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getOutputTimestamp.html
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getOutputTimestamp.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width" />
<title>getOutputTimestamp</title>
</head>
<body>
<h2>getOutputTimestamp</h2>
<button id="run">run</button> <span>default is 20 measurements: change "limit" in console to increase this</span>
<div><br><output></output></div>
<script>
'use strict';
// https://developer.mozilla.org/en-US/docs/Web/API/AudioContext/getOutputTimestamp
const runBtn = document.querySelector("#run");
const output = document.querySelector("output");
let audioCtx, source, rAF, oTime = {}, tStart, limit = 20, newlimit
let calc1 = new RegExp('^-?\\d+(?:\.\\d{0,' + (1 || -1) + '})?')
// Press the play button
runBtn.addEventListener("click", () => {
try {
newlimit = limit - 1
output.innerHTML = ''
// We can create the audioCtx as there has been some user action
if (!audioCtx) {audioCtx = new AudioContext()}
oTime = {'contextTime': [],'performanceTime': []}
tStart = performance.now()
source = new AudioBufferSourceNode(audioCtx);
source.start(0);
runBtn.disabled = true;
rAF = requestAnimationFrame(collectTimestamps);
} catch(e) {
output.innerHTML = e+''
}
})
function stop() {
let timeTaken = Math.round(performance.now() - tStart)
source.stop(0)
cancelAnimationFrame(rAF)
let display = []
for (const k of Object.keys(oTime)) {
let data = oTime[k], count = data.length
let str = ' ['+ count +' | ' + timeTaken +' ms | '+ Math.floor(timeTaken/count) +']'
display.push('<b>'+ k +'</b>'+ str +'<br>')
data = data.filter(function(item, position) {return data.indexOf(item) === position})
// contextTime: if the first value is 0 then we need to drop it
// otherwise the first diff causes an offset to our 60FPS timing as rAF catches up: e.g.
// 10, 26.6, 43.3, 76.6, 110, 143.3, 160, 176.6, 193.3, 210, 243.3
// 10, 26.6, 43.3
// ^ should be 0, 16.6, 33.3: i.e the [0, 10, 26.6...] we drop the start point of 0
// after that everythng is in sync
if ('contextTime' == k && 0 == data[0]) {data = data.slice(1)}
let setDiffs = new Set(), aTotal = [], start = data[0]
for (let i=1; i < data.length ; i++) {
let end = data[i]
// truncate to 1 decimal place
let totaldiff = ((end - start).toString().match(calc1)[0]) * 1
aTotal.push(totaldiff)
let diff = (totaldiff % 50).toFixed(2) * 1 // drop 50s
setDiffs.add(diff)
}
let aDiffs = Array.from(setDiffs)
console.log(k, 'data', data)
//console.log(k, 'diffs', aDiffs)
if (newlimit > 19) {
console.log(k, 'total', aTotal)
// just get the first 10 + last 5
let len = aTotal.length
let newTotal = aTotal.slice(0, 10)
let lastTotal = aTotal.slice(len - 5, len)
str = newTotal.join(', ') + ' ... see console for full total list ... ' + lastTotal.join(', ')
} else {
str = aTotal.join(', ')
}
display.push(str +'<br>')
display.push(aDiffs.join(', ') +'<br>')
}
output.innerHTML = display.join('<br>')
runBtn.disabled = false
}
// collect timestamps
function collectTimestamps() {
const ts = audioCtx.getOutputTimestamp();
oTime.contextTime.push(ts.contextTime * 1000)
oTime.performanceTime.push(ts.performanceTime)
rAF = requestAnimationFrame(collectTimestamps); // Reregister itself
if (newlimit > 19) {
output.innerHTML = oTime.contextTime.length + ' of '+ limit
}
if (oTime.contextTime.length > newlimit) {stop()}
}
</script>
</body>
</html>