webaudiomodules/wam-examples

outputChannelCount not working when I inherit from AudioWorkletProcessor

KnappSas opened this issue · 4 comments

KnappSas commented

Hi, I am facing this issue, trying out the example in the WamExample folder. The example passes the outputChannelCount: [2] with the options to the processor which is then passed to the actual AudioWorkletProcessor via the super call to the parent class.
This doesn't work on my system in any browser, I always have a channel count of 1 ... I also just tried a minimal example:

The following code doesn't work.

// processor.js
class Processor extends AudioWorkletProcessor {
    constructor() {
        super({outputChannelCount: [2]});
    }

    process(inputs, outputs, parameters) {
        console.log("output channels: ", outputs[0].length);
        return true;
    }
}

registerProcessor('processor', Processor);

But when I leave the options in the Processor class out like:

// processor.js
class Processor extends AudioWorkletProcessor {
    constructor() {
        super();
    }

    process(inputs, outputs, parameters) {
        console.log("output channels: ", outputs[0].length);
        return true;
    }
}

registerProcessor('processor', Processor);

and pass the options to the AudioWorkletNode instead

// app.js
let audioContext = new AudioContext();
(async () => {
    await audioContext.audioWorklet.addModule('processor.js');
    audioWorkletNode = new AudioWorkletNode(audioContext, 'processor', {outputChannelCount: [2]});
    audioWorkletNode.connect(audioContext.destination);
})();

it works and I get my 2 channels now.

So passing options in the class that inherits from AudioWorkletProcessor doesn't seem to work anymore? Is this a bug in the Web Audio API or is there something that I am missing from the specification?

KnappSas commented

Anyway,... whatever is wrong with my code above, the real cause seems to be either in WamExampleNode.js or WamExampleProcessor.js..
To fix it on my side it is enough to rewrite the following in WamExampleNode.js

options.processorOptions = {
	numberOfInputs: 1,
	numberOfOutputs: 1,
	outputChannelCount: [2],
	useSab: true,
};
super(module, options);

to

options.outputChannelCount = [2];
options.processorOptions = {
	numberOfInputs: 1,
	numberOfOutputs: 1,
	outputChannelCount: [2],
	useSab: true,
};
super(module, options);
Fr0stbyteR commented

Thanks @KnappSas,
I think it should be a misplacement of some options.

options.numberOfInputs = 1;
options.numberOfOutputs = 1;
options.outputChannelCount = [2];
options.processorOptions = { useSab: true };
super(module, options);

@owengc Is this what we need?

  • 👍1
KnappSas commented

I see you removed the options from the ctor-call in WamProcessor in the sdk. This was also discussed here: WebAudio/web-audio-api#2491

So this thread can be closed then.