Real time microphone noise cancellation on Linux

This article will focus on configuring the Noise cancelling plugin with PipeWire and creating a Virtual Source to use as an input for any application, even web-based applications like Discord or Steam.

Prerequisites:

- PipeWire
- Arch Linux based Distro

1. Plugin Installation

sudo pacman -S noise-suppression-for-voice  

2. Create Filter chain for PipeWire
A filter chain provides the capability to insert an arbitrary graph of LADSPA (Linux Audio Developer’s Simple Plugin API) and built-in plugins in front of a sink or a source to create a new Virtual filtered sink/source.

2.1 Create a configuration directory to store filter chain configuration files.

mkdir -p ~/.config/pipewire/ 

2.2 Create a filter chain file with the name “input-filter-chain.conf”.

You can use any name you prefer, but make sure to use it throughout the configuration.

nano ~/.config/pipewire/input-filter-chain.conf

Paste the following content to the above file.

# Noise canceling source
#
# start with pipewire -c filter-chain/input-filter-chain.conf
#
context.properties = {
    log.level        = 0
}

context.spa-libs = {
    audio.convert.* = audioconvert/libspa-audioconvert
    support.*       = support/libspa-support
}

context.modules = [
    {   name = libpipewire-module-rtkit
        args = {
            #nice.level   = -11
            #rt.prio      = 88
            #rt.time.soft = 200000
            #rt.time.hard = 200000
        }
        flags = [ ifexists nofail ]
    }
    {   name = libpipewire-module-protocol-native }
    {   name = libpipewire-module-client-node }
    {   name = libpipewire-module-adapter }

    {   name = libpipewire-module-filter-chain
        args = {
            node.name =  "rnnoise_source"
            node.description =  "Noise Canceling source"
            media.name =  "Noise Canceling source"
            filter.graph = {
                nodes = [
                    {
                        type = ladspa
                        name = rnnoise
                        plugin = /usr/lib/ladspa/librnnoise_ladspa.so
                        label = noise_suppressor_stereo
                        control = {
                            "VAD Threshold (%)" 50.0
                        }
                    }
                ]
            }
            capture.props = {
                node.passive = true
            }
            playback.props = {
                media.class = Audio/Source
            }
        }
    }
]

3. Persist the configuration

To load this filter chain to the PipeWire, we need to create a systemd service. The service we will be making as a systemd user instance and it will start at the first login. The systemd user instance is a per-user process and not per-session.

3.1 Create the systemd user configuration directory if it does not exist.

mkdir -p ~/.config/systemd/user/

3.2 Create a new systemd unit file.

nano ~/.config/systemd/user/pipewire-input-filter-chain.service

Make sure to replace the <username> with your account username. 

[Unit]
Description=PipeWire Input Filter Chain
After=pipewire.service
BindsTo=pipewire.service

[Service]
ExecStart=/usr/bin/pipewire -c /home/<username>/.config/pipewire/input-filter-chain.conf
Type=simple
Restart=on-failure

[Install]
WantedBy=pipewire.service

3.3 Reload systemd user unit files.

systemctl --user daemon-reload

3.4 Enable the created systemd service.

systemctl --user enable pipewire-input-filter-chain.service

Logout and log back in and check the sound control panel on your DE and you will see a new input source with the name “Noise cancelling source”.

4. Finally select the new audio source on applications.