How can I use ffmpeg to set the frame rate (fps) of a video file?

To set the frame rate (fps) of a video file using ffmpeg, you can use the "-r" flag followed by the desired frame rate value. For example, to set the frame rate to 30 fps, you would use the command:

ffmpeg -i input.mp4 -r 30 output.mp4

This command will change the frame rate of the video file "input.mp4" to 30 frames per second and save it as "output.mp4".