Rockbox is an open source firmware replacement and operating system that can run on several digital audio players. The firmware supports dozen of audio, video, image, and document formats and, though it uses a spartan interface, is highly customizable.
I don't remember when I learned about Rockbox, sometime in the 2000s, but believe I found it while looking for a way to fix problems with my Toshiba Gigabeat. At the time, Rockbox was still unstable on the device, but it was still a great improvement over the default firmware. I have used Rockbox on five devices. Although I used to tout the product, the stability of the program has been steadily dropping for the past five years or so and development has slowed, so I no longer recommend it. If you are looking for a jukebox program for your smartphone or tablet, I suggest foobar2000 Mobile.
- The firmware supports a vast array of audio formats as well as some video, image, and document formats. Far more than any default firmware.
- The firmware is nicely optimized and out-performs the default firmware for every device it supports when it comes to supporting large collections of files and audio decoding.
- There are a lot of customizable options, far more than any default firmware.
- By using a standard firmware across multiple DAPs, you don't need to re-learn the interface each time you get a new device.
- The software takes advantage of most of the features of various hardware including radio, and microphone options. It even supports voice-commands.
- Since smart phones have mostly replaced DAPs, most of the programmers have left the project so new development has slowed to a crawl. The team rarely releases stable updates, and, when they do, they're not even remotely stable.
- The developers have been pretty dismissive about implementing features desired by a large percentage of the community such as customizing the behavior of the buttons, handling meta tags of multiple artists according to proper specs, including album art in formats whose specs don't support it, and various others.
- For the past few years, the firmware has gotten more and more unstable, so much that I no longer endorse or even use the product. I have two previous devices that routinely crash, even on the latest "stable" release of the program.
- The known bug list has ballooned to over 450 problems, and many of the bugs have gone unfixed for years. I personally discovered a few bugs and documented them thoroughly, but they too were never fixed.
- While a lot of the support administrators are helpful, there is one in particular who has been mean to newcomers in several instances I've witnessed, myself included. He or she is a major reason I didn't want to contribute further to the project.