title: c# IVMRWindowlessControl9 query failed
body: <p>Why I can do something like this without any problem
  <code>((IVMRFilterConfig9)pVideoMixingRenderer1).SetRenderingMode(VMR9Mode.Windowless);
  </code>
  but when I try this</p>
  
  <pre><code>IVMRWindowlessControl9 vc1 = (IVMRWindowlessControl9)pVideoMixingRenderer1;
  </code></pre>
  
  <p>i have invalid cast exception ( HRESULT: 0x80004002 (E_NOINTERFACE))?</p>
  
  <p>The VMR9 renderer itself is working just fine btw.</p>