I use this to cut a part out of a mp4 file:
ffmpeg -i input.mp4 -vcodec copy -acodec copy -ss 00:36:18 -to 00:39:50 output.mp4
It works good but the video image is always freezed in the beginning for 1 second.
Doesnt matter which video file I try and cut a part out of, it takes like 1 second before the video start.
Heres an example: