title: Issue with running open CV face detection on Mac mountain lion
body: <p>I ran into an issue getting the standard open CV face detection (<code>facedetect</code>) working.  The web cam light comes on but noting happens, the program is launched with a tiny sized window like this:</p>
  
  <p><img src="https://i.stack.imgur.com/S7O2Y.png" alt="enter image description here"></p>
  
  <p>I am working from an <a href="http://coding-robin.de/2013/07/22/train-your-own-opencv-haar-classifier.html" rel="nofollow noreferrer">excellent blog post</a> and <a href="https://github.com/mrnugget/opencv-haar-classifier-training" rel="nofollow noreferrer">sample code</a>.  Here I what I have done:</p>
  
  <ol>
  <li><p>Install OpenCV &amp; get OpenCV source</p>
  
  <pre><code>brew tap homebrew/science
  brew install --with-tbb opencv
  wget http://downloads.sourceforge.net/project/opencvlibrary/opencv-unix/2.4.6/opencv-2.4.6.tar.gz
  tar xvzf opencv-2.4.6.tar.gz
  </code></pre></li>
  <li><p>Run the <code>facedetect</code> sample with the standard classifier. </p>
  
  <pre><code>cd ~/opencv-2.4.6/samples/c
  chmod +x build_all.sh
  ./build_all.sh
  ./facedetect --cascade="../../data/haarcascades/haarcascade_frontalface_alt.xml"
  </code></pre></li>
  </ol>
  
  <p>I can modify the C++ sample code and recompile and run, but I have no idea what the issue is.  </p>
  
  <p>Does anyone have a suggestion?</p>
  
  <p><em>Update</em> The issue is the image from <code>cvQueryFrame</code> is empty:</p>
  
  <pre><code>IplImage* iplImg = cvQueryFrame( capture );
  frame = iplImg;
  if( frame.empty() ) 
  {
      cout &lt;&lt; "FRAME EMPTY\n";  // This is getting logged
      break;
  }
  </code></pre>
  
  <p><em>Update</em>: It works ok when the source is a static image, so the issue is something related to the webcam source.</p>
  
  <p><img src="https://i.imgur.com/2rv5Cxd.png" alt="Lena"> </p>