How to write silence on no data with BluetoothA2DPSink and callbacks

[unpapardo]

Hello everyone, I'm using an ESP32 as a bluetooth receiver to SPDIF output for an old car.
My issue starts when the phone audio stream stops (like when you pause a song), leaving the output pin floating, ready for noise to be induced on the output and resulting in some very loud and annoying pops.

I noticed that the A2DPStream class has a silence_on_nodata attribute that works great, but it also warns that using BluetoothA2DPSink with callbacks would be better. With that, I imagine that I should monitor the esp_a2d_audio_state property, and when it is stopped, I should write silence, similar to the silence_on_nodata method.

However, whenever I try to use writeSilence() as in
if (audio_state != ESP_A2D_AUDIO_STATE_STARTED) out.writeSilence(1024);
(out being an AnalogAudioStream instance I use for testing) my ESP32 just freezes, no warning or crash log. I've tried also using the bluetooth buffer size (3584) with no success either.

What can I do to fix this issue?

[pschatzmann]

Something does not add up: silence_on_nodata is only relevant for the AudioSource scenario.

The only disadvantage of the A2DPStream is that it uses some additional RAM for a queue, so if you run low of RAM you can just activate PSRAM!

Maybe you get these issues because the internal DAC is deactivated when the output is stopped. You can prevent this by not defining any output to the BluetoothA2DPSink and do the output yourself in the data callback.