Qt 5.8 CPU rendering in QML for video playback

[theonlylawislove]

For reasons I won't explain here, I have to use the CPU to render my video. I call this static method in my main.

QQuickWindow::setSceneGraphBackend(QSGRendererInterface::Software)

Then, I have the following QML to playback video.

VideoOutput {
    id: videoOut
    anchors.fill: parent
    source: player
}

MediaPlayer {
    id: player
    source: "file:///test.mp4"
    autoPlay: true
}

As you can guess, this doesn't work. You just see a black rectangle. If I comment out the setSceneGraphBackend call, it works.

So my question is, how do I customize the VideoOutput element so that it works using the CPU (not GPU/OpenGL/etc)?