Open CV to Capture Unique Objects from a Video
Do you need to detect license plates, etc? Or just notice if something happens? For the latter, you could use a very simple approach. Take an average of say the frames of the last 30 seconds and subtract that from a current frame. If the mean absolute average of the delta image is above a threshold, that could be the change you are looking for.
I was doing a frame slicing from the OpenCV Library in Python, and I am successfully able to create frames from the video being tested on. 
I am doing it on a CCTV Camera installed at a parking entry gateway where the video plays 24x7, and at times the car is standing still for good number of minutes, leading to having consecutive frames of the same vehicle. 
My question is how can I create a frame only when a new vehicle enters the parking lot?