Web Audio Worker Example - Shared Parallel

main.js

let context = new AudioContext();

let noiseWorker = context.createAudioWorker("worker.js");

let noiseNode1 = context.createScriptProcessor(noiseWorker);
let noiseNode2 = context.createScriptProcessor(noiseWorker);
let oscillator = context.createOscillator();

noiseNode1.connect(oscillator.detune);
noiseNode2.connect(context.destination);
oscillator.connect(context.destination);

oscillator.start(context.currentTime);

subworker.js

this.onmessage = function (event) {
    if ( !event.data || event.data.type !== "fillBuffer" ) {
        return;
    }

    let buffer = new Float32Array(event.data.length);

    for ( let i = 0; i < buffer.length; i++ ) {
        buffer[i] = Math.random() * 2 - 1;
    }

    this.postMessage({
        type: "buffer",
        buffer: buffer
    });
};

worker.js

let fillQueue = [];

let workerPool = [0, 1, 2, 3].map(function () {
    let worker = new Worker("subworker.js");

    worker.onmessage = function (event) {
        if ( !event.data || event.data.type !== "buffer" ) {
            return;
        }

        fillQueue.shift(event.data.buffer);
    };

    return worker;
});

let workerPoolIndex = 0;

let queueFill = function (size, callback) {
    let worker = workerPool[workerPoolIndex];
    workerPoolIndex = (workerPoolIndex + 1) % workerPool.length;
    fillQueue.push(callback);
    worker.postMessage({
        type: "fillBuffer",
        size: size
    });
};

let fillBuffer = function (buffer) {
    let deferred = Promise.defer();

    queueFill(buffer.length, function (filledBuffer) {
        buffer.set(filledBuffer);
        deferred.resolve();
    });

    return deferred.promise;
};

this.onaudioprocess = function (event) {
    let buffers = event.data.channels;

    return Promise.all(buffers.map(fillBuffer)).then(function () {
        event.finish();
    });
};