People Counter With Raspberry Pi 3

I have a Raspberry PI 3 and a Raspberry PI cam module V2. I need to develop a people counting solution, based on OpenCV and Python. The system must save the incomes and outcomes registers into a MySQL database in the same raspberry. The idea is to install the rasberry in the roof, so it is going to work like a head counter. The program must show the video in real time . All the records must be saved with a time-stamp. The idea is to reach a accuracy of 90%. Examples: [login to view URL] [login to view URL]