esp-idf
API Reference » Peripherals API » I2S
xtronical.com
ESP32 – Intro to I2S Part 1
I2S on ESP3 – Part 2, WAV’s
ESP32 I2S Part 3 – Playing Wavs from SD Cards
I2S Player (Part 4) : Adding volume control
YouTube
ESP32 – Intro to I2S Episode 1, explanation with basic example outputting a square wave
Understanding & playing WAV files on ESP32 using I2S. An In-Depth Tutorial with very simple example.