Using SDL with C++

[multiholle]

I wan't to compile the following program with g++. Using SDL I wan't to play a mp3 file. I installed libsdl-dev and libsdl-mixer-dev. How could I use the libs?


holle@x300:~/cpp$ g++ sound.cpp
/tmp/ccq8XZ82.o: In function `playMP3(char const*)':
sound.cpp:(.text+0x82): undefined reference to `Mix_OpenAudio'
sound.cpp:(.text+0x8d): undefined reference to `Mix_LoadMUS'
sound.cpp:(.text+0x9c): undefined reference to `Mix_VolumeMusic'
sound.cpp:(.text+0xaf): undefined reference to `Mix_PlayMusic'
collect2: ld gab 1 als Ende-Status zurück

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <iostream>

#include <SDL/SDL.h>
#include <SDL/SDL_mixer.h>

void playMP3(const char *mp3) {
Mix_Music *music;
Mix_OpenAudio(44100, AUDIO_S16SYS, 2, 2048);
music = Mix_LoadMUS(mp3);
Mix_VolumeMusic(100);
Mix_PlayMusic(music, -1);
}

int main() {
playMP3("/home/holle/test.mp3");
}

[MadCow108]

you need to link against the sdl library.
g++ -lSDL_mixer file.cpp

also the headers you include are C headers not C++ headers (although that won't stop it from working, its bad style).

[Sockerdrickan]

basically
g++ sound.cpp -lSDL_mixer

[multiholle]

also the headers you include are C headers not C++ headers (although that won't stop it from working, its bad style). what would be a better style?

g++ sound.cpp -o sound -l SDL_mixerworks. but when I start the program with
./sound nothing happens. the program terminates in the moment I started it.

[MadCow108]

can't help with sdl_mixer as I don't know it.

But in c++ the c headers have no .h and a c infront.
e.g:
instead of
#include <stdio.h>
use:
#include <cstdio>

generally you should avoid using standard c libraries and stick to c++ standard libraries (strings,vectors,streams etc...). Their often easier to use and less error prone.

[monraaf]

You probably have to initialize the sound system first. See SDL_Init. You can use sdl-config to get the compiler and linker flags for the sdl library (e.g. `sdl-config --cflags --libs`)

[multiholle]

Now it works. I have to wait for the music to end playback before closing the program. Is this a better c++ style? What should I do with the includes "SDL/SDL.h,..."?


You can use sdl-config to get the compiler and linker flags for the sdl library (e.g. `sdl-config --cflags --libs`)
What do you mean with this?



#include <iostream>
#include <SDL/SDL.h>
#include <SDL/SDL_mixer.h>

using namespace std;

int main() {
// Init
if (SDL_Init(SDL_INIT_AUDIO) != 0)
cout << "SDL_Init ERROR: " << SDL_GetError() << endl;
else
cout << "SDL_Init SUCCESS" << endl;

// Open Audio device
if (Mix_OpenAudio(44100, AUDIO_S16SYS, 2, 2048) != 0)
cout << "Mix_OpenAudio ERROR: " << Mix_GetError() << endl;
else
cout << "Mix_OpenAudio SUCCESS" << endl;

// Set Volume
Mix_VolumeMusic(100);

// Open Audio File
Mix_Music *music;
music = Mix_LoadMUS("sound.mp3");
if (music == 0)
cout << "Mix_LoadMuS ERROR: " << Mix_GetError() << endl;
else
cout << "Mix_LoadMus SUCCESS" << endl;

// Start Playback
if (Mix_PlayMusic(music, 1) != 0)
cout << "Mix_PlayMusic ERROR: " << Mix_GetError() << endl;
else
cout << "Mix_PlayMusic SUCCESS" << endl;
int startTime = SDL_GetTicks();

// Wait
while (Mix_PlayingMusic()) {
SDL_Delay(1000);
cout << "Time: " << (SDL_GetTicks() - startTime) / 1000 << endl;
}

// Free File
Mix_FreeMusic(music);
music = 0;

// End
Mix_CloseAudio();
return 0;
}

[MadCow108]

my comment was just directed at those includes:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
these exist as seperate c++ headers cstdio,cstdlib,cstring and cmath.
the other includes are fine.


sdl-config --cflags --libs
is a tool of sdl that prints the compilerflags (--cflags) and libraries (--libs) needed to compile a program linking with sdl.
it will output something like that:
> sdl-config --cflags --libs
-I/usr/include/SDL -D_GNU_SOURCE=1 -D_REENTRANT
-L/usr/lib -lSDL

so
g++ `sdl-config --cflags --libs` file.cpp
will "expand" to:
g++ -I/usr/include/SDL -D_GNU_SOURCE=1 -D_REENTRANT -L/usr/lib -lSDL file.cpp

In your case it won't help as your using sdl_mixer which is not printed by sdl-config.

(A similar tool worth looking at is pkg-config)

[multiholle]

Is it possible to get the playback time and total time of the current playing song from the sdl library?