Trimming video with ffmpeg

If you need to trim an mp4 video quickly without re-encoding the output, try this:

ffmpeg -i input.mp4 -ss <position> -t <duration> -vcodec copy -acodec copy output.mp4

-ss <position> is the starting time. It can be in seconds or in hh:mm:ss[.xxx] format.
-t <duration> is the length of the video to copy. It can also be in seconds or hh:mm:ss[.xxx] format.