In the days of the iPod, when travelling on public transport, in the UK at least, those trademark white earphones were everywhere. But it seems that portable audio players have become a thing of history; with the advent of phones as all-in-one devices, these have pretty much replaced audio players (and cameras too). Why carry extra devices when the one you've already got in your pocket will do?
Returning back to those past days, I'd put up with a couple of very cheap MP3 players, which would often glitch in all kinds of infuriating ways. That ranged from failing to read certain MP3s, going further in their obstinance and just locking up entirely, or further still and actively protesting noisily. I'm not sure that "randomly firing a loud burst of white noise into my ears until power off" is a particular bullet point to stick on the box blurb.
Fortunately, it didn't take long before I'd spotted Rockbox, a open source replacement firmware for audio players. Since then, Rockbox has become one of the open source projects that I use most. I've used it near daily on some device or other for probably around a decade, and I don't see that changing anytime soon.
As an audio player is one of the things I'm using all the time, I like having a separate device with its own, usually lengthy, battery life. With that in mind, I'm probably a little ignorant if there's phone audio player software that's as competent and fully featured as Rockbox. It's certainly possible there's a suitable competitor. But I'd be surprised.
In terms of the range of audio formats supported and the number of features Rockbox offers, it seems difficult to match. There's gapless playback, bookmarking, equalizer, compressor, crossfeed, control of pitch and speed, and ReplayGain support. On top of that, adjusting many aspects of a Rockbox-enabled device is possible. Even the display theme is fully customisable should you wish to create your own. Furthermore, if a device has the option of adding external media card storage, such as microSD, Rockbox sometimes goes beyond a device's official support, enabling the use of larger memory cards.
If you want to give it a try, the first step is to take a look at the official site and see what devices are currently supported. It's also worth checking around the forums there too, particularly under "New Ports" as there may be newer devices where less stable ports-in-progress are available, but not listed on the main site.
Devices that run Rockbox are commonly fairly cheap as it's usually older, out of demand hardware that's supported. It does mean getting hold of one in good condition might not be necessarily easy. I've used Rockbox on several different devices, first and second generation iPod Nanos, and the Sansa Fuze and Fuze+. There have been devices I have preferred, but most devices are quite usable since once you've selected what to play, there's little more to do. The main differences really come down to screen size, ease of accessing the user interface (for instance, the Fuze+ has a touch sensitive pad which isn't ideal compared with the definite precision of the iPod Nano or Fuze wheels), and whether a device supports storage expansion.
When you've got a compatible device, it's relatively straightforward to get things going. The Rockbox Utility is a program that you can use to install Rockbox directly to hardware that's plugged into your PC, or you can install manually if you prefer, although it may involve using a compiler. The actual installation process varies depending on hardware, for instance, you may also have to download some official firmware file for your hardware first so that it can be patched to add Rockbox. After that, you should be ready to copy files onto your player's storage and start using it.
On a security point: when I last used the Rockbox Utility, only a few weeks back, it was using insecure HTTP URLs for downloading from the site. This is despite the download servers the Utility downloads files from during installation actually supporting HTTPS. I don't have the changes I made to hand, but it's possible to use your favourite find-replace tool to patch the source to replace URLs that match, for example (but not limited to) http://download.rockbox.org to use HTTPS. I really should have submitted a patch but I couldn't face the hassle of creating a account to access Rockbox's Gerrit instance at the time.
What's the long, long term future of the project? If you've hardware for which Rockbox is claimed to be stable, you'll probably find that's the case. I've had devices occasionally lock up, but these haven't happened frequently enough to be frustrating. As mentioned above, it's as feature-filled as you'd likely require too, so even if development stopped on it entirely it would still continue to be usable too. Nonetheless, it's still actively maintained with a steady run of code changes being made.
You're limited to what devices you can install Rockbox on, but these were often produced in large quantities (e.g. iPods) so there should be an abundance of them on the market. All this makes it relatively simple to pick up a working used one to install Rockbox. For now. Getting hold of one of these is unlikely to be a problem as there are so many out there, but getting one in good working order may prove increasingly difficult as time goes on. If it's a failed battery that's a problem, it's probably easy to get a replacement, although replacing the battery may prove trickier: these devices weren't often designed to be user-serviceable.
There has been work on making Rockbox an Android app. Ultimately, that's likely the way things will go in the far distant future as old audio hardware becomes scarce and fewer new devices are designed and manufactured. In the meantime, it's nice to have software that does one thing and does it particularly well. As nothing better seems to have come along to usurp Rockbox's place, it's quite possible that I'll be using it over the next ten years as I have for the last ten.