If you've ever tried encoding GIFs with `ffmpeg` there's a good chance your results came out looking pretty bad. This is because GIFs are limited to a palette of 256 colours and `ffmpeg` just uses a generic palette to be able to cover a wide range of colours.
`gifgen` produces much better results by doing a 2-pass encode. The first pass generates a custom colour palette based on all of the pixels from each frame. The second pass encodes the GIF using this palette instead of the default one bundled with `ffmpeg`.
`gifgen` is pretty much just the information from [this blog article](http://blog.pkh.me/p/21-high-quality-gif-with-ffmpeg.html) wrapped up in a shell script. Full credit goes to the original [author](http://ubitux.fr/).