title: Using Qt to make audio loopback capture
body: <p>Is it possible to use Qt to capture user output sound ?
  I've trying to use my default output device (= my sound card) as input device, but it does not work :</p>
  
  <pre><code>QAudioDeviceInfo inputDevices = QAudioDeviceInfo::availableDevices(QAudio::AudioOutput).at(0);
  
  m_audioInput = new QAudioInput(inputDevices, formatAudio, this);
  
  m_device = new MyIODevice(this);
  m_device-&gt;open(QIODevice::WriteOnly);
  
  m_audioInput-&gt;start(m_device);
  </code></pre>
  
  <p>If it's not possible with Qt, are here any multiplatform library to do that ? maybe OpenAL ? My target are Windows, Android, MacOS, iOS.</p>