 0.05, increase this setting by 0.01 until the crackling/pops disappear.

Increasing RLIMIT_MEMLOCK for PulseAudio clients (systemd specific)

Note
While the general issue of insufficient lockable memory limit is common among Gentoo and, indeed, most Desktop GNU/Linux distributions, this subsection chiefly addresses an additional resource limit on systemd units. Readers not using systemd's user services should follow instructions on JACK clients instead.

In case if messages such as this are observed:

user $systemctl --user status pipewire-pulse.service
...
.. pipewire-pulse[pid]: Failed to mlock memory [address] 32816: This is not a problem but for best performance, consider increasing RLIMIT_MEMLOCK
...

The amount of memory that pipewire-pulse process can lock can be adjusted via:

user $systemctl edit --user pipewire-pulse.service

and add in the blank space in the upper section of the editor window (not forgetting to save the file afterwards, of course):

...
### Anything between here and the comment below will become the new contents of the file

[Service]
LimitMEMLOCK=256K

### Lines below this comment will be discarded
...
Important
systemd is case sensitive and does not recognize the SI abbreviation for kilo, so be sure to use the capital letter K or will print a warning about illegal value and not apply the override!

If the system is shared between multiple users, this has to be done for each user (or the created override file has to be copied over with appropriate permissions).

Finally, to have the override applied, reload the configuration and then restart the service:

user $systemctl --user daemon-reload
user $systemctl --user restart pipewire-pulse.service

The current unit default is set to LimitMEMLOCK=131072 (same as 128K) by the Gentoo package which as of PipeWire 0.3.21 appears to allow for 1 PulseAudio client (subsequent clients will receive buffers backed by unlocked memory). Increasing the number to 256K as seen above should allow for 3 clients with buffers locked to memory at the same time.

While this is just a conjecture, it seems very likely that the LimitMEMLOCK which sets the per-unit hard limit (and implicitly also the LimitMEMLOCKSoft to the same value) must be within the bounds set on the user in question, which is 64 kilobytes for users without realtime capability. To actually have the default 128K or any other value above 64 kilobytes applied, set a new limit for non-system accounts:

FILE /etc/security/limits.d/50-custom.conf
# This raises the lockable memory upper limit of every process running under a non-system account (except for nobody) from default 64 to 256 kilobytes (in increments of page size); default (soft limit) remains at 64 kilobytes
1000:65533      hard    memlock 256

The new limits are only in effect on new logins, therefore the user must log out and back in. This is usually enough but if pipewire-pulse.service survived the logout, then it must be manually restarted as described previously in this subsection.

Increasing RLIMIT_MEMLOCK for JACK clients (and PulseAudio clients with OpenRC)

Unlike the case of PulseAudio clients, for which the user service does memory locking of buffers, JACK clients do it themselves. In the likely event that the clients report being unable to lock memory, in addition to the hard limit (max permitted value) described in previous sub-section on PulseAudio RLIMIT_MEMLOCK, the soft limit (the default value) must also be raised:

FILE /etc/security/limits.d/50-custom.conf
# This both raises the max and sets the default lockable memory limit of every process running under a non-system account (except for nobody) from default 64 to 256 kilobytes (in increments of page size)
1000:65533      -    memlock 256

Bluetooth

Important
PipeWire should already be enabling the bluez5 module when built with the pulseaudio USE flag. Please check if it's being set system-wide as PulseAudio API for clients is not going anywhere in a hurry.

By default, Bluetooth support is disabled to avoid clashes with PulseAudio's Bluetooth stack since currently the main use case is as an addition to not a replacement for PA. Uncomment PipeWire's bluez5 module for Bluetooth devices to be listed:

FILE /etc/pipewire/media-session.d/media-session.conf
...
modules = {
    ...
    default = [
        ...
        bluez5          # bluetooth support
        ...
    ]
    ...

Then run:

user $systemctl --user restart pipewire-pulse.service

See also

External resources

References