How to transpose a video with ffmpeg

ffmpeg -i input.mp4 -vf "transpose=1" output.mp4

or

ffmpeg -i input.mp4 -vf "transpose=clock" output.mp4

for one 90-deg clockwise rotation.

Reference: https://ostechnix.com/how-to-rotate-videos-using-ffmpeg-from-commandline/#:~:text=FFMpeg%20has%20a%20feature%20called,flip%20them%20vertically%20and%20horizontally.&text=Here%2C%20transpose%3D1%20parameter%20instructs,video%20by%2090%20degrees%20clockwise.