Sounds like a weird question.
The short answer is always Unix.
Until you realize you have the equivalent processing power
of an iPhone 4 in *each* ear.
Though often overlooked, the realm of Bluetooth audio
System-on-a-Chip (SoCs) is a fascinating field.
AirPods in particular run RTKit, a Real-time Operating system targeting small ARM chips, written mostly in C++.
Small Real-time OS are often used in audio devices and peripherals, as the slightest hiccup in scheduling would
be immediately (aka audibly) obvious.
Timings are extremely tight.
Much of the public knowledge about RTKit comes from the
Asahi Linux project.
Linux on Apple
RTKit firmware is actually bundled into iOS updates; a simple extraction of the firmware will show numerous .im4p files.
When it comes to non-Apple devices, the information gets even harder to find.
If you ever wonder what makes a cellphone’s operating system secure, or what that app you just installed is saying about you behind your back, @jiska has made a great set of videos explaining the reverse engineering process of it all for HackaDay (shot out to one of our favorite websites).
There’s only 4 players in the Bluetooth SoC space:
– MediaTek,
– BES,
– Broadcom,
– Qualcomm
These 4 companies are, as expected, really deterrent before disclosing any code, mostly for all the security that’s at risk and because, well, they own the engineering behind it, so you can’t blame them for choosing what to do with it.
But reverse engineering can change all that by shedding some light.
I’d like to finish up by linking to a great overview of RTKit by @jiska.
https://www.youtube.com/watch?v=lXMawXNtXrQ
That, plus reading the Asahi Linux progress reports on the Apple Wiki will help you understand this neat little OS!
