Problem
We have a video file named `ben.mkv` with a frame rate of 25 fps. Every 25th frame is duplicated, and we want to delete every 25th frame, and change the timestamp of every 24th frame to 23.976 frames.
Solution
ffmpeg -i ben.mkv -vf "select='not (mod(n\,25))' , setpts=23.976*PTS" output.mkv
Explanation
The command uses the `select` and `setpts` filters to achieve the desired result. The `select` filter selects frames that do not have a remainder when divided by 25 (i.e., every frame except the 25th). The `setpts` filter changes the timestamp of every 24th frame to 23.976 frames.