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    🎼 How to Play MP3 with C++ 🎻

    Using libmpg123 and libao!

    🎼 How to Play MP3 with C++ 🎻

    In this article/video we will see a code with OOP on how to play MP3 with C++, there are other libraries that also do this, some others only play WAV, for example, the gamedev libraries.

    First of all we need to know which libraries we need to know the differences between: Mpg123, LibMPG123 and Libao:

    Mpg123

    It is a free and open source audio player. Supports MPEG audio formats, including MP3. It is an application that works via command line and does not have a graphical interface.

    Libmpg123

    It is the library developed and used by the Mpg123 application. It is also the same one used in applications: Audacious, XMMS and Winamp.

    Libao

    It is a cross-platform audio library that allows programs to produce audio using a simple API across a wide variety of platforms.

    It is a tool developed by Xiph.Org, the same one that created the file type: ogg and also the FLAC format, which is a free alternative to mp3 and other formats.

    Watch the video

    Code created in the video

    Create a project

    mkdir playmp3
cd playmp3

    Add the files with the codes below:

    playmp3.hpp

    #pragma once

#include <mpg123.h>
#include <ao/ao.h>
#include <memory>
#include <iostream>

class PlayMP3 {
  // Primitive types
  std::size_t buffer_size, done;
  int driver, err, channels, encoding;
  long rate;
  std::string track;

  // LibMPG123 type and smart pointer
  mpg123_handle *mh;
  std::shared_ptr<char> buffer;

  // AO types
  ao_sample_format format;
  ao_device *dev;

  public:
    PlayMP3();
    ~PlayMP3();
    void music(char*);
    void play();
};

    playmp3.cpp

    #include "playmp3.hpp"

PlayMP3::PlayMP3(){
  ao_initialize();
  driver = ao_default_driver_id();
  mpg123_init();
  mh = mpg123_new(NULL, &err);
  buffer_size = mpg123_outblock(mh);

  // Dont use make_shared here
  buffer = std::shared_ptr<char>(
    new char[buffer_size], 
    std::default_delete<char[]>()
  );
}

void PlayMP3::music(char* mp3){
  track = mp3;
  mpg123_open(mh, mp3);
  mpg123_getformat(mh, &rate, &channels, &encoding);

  format.bits = mpg123_encsize(encoding) * 8;
  format.rate = rate;
  format.channels = channels;
  format.byte_format = AO_FMT_NATIVE;
  format.matrix = 0;
  dev = ao_open_live(driver, &format, NULL);
}

void PlayMP3::play(){
  std::cout << "\033[33;1m\u25B6 Playing the song: \033[35;1m ";
  std::cout << track << "\033[m\n";

  while(mpg123_read(mh, buffer.get(), buffer_size, &done) == MPG123_OK){
    ao_play(dev, buffer.get(), done);
  }
}

PlayMP3::~PlayMP3(){
  ao_close(dev);
  mpg123_close(mh);
  mpg123_delete(mh);
  mpg123_exit();
  ao_shutdown();
}

    main.cpp

    #include "playmp3.hpp"

int main(int argc, char **argv){
  if(argc > 1){
    auto p = std::make_unique<PlayMP3>();
    p->music(argv[1]);
    p->play();
  }else{
    std::cerr << "Enter the song\n";
    return EXIT_FAILURE;
  }
  return 0;
}

    Compiling and playing an MP3

    Use the song you want as an example, download the song.

    music.mp3

    Music: SAINt JHN - “Trap” ft. Lil Baby (Music available at https://en.mygomp3.com/):

    wget -q https://cutt.ly/musicmp3 -O music.mp3.

    g++ main.cpp playmp3.cpp -o playmp3 -lmpg123 -lao
./playmp3 music.mp3

    Useful links

    music cpp

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