// Run in main thread
auto mpExtractor = new QtAV::VideoFrameExtractor();
mpExtractor->setAsync(false);
mpExtractor->setSource("file://whatever.mp4"); // This call will unnecessarily start the ExtractThread which will unload the demuxer in p->releaseResourceInternal()
mpExtractor->setPosition(0);
mpExtractor->extract(); // The frame extraction is only successful if the demuxer is loaded. Racing happens because the ExtractThread simultaneously unloads the demuxer while the main thread loads the demuxer in checkAndOpen()