How to recalculate duration in video metadata?

Question

Video

After acceleration

ffmpeg -i in.mp4 -vf "setpts=PTS/4000" -r 120 0(4kx).mp4

the video is a fraction of a second long, but the duration in the metadata remains several hours. Because of what the same ffmpeg does not process it correctly. How can you set the correct duration in the metadata for a lot of videos?

Answer 1

Is there audio in the source? If yes, then its duration remained a few hours.