Can't hear sound using ofSoundStream on Emscripten (Minimal Example Included)

[cuinjune]

I could successfully build audioOutputExample using emmake make.

And when I run the project using emrun --browser chrome bin/audioOutputExample.html, I see the following screen:

But I can neither hear any sound nor see the graphs move.

I also have the following warning in the console:

[warning] ofSoundStream::getDeviceList() not supported in emscripten

Is it possible to properly run ofSoundStream based examples using Emscripten?

[arturo]

yes it should work

[cuinjune]

Can anyone please confirm that audioOutputExample works using Emscripten?

Or I would appreciate if anyone can post a minimal working example that uses ofSoundStream.

---

Here’ my minimal example code that works on macOS but doesn’t work on Emscripten.

ofApp.h:

#pragma once

#include "ofMain.h"

class ofApp : public ofBaseApp{
    public:
    void setup();
    void update();
    void draw();
    
    void keyPressed(int key);
    void keyReleased(int key);
    void mouseMoved(int x, int y);
    void mouseDragged(int x, int y, int button);
    void mousePressed(int x, int y, int button);
    void mouseReleased(int x, int y, int button);
    void mouseEntered(int x, int y);
    void mouseExited(int x, int y);
    void windowResized(int w, int h);
    void dragEvent(ofDragInfo dragInfo);
    void gotMessage(ofMessage msg);
    
    void audioOut(ofSoundBuffer & buffer);
};

ofApp.cpp:

#include "ofApp.h"

//--------------------------------------------------------------
void ofApp::setup(){
    
    ofSoundStreamSettings settings;
    settings.numInputChannels = 0;
    settings.numOutputChannels = 2;
    settings.sampleRate = 44100;
    settings.bufferSize = 512;
    settings.setOutListener(this);
    ofSoundStreamSetup(settings);
}

//--------------------------------------------------------------
void ofApp::audioOut(ofSoundBuffer & buffer)
{
    for (size_t i = 0; i < buffer.getNumFrames(); ++i)
    {
        buffer[i*buffer.getNumChannels()    ] = ofRandom(0, 1) * 0.1;
        buffer[i*buffer.getNumChannels() + 1] = ofRandom(0, 1) * 0.1;
    }
}

Result: When I run it, it says Exception thrown, see JavaScript console.

In the Javascript console, I get the following error message:

Uncaught TypeError: Runtime.dynCall is not a function at ScriptProcessorNode.stream.onaudioprocess

In the Terminal console, I get no specific message.
And of course, I hear no sound at all.

---

Added: I found out ofxEmscriptenSoundStream::audio_cb() function is not being called at all although the function pointer is passed to html5audio_stream_create() function when ofxEmscriptenSoundStream::setup() is called.

html5audio_stream_create function is implemented in library_html5audio.js file and I think the following part is where it calls the ofxEmscriptenSoundStream::audio_cb() function:

Runtime.dynCall('viiii',callback,[bufferSize,inputChannels,outputChannels,userData]);

However I have no idea why it fails to call the callback function. (I cannot code JS)

[cuinjune]

I could fix this issue by changing Runtime.dynCall to just dynCall in library_html5audio.js file.

I followed the advice from this post:

The Runtime object has been removed for quite some time at this point (to fix that issue, you should remove Runtime. from your code, and just call dynCall).

After the fix and rebuilding the project, I could successfully hear the sound on a Chrome browser.

[cuinjune]

I added a pull request:

Fix Uncaught TypeError: Runtime.dynCall