Unable to play mp3/mp4 with Qt 5.15.10 on Rapsberry Pi 3 B+

Mark81

I set up a Buildroot environment, so I have a working cross-compiler toolchain with Qt/QML 5.15.10 that runs on a Raspberry Pi 3 B+.
It works fine, but I cannot play any multimedia file.

I installed gstreamer-1.0 with some plugins along with gst1-libav.
I'm aware there are tons of plugins, but I just need to play mp3 and mp4 H264 files.

Enabling QT_DEBUG_PLUGINS I get:

13:41:01: Starting /opt/foo-qml/bin/foo-qml on test-project...
QML debugging is enabled. Only use this in a safe environment.
QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/qt/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqeglfs.so"
Found metadata in lib /usr/lib/qt/plugins/platforms/libqeglfs.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "eglfs"
        ]
    },
    "archreq": 0,
    "className": "QEglFSIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("eglfs")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqminimal.so"
Found metadata in lib /usr/lib/qt/plugins/platforms/libqminimal.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimal"
        ]
    },
    "archreq": 0,
    "className": "QMinimalIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("minimal")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqminimalegl.so"
Found metadata in lib /usr/lib/qt/plugins/platforms/libqminimalegl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimalegl"
        ]
    },
    "archreq": 0,
    "className": "QMinimalEglIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("minimalegl")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqoffscreen.so"
Found metadata in lib /usr/lib/qt/plugins/platforms/libqoffscreen.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "offscreen"
        ]
    },
    "archreq": 0,
    "className": "QOffscreenIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("offscreen")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqvnc.so"
Found metadata in lib /usr/lib/qt/plugins/platforms/libqvnc.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "vnc"
        ]
    },
    "archreq": 0,
    "className": "QVncIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("vnc")
QFactoryLoader::QFactoryLoader() checking directory path "/opt/foo-qml/bin/platforms" ...
loaded library "/usr/lib/qt/plugins/platforms/libqeglfs.so"
QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/qt/plugins/egldeviceintegrations" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/egldeviceintegrations/libqeglfs-emu-integration.so"
Found metadata in lib /usr/lib/qt/plugins/egldeviceintegrations/libqeglfs-emu-integration.so, metadata=
{
    "IID": "org.qt-project.qt.qpa.egl.QEglFSDeviceIntegrationFactoryInterface.5.5",
    "MetaData": {
        "Keys": [
            "eglfs_emu"
        ]
    },
    "archreq": 0,
    "className": "QEglFSEmulatorIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("eglfs_emu")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/egldeviceintegrations/libqeglfs-kms-egldevice-integration.so"
Found metadata in lib /usr/lib/qt/plugins/egldeviceintegrations/libqeglfs-kms-egldevice-integration.so, metadata=
{
    "IID": "org.qt-project.qt.qpa.egl.QEglFSDeviceIntegrationFactoryInterface.5.5",
    "MetaData": {
        "Keys": [
            "eglfs_kms_egldevice"
        ]
    },
    "archreq": 0,
    "className": "QEglFSKmsEglDeviceIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("eglfs_kms_egldevice")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/egldeviceintegrations/libqeglfs-kms-integration.so"
Found metadata in lib /usr/lib/qt/plugins/egldeviceintegrations/libqeglfs-kms-integration.so, metadata=
{
    "IID": "org.qt-project.qt.qpa.egl.QEglFSDeviceIntegrationFactoryInterface.5.5",
    "MetaData": {
        "Keys": [
            "eglfs_kms"
        ]
    },
    "archreq": 0,
    "className": "QEglFSKmsGbmIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("eglfs_kms")
QFactoryLoader::QFactoryLoader() checking directory path "/opt/foo-qml/bin/egldeviceintegrations" ...
loaded library "/usr/lib/qt/plugins/egldeviceintegrations/libqeglfs-kms-integration.so"
QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/qt/plugins/imageformats" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/imageformats/libqico.so"
Found metadata in lib /usr/lib/qt/plugins/imageformats/libqico.so, metadata=
{
    "IID": "org.qt-project.Qt.QImageIOHandlerFactoryInterface",
    "MetaData": {
        "Keys": [
            "ico",
            "cur"
        ],
        "MimeTypes": [
            "image/vnd.microsoft.icon",
            "image/vnd.microsoft.icon"
        ]
    },
    "archreq": 0,
    "className": "QICOPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("ico", "cur")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/imageformats/libqjpeg.so"
Found metadata in lib /usr/lib/qt/plugins/imageformats/libqjpeg.so, metadata=
{
    "IID": "org.qt-project.Qt.QImageIOHandlerFactoryInterface",
    "MetaData": {
        "Keys": [
            "jpg",
            "jpeg"
        ],
        "MimeTypes": [
            "image/jpeg",
            "image/jpeg"
        ]
    },
    "archreq": 0,
    "className": "QJpegPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("jpg", "jpeg")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/imageformats/libqsvg.so"
Found metadata in lib /usr/lib/qt/plugins/imageformats/libqsvg.so, metadata=
{
    "IID": "org.qt-project.Qt.QImageIOHandlerFactoryInterface",
    "MetaData": {
        "Keys": [
            "svg",
            "svgz"
        ],
        "MimeTypes": [
            "image/svg+xml",
            "image/svg+xml-compressed"
        ]
    },
    "archreq": 0,
    "className": "QSvgPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("svg", "svgz")
QFactoryLoader::QFactoryLoader() checking directory path "/opt/foo-qml/bin/imageformats" ...
loaded library "/usr/lib/qt/plugins/imageformats/libqico.so"
loaded library "/usr/lib/qt/plugins/imageformats/libqjpeg.so"
loaded library "/usr/lib/qt/plugins/imageformats/libqsvg.so"
*** INFO *** ()
Found metadata in lib /usr/qml/QtQuick.2/libqtquick2plugin.so, metadata=
{
    "IID": "org.qt-project.Qt.QQmlExtensionInterface/1.0",
    "archreq": 0,
    "className": "QtQuick2Plugin",
    "debug": false,
    "uri": [
        "QtQuick.2"
    ],
    "version": 331520
}


