Using ffmpeg to change framerate

Question

I am trying to convert a video clip (MP4, yuv420p) from 30 fps to 24 fps. The number of frames is correct so my output should change from 20 minutes at 30fps to 25 minutes a

Answer 1

With re-encoding:

ffmpeg -y -i seeing_noaudio.mp4 -vf "setpts=1.25*PTS" -r 24 seeing.mp4

Without re-encoding:

First step - extract video to raw bitstream

ffmpeg -y -i seeing_noaudio.mp4 -c copy -f h264 seeing_noaudio.h264

Remux with new framerate

ffmpeg -y -r 24 -i seeing_noaudio.h264 -c copy seeing.mp4