The GBA Music Player 2000 (wicmp11)

Game soundtracks shape the way we experience playing games. On the Game Boy Advance (GBA) quite a few popular titles were released and some of them do have very well known soundtracks. People sometimes like them for their '16 bit sound', which is of course a misleading description at best. But if it's not '16 bit sound', what makes those games sound the way they sound? How does the sound on the GBA actually work? In this talk we discuss what the GBA hardware is capable of, how most games used the so called "Music Player 2000" software to make those iconic GBA soundtracks. how to modify music in GBA games, and how we can use that knowledge to rip music from those games. To Nintendo's misfortune the Music Player 2000 was also used to discover the first GBA BIOS exploit, which we will cover of course. The GBA is quite a beefy hardware upgrade compared to the Game Boy (Color). The memory capacity is greatly increased, the video hardware is much more powerful, and the CPU is upgraded to a hefty 16 MHz 32 bit ARM CPU. However, in terms of sound the GBA appears like it's a bit underwhelming. It keeps the old (albeit slightly altered) GB sound hardware, but additionally gets proper PCM sample support. However, in practice this is rather difficult for developers to use. At the time, Nintendo possibly was aware of this and therefore they provided a powerful sound engine with their SDK called "Music Player 2000" (MP2K). The majority of commercial games use this sound engine, which gives them some of their characteristic sound. So what can the GBA hardware do, and where does the software take over? How does one emulate it? While I could probably discuss many things in great deal, the talk will try to take a few shortcuts and try to focus on the mentioned questions and what my own personal story with the GBA is. Speaking of story, my context for all of this is that I used to have fun in the ROM Hacking scene. Essentially the people there were modding games. Sometimes just for fun, sometimes they'd create complete custom games. often this focused on graphics and a bit of coding, but very often nobody really cared about sound. This drew my attention and lead me to a road of spending very much time with the Game Boy Advance and how games were doing sound on it. The work under which people from the community got to know me was reverse engineering work on the sound mixing from the MP2K and a ripping tool called "agbplay". Licensed to the public under https://creativecommons.org/licenses/by-sa/4.0/ about this event: https://cfp.w.icmp.camp/wicmp11/talk/MJZGF7/