Kinovea (open source freeware) is really useful for analyzing your video. It can vary playback speed or advance frame by frame, lots of other tools included for measuring angles etc.
Nice! I'm a mac user, so I can't give it a try.
There is a iPhone/iPad app called Coach's Eye that does similar.
https://www.coachseye.com/
It's kinda pricey now. I was an early user of it before it got expensive. The problem for me was the the videos ate up all of the storage on my iPhone and I also had to do the analysis there...on the small screen. So, it wasn't optimal. I found it better for me to download the videos/images and work off of my computer.