How did Apple make this work??

Apple's HomePod minis can pair up into stereo pairs.

But how do they do it?

Resources mentioned in this video:

- HomePod mini: https://www.apple.com/shop/buy-homepod/homepod-mini/midnight
- IEEE 802.1AS: https://www.ida.liu.se/~sohsa65/courses/tsn-course-2021/stds/8021AS-2020.pdf
- AirPlay 2 RS (open source project): https://github.com/lmcgartland/airplay2-rs
- What is gPTP: https://blog.meinbergglobal.com/2024/03/27/what-is-gptp/
- What is PTP: https://en.wikipedia.org/wiki/Precision_Time_Protocol
- Wireshark: https://www.wireshark.org
- HomePod mini intro video: https://www.youtube.com/watch?v=cPakvOuwg48
- MacRumors buyers guide: https://buyersguide.macrumors.com/#Homepod-Mini

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Contents:

00:00 - What did Apple do
01:22 - How hard can it be
06:36 - Now there are two
08:30 - Testing a stereo pair
09:46 - Wireshark
10:52 - WiFi snooping with Apple
12:46 - Finding gPTP
15:03 - Timing packets
17:09 - How PTP works
17:55 - Brief look at IEEE 802.1AS and AVB
19:51 - Apple using standards