How do TWS headphones like AirPods work individually?

Question

My understanding of Bluetooth pairing in general is that the phone and the gadget exchange some encryption keys and other pairing data.

• How can TWS headphones like AirPods be seen as one entity by the phone, although there are clearly two Earbuds?
• Which of the Buds does the Phones communicate with during the pairing?
• Do the buds exchange the pairing information, and if so, how?
• How can the phone be connected with seemingly one device, but play stereo audio on both headphones?

Answer 1

I dont know about AirPods specifically, but most TWS products on the market use Qualcomm chips. Those work where each bud has its own Bluetooth radio. The buds are paired at the factory and have MAC addresses which are identical, save for the least sig bit. When you pair the buds to a phone, only one bud is actually performing pairing, and the phone sees just one MAC address. The buds are connected to each other and share some propriety Bluetooth commands which enable them to switch MAC addresses in real time and "handover" the logical link to the phone, depending on which bud is serving as the gateway to the phone. In practice, the phone will be streaming the music/voice data to one bud, which will forward it to the second bud alongside some synchronization metadata so that you end up hearing the audio data from both buds at the same time. Sorry I can't really go into more technical details than that.

By the way, I'm not 100% sure but I think that AirPods have some additional radio comms with iOS devices, besides just the Bluetooth spec. That's how they can do "magic" stuff like automatic pairing.