Why is my SDL_mixer playing my wav. file too fast?

Question

From this Lazy Foo tutorial ( https://lazyfoo.net/tutorials/SDL/21_sound_effects_and_music/index.php ) I wrote the following lines of code:

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

bool running = true;
int main(int argc, char** argv) {
    SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO);
    SDL_Window* window = SDL_CreateWindow("testing musique", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, 0);
    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
    SDL_Event quit;
    Mix_Music* music;

    while (running) {
        while(SDL_PollEvent(&quit)){
            switch(quit.type) {
            case SDL_QUIT:
                running = false;
                break;
            }
        }

        Mix_OpenAudio(44100, MIX_DEFAULT_FORMAT, 2, 2048);
        music = Mix_LoadMUS("../pikachu/keypress_BMP/beat.wav");
        Mix_PlayMusic(music, -1);

        SDL_SetRenderDrawColor(renderer, 20, 20, 255, 255);
        SDL_RenderClear(renderer);
        SDL_RenderPresent(renderer);
    }

    Mix_FreeMusic(music);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
}

I even used the same audio file (beat.wav) as Lazy Foo did in his tutorial, but while his program runs without a hitch, mine plays the wav too fast (despite the fact that I checked every parameters to make sure mine matched with his). I tried decreasing the frequency parameter in Mix_OpenAudio, but while the wav did slow down, so did the pitch, and it should not have made sense to do this in the first place. What should I do?

Answer 1

The audio subsystem should only be opened once, before the main loop , meanwhile you open it in each iteration of the loop. The same goes for loading the file into memory — again on each iteration of the loop, instead of once. So the correct code structure should look like this:

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

int main(int argc, char** argv) {
    bool running = true;
    SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO);

    SDL_Window* window = SDL_CreateWindow("testing musique", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, 0);
    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

    // open audio and load music file before main loop
    Mix_OpenAudio(44100, MIX_DEFAULT_FORMAT, 2, 2048);
    Mix_Music* music = Mix_LoadMUS("../pikachu/keypress_BMP/beat.wav");

    SDL_Event event;

    while (running) {
        while(SDL_PollEvent(&event)){
            switch(event.type) {
            case SDL_KEYDOWN:
                switch(event.key.keysym.sym) {
                case SDLK_P:
                    Mix_PlayMusic(music, -1);
                    break;
                case SDLK_S:
                    Mix_HaltMusic();
                    break;
                }
            case SDL_QUIT:
                running = false;
                break;
            }
        }

        SDL_SetRenderDrawColor(renderer, 20, 20, 255, 255);
        SDL_RenderClear(renderer);
        SDL_RenderPresent(renderer);
    }

    // close audio and free the music after main loop
    Mix_CloseAudio();
    Mix_FreeMusic(music);

    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
}

Don't forget about Mix_CloseAudio and about error checking.