mp4 files resize

Hello
Is there a plugin I can use to resize MP4 files on my server?
I have hundreds of very large MP4 files on the server (each is around 2 or 3 GB). I use FV Player to display them, but because they are so big, they are sometimes buffering, and that’s a very bad user experience. Also I want to give the user the option to download the videos, but that’s gonna take him a life time in my situation. Therefor I want to make all these files smaller and I’m asking for help.
If there is no such a plugin, can someone please suggest me how I can do it straight on the server?

Thank you!