ios vlckit - no video when playing recorded avi file

I am using vlckit in xcode for an ios app. I am playing a RTSP-Stream with vlckit which works. Then I am recording the stream with the startRecordingAtPath function and stopRecording function, which also works. The avi file of the record gets created at the choosen path. When I want to play this avi file with the play function it only plays the audio, not the video. I only see a white screen instead of the video. Is this a bug or am I doing something wrong?

This is my playback function:

func makeUIViewRecord(){
    var path = FileManager.default.urls(for: .moviesDirectory, in: .userDomainMask)[0]
    let recordname = "filename.avi"
    path = path.appendingPathComponent(recordname)
    mediaPlayer.stop()
    let media = VLCMedia(url: path)
    mediaPlayer.media = media
    DispatchQueue.main.async(){
                mediaPlayer.play()
            }  
}