SDL_mixer 2?

[ooxi]

Hi,

has there been an attempt to port SDL_mixer 2? It seams like SDL_mixer 1.2 is embedded but does rely one the browser to do the decoding (just like SDL 1 is embedded but the SDL 2 port is far more advanced)

-- ooxi

[iboB]

Actually you can build SDL2_mixer without the plugins from source just as you would any other library.

To support the mp3 or mod plugins you would need support from libmpeg and libmodplug for emscripten (I don't know whether such exist)

To add ogg support you can use the ogg and vorbis ports by adding -s USE_OGG=1 -s USE_VORBIS=1 to the compiler and linker settings

You actually may use all SDL_mixer dependencies, it works as expected.

Update: the following patches are not needed anymore with SDL 2.0.7 and SDL_mixer 2.0.2.

If you want to make MIDI music (internal timidity) and tracker music (libmodplug) work in emscripten, you need to patch SDL2_mixer because timidity and libmodplug drivers in SDL2_mixer don't support 32 bit device mixing (used by Web Audio).

Here is the new proposed custom Mix_OpenAudioDevice() function to properly set the frequency change, unsupported by SDL_mixer, which uses legacy SDL_OpenAudio(). Once the patch is applied, it will work:

#ifdef EMSCRIPTEN
    // Note: this requires a patched SDL_mixer currently
    Mix_OpenAudioDevice(NULL, 0, frequency, MIX_DEFAULT_FORMAT, MIX_DEFAULT_CHANNELS, 4096, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE);
#else
    Mix_OpenAudio(frequency, MIX_DEFAULT_FORMAT, MIX_DEFAULT_CHANNELS, 4096)
#endif

Another trick: to prevent noise when using wav and ogg, don't use Mix_PlayMus() because it is buggy, use Mix_PlayChannel() in the meanwhile.

Final suggestion: to prevent resampling buffering issues (choppy audio) due to another (SDL2?) bug, you should also patch the audio initialization to get the native browser frequency, e.g.:

#if EMSCRIPTEN
#  include <emscripten.h>
#endif

// (...)
#if EMSCRIPTEN

    int const frequency = EM_ASM_INT_V({
        var context;
        try {
            context = new AudioContext();
        } catch (e) {
            context = new webkitAudioContext();
        }
        return context.sampleRate;
    });
#else
    int const frequency = 44100;
#endif

[ooxi]

Thanks for the hints @fdelapena! Do you have SDL2_mixer already compiled? Could you maybe provide the binaries?

Thanks for the hints @fdelapena! Do you have SDL2_mixer already compiled? Could you maybe provide the binaries?

We have an automated toolchain with generated .a static files, you might need to rename needed .a to .bc (bitcode) to make them work with emcc.
https://ci.easyrpg.org/view/Toolchains/job/toolchain-emscripten/ws/

Here is the relevant part of our automated build script of SDL2 and SDL2_mixer for Emscripten.

By the way, if you want to play midi files you need to include GUS patches for timidity support and embed them in the dat file.

SDL_mixer from Hg just added Mix_OpenAudioDevice at https://hg.libsdl.org/SDL_mixer/rev/fb0562cc1559 so you don't need to patch SDL_mixer anymore with the current Mercurial version 👍.

[Fighter19]

I tried builidng my game. But when running it, it fails when using Mix_LoadWAV_RW
Type error: "rwops is null"
Maybe he couldn't find the file, but the html is being loaded in the same folder the executable normally is. And loading a file format it does not support cannot be the problem (tested in an empty directory).
So for me SDL_mixer with SDL2 does not really work.

[hyp1]

@Fighter19 i had the same problem.
Everything worked to the point when, to play .wav files.
I solved it by using the buildscipt from @fdelapena to build the SDL_mixer and coping the SDL_mixer folder to $EMSCRIPTEN/system/include/SDL.
Good luck

[rchaser53]

I try to convert the rust application to wasm.
And I have the same problem.

Acutually I also want to use the buildscript.
Please give me the buildscript from @fdelapena.
Thank you.

[hyp1]

Hi,
the build script from felapenais in this thread.
Here is the relevant part of our automated build script of SDL2 and SDL2_mixer for Emscripten.*
I managed to get it work for my project (a gamelibrary für sprite based games), but i now believe there is a bug.in the SDL_mixer implementation.
That only affects wenn i try to play audio Mix_L
oadWAV from a class that ist compiled to a library.
Best Regards

[rchaser53]

Sorry. I missed it.
Honestly I also think it's the bug in the SDL_mixer implementation.
Anyway I'll try the build script.
Thank a lot.

By the way, with SDL 2.0.7 and SDL_mixer 2.0.2 have been released, the patch I suggested is not needed anymore, the noise resampling issue has been fixed too, it should work nicely out of the box with Mix_PlayMus() at any audio frequency.

Update: I've updated the CI link to our toolchain build job.

[Shchvova]

So, is there a way to include SDL2/SDL_mixer.h at this point without rebuilding it myself?

[kripken]

Not yet. @aidanhs mentioned on the mailing list he might add an emscripten port for it - @aidanhs, any update there?

[aidanhs]

I've made a PR for an initial iteration of SDL2_mixer at #5995 (the test uses the sample detection trick, thanks @fdelapena)

It's pretty rough and is intended as a first attempt for people who actually care about audio to create new PRs on top of - I only built mixer in the first place because it was easier than ripping it out of the program I was porting to emscripten :)

The PR currently:

• is deliberately configured to just support OGG (supporting WAV may be as easy as just changing a flag and adding a test)
• is sdl_mixer release 2.0.0 (2.0.2 requires a more recent version of sdl2 than emscripten has available -
  see Merge upstream 2.0.7 emscripten-ports/SDL2#52)

[kripken]

Fixed by #7599, we now have SDL2_mixer in ports thanks to @aidanhs and @superzazu!