I think this is the easiest. But, -to
can’t do negative times. You need to nest a different comment inside the FFmpeg command to to the math.
I think this might work to remove 2 seconds from the end of a video
ffmpeg -ss 0 -i in.mp4 -t $(( $(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 in.mp4 |cut -d\. -f1) - 2 )) -c copy out.mp4
I use framaforms