If this is for iphone then you can download VLC to play without converting. If it's for anything else then I'd suggest not using iTunes.
Assuming there is no way for iTunes or whatever to play different files (I don't use iTunes as it's shit but only one video format seems massively dated), then I'd suggest Handbrake. It has pre-set profiles for mp4 or you can set one yourself.
Just set it going as one big batch and, assuming your PC's not too slow, leave it for a while and it'll do them one after another.
If this is for iphone then you can download VLC to play without converting. If it's for anything else then I'd suggest not using iTunes.
Assuming there is no way for iTunes or whatever to play different files (I don't use iTunes as it's shit but only one video format seems massively dated), then I'd suggest Handbrake. It has pre-set profiles for mp4 or you can set one yourself.
Just set it going as one big batch and, assuming your PC's not too slow, leave it for a while and it'll do them one after another.