The fastest and best ffmpeg-based method I have figured out is:
ffmpeg -ss 00:01:00 -to 00:02:00 -i input.mp4 -c copy output.mp4
This command trims your video in seconds!
Explanation of the command:
| Command | Explanation |
|---|---|
| -i | This specifies the input file. In that case, it is (input.mp4). |
| -ss | Used with -i, this seeks in the input file (input.mp4) to position. |
| 00:01:00 | This is the time your trimmed video will start with. |
| -to | This specifies duration from start (00:01:00) to end (00:02:00). |
| 00:02:00 | This is the time your trimmed video will end with. |
| -c copy | This is an option to trim via stream copy. (NB: Very fast) |
The timing format is hh:mm:ss.
Please note that the previous highly upvoted answer forces a reencode, and so the trim would be extremely slow. For more information, look at this official ffmpeg article.