I have seen few options of haar-cascades for frontal face recognition such as:
"haarcascade_frontalface_alt.xml"
"haarcascade_frontalface_alt_tree.xml"
"haarcascade_frontalface_alt2.xml"
"haarcascade_frontalface_default.xml"
Basically they all do the same task. What are the major differences between them?