Just some tips apply filters to an audio from video stream

webaudio-tests.js

// # 1st way

var context = new AudioContext();
var source = context.createMediaElementSource(document.querySelector('.video-stream.html5-main-video'));

//Now we want to create a filter
var filter = context.createBiquadFilter();
source.connect(filter); //and of course connect it
filter.type = "highshelf"; //this is a lowshelffilter (try excuting filter1.LOWSHELF in your console)
filter.frequency.value = 200; //as this is a lowshelf filter, it strongens all sounds beneath this frequency
filter.gain.value = 50; //the gain with which it should increase

//now we want to connect that to the output
filter.connect(context.destination);


// # 2nd way
var context = new AudioContext();
var source = context.createMediaElementSource(document.querySelector('.video-stream.html5-main-video'));
var gainNode = context.createGain();
gainNode.gain.value = 10;
source.connect(gainNode);
gainNode.connect(context.destination);