Media Session Module: ALSA Monitor

This module monitors udev for ALSA devices and creates the required PipeWire Device objects for each ALSA device.

Devices advertised by udev are reserved using the DBus ReserveDevice API and exported as SPA_TYPE_INTERFACE_Device in the Core. For each device, objects of type SPA_TYPE_INTERFACE_Node are then created as required.

Additionally, extra configuration is applied as shown below. This configuration is applied before the device is exported.

Configuration

This module loads the alsa-monitor.conf configuration file. The main component in that file is the rules = [] array that consists of multiple dictionaries that matches a device and specifying actions to take.

The following actions are supported:

• update-props: update properties on the matched object

For example:

rules = [
{
  # Matches is an array of dictionaries. For a dictionary to match, **all**
  # key/value matches must apply. For a match to be successful, **any**
  # dictionary must apply.
  matches = [
  {
    # A regular expression is prefixed with ~
    device.name = "~alsa_card.*"
  }
  {
    # standard string comparisons
    device.name = "alsa_card.abcdef"
    node.name = "alsa_input.12345"
  }
  {
    # 'null' matches if the property is unset
    some.random.property = "null"
  }
  ]
  actions = {
    update-props = {
      api.alsa.use-acp = true
    }
  }
}
]

Module-specific properties:

Ths modules supports the following entries in the properties dictionary:

• alsa.reserve = false: disable device reservation (default: enabled)
• alsa.jack-device = true: createa a JACK device (default: disabled), see the comment in the example configuration file.

See the alsa-monitor.conf provided by your installation for details on possible actions and matches.