Sorry for the triaging spam, after comparing to 24.04, I found this is a
wireplumber configuration problem. The general system performance is *a
lot* worse than using KVM via libvirt, but that doesn't seem to have
been the root cause here.
A workaround for this is,
mkdir -pv ~/.config/wireplumber/wireplumber.conf.d
sed 's/api.alsa.headroom.*/api.alsa.headroom = 8192/' <
/usr/share/wireplumber/wireplumber.conf.d/alsa-vm.conf >
~/.config/wireplumber/wireplumber.conf.d/90-alsa.vm.conf
systemctl --user daemon-reload
systemctl --user restart pipewire wireplumber
Now the audio is no longer choppy in 25.10.
The root cause is that the ALSA headroom parameter was dropped to 2048,
which is not enough for the virtual sound card in VMware, and I'd guess
in VirtualBox as well, but that would need additional testing. Upstream
changed this without testing these VMs, it would seem,
In Wireplumber commit ac0d8ee4a88113c831963b2c01d9139d79ddc4a1, quote
"""
monitors/alsa: remove vm.node.defaults and use match rules instead
The vm.node.defaults logic which was inherited from p-m-s is not really
good because it seems like different VM hardware requires different
values for the defaults. Also, passthrough USB hardware should not
inerhit these values, they just cause trouble.
Instead, we can use rules to match the vm.type and specific device
properties to set a more informed period & headroom.
For now, I am also decreasing the default headroom down to 2048, which
works for me and perhaps it's a good default. We can always add more
rules here and fine-tune per vm type and virtual hardware.
See !394, #316, #348, #507, #162, pipewire#3452
"""
Will propose something upstream to fine-tune for VMware. As Daniel said,
the GPU simulation is likely the cause of us bumping into this new
maximum. Pulseaudio used to workaround problems like this, but Pipewire
doesn't support IRQ based scheduling yet, so you have to manually fuss
with the headroom parameter.
** Summary changed:
- Severe Performance Lag on 25.10 Live CD in VirtualBox and VMware Workstation
on Windows 11 hosts
+ Audio stuttering in 25.10
** Package changed: linux (Ubuntu) => wireplumber (Ubuntu)
** Changed in: wireplumber (Ubuntu)
Status: New => Triaged
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https://bugs.launchpad.net/bugs/2127250
Title:
Audio stuttering in 25.10
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