https://bugs.kde.org/show_bug.cgi?id=513536
Bug ID: 513536
Summary: KDE Connect Bluetooth backend causes audio
crackling/stuttering in Bluetooth headset (A2DP) under
PipeWire
Classification: Applications
Product: kdeconnect
Version First 25.11.80
Reported In:
Platform: EndeavourOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: desktop-application
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Summary:
KDE Connect Bluetooth backend causes audio crackling/stuttering in Bluetooth
headset (A2DP) under PipeWire
Description:
After updating to KDE Connect 25.12.0-1 on EndeavourOS (Arch Linux-based, KDE
Plasma 6.5.4), enabling the Bluetooth backend in KDE Connect settings causes
severe audio crackling and stuttering when playing audio through a Bluetooth
headset (Sony WH-1000XM4) using A2DP profile with AAC codec in PipeWire. The
same issue occurs with the two previous versions, 25.11.80 and 25.11.90.
The issue did not occur with the previous version (KDE Connect 25.08.3-2).
Downgrading to 25.08.3-2 resolves the problem completely while keeping the
Bluetooth backend enabled.
Symptoms:
- Audio starts normally for a few seconds, then crackling persists for an
extended period (cycle of normal → heavy crackling → normal).
- The issue occurs only when the Bluetooth backend is enabled in KDE Connect
settings (Backends → Bluetooth checked).
- Disabling the Bluetooth backend immediately resolves the crackling (audio
becomes stable, though other KDE Connect features over Wi-Fi remain
functional).
- Switching to SBC codec reduces crackling but degrades sound quality
significantly.
- No issues with HSP/HFP profiles (mono, low quality).
Workaround:
- Disabling the Bluetooth backend in KDE Connect GUI (Settings > Backends >
uncheck Bluetooth) or setting disabled_providers=BluetoothLinkProvider in
~/.config/kdeconnect/config fully resolves the issue while keeping the latest
KDE Connect version.
- Downgrading KDE Connect to 25.08.3-2 allows using the Bluetooth backend
without issues.
This behavior resembles Bug 415976 (KDE Connect increasing Bluetooth buffer
size leading to laggy sound in PulseAudio), but occurs in a modern PipeWire
environment. It appears the Bluetooth backend interferes with PipeWire's
Bluetooth audio buffering or scheduling.
Steps to Reproduce:
1. Update to KDE Connect 25.12.0-1 on EndeavourOS/Arch Linux with PipeWire.
2. Pair a Bluetooth headset (e.g., Sony WH-1000XM4) and set A2DP Sink with AAC
codec.
3. Open KDE Connect settings → Backends → Enable Bluetooth.
4. Play audio (e.g., music or video).
5. Observe crackling after a few seconds.
6. Disable Bluetooth backend → Crackling stops immediately.
Environment:
- OS: EndeavourOS (up to date as of December 2025)
- KDE Plasma Version: 6.5.4
- KDE Frameworks Version: 6.21.0
- Qt Version: 6.10.1
- KDE Connect: 25.12.0-1
- Audio server: PipeWire (with WirePlumber)
- Bluetooth headset: Sony WH-1000XM4 (firmware up to date)
- Codec: AAC (default/high priority)
Additional Information:
- No relevant errors in journalctl for PipeWire/WirePlumber/Bluetooth during
the issue.
- Tested multiple buffer/quantum adjustments in PipeWire – no effect when
Bluetooth backend is enabled.
- Issue started after KDE Applications update to 25.12.0.
This significantly impacts usability for users relying on high-quality
Bluetooth audio. A fix to prevent the Bluetooth backend from interfering with
A2DP audio buffering would be appreciated.
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