QtMultimedia backend setup

Rotty

Hi,
I need to write multivideo player. I tried python+tkinter+tkvideoplayer. This failed to play smoothly fullhd video in fullscreen on raspberry 5. I switch to pyqt and the basic test failed with message:

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

So, I installed Qt using official install script and run Media player from examples. It end with the same error. No QtMultimedia backend.

My question: How to set/install any QtMultimedia backend on freshly installed 64bit official rasbian?

JonB

@Rotty
Because of https://stackoverflow.com/questions/78577031/pyqt6-6-7-0-how-to-fix-error-no-qtmultimedia-backends-found please start by stating the exact version of PyQt you are running.

Rotty

@JonB No version of PyQt now. I'm switched to C++ and Qt 6.7.3. I have installed it using qt-online-installer-linux-arm64-4.8.1.run from Qt web page. I have ran Qt creator then and tried Media Player example in C++.

SGaist

Hi,

Start your application with the QT_DEBUG_PLUGINS environment variable set to 1. It will print a lot of information and should tell you more about what is failing with the backend.

Rotty

@SGaist said in QtMultimedia backend setup:

QT_DEBUG_PLUGINS

Thank You, I one step closer to solution. It looks like missing library.

qt.core.library: "/home/aosp/Qt/6.7.3/gcc_arm64/plugins/multimedia/libffmpegmediaplugin.so" cannot load: Cannot load library /home/aosp/Qt/6.7.3/gcc_arm64/plugins/multimedia/libffmpegmediaplugin.so: libavformat.so.58: cannot open shared object file: No such file or directory
qt.core.plugin.loader: QLibraryPrivate::loadPlugin failed on "/home/aosp/Qt/6.7.3/gcc_arm64/plugins/multimedia/libffmpegmediaplugin.so" : "Cannot load library /home/aosp/Qt/6.7.3/gcc_arm64/plugins/multimedia/libffmpegmediaplugin.so: libavformat.so.58: cannot open shared object file: No such file or directory"
No QtMultimedia backends found. Only QMediaDevices, QAudioDevice, QSoundEffect, QAudioSink, and QAudioSource are available.
qt.core.plugin.loader: Found metadata in lib /home/aosp/Qt/6.7.3/gcc_arm64/qml/QtQml/WorkerScript/libworkerscriptplugin.so, metadata=
{
    "IID": "org.qt-project.Qt.QQmlEngineExtensionInterface",
    "archlevel": 0,
    "className": "QtQmlWorkerScriptPlugin",
    "debug": false,
    "uri": [
        "QtQml.WorkerScript"
    ],
    "version": 395008
}

Rotty

Quick update. liibavformat.so.58 is not available in current raspbian.

The following packages have unmet dependencies:
 libavformat58 : Depends: libavcodec58 (= 8:4.3.6-0+deb11u1+rpt5)
                 Depends: libsrt1.4-gnutls (>= 1.4.2) but it is not installable

Is there a way how to tell Qt to use version 59?

Temporary solution:
Switch multimedia backend: Set enviroment variable QT_MEDIA_BACKEND=gstreamer

SGaist

One other option is to rebuild the ffmpeg backend (just it) with your system provided librairies.