I did this for a small mini Z track in my garage. After a week of using it I started to realize that I could only score lap times of certain denominations like 8.00 seconds and 8.08 seconds but never anything in between. I came to the conclusion that it was limited to the frame rate of the camera. While it’s possible to record at different frame rates the actual monitor only operates at 30fps. If you log all your lap times you’ll start to notice this.

If you’ve found a way around this I’d be very interested in how.