Rockbox is a free open source firmware replacement and operating system that can run on several digital audio players. It is written in C, and various flavors of assembly. The firmware supports dozen of audio, video, image, and document formats and, though it uses a spartan interface, is highly customizable. It was first released on 2002-06-02.
I don't remember when I learned about Rockbox, but it must have been sometime in the mid-2000s. After not liking the default firmware of my iAudio M5, I found Rockbox could act as a replacement. However, my iAudio began to fall apart not much after that, so I got a Toshiba Gigabeat, which Rockbox also supported (though unstable). I later replaced that with a SanDisk Sansa Clip+, then a couple Clip Zips. Although I used to tout the product, the stability of the firmware has been steadily dropping for the past five years or so and development has slowed to a crawl, 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 pretty much every device it supports with the 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 riddled with bugs.
- The developers are 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.