What is this about? Rockbox is an OpenSource operating system for mp3 players. I had many mp3 players which were lacking functions which I would really have liked. Trivial things like allowing playback without pause between tracks, or loudness normalization. It does not stop there: Doom has been ported, one can play mod and sid files from the Commodore Amiga/C64 era, and much more. Rockbox is a replacement firmware for various mp3 players.