Is it possible to get the audio from an mp4 or webm video element in HTML5?
I'm trying to use https://github.com/corbanbrook/dsp.js to calculate FFTs for audio, however, I only have the mp4 and webm videos.
Not sure if this answers your question but you can run the audio of the video through the Web Audio API node graph. The code below can be demonstrated by changing the gain and filter parameters. I only tested this on Chrome.
<!DOCTYPE html>
<meta charset="UTF-8">
<title></title>
<body>
</body>
<script>
var video = document.createElement("video");
video.setAttribute("src", "ourMovie.mov");
video.controls = true;
video.autoplay = true;
document.body.appendChild(video);
var context = new webkitAudioContext();
var gainNode = context.createGain();
gainNode.gain.value = 1; // Change Gain Value to test
filter = context.createBiquadFilter();
filter.type = 2; // Change Filter type to test
filter.frequency.value = 5040; // Change frequency to test
// Wait for window.onload to fire. See crbug.com/112368
window.addEventListener('load', function(e) {
// Our <video> element will be the audio source.
var source = context.createMediaElementSource(video);
source.connect(gainNode);
gainNode.connect(filter);
filter.connect(context.destination);
}, false);
</script>
The above code is a modified version of this : http://updates.html5rocks.com/2012/02/HTML5-audio-and-the-Web-Audio-API-are-BFFs
I simply replaced the audio element with the video element.
Webm works as an audio source.
<audio controls="controls" class="full-width" preload="metadata">
<source src="//rack.international/samples/sample.webm" type="audio/mpeg">
</audio><video src="https://rack.international/samples/sample.webm" controls>
<p>Your browser doesn't support HTML5 video. Here is a <a href="rabbit320.webm">link to the video</a> instead.</p>
</video>来源：https://stackoverflow.com/questions/15118524/get-audio-from-an-html5-video