wiki/wiki/linux/pipewire.md

Pipewire

Pipewire is a graph based sound server.

Setup

For clients that use the PulseAudio API pipewire-pulse (on Arch-based distros or according packages on other distros) can be installed. It will automatically remove unneeded and conflicting PulseAudio packages. Additionally pipewire-alsa and pipewire-jack for JACK and Alsa clients are available and recommended to install for full compatibility with most software. Make sure to restart to be sure everything is running correctly.

Configuration

Pipewire has a few config files. The needed folder structure can be created by the following command for a global setup.

sudo mkdir -p /etc/pipewire/ && sudo mkdir -p /etc/wireplumber/wireplumber.conf.d/ && sudo cp /usr/share/pipewire/*.conf /etc/pipewire/ && sudo cp /usr/share/wireplumber/wireplumber.conf.d/* /etc/wireplumber/wireplumber.conf.d/ 

It can also be done locally for the user with the following, alternative setup.

mkdir -p ~/.config/pipewire/ && mkdir -p ~/.config/wireplumber/wireplumber.conf.d/ && cp /usr/share/pipewire/*.conf ~/.config/pipewire/ && cp /usr/share/wireplumber/wireplumber.conf.d/* ~/.config/wireplumber/wireplumber.conf.d/ 

Usage

This section will focus on the usage of Pipewire.

Mixing

For simple sound processing in the form of volume adjustment as well as setting the default input and output devices pavucontrol can be used as a simple mixer.

Routing

This section focusses on graph-based interfaces also called patchbays. For more advanced routing qpwgraph can be used, but the GTK-based Helvum is also available. The third available option is Patchance - this is the currently recommended software of this wiki.

Equalizer, Noise Reduction, etc

For further sound processing the easiest way to do so is using easyeffects which features a wide range of effects to apply to sound streams including noise reduction.

Get ID of an Input or Output

Using the following command a list of all connected input and output aswell as streams and devices can be displayed.

wpctl status

Under the Sinks the outputs are displayed and under Sources the inputs. Defaults are noted with an asterix. The identificator is displayed prior to the name of the input, output, device or stream.

If a device name is known (in this case "Starship/Matisse HD Audio Controller Analog Stereo"). The following command will return its identificator.

NAME=$(wpctl status | grep "Starship/Matisse HD Audio Controller Analog Stereo")
ID=$( echo $NAME | cut -d '.' -f 1 | cut -c 11-)

echo ID: $ID

Loopback Input

An input can be output to the default output by using the following command. In that command <id> is the identificator of the input that should be looped back. It needs to be set accordingly.

pw-loopback -C <id>

Virtual Devices

This section focusses on the temporary and permanent creation and removal of virtual devices like virtual sinks and sources aswell as coupled nodes like loopbacks.

Creating a Null Device

This section will focus on the creation of a dummy device. That is a virtual device that can be selected as output but is not used by default. This can be useful to record applications as their sound can cleanly be passed to the dummy device which will eliminate other applications sounds. If the goal is to record and listen to an application at the same time navigate to the application loopback section

The source for this section of the entry is derived by Pipewire Gitlab site.

A dummy device, or null sink, can be created permanently by creating a .conf file inside the ~/.config/pipewire/pipewire.conf.d directory with the following lines.

context.objects = [
    {   factory = adapter
        args = {
            factory.name     = support.null-audio-sink
            node.name        = "null-sink-0"
            node.description = "Null Sink 0"
            media.class      = Audio/Sink
            audio.position   = [ FL FR ]
            monitor.channel-volumes = true
            monitor.passthrough = true
            adapter.auto-port-config = {
                mode = dsp
                monitor = true
                position = preserve
            }
        }
    }
]

Multiple devices can be created by creating different files in the directory.

If the null sink is only needed temporarily (until the next restart) the following line can be used to create it. Use different sink_names to create multiple dummy devices.

pactl load-module module-null-sink media.class=Audio/Sink sink_name=null-sink-0 channel_map=stereo

This will return an id that can be used to remove the sink with the following command.

pactl unload-module <id>

Creating a Device Loopback

In this section a device loopback is defined as a loopback that takes a device as input. This can be useful to listen to input devices, such as audio interfaces with connected microphones, instruments, etc.

