jesserockz / arduino-libhelix

A simple MP3 and AAC Decoder (not only) for Arduino based on libhelix

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A MP3 and AAC Decoder using Helix

I am providing the Helix MP3 decoder from RealNetworks as a simple Arduino Library. The Helix decoders are based on 16bits integers, so they are a perfect fit to be used in Microcontrollers.

MP3 is a compressed audio file formats based on PCM. A 2.6 MB wav file can be compressed down to 476 kB MP3.

This project can be used stand alone or together with the arduino-audio_tools library. It can also be used from non Arduino based systems with the help of cmake.

The Helix MP3 decoder provides Layer 3 support for MPEG-1, MPEG-2, and MPEG-2.5. It supports variable bit rates, constant bit rates, and stereo and mono audio formats.

API Example

The API provides the decoded data to a Arduino Stream or alternatively to a callback function. Here is a MP3 example using the callback:

#include "MP3DecoderHelix.h"
#include "music_mp3.h"

using namespace libhelix;

void dataCallback(MP3FrameInfo &info, int16_t *pwm_buffer, size_t len) {
    for (int i=0; i<len; i+=info.channels){
        for (int j=0;j<info.channels;j++){
            Serial.print(pwm_buffer[i+j]);
            Serial.print(" ");
        }
        Serial.println();
    }
}

MP3DecoderHelix mp3(dataCallback);

void setup() {
    Serial.begin(115200);
    mp3.begin();
}

void loop() {
    Serial.println("writing...")
    mp3.write(music_data, muslic_len);    

    // restart from the beginning
    delay(2000);
    mp3.begin();
}

Installation

For Arduino, you can download the library as zip and call include Library -> zip library. Or you can git clone this project into the Arduino libraries folder e.g. with

cd  ~/Documents/Arduino/libraries
git clone pschatzmann/arduino-libhelix.git

This project can also be built and executed on your desktop with cmake:

cd arduino-libhelix
mkdir build
cd build
cmake ..
make

Documentation

Final Comments

This library is based on a adapted version of libhelix from Earle Phil Hower's ESP8288Audio library
The decoder code is from the Helix project and licensed under RealNetwork's RPSL license. For commercial use you might still going to need the usual AAC licensing.

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A simple MP3 and AAC Decoder (not only) for Arduino based on libhelix

License:GNU General Public License v3.0


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