https://bugs.kde.org/show_bug.cgi?id=508871
Bug ID: 508871
Summary: kasts 25.08.0 reset audio backend to QtMultimedia
(bisected to have regressed in
09c90105e5a8612fa733b90b3e31d1bf4f40d697)
Classification: Applications
Product: kasts
Version First 25.08.0
Reported In:
Platform: Debian unstable
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
Hi,
as you taught me, the audio backend QtMultimedia is kind-of-deprecated on Linux
(#473648) and can cause all kind of issues (#508302). Therefore, kasts on Linux
tries to use VLC backend whenever possible. This was true until kasts_25.04.3,
now kasts_25.08.0 resets the backend to QtMultimedia.
(I hope I haven't messed up Debian packaging, I've used the usual Qt/KDE team
packaging scripts to manage the update.)
I've bisected the git history between 25.04.3 and 25.08.0 : 8119acce works,
while 09c90105 has the regression (installing 09c90105 on top of 8119acce is
seen as a downgrade in the log here below simply due to alphabetic order).
QtMultimedia being used is evident in the terminal (qt.multimedia.ffmpeg
lines), then I can simply attach the terminal log without any screenshot.
mobian@mobian:~$ sudo apt install kasts/trixie
Selected version '25.04.3-1' (Debian:13.0/stable [arm64]) for 'kasts'
DOWNGRADING:
kasts
Summary:
Upgrading: 0, Installing: 0, Downgrading: 1, Removing: 0, Not Upgrading: 2
Download size: 863 kB
Freed space: 1055 kB
Continue? [Y/n]
Get:1 http://deb.debian.org/debian trixie/main arm64 kasts arm64 25.04.3-1 [863
kB]
Fetched 863 kB in 0s (2028 kB/s)
dpkg: warning: downgrading kasts (25.07.0+git09c90105-1) to (25.04.3-1)
(Reading database ... 142087 files and directories currently installed.)
Preparing to unpack .../kasts_25.04.3-1_arm64.deb ...
Unpacking kasts (25.04.3-1) over (25.07.0+git09c90105-1) ...
Setting up kasts (25.04.3-1) ...
Processing triggers for man-db (2.13.1-1) ...
Processing triggers for hicolor-icon-theme (0.18-2) ...
Processing triggers for libc-bin (2.41-12) ...
mobian@mobian:~$ rm -R .local/share/KDE/kasts
mobian@mobian:~$ rm -R .cache/KDE/kasts
mobian@mobian:~$ rm .config/KDE/kasts.conf
mobian@mobian:~$ kasts
Activating WAL mode on database: ok
Database version 0
Migrating database to version 1
Migrating database to version 2
Migrating database to version 3
Migrating database to version 4
Migrating database to version 5
Migrating database to version 6
Migrating database to version 7
Migrating database to version 8; this can take a while
Migrating database to version 9
Migrating database to version 10
Migrating database to version 11
qrc:/qt/qml/org/kde/kasts/qml/FeedListPage.qml:18:1: QML FeedListPage: Created
graphical object was not placed in the graphics scene.
file:///usr/lib/aarch64-linux-gnu/qt6/qml/org/kde/kirigami/PageRow.qml:1099:5:
QML RowLayout: StackView has detected conflicting anchors. Transitions may not
execute properly.
qrc:/qt/qml/org/kde/kirigamiaddons/settings/private/ConfigMobilePage.qml:126:
GeneralSettingsPage_QMLTYPE_276(0xaaaaf8967e30) should be coerced to void
because the function called is insufficiently annotated. The original value is
retained. This will change in a future version of Qt.
file:///usr/lib/aarch64-linux-gnu/qt6/qml/org/kde/kirigami/PageRow.qml:724:5:
QML StackView: replace: nothing to push
mobian@mobian:~$ sudo apt install ./kasts_25.07.0+git8119acce-1_arm64.deb
Note, selecting 'kasts' instead of './kasts_25.07.0+git8119acce-1_arm64.deb'
Upgrading:
kasts
Summary:
Upgrading: 1, Installing: 0, Removing: 0, Not Upgrading: 2
Download size: 0 B / 921 kB
Space needed: 1055 kB / 98.2 GB available
Get:1 /home/mobian/kasts_25.07.0+git8119acce-1_arm64.deb kasts arm64
25.07.0+git8119acce-1 [921 kB]
(Reading database ... 142088 files and directories currently installed.)
Preparing to unpack .../kasts_25.07.0+git8119acce-1_arm64.deb ...
Unpacking kasts (25.07.0+git8119acce-1) over (25.04.3-1) ...
Setting up kasts (25.07.0+git8119acce-1) ...
Processing triggers for man-db (2.13.1-1) ...
Processing triggers for hicolor-icon-theme (0.18-2) ...
Processing triggers for libc-bin (2.41-12) ...
