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PipeWire backend

The PipeWire backend creates filter nodes in the PipeWire graph. Unlike other backends that connect directly to devices, PipeWire nodes are meant to be connected via WirePlumber rules or tools like Helvum.

Build requirements

The PipeWire backend requires the PipeWire development libraries:

  • Debian/Ubuntu: sudo apt install libpipewire-0.3-dev
  • Fedora: sudo dnf install pipewire-devel
  • Arch Linux: sudo pacman -S pipewire

Build with the pipewire-backend feature:

cargo build --release --features pipewire-backend

Configuration

Like PulseAudio, PipeWire uses F32 internally, so no sample format configuration is needed.

Capture device

capture:
  type: PipeWire
  channels: 2
  node_name: camilladsp-capture (*)
  node_description: CamillaDSP Capture (*)
  node_group_name: camilladsp (*)
  autoconnect_to: null (*)

Playback device

playback:
  type: PipeWire
  channels: 2
  node_name: camilladsp-playback (*)
  node_description: CamillaDSP Playback (*)
  node_group_name: camilladsp (*)
  autoconnect_to: null (*)

The parameters marked (*) are optional. The values shown above are the defaults. These are used if the parameters are set to null or left out from the configuration.

Parameters

Parameter Description
channels Number of audio channels (required)
node_name PipeWire node name for WirePlumber matching (optional, defaults to camilladsp-capture or camilladsp-playback)
node_description PipeWire node description, shown in tools such as Helvum (optional, defaults to CamillaDSP Capture or CamillaDSP Playback)
node_group_name PipeWire node group name (optional, defaults to camilladsp)
autoconnect_to PipeWire name or serial (given as a string with quotes, "123") of a node to autoconnect to (optional)

Node groups

PipeWire nodes can be assigned to groups. Nodes in the same group are always scheduled by the same driver. This ensures that these nodes run in the same graph execution cycle, sharing the same clock and timing. Use the same group name for capture and playback. Leave at the default value unless more than one CamillaDSP instance is running.

Autoconnect

The autoconnect_to parameter takes either a name or a serial number of a PipeWire node. The property is a string, so serial numbers must be quoted in the yaml file (autoconnect_to: "123"). If given, CamillaDSP will ask PipeWire to try connect the CamillaDSP capture or playback node to the given node. This enables basic routing to be set up without any additional tools, and is useful when both the source and sink nodes already exist.

For anything more advanced, it is recommended to leave this parameter at the default null, and instead set up routing with WirePlumber rules.

Node names can be found with the pw-cli command:

pw-cli ls Node

Example of node names for audio playback devices:

  • Intel HD Audio headphone output: alsa_output.pci-0000_00_1f.3-platform-skl_hda_dsp_generic.HiFi__Headphones__sink
  • MOTU M4: alsa_output.hw_M4_0

WirePlumber routing

CamillaDSP by default creates nodes that do not auto-connect to any devices. Use WirePlumber rules to connect them to your audio sources and sinks.

Example WirePlumber rules (0.5+)

WirePlumber 0.5 and later use .conf files with SPA-JSON format instead of Lua.

Create ~/.config/wireplumber/wireplumber.conf.d/51-camilladsp.conf:

monitor.alsa.rules = [
  # Connect a USB microphone to CamillaDSP capture
  {
    matches = [
      { node.name = "alsa_input.usb-Some_Microphone-00.analog-stereo" }
    ]
    actions = {
      update-props = {
        target.object = "camilladsp-capture"
      }
    }
  }
  # Connect CamillaDSP playback to speakers
  {
    matches = [
      { node.name = "camilladsp-playback" }
    ]
    actions = {
      update-props = {
        target.object = "alsa_output.pci-0000_00_1f.3.analog-stereo"
      }
    }
  }
]

Restart WirePlumber after adding rules:

systemctl --user restart wireplumber

To find the correct node names, use:

wpctl status

Manual connection with pw-link

You can also connect nodes manually:

# List available nodes
pw-cli ls Node

# Connect capture
pw-link "alsa_input.usb-...:capture_FL" "camilladsp-capture:input_0"
pw-link "alsa_input.usb-...:capture_FR" "camilladsp-capture:input_1"

# Connect playback
pw-link "camilladsp-playback:output_0" "alsa_output.pci-...:playback_FL"
pw-link "camilladsp-playback:output_1" "alsa_output.pci-...:playback_FR"

Using Helvum

Helvum is a graphical patchbay for PipeWire. Install it and drag connections between CamillaDSP nodes and your audio devices.

Monitoring

Use pw-top to see active PipeWire nodes and their CPU usage:

pw-top

Use pw-cli to inspect CamillaDSP nodes:

pw-cli info camilladsp-capture
pw-cli info camilladsp-playback

Full example configuration

devices:
  samplerate: 48000
  chunksize: 1024
  capture:
    type: PipeWire
    channels: 2
    # node_name defaults to camilladsp-capture
  playback:
    type: PipeWire
    channels: 4
    # node_name defaults to camilladsp-playback

filters:
  lowpass:
    type: Biquad
    parameters:
      type: Lowpass
      freq: 80
      q: 0.707

mixers:
  stereo_to_quad:
    channels:
      in: 2
      out: 4
    mapping:
      - dest: 0
        sources:
          - channel: 0
            gain: 0
      - dest: 1
        sources:
          - channel: 1
            gain: 0
      - dest: 2
        sources:
          - channel: 0
            gain: 0
      - dest: 3
        sources:
          - channel: 1
            gain: 0

pipeline:
  - type: Mixer
    name: stereo_to_quad
  - type: Filter
    channel: 2
    names:
      - lowpass
  - type: Filter
    channel: 3
    names:
      - lowpass

This configuration:

  1. Captures 2-channel audio from whatever is routed to camilladsp-capture
  2. Mixes to 4 channels (stereo + subwoofer pair)
  3. Applies lowpass filter to channels 2 and 3 (subwoofers)
  4. Outputs 4 channels to camilladsp-playback