Arduino Audio Tools: FAAD AAC Decoder

This week I was looking into the FAAD AAC Decoder and tried to make it work on the ESP32.

I was struggling quite a bit with the memory requirements and I could only make it work with a stack of 60k and by using PSRAM. So to fulfill the stack requirement we need to run the decoder in a separate freertos task.

The Arduino Sketch

Here is a working sketch that streams AAC audio from the internet and decodes it using FAAT. I was testing on an AudioKit, but you are free to replace the AudioKitStream with any other supported output stream (e.g. I2SStream):

#include "AudioTools.h"
#include "AudioCodecs/CodecAACFAAD.h"
#include "AudioLibs/AudioKit.h"
#include "freertos-all.h"
#include "esp_heap_caps.h"


URLStream url("ssid","your password");  // or replace with ICYStream to get metadata
AudioKitStream i2s; // final output of decoded stream
EncodedAudioStream dec(&i2s, new AACDecoderFAAD()); // Decoding stream
StreamCopy copier(dec, url); // copy url to decoder
void playAAC();
Task task("play", 60000, 10, playAAC);


void playAAC(){
  // setup i2s
  auto config = i2s.defaultConfig(TX_MODE);
  i2s.begin(config);

  // setup I2S based on sampling rate provided by decoder
  dec.begin();

  // aac radio
  url.begin("http://peacefulpiano.stream.publicradio.org/peacefulpiano.aac","audio/aac");
  while(true){
    copier.copy();
  }
}

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

  // alloc > 1024 bytes in PSRAM
  const int limit = 1024;
  heap_caps_malloc_extmem_enable(limit);

  // start on core 1
  task.Start(1);
}

void loop(){
  delay(1000);
}

Don’t forget to activate PSRAM in the Arduino IDE!

Dependencies

You need to install the following libraries

• arduino-audio-tools
• arduino-libfaad
• arduino-freertos-addons
• arduino-audiokit (when using an AudioKit)

Conclusions

It’s nice to have another option for AAC Decoding, but in the light of the memory requirements, I rather stick to using libhelix.