Public bug reported:
I'm running Ubuntu 24.04.5 with PipeWire 1.0.5 and an ASUS USB audio
controller (USB ID `0b05:1a98`). The optical output is connected to an
Astro MixAmp Pro that supports Dolby Digital 5.1.
I can successfully output Dolby Digital 5.1 using the ALSA A52 encoder
directly through `hw:0,3`. All six channels work correctly.
I also created a temporary stereo PipeWire sink using `plughw:0,3`,
which works without issues, including in Steam games.
The problem occurs when I create a six-channel PipeWire sink using the
A52 encoder:
```bash
pactl load-module module-alsa-sink \
device="plug:{SLAVE=\"a52:0,'hw:0,3'\"}" \
sink_name=astro_ac3_test \
format=s32le rate=48000 channels=6 \
channel_map=front-left,front-right,rear-left,rear-right,front-center,lfe
```
PipeWire successfully creates the sink, and Steam games output six-
channel audio to it. However, actual gameplay produces severe crackling,
along with repeated errors:
```text
spa.alsa: plug:{SLAVE="a52:0,'hw:0,3'"}p: snd_pcm_start: Broken pipe
```
I also tried changing the buffering parameters (`fragments=4`,
`fragment_size=1536`, `mmap=false`), without resolving the issue.
This appears related to the existing ALSA issue:
https://github.com/alsa-project/alsa-plugins/issues/37
I'm not sure whether the root cause is PipeWire's ALSA scheduling or the
A52 plugin's interaction with PipeWire, but the direct ALSA comparison
suggests the problem is in that integration.
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: pipewire 1.0.5-1ubuntu3.3
ProcVersionSignature: Ubuntu 7.0.0-38.38~24.04.4-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
ApportVersion: 2.28.3-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Sun Oct 18 11:40:28 2026
InstallationDate: Installed on 2025-09-12 (401 days ago)
InstallationMedia: Ubuntu 24.04.3 LTS "Noble Numbat" - Release amd64
(20250805.1)
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
RebootRequiredPkgs: Error: path contained symlinks.
SourcePackage: pipewire
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: pipewire (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble
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https://bugs.launchpad.net/bugs/2171344
Title:
AC-3 5.1 output crackles with PipeWire, but works directly through
ALSA
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