Ondographics loopback

function readBands() {
analyser.getByteFrequencyData(bands);
var out = [];
for (var i = 0; i < 32; i += 1) {
var from = Math.floor(Math.pow(bands.length, i / 32));
var to = Math.max(from + 1, Math.floor(Math.pow(bands.length, (i + 1) / 32)));
var sum = 0;
for (var j = from; j < to; j += 1) sum += bands[j];
out.push(Math.min(1, (sum / (to - from) / 255) * 1.45));
}
return out;
}
function readWave() {
if (!timeDomain) timeDomain = new Uint8Array(analyser.fftSize);
analyser.getByteTimeDomainData(timeDomain);
var step = Math.floor(timeDomain.length / 96);
for (var i = 0; i < 96; i += 1) wave[i] = (timeDomain[i * step] - 128) / 128;
return wave;
}
function tick() {
if (analyser) {
var list = readBands();
post({
bands: list,
wave: readWave(),
level: list.reduce(function (a, b) { return a + b; }, 0) / list.length,
at: performance.now(),
});
}
setTimeout(tick, 50);
}
async function start() {
var stream = await navigator.mediaDevices.getDisplayMedia({ video: true, audio: true });
stream.getVideoTracks().forEach(function (track) { track.stop(); stream.removeTrack(track); });
var Ctx = window.AudioContext || window.webkitAudioContext;
audioCtx = new Ctx();
var source = audioCtx.createMediaStreamSource(stream);
analyser = audioCtx.createAnalyser();
analyser.fftSize = 2048;
analyser.smoothingTimeConstant = 0.75;
bands = new Uint8Array(analyser.frequencyBinCount);
source.connect(analyser);
if (audioCtx.state === 'suspended') audioCtx.resume();
post({ ready: true });
}
start().catch(function (err) {
post({ error: String((err && err.message) || err) });
});
tick();
})();