Arch Linux

Potomac

Member

Registered: 2011-12-25

Posts: 544

[SOLVED] No sound with ffmpeg Qt6 multimedia backend

Hello,

I use Plasma 6.4.5, I notice a recent problem with Gwenview 25.08.2-3 Arch Linux package :

- when I open a video file with Gwenview 25.08.2-3 then the sound doesn't work,

If I run Gwenview from the console then I see this output "No audio device detected" :

QGraphicsWidget::setAttribute: unsupported attribute 74
Input #0, matroska,webm, from '/home/Barto/retour_vers_le_present.mkv':
  Metadata:
    title           : Retour vers le présent
    CREATION_TIME   : 2017-11-29T19:05:48Z
    ENCODER         : Lavf57.7.2
  Duration: 00:03:00.02, start: 0.000000, bitrate: 925 kb/s
  Stream #0:0: Video: h264 (Main), yuv420p(tv, smpte170m/bt470bg/bt709, progressive), 718x404 [SAR 1:1 DAR 359:202], 25 fps, 25 tbr, 1k tbn, start 0,102000 (default)
  Stream #0:1(fre): Audio: mp3 (mp3float), 48000 Hz, stereo, fltp, 192 kb/s (default)
    Metadata:
      title           : Stereo
No audio device detected

When I use other player then I get the sound.

Is it a problem of configuration of Gwenview ?

I use Pulseaudio.

Thanks

Last edited by Potomac (2025-11-13 22:32:21)

teckk

Member

Registered: 2013-02-21

Posts: 562

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

Gwenview is an image viewer.
https://apps.kde.org/gwenview/

Or are you talking about something else?

Potomac

Member

Registered: 2011-12-25

Posts: 544

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

Gwenview can open and read video files, it is not only restricted to image files :

Raster image (including but not limited to BMP, PNG, JPEG, GIF, MNG, TIFF, and PSD), SVG, RAW (limited), and video support

https://en.wikipedia.org/wiki/Gwenview

If you browse a directory with gwenview that contains video files then you will be able to read videos files.

The problem is that Gwenview has a bug since a recent version of the package, the sound doesn't work, I can reproduce the bug on 2 different PCs.

Last edited by Potomac (2025-10-24 06:01:05)

Potomac

Member

Registered: 2011-12-25

Posts: 544

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

I upgraded to Plasma 6.5.0 but I still have the problem : no sound with Gwenview when I open a video file.

I notice also the same problem with Dragon player, same error message in the console when I open a video file :

"No audio device detected"

Arch Linux package is dragon 25.08.2-2, I suspect a problem with the audio backend of plasma.

I use "Phonon VLC" according to phononsettings tool.

Last edited by Potomac (2025-10-24 20:07:01)

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 24,923

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

Are the vlc plugin subpackages installed? It got split into plugin subpackages so people can pick and choose which kind of functionality they want, f you don't care to curate this and just want the functionality, make sure vlc-plugins-all is installed.

Last edited by V1del (2025-10-25 01:36:49)

Potomac

Member

Registered: 2011-12-25

Posts: 544

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

Yes vlc-plugins-all is installed, but I still have the problem.

arojas

Developer

From: Spain

Registered: 2011-10-09

Posts: 2,260

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

gwenview doesn't use phonon. Which qt multimedia backends do you have installed?

Potomac

Member

Registered: 2011-12-25

Posts: 544

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

Here is what I have installed :

$ pacman -Qs multimedia | grep "qt"
local/phonon-qt5 4.12.0-4
local/phonon-qt6 4.12.0-5
local/qt5-multimedia 5.15.17+kde+r2-1 (qt5)
local/qt6-multimedia 6.10.0-2 (qt6)
local/qt6-multimedia-ffmpeg 6.10.0-2

for phonon :

$ pacman -Qs phonon
local/phonon-qt5 4.12.0-4
    The multimedia framework by KDE
local/phonon-qt5-gstreamer 4.10.0-4
    Phonon GStreamer backend for Qt5
local/phonon-qt6 4.12.0-5
    The multimedia framework by KDE
local/phonon-qt6-vlc 0.12.0-5
    Phonon VLC backend

I use Pulseaudio and I have the problem on 2 differents PC :

- on recent PC (AMD Ryzen 9 7900, motherboard B650 chipset)
- on an old mini-pc based on Intel CPU core i5

both PCs use Pulseaudio and same multimedia Qt and phonon backends.

