Changes/WirePlumber

Switch to WirePlumber as the PipeWire session manager

Summary

PipeWire currently uses a simple example session manager. This proposal is to move to the more powerful WirePlumber session manager.

Owner

• Name: Wim Taymans
• Email: wim.taymans@gmail.com

Current status

• Targeted release: Fedora Linux 35
• Last updated: 2021-07-19
• FESCo issue: <will be assigned by the Wrangler>
• Tracker bug: <will be assigned by the Wrangler>
• Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

PipeWire requires a session manager that at least needs to implements the following features:

* create and configure detected devices in the system. This includes audio cards, video and bluetooth devices.
* configure applications and route audio/video to/from them to the devices and filters.
* keep track of prefered devices and volumes.
* move audio/video streams when devices appear and disappear.

PipeWire uses a simple example session manager with limited features and configuration options. The proposal is to move to WirePlumber.

WirePlumber is built on GNOME (GObject) technologies and has bindings for most languages using GObject introspection.

WirePlumber allows one to implement many of the rules for setup and configuration using small LUA scripts, which are easier to maintain and customize. These are some of the functions that are scriptable in LUA:

• setup and configuration of the devices and streams. This includes deciding if devices and streams need to operate in 5.1 or stereo mode, depending on the available devices.
• routing of the streams based on metadata of the streams (Roles) and overall state of the system.
• volume/mute restore of devices and streams

Benefit to Fedora

PipeWire currently uses a simple example session manager with mostly hardcoded logic and rules. This proposal wants to replace the session manager with a more advanced session manager, called WirePlumber.

WirePlumber brings to following improvements

• Drop-in replacement session manager for PipeWire, implements the exact same features as the example session manager
• built with GObject, which provides a richer development experience and adds bindings for most languages
• extensible with loadable modules
• scriptable policy using small lua scripts
• better integration with desktop settings

The main benefits will be that this session manager would allow for more customization of the policy and rules. Initially we aim for feature parity with the current solution and work on more features in the next releases.

Scope

• Proposal owners:

This is a rather isolated changed. Instead of starting the pipewire-media-session executable we would need to package and start WirePlumber instead.

WirePlumber has been kept up to data with the features in the example session manager and would need testing.

• Other developers:

None. This is an isolated PipeWire change.

• Release engineering: #Releng issue number

A new systemd service will need to be activated in the default install.

• Policies and guidelines: N/A (not needed for this Change)

• Trademark approval: N/A (not needed for this Change)

• Alignment with Objectives:

A more configurable and adaptable session manager will make it easier to adapt to the Audio and Video requirements and policy of the target use-case. We could more easily write desktop, PRO audio or mobile configurations.

Upgrade/compatibility impact

Should not cause any change.

How To Test

Experience should be the same as before. Retest all audio testcases.

User Experience

Should not cause any visible change.

Dependencies

None.

Contingency Plan

If the feature can not be completed we continue using the existing pipewire-media-session.

• Contingency mechanism: (What to do? Who will do it?) N/A (not a System Wide Change)
• Contingency deadline: N/A (not a System Wide Change)
• Blocks release? N/A (not a System Wide Change), Yes/No

Documentation

[WirePlumber](https://gitlab.freedesktop.org/pipewire/wireplumber)

N/A (not a System Wide Change)