AirPlay 2 surround (5.1 / 7.1) with one ESP32-S3 per speaker

esp32-airplay2-surround, by Kristian Dimitrov (Kristian8606), builds a wireless 5.1 or 7.1 surround system from one ESP32-S3 board per speaker. Every board is a full AirPlay 2 receiver that decodes only its own channel, and the boards stay in sync through AirPlay 2's PTP clock, so they never talk to each other and there's no AV receiver or hub. It needs an Apple TV: only the Apple TV sends surround, and an iPhone, iPad or Mac sends stereo to these boards. It also needs a 2.4 GHz Wi-Fi network with good coverage at every speaker. Surround arrives as 5.1 or 7.1 AAC (for example Apple Music Dolby Atmos or films); stereo works too, as ALAC 44.1 kHz/16-bit, lossless 48 kHz/24-bit and AAC, and the Apple TV can switch formats on the fly. Each board needs an ESP32-S3 with 8 MB flash and 8 MB PSRAM (N8R8), because the stream buffer alone takes 6 MB, plus either a MAX98357A I2S amplifier (the simplest, about 3 W) or a PCM5102A I2S DAC feeding any analogue amplifier. 5.1 takes 6 boards and 7.1 takes 8, but you can start with 2 or 3. A web page on each board sets its speaker position, a 2 × 24-band parametric EQ and crossover, loudness, latency, Wi-Fi and over-the-air updates, with live logs and a Wi-Fi speed test. The author measured about 31–34 % of one CPU core for one 7.1 speaker, using a patched Fraunhofer FDK AAC decoder. You build and flash it yourself with ESP-IDF v6.0.2. The author calls it experimental and under active development, tested with one Apple TV. The Subwoofer position plays only the LFE channel (no bass management). Licence: the repo has no licence file, so no licence is granted beyond viewing it on GitHub; the bundled Fraunhofer FDK AAC decoder has its own FDK license, which grants no patent rights. It is based on rbouteiller/airplay-esp32, and it isn't affiliated with Apple.