We use a program called handbrake which can be found here https://handbrake.fr/.
Here are some steps that you can take to reduce the file size of your videos while still retaining the quality.
1. For the output settings you want the container to be MP4 and have the web optimized tick box checked.
2. When you have added the video into handbrake and selected the desitination set the video size to 640 x 360. You do this in the picture tab by setting the anamorphic from 'loose' to custom and entering 640 into width and 360 into height.
3. The next setting you want to change can be found in the video tab, the setting is called 'quality' you want the constant quality radio bubble checked. We find that a setting of 23 has the best trade off of file size and quality. Feel free to play around with this to find a setting that you think works better.
4. Once you have these set up you can save a preset so you do not need to do this every time you want to resize a video. To save a preset click the 'add' button found in the bottom right corner of handbrake. Enter a name and the maximum picture size which is 640 x 360 also leave the save video filter settings box ticked.
5.Finally to start the process click the green start arrow found at the top of the screen.
If you have any questions just update this post.