Re: [PATCH v4 3/3] Run PipeWire and WirePlumber in the VMs

[Demi Marie Obenour <demiobenour@gmail.com>]

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On 7/19/25 05:22, Alyssa Ross wrote:
> Demi Marie Obenour <demiobenour@gmail.com> writes:
> 
>> On 7/18/25 07:27, 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.  I did build a
>>>> Spectrum OS image and found that PipeWire and WirePlumber both
>>>> successfully started.  PipeWire is configured to listen on the
>>>> PulseAudio socket, so PulseAudio compatibility works.  This does inject
>>>> a large number of completely unnecessary files into the VM, notably for
>>>> libcamera and Bluetooth support.
>>>>
>>>> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
>>>> ---
>>>>
>>>> Notes:
>>>>     I tested this with QEMU virtio-sound, but I am not sure if the paramters
>>>>     are correct.  In particular, the sample rate might well be wrong.
>>>>
>>>>  img/app/Makefile                              |  28 +-
>>>>  img/app/default.nix                           |  18 +
>>>>  img/app/etc/pipewire/pipewire.conf            | 291 ++++++++
>>>>  .../etc/s6-rc/app/dependencies.d/directories  |   0
>>>>  .../app/dependencies.d/directories.license    |   2 +
>>>>  .../etc/s6-rc/app/dependencies.d/wireplumber  |   0
>>>>  .../app/dependencies.d/wireplumber.license    |   2 +
>>>>  .../etc/s6-rc/dbus/dependencies.d/directories |   0
>>>>  .../dbus/dependencies.d/directories.license   |   2 +
>>>>  img/app/etc/s6-rc/directories/type            |   1 +
>>>>  img/app/etc/s6-rc/directories/type.license    |   2 +
>>>>  img/app/etc/s6-rc/directories/up              |  11 +
>>>>  .../s6-rc/pipewire/dependencies.d/directories |   0
>>>>  .../dependencies.d/directories.license        |   2 +
>>>>  img/app/etc/s6-rc/pipewire/notification-fd    |   1 +
>>>>  .../s6-rc/pipewire/notification-fd.license    |   2 +
>>>>  img/app/etc/s6-rc/pipewire/run                |  20 +
>>>>  img/app/etc/s6-rc/pipewire/type               |   1 +
>>>>  img/app/etc/s6-rc/pipewire/type.license       |   2 +
>>>>  .../dependencies.d/directories                |   0
>>>>  .../dependencies.d/directories.license        |   2 +
>>>>  img/app/etc/s6-rc/wayland-proxy-virtwl/run    |  11 -
>>>>  .../etc/s6-rc/wireplumber/dependencies.d/dbus |   0
>>>>  .../wireplumber/dependencies.d/dbus.license   |   2 +
>>>>  .../s6-rc/wireplumber/dependencies.d/pipewire |   0
>>>>  .../dependencies.d/pipewire.license           |   2 +
>>>>  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 +
>>>>  img/app/etc/wireplumber/wireplumber.conf      | 676 ++++++++++++++++++
>>>
>>> The PipeWire and WirePlumber config files are still very big.  Is it
>>> really not possible to make them smaller and rely on defaults where
>>> possible?  With a whole big config like this, it's difficult to see what
>>> Spectrum-specific stuff is going on.
>>
>> Both of these files are *smaller* than their upstream counterparts.
>> The main Spectrum-specific stuff is:
>>
>> - Nodes are statically set up.  This is because PipeWire relies on
>>   udev to enumerate device nodes, and Spectrum VMs don't have udev.
>>
>> - A lot of stuff in the upstream configuration files has been
>>   removed.  Spectrum's configs should be *smaller* than their
>>   upstream counterparts.
>>
>> Neither PipeWire nor WirePlumber has much in the way of a default
>> configuration.  Without a configuration file, neither PipeWire nor
>> WirePlumber does anything useful.  Overriding the defaults and
>> using the upstream configuration file might be possible, but it
>> seemed unlikely when I looked.  Spectrum VMs are more like
>> embedded systems than the desktop systems the defaults are made
>> for.
> 
> Okay, but there's still stuff that could definitely be trimmed.  The
> comments explaining the syntax of the config file, and the default
> values, for example.  I think they get in the way more than they help
> because they make the actual non-default settings very sparse.
> Similarly we probably don't need conditional overrides that are "only
> applied when running in a VM".

I'll fix this in v5 by only including comments explaining the differences
from upstream and removing the conditional overrides.

>> I recommend not including any of the upstream configuration
>> files and only an allowlist of SPA plugins and PipeWire and
>> WirePlumber modules.  Stuff like Bluetooth can also be excluded.
>> Just because upstream nixpkgs pulls it in as a dependency does
>> not mean the configuration in the VM actually needs it.
>> Ideally, the various plugins and modules would all be separate
>> build outputs with their own dependencies, and ‘pipewire’ and
>> ‘wireplumber’ would be meta-packages that pull in all of them.
> 
> That's an interesting idea.  I think it would probably be feasible?  And
> wouldn't share the same maintenance concerns as lots of overrides.

I'll add that to the list of debloating tasks.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)

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