[graphics/digikam] core/app/main: Prefer PulseAudio backend to avoid missing PipeWire audio outputs

Git commit ca48eb65bc754c157673784318e9a6b8dc5f7135 by Gilles Caulier, on behalf of Mark Cockram.
Committed on 22/07/2026 at 19:42.
Pushed by cgilles into branch 'master'.

Prefer PulseAudio backend to avoid missing PipeWire audio outputs

On PipeWire systems Qt >= 6.10 defaults to its native PipeWire audio
backend. Its asynchronous EnumFormat resolution can fail for sinks that
are owned by other PipeWire clients, such as module-filter-chain effect
sinks; the devices are then silently dropped and never appear in
QMediaDevices::audioOutputs(), leaving them missing from the media
player audio output selection. Observed with Qt 6.10.2 (the relevant
code is unchanged in 6.11): the device monitor logs "Could not resolve
audio format" for exactly those nodes while a minimal Qt client on the
same system resolves them fine.

The PulseAudio backend enumerates the same devices through
pipewire-pulse without this defect, so prefer it on Linux when the user
has not chosen a backend explicitly via QT_AUDIO_BACKEND.

M  +19   -0    core/app/main/main.cpp

https://invent.kde.org/graphics/digikam/-/commit/ca48eb65bc754c157673784318e9a6b8dc5f7135

diff --git a/core/app/main/main.cpp b/core/app/main/main.cpp
index 2619353d99..70b1387a61 100644
--- a/core/app/main/main.cpp
+++ b/core/app/main/main.cpp
@@ -181,6 +181,25 @@ MAIN_EXPORT int MAIN_FN(int argc, char** argv)
 
     qputenv("QT_MEDIA_BACKEND", system.videoBackend.toLatin1());
 
+#   if defined Q_OS_LINUX
+
+    if (!qEnvironmentVariableIsSet("QT_AUDIO_BACKEND"))
+    {
+        // On PipeWire systems Qt >= 6.10 defaults to its native PipeWire
+        // audio backend, whose asynchronous format enumeration can fail
+        // for sinks owned by other PipeWire clients (for example
+        // module-filter-chain effect sinks): the affected outputs then
+        // never appear in QMediaDevices::audioOutputs(), so they are
+        // missing from the audio output selection of the media player.
+        // The PulseAudio backend enumerates the same devices through
+        // pipewire-pulse without this defect, so prefer it until the Qt
+        // issue is fixed.
+
+        qputenv("QT_AUDIO_BACKEND", "pulseaudio");
+    }
+
+#   endif
+
 #endif