title: On what dataset was haarcascade_frontalface_default.xml trained?
body: <p>I'm trying to make my own cascade file, but so far with little success, because of the time it takes to train one decent file (2 days) I don't want to spend months failing. In the example files of Opencv, there is the  haarcascade_frontalface_default.xml file.</p>
  <p>my question is: Does anybody know on what data was this trained?</p>
  <p>I can see that it was 22stages, but I would like to see the images used to better understand how it was made.</p>
  <p>I have little hopes since this must be kept quite secret, but I thought I'd ask.</p>