This initially started as an attempt to get 4-bit SDIO working on an ESP32. I noticed an A2DP-SRC example that sent random data to a sink in the IDF and decided it could be a bit better.
Linked below is my hack to the example A2DP-SRC code so that it streams raw PCM data from a SD card. Also linked below is a video on YouTube of it playing the Super Mario Bros. theme song.
Source is here : https://github.com/gtalusan/esp-idf/tree/master/examples/bluetooth/a2dp_source
The author put it in links on the left but it is not very visible thow.