Changes/DefaultPipeWire

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Route all Audio to PipeWire

Summary

This change proposal is to route all audio from PulseAudio and JACK to the PipeWire Audio daemon by default.

Owner

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

Current status

• Targeted release: Fedora 34
• Last updated: 2020-11-23
• 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

Currently, all desktop audio is handled by the PulseAudio daemon. Applications make use of the PulseAudio client library to communicate with the PulseAudio daemon that mixes and manages the audio streams from the clients.

The desktop shell (gnome-shell) and the control panel (gnome-control-panel) both use the Pulseaudio client libraries to manage the volume and configuration of the PulseAudio daemon.

This proposal is to replace the PulseAudio daemon with a functionally compatible implementation based on PipeWire. This means that all existing clients using the PulseAudio client library will continue to work as before, as well as applications shipped as Flatpak.

All PRO audio is handled with the JACK client library, which talks to the JACK server. This proposal will install a JACK client library replacement that talks directly to PipeWire. All existing PRO audio jack applications will then work on top of PipeWire.

For legacy ALSA clients, we will install an ALSA plugin that routes the audio directly to PipeWire.

With these 3 changes, all audio will be routed to PipeWire. There will then be no more need to install the PulseAudio and JACK daemons.

Feedback

The owner of this proposal has been in context with both the PulseAudio and JACK maintainers and community. PipeWire is considered to be the successor of both projects.

Benefit to Fedora

The end goal is to end up with one audio infrastructure for both Desktop and Pro audio use cases. This will end the fragmentation of the audio landscape.

Some of the benefits that PipeWire will bring:

* PRO Audio features

  PipeWire can support both Desktop and PRO Audio use cases. PRO Audio application tend to use
  the JACK API and JACK daemon, which is hard to setup and integrates poorly with the rest of
  the system (and PulseAudio in particular). 

  With a replacement libjack library, PRO Audio application can run directly on PipeWire and
  integrate seamlessly with other ALSA and PulseAudio applications. This would bring Fedora
  closer to the experience of other operating systems.

* Flexibility/Integration
 
  PipeWire is designed to be multiprocess. It separates the processing of the multimedia graph
  and the management into separate processes. This makes it possible to better integrate with
  the other system components or swap out the default policy for a highly customized one (such as
  for automotive or embedded). This is in contrast to PulseAudio, which has all logic embedded
  into the daemon with limited configuration options.

  In the next phase we expect to greatly expand the user experience and configuration of the
  audio infrastructure with better integration throughout the system.

* Performance
 
  PipeWire was designed for high performance and low-latency, using much of the same design as
  JACK. JACK application should run with comparable performance even in low-latency situations.

* Security

  PipeWire enforces per client security. Object visibility and the actions on them can be
  configured independently per client. This makes it possible to enforce a security policy for
  sandboxed applications (Flatpak) such as denying access to certain audio capture devices or
  block them from interfering with other applications.

* Maintainability

  Both PulseAudio and JACK have very slow development cycles with few new features. The more
  flexible and distributed nature of the design of PipeWire should encourage more new features
  and use-cases. 

Scope

• Proposal owners:

We would make a pipewire-pulse package that provides the same features as the pulseaudio (daemon) package. We would only provide a drop-in replacement daemon, the pulseaudio client libraries will remain unchanged.

The idea is that when installing pipewire-pulse, only the pulseaudio package is removed and replaced by the pipewire-pulse implementation. In the same way, installing the pulseaudio package would remove the pipewire-pulse package, making it possible to switch between implementations. This will also allow for an easy rollback.

We also need to check and correct the dependencies of other packages. As of this writing, some packages do not state their dependencies correctly and get removed when pulseaudio is removed. We also need to check the JACK to make sure they still install with the replacement JACK client library.

The JACK client libraries will be installed in the same way, removing the old JACK client libraries.

• Other developers:

The distribution needs to default to the pipewire-pulse package instead of pulseaudio.

JACK applications need to install the pipewire-libjack client library.

• Release engineering: #Releng issue number (a check of an impact with Release Engineering is needed)

The distribution needs to default to the pipewire-pulse package instead of pulseaudio.

JACK applications need to install the pipewire-libjack client library.

• Policies and guidelines:

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

• Alignment with Objectives:

Upgrade/compatibility impact

The pulseaudio package will be uninstalled and pipewire-pulse will be installed.

pipewire-pulse does not yet implement all the features of pulseaudio but it is expected that comparable functionality will be implemented later. Most notable features that are likely not going to be available for fedora 34

* avahi network discovery and audio routing. This is not enabled by default but can be activated
  with paprefs. this includes TCP and RTP transport of audio.
* make devices available as UPNP media servers. Not enabled by default, paprefs can be used.
* easy configuration of combining all sinks. Questionable feature but possible via paprefs.

User scripts will still work but custom configurations of the pulseaudio daemon will not be used anymore.

Most of the JACK workflow of managing the JACK daemon is not going to be needed anymore as things will work out-of-the-box. As of this writing, these things are missing from the JACK implementation, we hope to implement them before fedora 34:

* latency reporting: useful to align streams
* freewheeling: used when rendering a project
* jackdbus: used by some tools to manage the graph

How To Test

This change needs to be tested on as many different audio cards as possible. The same test plan applies here as with PulseAudio.

To test, one needs to install the pipewire-pulse library (which removes the pulseaudio package).

To test the JACK support, one needs to install pipewire-libjack, which removes the original JACK client and server.

After these changes, a restart is needed to make sure the new pipewire-pulse daemon is running.

Audio functionality should be like it was before with the Pulseaudio daemon. Some things to verify:

- patcl info should now list: Server Name: PulseAudio (on PipeWire 0.3.x)
- gnome-control-center: check the audio tab, check the volume sliders and do the audio channel
                        test. Change the card profile, plug/unplug headphones and observe correct
                        switch.
- pavucontrol: check volumes in the input devices tabs and check the microphone volumes
- firefox: check out a website with audio/video such as youtube and verify that audio works as
           usual. Check out a website with a video chat test page (bluejeans.com/111).
- rhythmbox: check if playback works as expected
- bluetooth devices, connect as usual and verify working behaviour with PipeWire. Check volume
                     changes etc.
- Regular system usage and performance should not change.
- JACK tools such as catia, carla should run and can be used to inspect the graph.

User Experience

In general, users should not be able to see any change when using PulseAudio applications.

The big change is when using JACK application:

- They will start without having to configure and start the daemon. this includes
  the period size and sample rates.
- All devices will be visible in the graph with meaningful names. Devices will
  be automatically slaved when needed without needing any configuration.
- bluetooth devices will be usable as well.

Dependencies

Other packages might need to have their requirements fixed to work with the replacement packages but this is under our control.

Contingency Plan

• Contingency mechanism: Keep existing pulseaudio and JACK client libraries as defaults
• Contingency deadline: beta freeze
• Blocks release? No
• Blocks product? No

Documentation

• PipeWire website
• Video with Current status
• install guide
• how to use/test