On 7/29/25 09:08, Alyssa Ross wrote:
Demi Marie Obenour <demiobenour@gmail.com> writes:
WirePlumber is completely overkill as a session manager here, and ideally a trivial session manager would be used instead. PipeWire is configured to listen on the PulseAudio socket, so PulseAudio compatibility works. pw-record and pw-play both work, and if PulseAudio is installed paplay and parecord also work. This does install a lot of unnecessary files into the VMs, which will hopefully be removed later as part of a debloating effort.
Only run-qemu has had a virtio-sound device added, as crosvm and Cloud Hypervisor require a virtio-user sound device and that is more complex to set up.
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com> --- Changes since v8: - Add longer explanation for the priority.driver and priority.session values. - Give credit to George Kiagiadakis. - Fix spelling errors in comments.
Changes since v7: - Give the capture node a higher priority.session than the playback node, so WirePlumber links recording applications to the capture node instead of the monitor of the playback node. - Give the capture node a higher priority.driver than the playback node, so PipeWire has the capture node drive the graph. This is better because capture xruns lead to permanently corrupted data, whereas playback xruns do not. - Re-enable monitor node creation in WirePlumber.
Changes since v6: - Fix spelling errors in commit messages. - Sort lines in Makefile. - Don't disable support.settings as a comment in wireplumber.conf says to not do that. Instead, tell WirePlumber to not create monitor nodes. This is a workaround for WirePlumber bug 829. - Don't remove "-cpu host" from make run-qemu's QEMU command line. This was needed for local testing with KVM disabled but should not have been submitted upstream. Hardware with KVM support should be used instead.
Changes since v5:
- Use a drop-in configuration file for WirePlumber instead of overriding wireplumber.conf. This should be more robust to future WirePlumber changes. --- img/app/Makefile | 16 +- img/app/default.nix | 3 + img/app/etc/mdev.conf | 1 + img/app/etc/pipewire/pipewire.conf | 229 ++++++++++++++++++ .../etc/s6-rc/app/dependencies.d/wireplumber | 0 .../etc/s6-rc/pipewire/dependencies.d/dbus | 0 img/app/etc/s6-rc/pipewire/notification-fd | 1 + .../s6-rc/pipewire/notification-fd.license | 2 + img/app/etc/s6-rc/pipewire/run | 23 ++ img/app/etc/s6-rc/pipewire/type | 1 + img/app/etc/s6-rc/pipewire/type.license | 2 + .../etc/s6-rc/wireplumber/dependencies.d/dbus | 0 .../s6-rc/wireplumber/dependencies.d/pipewire | 0 img/app/etc/s6-rc/wireplumber/run | 4 + img/app/etc/s6-rc/wireplumber/type | 1 + img/app/etc/s6-rc/wireplumber/type.license | 2 + .../wireplumber.conf.d/99_spectrum.conf | 42 ++++ 17 files changed, 325 insertions(+), 2 deletions(-) create mode 100644 img/app/etc/pipewire/pipewire.conf create mode 100644 img/app/etc/s6-rc/app/dependencies.d/wireplumber create mode 100644 img/app/etc/s6-rc/pipewire/dependencies.d/dbus create mode 100644 img/app/etc/s6-rc/pipewire/notification-fd create mode 100644 img/app/etc/s6-rc/pipewire/notification-fd.license create mode 100644 img/app/etc/s6-rc/pipewire/run create mode 100644 img/app/etc/s6-rc/pipewire/type create mode 100644 img/app/etc/s6-rc/pipewire/type.license create mode 100644 img/app/etc/s6-rc/wireplumber/dependencies.d/dbus create mode 100644 img/app/etc/s6-rc/wireplumber/dependencies.d/pipewire create mode 100644 img/app/etc/s6-rc/wireplumber/run create mode 100644 img/app/etc/s6-rc/wireplumber/type create mode 100644 img/app/etc/s6-rc/wireplumber/type.license create mode 100644 img/app/etc/wireplumber/wireplumber.conf.d/99_spectrum.conf
We have app depending on wireplumber, but no notification-fd for wireplumber. What's actually required here? Does Wireplumber actually need to be running (for whatever definition thereof) by the time an application starts, or does it just need to start at some reasonable point?
The latter. In systemd terms, this is WantedBy=. I will fix this by having ok-all depend on WirePlumber, while the app no longer does.
