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jbodah/audio-edge-test.html

Created January 20, 2018 18:53
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detecting audio edges for auto-trimming using the web audio api
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audio-edge-test.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>audio edge test</title>
</head>
<body>
</body>
<script>
var audioCtx = new AudioContext();
var audio = new Audio('file:///Users/jbodah/desktop/audio-edge-test.flac');
var source = audioCtx.createMediaElementSource(audio);
var bandpass = audioCtx.createBiquadFilter();
bandpass.type = 'bandpass';
bandpass.frequency = 3700/2;
bandpass.Q.value = 100;
var analyser = audioCtx.createAnalyser();
analyser.fftSize = 256;
var dataArray = new Uint8Array(analyser.frequencyBinCount);
var gainNode = audioCtx.createGain();
gainNode.gain.value = 20;
function getVolume(arr) {
return arr.reduce((acc, n) => acc + n, 0) / arr.length;
}
// Edge Detection
var threshold = 1.5;
var firstEdge = null;
var lastEdge = null;
var sampleRate = 100;
setInterval(function () {
analyser.getByteFrequencyData(dataArray);
var volume = getVolume(dataArray);
if (volume > threshold) {
console.log(volume);
var pos = audio.currentTime;
if (firstEdge === null)
firstEdge = pos;
lastEdge = pos;
}
}, sampleRate);
audio.addEventListener("ended", function(){
console.log("firstEdge: " + firstEdge);
console.log("lastEdge: " + lastEdge);
setTimeout(function () {
console.log("starting over");
audio.currentTime = firstEdge - 0.3;
audio.play();
var stopIn = Math.round((lastEdge - firstEdge) * 1000) + 1000;
setTimeout(function () {
audio.pause();
}, stopIn);
}, 500);
});
source.connect(bandpass);
bandpass.connect(analyser);
analyser.connect(gainNode);
source.connect(audioCtx.destination);
//gainNode.connect(audioCtx.destination);
audio.play();
</script>
</html>
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