How to run a script on file upload.

Hi. I wonder if someone can point me in the right direction. I upload alot of mp4 movies at work and was wondering if I could incorporate a script to make the clips faststart on upload rather than having to do it first and then uploading the files.

The script I use to make the movies faststart is a python script from https://github.com/danielgtaylor/qtfaststart

Where abouts in the Gallery's code would I need to be looking at to insert the lines to make the script process my movies?

Thank you.