title: Showing a rectangle over a video from camera
body: <p>Basically I need to capture the video from videocamera do some processing on frames and for each frame show a rectangle of detection.</p>
  
  <p>Example: <a href="http://www.youtube.com/watch?v=aYd2kAN0Y20" rel="nofollow">http://www.youtube.com/watch?v=aYd2kAN0Y20</a></p>
  
  <p>How would you superimpose this rectangle on the output of videocamera (usb)? (c++)</p>