For the I2S codec, pick whatever chip or board works for you; this code was written using a PCM5102 chip, but other I2S boards and chips will probably work as well. The default I2S connections are shown below, but these can be changed in menuconfig:
If the internal DAC is selected, analog audio will be available on GPIO25 and GPIO26. The output resolution on these pins will always be limited to 8 bit because of the internal structure of the DACs.
After the program is started, other bluetooth devices such as smart phones can discover a device named "ESP_SPEAKER". Once a connection is established, audio data can be transmitted. This will be visible in the application log including a count of audio data packets.