I've ported the GSM RPE-LTP codec, which has been used in mobile phones, to the GBA. Now you can use your GBA as a portable music player, with up to 150 minutes of Good Sounding Music on a 256 Mbit flash cart.
In mid-2019, development was moved to a repository on GitHub.
Release 20040823 switches to devkitARM, makes the UI much less ugly, and (on Windows 2000 and Windows XP) hides the double .wav.gsm extension.
Windows binary (you probably want this): GSM Player binary and music ROM builder
Source code (if you redistribute the binaries you're obligated to redistribute these as well): GSM Player source code (build 20040627) (decoder license), and Sox encoder source code.
No, I'm not affiliated with the GSM Association. I just use their audio compression format.
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