Why does ffmpeg change framerate when merging multiple videos?

Question

fmpeg

The video is split into several parts, with a frame rate of 23.98, when they are glued together, the output frame rate is 24. How to leave the frame rate unchanged?
I write ffmpeg -f concat -i file.txt -c copy output.mp4,
in file.txt

file 'input1.mp4'
file 'input2.mp4'
file 'input3.mp4'

Answer 1

Does not change. With -c copyall codec parameters remain unchanged. No recoding takes place. Look at the screen (do not break your eyes - it would be better if you copied it in text) in Input #0 - Stream #0 ... 23.98 fpsand the same frequency inOutput #0 - Stream #0:0 ... 23.98 fps