FFmpeg backend: GUI thread freezes when initializing an network source

import QtQuick
import QtMultimedia
import QtQuick.Controls.Fusion

Window {
    id: root
    width: 800
    height: 600
    visible: true
    title: `${video.source} (${video.playbackState})`

    Video {
        id: video
        anchors.fill: parent
    }
    Column {
        Button {
            text: "Load"
            onClicked: video.source = "rtsp://google.com/stream" // Invalid URL causes GUI to freeze for 5s
            // onClicked: video.source = "http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4" // Valid URL causes a shorter (but still significant) freeze
         }
        Button {
            text: video.playbackState === MediaPlayer.StoppedState ? "Play" : "Stop"
            onClicked: {
                if (video.playbackState === MediaPlayer.StoppedState)
                    video.play()
                else
                    video.stop()
            }
        }
        ProgressBar {
            width: root.width
            NumberAnimation on value {
                loops: Animation.Infinite
                duration: 1000
                from: 0.0
                to: 1.0
            }
        }
    }
}