+ # PipeWire chooses the node with the highest priority.driver value as + # graph driver, which is the node that decides when the processing graph + # is going to run. If both the capture node and playback node are in + # the same graph, the capture node should be chosen as the driver. This + # is because the driver gets to choose the rate of the graph and so is + # much less likely to xrun. Since capture xruns result in corrupted + # audio recordings, while playback xruns just result in a glitch, it + # is more important to avoid capture xruns. + # + # When there are multiple sources or sinks that could be used, + # WirePlumber links application nodes to the one with the highest + # priority.session value. In the configuration created here, + # there are two valid audio sources: the virtio sound card's + # capture stream and the monitor of its playback stream. The + # capture stream is the correct choice, so its priority.session + # should be higher. + # + # The recommendation to give the capture device higher values + # for priority.driver and priority.session comes from George + # Kiagiadakis of Collabora, who also provided the values + # used (2000 and 1000) and why they must be different. + # The explanation for why it is more important to avoid + # capture xruns than playback xruns comes from past discussions + # that I (Demi Marie Obenour) had with Wim Taymans.
Just checking: they're okay with being credited, right? (Important for me to be confident before mentioning anybody in an immutable log.)
That's actually not something I had checked. I asked both if they are okay with this. Should I sent V10 without these, or should I wait for a response from them?
diff --git a/img/app/etc/s6-rc/app/dependencies.d/wireplumber b/img/app/etc/s6-rc/app/dependencies.d/wireplumber new file mode 100644 index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 diff --git a/img/app/etc/s6-rc/pipewire/dependencies.d/dbus b/img/app/etc/s6-rc/pipewire/dependencies.d/dbus
This dependency wasn't needed and wasn't included in the VMs. v10 will leave it out.
--- /dev/null +++ b/img/app/etc/s6-rc/pipewire/run @@ -0,0 +1,23 @@ +#!/bin/execlineb -P +# SPDX-License-Identifier: EUPL-1.2+ +# SPDX-FileCopyrightText: 2023-2024 Alyssa Ross <hi@alyssa.is> +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour <demiobenour@gmail.com> + +s6-ipcserver-socketbinder -B /run/user/0/pipewire-0 +fdmove -c 3 0 + +s6-ipcserver-socketbinder -B /run/user/0/pipewire-0-manager +fdmove -c 4 0 + +redirfd -r 0 /dev/null + +# Wait for sound devices to be available +if { /etc/mdev/wait controlC0 } + +# Notify readiness. +if { fdmove 1 5 echo } +fdclose 5
We could move this earlier, right? If things connect before the sound devices are available, PipeWire won't have been started yet so the connection will just not be accepted until they are.
That is indeed correct. Will change in v10.
diff --git a/img/app/etc/wireplumber/wireplumber.conf.d/99_spectrum.conf b/img/app/etc/wireplumber/wireplumber.conf.d/99_spectrum.conf new file mode 100644 index 0000000000000000000000000000000000000000..277e6019c46582afba12af9b1a27bb16ddd9e804 --- /dev/null +++ b/img/app/etc/wireplumber/wireplumber.conf.d/99_spectrum.conf @@ -0,0 +1,42 @@ +# SPDX-License-Identifier: MIT +# SPDX-FileCopyrightText: 2019-2021 Collabora Ltd. +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour + +# Copyright © 2019-2021 Collabora Ltd.
Once again I'm surprised any of this is © Collabora…
It's out of an abundance of caution. All of this is taken from the wireplumber.conf files in Arch and Nixpkgs, which I believe are just the upstream ones. I suspect you are correct, but it's much better to keep a copyright notice that is not needed than to remove one that actually *is* needed.
+# +# Permission is hereby granted, free of charge, to any person obtaining a +# copy of this software and associated documentation files (the "Software"), +# to deal in the Software without restriction, including without limitation +# the rights to use, copy, modify, merge, publish, distribute, sublicense, +# and/or sell copies of the Software, and to permit persons to whom the +# Software is furnished to do so, subject to the following conditions: +# +# The above copyright notice and this permission notice (including the next +# paragraph) shall be included in all copies or substantial portions of the +# Software. +# +# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL +# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING +# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +# DEALINGS IN THE SOFTWARE. + +wireplumber.profiles = { + spectrum = { + # Spectrum VMs are essentially embedded systems, in that they are + # not at all general-purpose. + inherits = [ main-embedded ] + # Disable video and Bluetooth + hardware.video-capture = disabled + hardware.bluetooth = disabled + # Media Session is definitely not running + check.no-media-session = disabled + } +} + +wireplumber.settings = { + # Default to 100% sink volume. The host will adjust this as needed. + device.routes.default-sink-volume = 1.0 +}
-- Sincerely, Demi Marie Obenour (she/her/hers)