Avidemux is a free, open source, video editing program for Windows, macOS, and Linux. Avidemux has a number of advance features that allow you to edit the underlying structure of the file format. This allows you to use Avidemux to optimize files or create Glitch Art.
You can download Avidemux from http://avidemux.sourceforge.net/. Launch the installer and follow the directions.
While you can use Avidemux for many different things, this guide will focus mainly on using Avidemux to cause glitches in files. Done creatively, this can be used to make art.