AudioCompressor.js

(function() {

    console.log("Creating compressor");

    let context = new AudioContext();

    let compressor = context.createDynamicsCompressor();
    compressor.threshold.value = -50;
    compressor.knee.value = 40;
    compressor.ratio.value = 12;
    compressor.attack.value = 0;
    compressor.release.value = 0.25;

    let source = null;
    let active = false;

    window.toggleCompressor = () => {
        if (!source) {
            let videoElements = document.getElementsByTagName('video');
            source = videoElements.length ? context.createMediaElementSource(videoElements[0]) : null;
            source.connect(context.destination);
        }
        if (!source) return;

        active = !active;

        if (active) {
            console.log("Enabling compressor");
            source.disconnect(context.destination);

            source.connect(compressor);
            compressor.connect(context.destination);
        } else {
            console.log("Disabling compressor");
            source.disconnect(compressor);

            compressor.disconnect(context.destination);
            source.connect(context.destination);
        }
    };

})();