PipeWire sound server migration - 29/07/2022 00:00 GMT

PipeWire has gained a new USE flag "sound-server" for enabling/disabling its
sound server capabilities.

This change is needed to avoid PipeWire and PulseAudio conflicting over control
of audio devices. Before this change, OpenRC users were in some cases
accidentally migrated to PipeWire which was difficult to override without
manually editing launcher files.

For non-audio purposes, PipeWire is installed in many configurations as more
and more software depends on it for e.g. screensharing, sandboxing,
and window previews, so users will need to act based on their preferred
setup rather than simply avoiding installing PipeWire, as it is
increasingly required as a dependency.

Packages needing PulseAudio's APIs will be migrated from the now-meta package
media-sound/pulseaudio to depending on media-libs/libpulse. The runtime
PulseAudio server can be provided by either PipeWire (media-video/pipewire)
or the original PulseAudio (media-sound/pulseaudio-daemon).

The new sound-server USE flag for PipeWire allows easily controlling
this behavior.

There are several options available:

1. To use PipeWire for sound, users should enable USE=sound-server for PipeWire:

  Place the following entries in /etc/portage/package.use:
  ```
  media-video/pipewire sound-server
  media-sound/pulseaudio -daemon
  ```

  First, sync:
  # emerge --sync

  Deselect media-sound/pulseaudio-daemon:
  # emerge --deselect media-sound/pulseaudio-daemon

  Then perform a world upgrade with PipeWire on the command line to add
  it to the world file:
  # emerge --ask --update --changed-use --deep @world media-video/pipewire

  Then depclean:
  # emerge --ask --depclean

  OpenRC users on an XDG-compliant desktop which respects autostart files
  will not need to take any further action.

  OpenRC users using a minimal desktop which does not respect autostart
  files will need to run `gentoo-pipewire-launcher &` in e.g.
  `~/.xprofile`.

  Users who want to switch to PipeWire providing a PulseAudio daemon
  may need to `emerge --deselect` packages in their world file which
  hard-require media-sound/pulseaudio-daemon. There are only a handful
  of these. A non-exhaustive list:
  * media-sound/paprefs
  * media-sound/pasystray
  * media-sound/pulseaudio-modules-bt (shouldn't be needed anyway)
  * net-misc/pulseaudio-dlna

  If not using any of those packages anymore, please emerge --deselect
  them. If still using these, PipeWire as a PulseAudio is not an
  option at this time.

  (Note that media-libs/libpulse (which PipeWire will be using, don't emerge
  libpulse manually) provides 'pactl' which can be used as a replacement for
  e.g. media-sound/pulseaudio-ctl, so personal scripts can be adapted to this
  if desired.)

  systemd users will also need to run the following commands:
  $ systemctl --user --now disable pulseaudio.service pulseaudio.socket
  $ systemctl --user --now enable pipewire.socket pipewire-pulse.socket
  $ systemctl --user --now disable pipewire-media-session.service
  $ systemctl --user --force enable wireplumber.service
  
  Root user may replace --user with --global to change system default
  configuration for all of the above commands.

2. To use PulseAudio's daemon for sound, users should disable USE=sound-server
  for PipeWire, enable USE=daemon on media-sound/pulseaudio, and add
  media-sound/pulseaudio-daemon to their world file:

  Place the following entries in /etc/portage/package.use:
  ```
  media-video/pipewire -sound-server
  media-sound/pulseaudio daemon
  ```

  Add media-sound/pulseaudio-daemon to @world:
  # emerge --noreplace media-sound/pulseaudio-daemon

  Then perform a world upgrade:
  # emerge --ask --update --changed-use --deep @world

  Then depclean:
  # emerge --ask --depclean

  OpenRC users on an XDG-compliant desktop which respects autostart files
  will not need to take any further action.

  OpenRC users using a minimal desktop which does not respect autostart
  files should consider adding `gentoo-pipewire-launcher &` in e.g.
  `~/.xprofile` but it's not strictly required in terms of audio
  handling. It may be required in future for the non-audio usecases
  described above.

  systemd users will also need to run the following commands:
  $ systemctl --user --now enable pulseaudio.service pulseaudio.socket
  $ systemctl --user --now disable pipewire.socket pipewire-pulse.socket

  Alternatively, systemd users can run the following commands as root to change
  the default for all users:
  # systemctl --global enable pulseaudio.service pulseaudio.socket
  # systemctl --global --force disable pipewire.socket pipewire-pulse.socket

  (If taking this option, the services must be started manually as a one-off as
  a user.)

3. For users without sound on their system, those using JACK without
   PipeWire, or those using pure ALSA without PipeWire, the following steps
   are recommended:

   Place the following entries in /etc/portage/package.use:
   ```
   media-video/pipewire -sound-server
   media-sound/pulseaudio -daemon
   ```

   Then perform a world upgrade:
   # emerge --ask --update --changed-use --deep @world

   Then depclean:
   # emerge --ask --depclean

   OpenRC users on an XDG-compliant desktop which respects autostart files
   will not need to take any further action.

   OpenRC users using a minimal desktop which does not respect autostart
   files will need to run `gentoo-pipewire-launcher &` in e.g.
   `~/.xprofile`.

   systemd users will also likely want to run the following commands as a user, again
   for the purposes of non-audio PipeWire use:
   $ systemctl --user --now enable pipewire.socket
   $ systemctl --user --now --force enable wireplumber.service

   Alternatively, systemd users can run the following commands as root to change
   the default for all users,  again for the purposes of non-audio PipeWire use:
   # systemctl --global enable pipewire.socket
   # systemctl --global --force enable wireplumber.service

   (If taking this option, the services must be started manually as a one-off as
   a user.)

Further resources:
* https://wiki.gentoo.org/wiki/PipeWire