title: Setting volume per instance in QML Audio/Video elements?
body: <p>I want to fade out the volume of an audio file while fading in the sound of a video in QML.
  This should be no problem with animations, but I'm hitting a wall here.
  It seems like the <code>volume</code> property is somehow shared between all instances of all media elements in QML. See for example the following code:</p>
  
  <pre><code>Rectangle
  {
      id:mainScreen
      focus: true
  
      Video
      {
          id:video
          anchors.fill: parent
          source: "path/to/file.mp4";
          volume:1
          onVolumeChanged: console.warn("video: "+volume)
          autoPlay: true
      }
      Audio
      {
          source: "path/to/file.mp3";
          id:audio
          volume:1
          onVolumeChanged: console.warn("audio: "+volume)
          autoPlay: true
      }
  
  
      Keys.onPressed:
      {
          audio.volume = Math.random(1);
      }
  }
  </code></pre>
  
  <p>When I press a key, the <code>onVolumeChanged</code>-Handlers of both <code>video</code> and <code>audio</code> are called.
  Is there a way to control the volume of the elements independently?</p>
  
  <p>Or should I file a Qt bug report? This is the OpenGL MSVC2010 build of Qt 5.2.0 in case it matters.</p>