title: Audio output with video processing with opencv
body: <p>I am processing video with opencv, but at the same time I need to play audio and simply control it, like loud or current frame number.</p>
  
  <p>I think I should create a parallel process with ffmpeg, but I don't know how to do so.  Can you explain what to do?</p>
  
  <p>Or do you know another solution?</p>