SD (mp3) to analogue

[francesco-miccoli]

Hello everyone. I am trying to use my ESP32 to play an mp3 file stored in a SD card module and send an analogue output to an Adafruit MAX9744 amplifier. I see there is no explicit example for this so I tried putting something together but in the process of doing that I encountered an error. I get conflicting declaration 'audio_tools::EncodedAudioStream out' when trying to compile

how can I solve this? From what I understand both the codec and analogue are outputs (as in the streams-memory_mp3-analog example. Thanks in advance!

[LinusHeu]

You can't have two variables (objects) with the same name (out).
(Generally, in C++. This has nothing to do with this particular library.)

[LinusHeu]

Oh, looks to me like there is a mistake in https://github.com/pschatzmann/arduino-audio-tools/blob/main/examples/examples-stream/streams-memory_mp3-analog/streams-memory_mp3-analog.ino

[LinusHeu]

/**
 * @file stream-memory_mp3-out.ino
 * @author Phil Schatzmann
 * @brief decode MP3 stream and output as out signal
 * @version 0.1
 * @date 2021-01-24
 * 
 * @copyright Copyright (c) 2021
 
 */

// install https://github.com/pschatzmann/arduino-libhelix.git

#include "AudioTools.h"
#include "AudioCodecs/CodecMP3Helix.h"
#include "BabyElephantWalk60_mp3.h"


MemoryStream mp3(BabyElephantWalk60_mp3, BabyElephantWalk60_mp3_len);
AnalogAudioStream out;  // Analog output 
EncodedAudioStream decoder(&out, new MP3DecoderHelix()); // decoder -> out
StreamCopy copier(decoder, mp3);    // copy mp3 -> decoder -> out

void setup(){
  Serial.begin(115200);
  AudioLogger::instance().begin(Serial, AudioLogger::Info);  

  // begin processing
  auto cfg = out.defaultConfig();
  out.begin(cfg);

  out.begin();
}

void loop(){
  if (mp3) {
    copier.copy();
  } else {
    auto info = out.decoder().audioInfo();
    LOGI("The audio rate from the mp3 file is %d", info.sample_rate);
    LOGI("The channels from the mp3 file is %d", info.channels);
    out.end();
    stop();
  }
}

Can you try it like this? Notice, how I renamed EncodedAudioStream out to EncodedAudioStream decoder

[pschatzmann]

It seems that this bug has been introduced by this change

The correction has been committed...

[francesco-miccoli]

I updated the code according to the correction. Still when I connect the speaker I cannot hear anything if not a faint "beep" like sound. What am I missing? Thanks in advance

[pschatzmann]

You are the only one who can find this out!

You need to have some structured testing approach to identify and resolve your issue. Start simple and extend the complexity:

https://github.com/pschatzmann/arduino-audio-tools/wiki/It's-not-working

As a first test you could replace the AnalogAudioStream with a CSVStream to check if you get some valid audio data.
You did not provide any logging data, so I assume that you see the copy entries...

ps. don't forget to clean up the unused typedf