As promised here is a short video demonstrating the active track on the Phantom 4.  I have to say it is amazingly impressive.   If you watch the video, please note that the active track will actually decipher the individual in a group and follow the individual. So you can follow one person or one person in a group of people.  As you can also see the  framing is also pretty good. The camera tilts towards the subject and keeps the subject in the middle of your frame.  You can also do a 360 around your subject while Active Track is engaged on the subject. (however that will be a different video).
  The video is nothing special at all however seeing the effectiveness of the active track could help make your decision about whether or not to purchase this drone.  
http://youtu.be/X3AmYyBWOsM

I have been told the Phantom 3 Pro is capable of Active Track.  Is this correct?

Sorry for the poor grammar, that was written in haste

active track is good in Open Place ! cause i already saw many video on youtube crashing P4 with tree branches .