Last edited by Potomac (2025-10-25 12:29:37)

arojas

Developer

From: Spain

Registered: 2011-10-09

Posts: 2,260

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

Do you get sound with ffplay?

Potomac

Member

Registered: 2011-12-25

Posts: 544

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

Yes I have sound when I use ffplay for opening video and audio files.

Last edited by Potomac (2025-10-25 16:04:32)

Potomac

Member

Registered: 2011-12-25

Posts: 544

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

I made progress :

- I discover that if I set the QT_MEDIA_BACKEND environment variable to "gstreamer" then I have sound on gwenview :

QT_MEDIA_BACKEND=gstreamer gwenview <audio or video file>

the output :

qt.multimedia.gstreamer: Using Qt multimedia with GStreamer version: "GStreamer 1.26.7"

If I try ffmpeg backend for qt6-multimedia then I get no sound with gwenview :

QT_MEDIA_BACKEND=ffmpeg gwenview <audio or video file>

the output :

qt.multimedia.ffmpeg: Using Qt multimedia with FFmpeg version n8.0 GPL version 3 or later

(...)

No audio device detected

And if try without setting QT_MEDIA_BACKEND then I have also no sound.

I have both ffmpeg and gstreamer backend installed :

local/qt6-multimedia-ffmpeg 6.10.0-2
    FFMpeg backend for qt6-multimedia

local/qt6-multimedia-gstreamer 6.10.0-2
    Gstreamer backend for qt6-multimedia

libvlc package and all vlc-plugin-* packages are installed :

local/libvlc 3.0.21-31
    Free and open source cross-platform multimedia player and framework - library

local/vlc-plugin-ffmpeg 3.0.21-31
    Free and open source cross-platform multimedia player and framework - FFMPEG plugins

local/vlc-plugins-all 3.0.21-31
    Free and open source cross-platform multimedia player and framework - all plugins

local/vlc-plugins-base 3.0.21-31
    Free and open source cross-platform multimedia player and framework - base plugins

local/vlc-plugins-extra 3.0.21-31
    Free and open source cross-platform multimedia player and framework - extra plugins

So why I have this problem ?
Is it a bug with the ffmpeg qt6-multimedia backend ?
A problem with pulseaudio ?

Last edited by Potomac (2025-11-08 00:08:27)

Potomac

Member

Registered: 2011-12-25

Posts: 544

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

I found another workaround :

setting QT_AUDIO_BACKEND to pulseaudio solves the problem, ffmpeg Qt6 multimedia backend can now detect my sound card.

export QT_AUDIO_BACKEND=pulseaudio 

It seems that ffmpeg Qt6 multimedia selects by default pipewire, even if Pulseaudio is the main sound server, it seems a bug related to Qt6,

I have both Pulseadio and Pipewire, but Pulseaudio is the main sound server.

Pipewire packages installed on my system :

local/kpipewire 6.5.2-1 (plasma)
    Components relating to pipewire use in Plasma

local/libpipewire 1:1.4.9-1
    Low-latency audio/video router and processor - client library

local/libwireplumber 0.5.12-1
    Session / policy manager implementation for PipeWire - client library

local/pipewire 1:1.4.9-1
    Low-latency audio/video router and processor

local/qemu-audio-pipewire 10.1.2-2
    QEMU PipeWire audio driver

local/wireplumber 0.5.12-1
    Session / policy manager implementation for PipeWire

local/wireplumber-docs 0.5.12-1
    Session / policy manager implementation for PipeWire - documentation

Last edited by Potomac (2025-11-09 02:49:31)

Potomac

Member

Registered: 2011-12-25

Posts: 544

Re: [SOLVED] No sound with ffmpeg Qt6 multimedia backend

A fix has been found by the Qt team :
https://codereview.qt-project.org/c/qt/ … a/+/689934

The bug is now solved.

Last edited by Potomac (2025-11-13 22:31:24)