Program crash in QAudioDecoder destructor or constructor

QByteArray ba_buffer;
QAudioDecoder decoder;
 //decoder.audioFormat() is empty after finished
 QAudioFormat aFormat;
 decoder.setSourceFilename(fileInfo.absoluteFilePath());
 decoder.start();
 QEventLoop loop;
 connect(&decoder, &QAudioDecoder::bufferReady,
 &loop, [&decoder, &ba_buffer, &aFormat]()
 {
 auto audio_buffer = decoder.read();
aFormat = audio_buffer.format();
ba_buffer.append(audio_buffer.constData<char>(), audio_buffer.byteCount());
 });
 connect(&decoder, &QAudioDecoder::finished,
 &loop, &QEventLoop::quit, Qt::QueuedConnection);
 connect(&decoder, QOverload<QAudioDecoder::Error>::of(&QAudioDecoder::error),
 &loop, [&loop](){loop.quit();}, Qt::QueuedConnection);
 QTimer timer_stop;
 connect(&timer_stop, &QTimer::timeout, &loop, [&loop, this, &timer_stop]()
 {
 if(stopLoadDir)
 {
 loop.quit();
 timer_stop.stop();
 }
 }, Qt::QueuedConnection);
 timer_stop.start(100);
....
 if(stopLoadDir)
 {
 return data;
 }