There are two ways to chose video frame rate in your iPhone. Frame rate of fps (frames per second). Frames per second is a measure of how many frames are taking in a second of video. The more frames are there, the smoother the video. So, How to change video frame rate in iPhone?
Open the Camera App. On the top right corner, you would see a number 30 or 60 based on the currently selected fps.
Tap on it. That would switch between 30 fps and 60 fps.
There’s a way to change the default option in the Settings. Open Settings.
Choose Camera. Open Record Video.
Choose among the list of options as you can see above.