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Wavesurfer.js doesn't work in Firefox 51

wavesurfer.js doesn't play audio for me in Firefox, unless you set the backend option to MediaElement.

Fault description

When not working, it will draw the waveform and allow you to click around to move the seek point, but it won't play any sound. The ready event is fired during setup. After this, I can trigger play, and the play event will fire. The wavesurfer.isPlaying property will change to true, but the seek bar does not move, and the sound does not play. My Firefox is v51.0.1 (32 bit) on Windows.


I have tried to make sure the ready event was fired before playing, and other tricks, but they didn't work. Eventually my solution was to use the MediaElement backend. The added upside is that I no longer need to care about the ready event because the MediaElement can play even before the waveform is drawn.

Here's my most minimal test case which does work in Firefox (it uses some local audio which you will need to replace):

<meta http-equiv="content-type" content="text/html; charset=utf-8">
<script src=""></script>
    <div class="js-waveform"></div>
    <button onclick="play()">Play</button>
    var wavesurfer = null;

    var play = function()

    var prepare = function ()
        wavesurfer = WaveSurfer.create({
            container: ".js-waveform",
            backend: 'MediaElement'

        wavesurfer.on('ready', function () {