I have been looking for the same thing for two weeks now, tried about 7 or 8 different programs and the one that fits my needs best is avidemux.
http://fixounet.free.fr/avidemux/
You'll have to find out how to set it (and all the necessary codecs) up on your platform. Also you'll have to learn a few things about video codecs, their settings and their parameters and you'll have to experiment, encode, change settings, encode again, etc. But that's what you have to do if you want to get the most out of your videos.