No QtMultimedia backends found. Only QMediaDevices, QAudioDevice, QSoundEffect, QAudioSink, and QAudioSource are available.

[Newtron]

I am working on a project on Asahi Linux on Macbook air m1 and tried Camera class in qml file.
Tried to load qml in pyside 6 using qqmlapplicationengine

.........
CaptureSession {
            camera: Camera {
                id: camera

                focusMode: Camera.FocusModeAutoNear
                customFocusPoint: Qt.point(0.2, 0.2) // Focus relative to top-left corner
            }
            videoOutput: videoOutput
        }

        VideoOutput {
            id: videoOutput
            anchors.fill: parent
        }
    }
.......

It shows the following error:

No QtMultimedia backends found. Only QMediaDevices, QAudioDevice, QSoundEffect, QAudioSink, and QAudioSource are available.
Failed to initialize QMediaCaptureSession "Not available"
Failed to initialize QCamera "Not available"
Failed to create QVideoSink "Not available"

By I've seen similar posts talking about the same issue but not in asahi linux. From those articles I tried to downgrade pyside6 to a lower version(6.7.0 from 6.8) but it didn't work.

[JoeCFD]

The main media backend, built on FFmpeg, ensures seamless cross-platform functionality, and is the default on all platforms
from https://doc.qt.io/qt-6/qtmultimedia-index.html

FFmpeg package needs to be installed.

[SGaist]

Hi,

One way to determine what goes wrong is to start your application with the QT_DEBUG_PLUGINS environment set to 1. It will dump everything that goes on with the plugins.

[Newtron]

It shows this error libavformat.so.58: cannot open shared object file: No such file or directory

[SGaist]

Do you have that library in your system ?

[Newtron]

It's a subpackage of old ffmpeg but in my system I'm using latest version of ffmpeg.

[SGaist]

Sorry to say that but: you did not answer the question. The library searched is libavformat version 58. Do you have that version available ? Based on the message, no, but it could be a path issue.

[friedemannkleint]

Can you please try the recent version (6.8.0.2)? There were some Multimedia libraries missing in some of the 6.7 versions.

[Big_bo]

@SGaist I have the same issue. The version of Qt I am using is 6.7.3.
qt.core.library: "/opt/Qt/6.7.3/gcc_arm64/plugins/imageformats/libqwebp.so" cannot load: Cannot load library /opt/Qt/6.7.3/gcc_arm64/plugins/imageformats/libqwebp.so: libwebp.so.6:cannot open
qt.core.plugin.loader: QLibraryPrivate::loadPlugin failed on "/opt/Qt/6.7.3/gcc_arm64/plugins/imageformats/libqwebp.so" : "Cannot load library /opt/Qt/6.7.3/gcc_arm64/plugins/imageformats/libqwebp.so: libwebp.so.6: cannot open

[JoeCFD]

@Big_bo ldd /opt/Qt/6.7.3/gcc_arm64/plugins/imageformats/libqwebp.so to see what is missing.

[Big_bo]

@JoeCFD
here is it

[Big_bo]

@JoeCFD When I execute the command:ldd /opt/Qt/6.7.3/gcc_arm64/plugins/imageformats/libqwebp.so

libwebp.so.6 => not found
libwebp.so.7 => /lib/aarch64-linux-gnu/libwebp.so.7 (0x0000007fa2330000)

I’m not quite sure what happened. Could you please help me? greatly appreciate it.

[Big_bo]

@JoeCFD
oh，I forgot to mention, I don't have this issue when using Qt5.

[JoeCFD]

@Big_bo libqwebp.so needs libwebp.so.6. Type command:
locate libwebp.so.6
to find its path. Then add its path to your env lib path