Help with Emscripten and SDL2_mixer

SDL Development
1

Hello, I am trying to make a webapp that uses SDL2_mixer to create sound. I have been able to use SDL2 and SDL2_image in the code and it works fine. However, as soon as I include SDL2_mixer, the program breaks and the console says: Mix_Init: no sound/music loaders supported (). My current compile command is: emcc source/main.c -o main.html -s USE_SDL=2 -s USE_SDL_IMAGE=2 -s USE_SDL_MIXER=2 -s SDL2_IMAGE_FORMATS=["png"] -s ALLOW_MEMORY_GROWTH=1 --preload-file assets . However I have tried a lot of different variations but they all give me that same error.(like including -sUSE_OGG=1, -sUSE_VORBIS=1, or SDL2_MIXER_FORMATS=‘[“ogg”]’) I have searched around and it seems like I could find very few tutorial or examples of SDL2_mixer being used with emscripten (most tutorials seem to end once an image is on the screen). Any advice or examples someone could give me would be much appreciated.

Also, I am on windows if that matters. I also the python library http to create localhost to test my code on the browser.

2

Last time I used Emscripten, I managed to get SDL_Mixer to work quite easily together with Emscripten.

I used the following command when building the project:
emcc /mySourceFilesSpecifiedHere/ -o test.html -s USE_SDL=2 -s USE_SDL_IMAGE=2 -s SDL2_IMAGE_FORMATS='["png"]' -s USE_SDL_TTF=2 -s USE_FREETYPE=1 -s USE_SDL_MIXER=2 -s USE_OGG=1

To start up SDL_Mixer, I do this:

const int result = Mix_Init(MIX_InitFlags::MIX_INIT_OGG);

if((result & MIX_InitFlags::MIX_INIT_OGG) == 0)
{
	printf("Error: failed to initialize SDL_Mixer. %s\n", Mix_GetError());

	return false;
}

if(Mix_OpenAudio(44100, MIX_DEFAULT_FORMAT, MIX_DEFAULT_CHANNELS, 2048) == -1)
{
#ifdef _DEBUG
	printf("Error: failed to open audio device. %s\n", Mix_GetError());
#endif

	return false;
}

Can you confirm that you’re doing it the same way?

3

Hi thanks for the response! I have some similar code to that, but I still have the same error. I start getting the error as soon as I add the -sUSE_SDL_MIXER=2 flag. It happens when even when I don’t use any code involving the mixer. This doesn’t seem to happen when I add the flag -sUSE_TTF=2 even when I don’t use it. Maybe I need try using an older version of emscripten. I think I will try to do that.

Here is my code below where I did attempt to use the mixer:

#include <stdio.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <SDL2/SDL_mixer.h>
#include <emscripten.h>
#include <stdlib.h>

SDL_Window *window = NULL;
SDL_Renderer *renderer = NULL;
SDL_Texture *texture = NULL;
SDL_Rect destinationRect = {100, 100, 0, 0};

Mix_Music *music = NULL;

void playMusic() {
Mix_PlayMusic(music, 0);
}

void render_loop() {
SDL_Event event;
while (SDL_PollEvent(&event)) {
if (event.type == SDL_QUIT) {
emscripten_cancel_main_loop();
break;
}
}

SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, texture, NULL, &destinationRect);
SDL_RenderPresent(renderer);

}

int main() {

SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO);
IMG_Init(IMG_INIT_PNG);

Mix_Init(MIX_INIT_OGG);


if (Mix_OpenAudio(44100, MIX_DEFAULT_FORMAT, 2, 1024) < 0) {
    printf("Failed to initialize SDL_mixer: %s\n", Mix_GetError());
    return 1;
}

music = Mix_LoadMUS("assets/test_song.ogg");
if (!music) {
    printf("Failed to load music: %s\n", Mix_GetError());
    return 1;
}

window = SDL_CreateWindow("SDL2_image Example",
                          SDL_WINDOWPOS_CENTERED,
                          SDL_WINDOWPOS_CENTERED,
                          800, 600,
                          0);
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

SDL_Surface *surface = IMG_Load("assets/triangle.png");
if (!surface) {
    printf("Failed to load image: %s\n", IMG_GetError());
    return 1;
}

destinationRect.w = surface->w;
destinationRect.h = surface->h;

texture = SDL_CreateTextureFromSurface(renderer, surface);
if (!texture) {
    printf("Failed to create texture: %s\n", SDL_GetError());
    return 1;
}


emscripten_set_main_loop(playMusic, 0, 1);
emscripten_set_main_loop(render_loop, 0, 1);

SDL_FreeSurface(surface);
SDL_DestroyTexture(texture);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
IMG_Quit();
SDL_Quit();

return 0;

}

4

Hi, I was able to get it working. I had to revert to an older version of the emsdk(I used 3.1.44). I think there must be a bug of some sort.

5

I couldn’t see any obvious error in your code so it might, like you wrote, be a bug in the newest version of Emscripten.

Nice that you got it working :slight_smile:

6

Thanks for the help! Your compile command helped identify it!

7

Also the most it seem like both builds 3.1.53(the current build) and 3.1.52 have this issue. Build 3.1.51 seems to work.