Notice: Download is performed unsandboxed as root as file
'/home/mobian/kasts_25.07.0+git8119acce-1_arm64.deb' couldn't be accessed by
user '_apt'. - pkgAcquire::Run (13: Permission denied)
mobian@mobian:~$ kasts
Database version 11
qrc:/qt/qml/org/kde/kasts/qml/FeedListPage.qml:18:1: QML FeedListPage: Created
graphical object was not placed in the graphics scene.
file:///usr/lib/aarch64-linux-gnu/qt6/qml/org/kde/kirigami/PageRow.qml:1099:5:
QML RowLayout: StackView has detected conflicting anchors. Transitions may not
execute properly.
qrc:/qt/qml/org/kde/kirigamiaddons/settings/private/ConfigMobilePage.qml:126:
GeneralSettingsPage_QMLTYPE_303(0xaaaac386c510) should be coerced to void
because the function called is insufficiently annotated. The original value is
retained. This will change in a future version of Qt.
file:///usr/lib/aarch64-linux-gnu/qt6/qml/org/kde/kirigami/PageRow.qml:724:5:
QML StackView: replace: nothing to push
mobian@mobian:~$ sudo apt install ./kasts_25.07.0+git09c90105-1_arm64.deb
Note, selecting 'kasts' instead of './kasts_25.07.0+git09c90105-1_arm64.deb'
DOWNGRADING:
kasts
Summary:
Upgrading: 0, Installing: 0, Downgrading: 1, Removing: 0, Not Upgrading: 2
Download size: 0 B / 921 kB
Space needed: 0 B / 98.2 GB available
Continue? [Y/n]
Get:1 /home/mobian/kasts_25.07.0+git09c90105-1_arm64.deb kasts arm64
25.07.0+git09c90105-1 [921 kB]
dpkg: warning: downgrading kasts (25.07.0+git8119acce-1) to
(25.07.0+git09c90105-1)
(Reading database ... 142087 files and directories currently installed.)
Preparing to unpack .../kasts_25.07.0+git09c90105-1_arm64.deb ...
Unpacking kasts (25.07.0+git09c90105-1) over (25.07.0+git8119acce-1) ...
Setting up kasts (25.07.0+git09c90105-1) ...
Processing triggers for hicolor-icon-theme (0.18-2) ...
Processing triggers for libc-bin (2.41-12) ...
Notice: Download is performed unsandboxed as root as file
'/home/mobian/kasts_25.07.0+git09c90105-1_arm64.deb' couldn't be accessed by
user '_apt'. - pkgAcquire::Run (13: Permission denied)
mobian@mobian:~$ kasts
Database version 11
qt.multimedia.ffmpeg: Using Qt multimedia with FFmpeg version 7.1.1-1+b1 GPL
version 2 or later
qt.multimedia.ffmpeg: Available HW decoding frameworks:
Failed to open VDPAU backend libvdpau_nvidia.so: cannot open shared object
file: No such file or directory
qt.multimedia.ffmpeg: Available HW encoding frameworks:
qrc:/qt/qml/org/kde/kasts/qml/FeedListPage.qml:18:1: QML FeedListPage: Created
graphical object was not placed in the graphics scene.
file:///usr/lib/aarch64-linux-gnu/qt6/qml/org/kde/kirigami/PageRow.qml:1099:5:
QML RowLayout: StackView has detected conflicting anchors. Transitions may not
execute properly.
qrc:/qt/qml/org/kde/kirigamiaddons/settings/private/ConfigMobilePage.qml:126:
GeneralSettingsPage_QMLTYPE_303(0xaaab0dc21250) should be coerced to void
because the function called is insufficiently annotated. The original value is
retained. This will change in a future version of Qt.
file:///usr/lib/aarch64-linux-gnu/qt6/qml/org/kde/kirigami/PageRow.qml:724:5:
QML StackView: replace: nothing to push
mobian@mobian:~
I've also tried the following on top of 25.08.0
--- kmediasession.cpp 2025-08-28 22:04:37.437475309 +0200
+++ build_kasts/kasts/src/kmediasession/kmediasession.cpp 2025-08-27
21:36:14.228985872 +0200
@@ -65,11 +65,14 @@
setCurrentBackend(mediaBackend);
} else {
#ifdef HAVE_LIBVLC
+ qWarning() << "setting VLC backend";
setCurrentBackend(KMediaSession::MediaBackends::Vlc);
#else
#ifdef HAVE_GST
+ qWarning() << "setting Gstreamer backend";
setCurrentBackend(KMediaSession::MediaBackends::Gst);
#else
+ qWarning() << "setting QtMultimedia backend";
setCurrentBackend(KMediaSession::MediaBackends::Qt);
#endif
#endif
but I haven't seen any of those debug lines in the terminal, then either I've
done it wrong or those lines are not relevant for the Linux usecase.
It would be nice that the Linux build got back to using VLC backend by default.
Thank you
SOFTWARE/OS VERSIONS
Linux: 6.16-sm6350
KDE Plasma Version: 6.3.6
KDE Frameworks Version: 6.13.0
Qt Version: 6.8.2
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