title: Multiple audio tracks for video playback in Qt
body: <p>I'm developing a small video editor to make quick edits to a multiple audio track video, using Qt. I'm a bit confused about whether it is possible or not to handle multiple audio tracks in payback and processing in Qt.</p>
  <h5>What I want to do with the video</h5>
  <ul>
  <li>list audio tracks</li>
  <li>for each track, manage its volume, and choose to perform channel duplication on a mono track (to make it stereo).</li>
  <li>play the video with the setting I chose for audio tracks, eventually being able to change settings on the fly.</li>
  <li>extract a part of the video with the settings I chose.</li>
  </ul>
  <p>I'm not sure if Qt can handle this by itself, or if I need to rely on a library specialized in video processing. Therefore, my question is double</p>
  <h5>If it is possible in Qt-only : how ?</h5>
  <p>I suppose I need to use <code>QMediaPlayer</code> class, but it doesn't look like it can handle multiple tracks at once.</p>
  <p>Maybe by splitting the media into several sub-media, but then how to synchronize their playback?</p>
  <h5>Otherwise : external library. Are there any caveats to avoid?</h5>
  <p>I wonder what is the best way, if there is one, to display video frames (assuming audio will be handled by external lib)?</p>
  <p>Should I draw frames directly on a QWidget, or should I use OpenGL directly? Or another method?</p>
  <p><strong>Note: I'm not forcibly looking for a detailed answer, I'm fine with short ones and/or external resources.</strong></p>