max volume

[kopmand]

Hi.
First of all, thank you for this awsome library.

I could not find any answers in the wiki or in the discussions, so i am trying here.

Qestion:
Are there any possibility to set a maximum volume?
I am using af a PCM5102 DAC decoder module and when i turn the volume to max the sound gets very distorted.
By default get_volume() returns values between 0 and 127 (0-100%)

So i was thinking, would it be possible to change this behavior to for example 0 -> 127 = 0 -> 80% ?

Regards Stefan.

[harryberlin]

I'm using such Hifi DAC device on Raspberry.
https://github.com/harryberlin/AVR-IBus.public

Did add 150 Ohm Resistors between Audio R+ & GND and L+ & GND to solve the audio overdrive issue.

[kopmand]

That is a great solution.
But in my project i am using 2 libraries, ESP32-A2DP and ESP32-audioI2S.
ESP32-audioI2S does not distort the sound at maximum volume, so i need a solution where i can use both libraries at max volume.
I think that if i ad the resistors to the output, the sound would be to low when i use ESP32-audioI2S ?

[XPMonline]

Hi Stefan,
simply use arduino map() function. For example
volume map(volume,0,127,0,80);

[kopmand]

I am actually already using the map() function, and it is working perfect on the "device"
But when i am controlling the volume from my phone, get_volume() overrules the map() function.

[harryberlin]

Did read in other Forum, Bridge between sck (if not used) and gnd can solve sound disruption.

[kopmand]

I already did that :-)
Without the bridge i doesen't even play.

[XPMonline]

As Mr. Schatzmann wrote in another topic:

As a side note I just wanted to highlight that you could easily implement a "volume control" by applying a multiplier on the sound data in the stream reader callback that you set via set_stream_reader() e.g.

multiplying by 0 is muting
multiplying by 0.5 is giving a lower volume

// In the setup function:
a2dp_sink.set_stream_reader(read_data_stream);

// Then somewhere in your sketch:

void read_data_stream(const uint8_t *data, uint32_t length)
{
      int16_t *ptr16 = (int16_t*) data; 
      uint21_t len16 = length/2;
      for(int j=0;j<len16;j++){
           ptr16[j] = 0.5 * ptr16[j];
      }
}

[kopmand]

That looks exactly like the thing i am missing :-)
I tried it, but i get this compile error: 'uint21_t' was not declared in this scope

I am not skilled at programming at all.
Can you tell me what i am doing wrong?
Here are my sketch, based on "bt_music_receiver_simple" with the void read_data_stream()

#include "BluetoothA2DPSink.h"

BluetoothA2DPSink a2dp_sink;

void setup() {
i2s_pin_config_t my_pin_config = {
.mck_io_num = I2S_PIN_NO_CHANGE,
.bck_io_num = 23,
.ws_io_num = 21,
.data_out_num = 22,
.data_in_num = I2S_PIN_NO_CHANGE
};
a2dp_sink.set_pin_config(my_pin_config);
a2dp_sink.set_auto_reconnect(true);
a2dp_sink.set_stream_reader(read_data_stream);
a2dp_sink.start("MyMusic");
}

void loop() {
delay(1000); // do nothing
}

void read_data_stream(const uint8_t *data, uint32_t length)
{
int16_t ptr16 = (int16_t) data;
uint21_t len16 = length/2;
for(int j=0;j<len16;j++){
ptr16[j] = 0.5 * ptr16[j];
}
}

[XPMonline]

Try replace it with uint32_t. In my project I also use a solution with resistor placement at the input of the power amplifier.
I have not tested this solution with stream reader modification

[kopmand]

uint32_t did not help...

[pschatzmann]

Why don't you just implement your own A2DPVolumeControl?
There you can easily limit the value.

Or with the latest release you can wrap the I2SStream in a VolumeStream using the AudioTools