loaded library "/usr/qml/QtQuick.2/libqtquick2plugin.so"
Found metadata in lib /usr/qml/QtQuick/Window.2/libwindowplugin.so, metadata=
{
    "IID": "org.qt-project.Qt.QQmlEngineExtensionInterface",
    "archreq": 0,
    "className": "QtQuick2WindowPlugin",
    "debug": false,
    "uri": [
        "QtQuick.Window.2"
    ],
    "version": 331520
}


loaded library "/usr/qml/QtQuick/Window.2/libwindowplugin.so"
Found metadata in lib /usr/qml/QtMultimedia/libdeclarative_multimedia.so, metadata=
{
    "IID": "org.qt-project.Qt.QQmlExtensionInterface/1.0",
    "archreq": 0,
    "className": "QMultimediaDeclarativeModule",
    "debug": false,
    "uri": [
        "QtMultimedia"
    ],
    "version": 331520
}

Key points:

QAudioDeviceInfo info;
qDebug() << info.supportedCodecs();

returns an empty list.

Audio {
    source: "file:///root/test.mp3"
    autoLoad: true
    autoPlay: true

    onError: console.log(errorString)
}

returns:

Got keys from plugin meta data ("gstreamermediaplayer")
QFactoryLoader::QFactoryLoader() checking directory path "/opt/foo-qml/bin/mediaservice" ...
loaded library "/usr/lib/qt/plugins/mediaservice/libgstmediaplayer.so"
QMediaPluginLoader: loaded plugins for key "org.qt-project.qt.mediaplayer" : ("gstreamermediaplayer")
QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/qt/plugins/resourcepolicy" ...
QFactoryLoader::QFactoryLoader() checking directory path "/opt/foo-qml/bin/resourcepolicy" ...
qml: play
QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/qt/plugins/accessible" ...
QFactoryLoader::QFactoryLoader() checking directory path "/opt/foo-qml/bin/accessible" ...
QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/qt/plugins/accessiblebridge" ...
QFactoryLoader::QFactoryLoader() checking directory path "/opt/foo-qml/bin/accessiblebridge" ...
qml: Internal data stream error.
Error: "Internal data stream error."

while:

Video {
        source: "file:///root/sample.mp4"
        autoLoad: true
        autoPlay: true

        onErrorStringChanged: console.log(errorString)
        onPlaying: console.log("play")
}

returns:

loaded library "/usr/qml/QtMultimedia/libdeclarative_multimedia.so"
13:41:02: /opt/foo-qml/bin/foo-qml on test-project exited with code 255

and it exits the program.

What specific plugins I need to add in order to play those files?

Mark81

After making a clean build of Buildroot, the mp3 file plays fine, even if QAudioDeviceInfo::supportedCodecs() still returns an empty list.

Instead, enabling the Video section in QML leads to the same "crash" with error -255.

Mark81

Sorry, another update. This snippet:

MediaPlayer {
    id: mediaplayer
    source: "file:///root/sample.mp4"
    autoPlay: true
}

VideoOutput {
    anchors.fill: parent
    source: mediaplayer
}

works fine.
So it's only the Video object that does not work.
I can live with MediaPlayer + VideoOutput but I'd like to understand why the first option does not work.