Implementing an equaliser example

[AvishkaDon]

Hi,
I am using your a2dp library as sink on my esp32 to send data from a Bluetooth device and the esp32 connected to a I2S DAC. I would like do some media processing on esp32 before outputting the data to the DAC (I.e an equaliser or some kind of a bass boost function). I was wondering if it’s possible to use arduino audio tools library do this? If so do you have any examples?

Many thanks 🙏

[pschatzmann]

Unfortunately I do not provide any easy to use Equalizer. Though it would be possible to build one using Filters, I guess that might be a bit challenging to calculate the input parameters.

[AvishkaDon]

I was going through some of the examples on the filters and I found stream-i2s-filter-i2s
Is there a way to get the Bluetooth sink stream as I2SStream in? or is it possible to pass in [A2DPStream] to FilteredStream?

[pschatzmann]

Yes, that should work. Or if you use this example you can wrap the I2SStream in a FilteredStream.

[AvishkaDon]

oh cool! - did you mean something like this? :) `/**

• @file basic-a2dp-audioi2s.ino
• @brief A2DP Sink with output to I2SStream. This example is of small value
• since my Bluetooth Library already provides I2S output out of the box.
• @author Phil Schatzmann
• @copyright GPLv3
  */

#define USE_A2DP
// #include "AudioConfigLocal.h"
#include "AudioTools.h"

uint16_t sample_rate=44100;
uint16_t channels = 2;
BluetoothA2DPSink a2dp_sink;
I2SStream i2s_in;
I2SStream i2s_out;

// copy filtered values
FilteredStream<int16_t, float> filtered(i2s_in, channels); // Defiles the filter as BaseConverter
StreamCopy copier(i2s_out, filtered);// copies sound into i2s

float coef[] = { 0.021, 0.096, 0.146, 0.096, 0.021}; //these values will change for a low-pass!

// Write data to SPDIF in callback
void read_data_stream(const uint8_t *data, uint32_t length) {
i2s_in.write(data, length); //input data to the filter
}

void setup() {
Serial.begin(115200);
AudioLogger::instance().begin(Serial, AudioLogger::Warning);
filtered.setFilter(0, new FIR(coef));
filtered.setFilter(1, new FIR(coef));

// register callback
a2dp_sink.set_stream_reader(read_data_stream, false);

// Start Bluetooth Audio Receiver
a2dp_sink.set_auto_reconnect(true);
a2dp_sink.start("a2dp-i2s");

//i2s_out internal DAC
auto config = i2s_out.defaultConfig(TX_MODE);
config.sample_rate = sample_rate;
i2s_out.begin(config);

//i2s_out to expternal DAC
auto config_out = i2s_out.defaultConfig(TX_MODE);
config_out.sample_rate = sample_rate;
config_out.bits_per_sample = 16;
config_out.i2s_format = I2S_STD_FORMAT;
config_out.is_master = true;
config_out.port_no = 1;
config_out.pin_ws = 17;
config_out.pin_bck = 18;
config_out.pin_data = 19;
i2s_out.begin(config_out);
config_out.fixed_mclk = sample_rate * 256;
config_out.pin_mck = 0;

Serial.println("I2S started...");
}`

[pschatzmann]

No, it would be something as follows:

BluetoothA2DPSink a2dp_sink;
I2SStream i2s_out;
FilteredStream<int16_t, float> filtered(i2s_out, channels);  // filter on output
// copy and filter values
StreamCopy copier(filtered, a2dp_sink);// copies sound into i2s

Or if you use this example you can omit the StreamCopy and write to filtered inesead of i2s

[AvishkaDon]

Is this what you meant by bypassing the StreamCopy with the "basic-a2dp-i2s" example?
Also, I am writing to the internal DAC of the esp32 and I am don't think I am doing this correctly as I am not getting any signals out of the pin 25 and 26.

#define USE_A2DP
#include "AudioTools.h"

uint16_t sample_rate=44100;
uint16_t channels = 2;

BluetoothA2DPSink a2dp_sink;
I2SStream i2s;
FilteredStream<int16_t, float> filtered(i2s, channels);  // filter on output
float coef[] = { 0.021, 0.096, 0.146, 0.096, 0.021}; //these values will change for  a low-pass!


// Write data to SPDIF in callback
void read_data_stream(const uint8_t *data, uint32_t length) {
  i2s.write(data, length); //input data to the filter
}

void setup() {
  Serial.begin(115200);
  AudioLogger::instance().begin(Serial, AudioLogger::Warning);
  filtered.setFilter(0, new FIR<float>(coef));
  filtered.setFilter(1, new FIR<float>(coef));

  // register callback
  a2dp_sink.set_stream_reader(read_data_stream, false);

  // Start Bluetooth Audio Receiver
  a2dp_sink.set_auto_reconnect(true);
  a2dp_sink.start("a2dp-i2s");

  //i2s_out esp32 internal DAC
  auto config = i2s.defaultConfig(TX_MODE);
  config.sample_rate = a2dp_sink.sample_rate();
  config.channels = 2;
  config.sample_rate = sample_rate; 
  config.bits_per_sample = 16;
  i2s.begin(config);
}

void loop() { }

[pschatzmann]

Two points:

• If you want to use the internal DAC you need to replace I2SStream with AnalogAudioStream.
• If you want to apply the filter you need to replace i2s.write() with filtered.write() - otherwise you just write directly to i2s w/o giving the filter a chance to do anything...

[AvishkaDon]

Many thanks! 🙏 this helped out quite a lot

[pschatzmann]

In the meantime I have added a draft version of Equilizer3Bands.

[daviti231]

thank you very much for your reply, sorry if I trouble you.

…

On Thu, Apr 4, 2024 at 6:09 AM Phil Schatzmann ***@***.***> wrote: I will delete your comment: - don't abuse comments to post completeley unrelated things! - check the other discussions first. I have already answered this question too many times <#1336> — Reply to this email directly, view it on GitHub <#124 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BAWUXHJ5JWVAKKD75NWIGRDY3SY63AVCNFSM5QL4YHM2U5DIOJSWCZC7NNSXTOKENFZWG5LTONUW63SDN5WW2ZLOOQ5TSMBQGM4TAMA> . You are receiving this because you commented.Message ID: <pschatzmann/arduino-audio-tools/repo-discussions/124/comments/9003900@ github.com>

[burnutec]

Hey , it may not be relatable to this , but would it be possible to use this library with the pcm5101/5102 dac ? Since that has a better solderability to do as a DIY -er.
Thanks, and sorry if it is completely irrelevant. :)

[pschatzmann]

Just read the external DAC documentation