The HandBrake for video compression software.

The HandBrake is a tool for converting video from nearly any format to a selection of modern, widely supported codecs.
The good reasons you’ll love HandBrake:

• convert video from nearly any format 
• is free and Open Source 
• used on multi-Platform :Windows, Mac and Linux;

If you take a look to next screenshot with this software will see how many options have it. From selected size for youtube , gmail and size of display devices to filters and subtitles. Is a very good tool for video compression issue.