A2DP -> Mono -> I2S distorted

[fscii]

I believe had a mono example working a while back, went on vaction, did various number of git-pulls and now there's horrible sound (distorted and about an octave or more lower) when using mono. Works fine in stereo. Any advice?

PS: I saw this said only change channels = 1;

(#836)

`#include "AudioTools.h"
#include "BluetoothA2DPSink.h"

I2SStream i2s;
BluetoothA2DPSink a2dp_sink(i2s); // I2S Source -> A2DP Sink

void setup() {

// I2S DAC settings
auto cfg         = i2s.defaultConfig(TX_MODE); 

// cfg.i2s_format = I2S_STD_FORMAT; // PCM5102A seems obvlivious to format

// ESP32 pins                                  // library default bck=14, ws=15, data=22

cfg.pin_bck     = 15;  //12 - 15
cfg.pin_ws      = 27;  //14 - 27
cfg.pin_data   = 26;  //27 - 26

cfg.channels = 1;  // Mono

i2s.begin(cfg);                                // Begin source before sink
a2dp_sink.start("I2S_Mono_Test");

}

void loop() {
}`

I tried both yellow and purple PCM5102 DAC boards on this page w/same restults:
https://github.com/pschatzmann/arduino-audio-tools/wiki/External-DAC

Code works fine in stereo (cfg.channels = 2;) but not mono.

[pschatzmann]

In Arduino ESP32 3.0 core the I2S has changed and might therefore behave slightly differently.
A2DP provides stereo data, so only specifying channels = 1 in I2S will not work.

You can use a2dp_sink.set_mono_downmix (bool enabled) to output the same (mono) signal on the 2 i2s channels.

If you want to limit the I2S signal to 1 output pin you need to convert the number of channels first!

[pschatzmann]

You can give it a try: I did not consider this as an issue so far because I2S is a stereo protocol

[fscii]

SUCCESS!! by updating to Core 3 and removing: cfg.channel_format = I2S_CHANNEL_FMT_ONLY_LEFT;

However this brings more questions... in core 2 you went through the trouble of adding: I2S_CHANNEL_FMT_ONLY_LEFT and other formats (right only etc) but they are not behaving properly? I don't ask you to do more work to a core going away, but these options are not present for core 3? I really like them for a project I'm working on. Happy to donate a little bit here and there and hoping this functionality (if possible) is added in at least Core 3, but perhaps adjusted somehow for Core 2?

Any opinion on doing these things? I'm interested and very much appreciate your work on this project and attention to questions is top notch on Github or anywhere.

Thank you very much!

[pschatzmann]

I think In the core 2 this might have been done for the ADC and not for the DAC.
In the core 3 the API is very different and I don't remember having seen any option to specify this.

Fee free to have a look at the implementation

[pschatzmann]

I committed some DRAFT implementation for the 3.0.1 core: Can you double check ?
For a mono signal you can select
cfg.channel_format = I2SChannelSelect::Right;
cfg.channel_format = I2SChannelSelect::Left;

[fscii]

Confirmed both work as expected! Very nice!!! Thank you!