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analyzer.html
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analyzer.html
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<html>
<head>
<title>NEJS 2016 - Analyzer</title>
<style>
body {
align-items: center;
display: flex;
flex-direction: column;
height: 100%;
justify-content: center;
}
.vis {
align-items: flex-end;
background: #222;
display: none;
height: 190px;
margin-bottom: 40px;
padding: 20px 0 0;
width: 680px;
}
.vis__bar {
transition: .1s;
width: 5%;
height: 0;
background: #777;
}
.vis__bar--max {
border-top: solid 10px #f28832;
}
.main {
align-items: center;
display: flex;
justify-content: center;
}
pre {
background: #ddd;
box-sizing: border-box;
display: block;
font-size: 14px;
margin: 20px 0 20px 20px;
padding: 20px;
width: 640px;
}
button {
font-size: 24px;
margin: 20px 10px 0;
}
</style>
</head>
<body>
<div data-vis class="vis">
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
<span data-vis-bar class="vis__bar"></span>
</div>
<div class="main">
<div class="main__block">
<video
src="/assets/digitalsurgeons.mp4"
controls
data-video-source>
</video>
</div>
<div class="main__block">
<pre><code data-analysis></code></pre>
</div>
</div>
<button data-show-vis>Show visualization</button>
<script>
// create web audio context
const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
// DOM nodes
const ui = {
video: document.querySelector('[data-video-source]'),
analysis: document.querySelector('[data-analysis]'),
vis: document.querySelector('[data-vis]'),
visBars: document.querySelectorAll('[data-vis-bar]'),
visBtn: document.querySelector('[data-show-vis]'),
};
// create media element source node
const videoSource = audioCtx.createMediaElementSource(ui.video);
// create analyzer node
const analyser = audioCtx.createAnalyser();
// set size of fast fourier transform
analyser.fftSize = 64;
// construct Uint8Array for analysis data
const bufferLength = analyser.frequencyBinCount;
const dataArray = new Uint8Array(bufferLength);
// connect video source to analyzer
// connect analyzer to output
videoSource.connect(analyser);
analyser.connect(audioCtx.destination);
// toggle visualisation display
ui.visBtn.addEventListener('click', e => {
if (ui.vis.style.display === 'flex') {
ui.vis.style.display = 'none';
ui.visBtn.innerHTML = 'Show visualization';
} else {
ui.vis.style.display = 'flex';
ui.visBtn.innerHTML = 'Hide visualization';
}
});
// call analyze function at 60fps
function analyze() {
const middleSection = Uint8Array.from(dataArray);
// get frequency data of audio at this point in time
analyser.getByteFrequencyData(dataArray);
// update height of each visualization bar
dataArray.forEach((val, index) => {
// only using first 24 as audio not hitting top end of spectrum
if (!ui.visBars[index]) {
return;
}
ui.visBars[index].style.height = `${val / 1.5}px`;
// add orange cap to par if peaking
if (val > 200) {
ui.visBars[index].classList.add('vis__bar--max');
} else {
ui.visBars[index].classList.remove('vis__bar--max');
}
});
// update analaysis in DOM, prettify JSON
ui.analysis.innerHTML = JSON.stringify(middleSection.slice(8, 24))
.replace(/{/, '{\r\n ')
.replace(/,"/g, ',\r\n "')
.replace(/}/, '\r\n}');
// recursivly call function every 60fps
requestAnimationFrame(analyze);
}
// kick off analysis
requestAnimationFrame(analyze);
console.log(audioCtx);
console.log(analyser);
</script>
</body>
</html>