Ask HN: Can anyone recommend me an open source software to calculate footfall?

Hi I am organising an open event for public to celebrate a festival, in which more than 3000 are expected to come. I need to count how many people are coming in and outgoing from the event. I can have a camera attached at the entrance with a top view. Software/library can use ai or image processing, anything to keep track of how many have entered the event and how many have exited over a period of time. The data can help me to be more efficient in my future events.

Thanks in advance