ffmpeg

Table of contents:

Slowing down / speeding up a video

Increase PTS value for slowing down even more. Decrease below 1.0 to speed up:

ffmpeg -i input_video_or.gif -filter:v "setpts=1.5*PTS,minterpolate='mi_mode=mci:mc_mode=aobmc:vsbmc=1:fps=120'" output.mp4

You can remove minterpolate section on speedups.

Cutting a part of a video

-ss gives "start time" and -t gives "duration":

ffmpeg -ss 00:57:42.0 -i input.mp4 -c copy -t 00:00:08.0 output.mp4

If there are some sync issues (e.g. black screen, late sound etc.) that means you need to re-encode, use something like: -c:v libx264 -crf 18 -c:a copy instead of -c copy