The source for this section of the entry is derived by Pipewire Gitlab site and the official website.

A device loopback can be created permanently by creating a .conf file inside the ~/.config/pipewire/pipewire.conf.d directory with the following lines.

context.modules = [
  {
    name = libpipewire-module-loopback
    args = {
      audio.position = [ FL FR ]
      capture.props = {
        media.class = "Stream/Input/Audio"
        node.name = "device-loopback-1-recording"
        node.description = "Device-Loopback 1 Recording"
      }
      playback.props = {
        media.class = "Stream/Output/Audio"
        node.name = "device-loopback-1-playback"
        node.description = "Device-Loopback 1 Playback"
      }
      audio.volume = 0.5
      audio.mute = true
    }
  }
]

The created device loopback is made up by two parts that can be found in different places inside a mixer like pavucontrol. The part called Device-Loopback 1 Recording in the example config can be found in the Recording tab. There the device to loopback can be selected. The second part called Device-Loopback 1 Playback is available under the Playback tab and allows to switch the selection of the output device.

Creating an Application Loopback

This section will focus on the creation of an application loopback. In this section an application loopback is defined as a loopback that takes an application as input. This can be useful to record applications as their sound can cleanly be passed to the sink sink of the applicatino loopback which will eliminate other applications sounds. If the goal is to record and not listen to the application at the same time navigate to the null device section. Alternatively the null device can also be selected as a output device for the playback part of the application loopback which makes it easily and seemlessly possible to switch between listening in and not listening without changing the device that is recorded by the capturing program.

The source for this section of the entry is derived by Pipewire Gitlab site and the official website.

An application loopback can be created permanently by creating a .conf file inside the ~/.config/pipewire/pipewire.conf.d directory with the following lines.

context.modules = [{
    name = libpipewire-module-loopback
    args = {
        audio.position = [ FL FR ]
        capture.props = {
            media.class = "Audio/Sink"
            node.name = "application-loopback-1-sink"
            node.description = "Application-Loopback 1 Sink"
        }
        playback.props = {
            media.class = "Stream/Output/Audio"
            node.name = "application-loopback-1-playback"
            node.description = "Application-Loopback 1 Playback"
        }
    }
}]

The created device loopback is made up by two parts that can be found in different places inside a mixer like pavucontrol. The part called Application-Loopback 1 Sink in the example config can be found in the Output Devices tab. The second part called Application-Loopback 1 Playback is available under the Playback tab and allows to switch the selection of the output device. Also in the Playback tab Application-Loopback 1 Sink can be selected as an output for currently running applications which will loopback the sound to the selected output device.

Troubleshooting

This section will focus on errors and the fixing of errors of Pipewire.

Fix Crackling

Crackling can occur in various situations. There is a post by rabcor that features multiple possibilities to fix this. This section will list a few of them.

Firstly suspend can be deactivated to try to fix crackling. In alsa-vm.conf the suspend_timeout_seconds have to be set to 0 like the following lines show. This also shows the general structure but only the line starting with session is to be added.

monitor.alsa.rules = [
  { 
    actions = { 
      update-props = { 
        session.suspend-timeout-seconds = 0
  }
]

Another possibility for crackling to occur is when the allowed rates are mismatched. In pipewire.conf locate the following line.

#default.clock.allowed-rates = [ 48000 ]

Change this line to look like the following.

default.clock.allowed-rates = [ 44100 48000 ]

A third possibility to fix crackling is by adjusting the alsa headroom. In alsa-vm.conf the locate the following line.

api.alsa.headroom      = 2048

Change it to look like the following line.

api.alsa.headroom      = 0

If this doesn't work values like 2048, 512, 256, 128, 64, 32 can also be tried.

A fourth possibility to fix crackling is by adjusting the alsa period size. In alsa-vm.conf the locate the following line.

api.alsa.period-size   = 1024

Change it to look like the following line.

api.alsa.period-size   = 256

If this doesn't work values like 2048, 512, 128, 64 can also be tried.