Skips annoying silences in lecture recordings, and suppresses noise

silenceRemover.user.js

// ==UserScript==
// @name         Lecture recording silence and noise remover
// @namespace    https://gist.github.com/daniilS/
// @downloadUrl  https://gist.github.com/daniilS/32ddbd3557bf34385ab6539bd4154007/raw/silenceRemover.user.js
// @version      2.0.0
// @description  Puts more effort into making online lectures tolerable than the rest of the chemistry department combined
// @author       daniilS
// @include      *://*.panopto.*/Panopto/Pages/Viewer.aspx*
// @grant        GM_registerMenuCommand
// @grant        unsafeWindow
// ==/UserScript==

(function(){
	'use strict';

	//global variables so that you can also change them through the console. These should really be sliders in a browser extension popup if I had done this properly
	unsafeWindow.threshold = -28; //silence threshold in decibels, video will get sped up below this threshold
	unsafeWindow.maxGap = 0.300; //max silence length in seconds, video will be sped up after this length of silence
	unsafeWindow.normalSpeed = 1; //default normal video playback rate, set to whatever you normally watch videos at. Can also be changed the way you normally change speed in Panopto
	unsafeWindow.fastSpeed = 4; //playback rate during silences, values above 4 sometimes make the audio go weird in Chrome, set it to the highest value your browser can handle
	unsafeWindow.disableScript = false; //set to true to disable the script
	unsafeWindow.verboseScript = false; //set to true if you want your console spammed to see if the extension is working

	unsafeWindow.filterQ = 1.1; //Q-factor of the band-pass filter, applied when enabling noise supression
	unsafeWindow.filterFrequency = 300; //frequency band of the band-pass filter, applied when enabling noise supression

	let filter;

	let waitForVideo = function(){
		if(document.getElementsByClassName("video-js").length < 1){
			setTimeout(waitForVideo, 100);
			return;
		}

		//check if the browser is Firefox and warn the user if it is
		//the bug in question: https://bugzilla.mozilla.org/show_bug.cgi?id=1517199
		if(unsafeWindow.Panopto.Core.Browser.isFirefox){
			alert("Due to a known but unfixed bug in Firefox, the silence remover script doesn't work. Please try a different browser (Chrome recommended).");
			return;
		}

		if(document.getElementsByClassName("video-js")[0].paused){
			setTimeout(waitForVideo, 100);
			return;
		}

		let context = new AudioContext();
		let videoElement = document.getElementsByClassName("video-js")[0]; //audio, or video of the lecturer's face, or the screen if there's only one video
		let videoElement1 = document.getElementsByClassName("video-js")[1] || {}; //video of the screen, if separate
		let video = context.createMediaElementSource(videoElement);
		let analyser = context.createAnalyser(); //yes I know this should really be an AudioWorkletNode but this was less effort
		analyser.fftSize = 512;

		filter = context.createBiquadFilter();
		filter.Q.value = 0;
		filter.frequency.value = unsafeWindow.filterFrequency;
		filter.type = 'bandpass';

		filter.connect(analyser);
		analyser.connect(context.destination);

		video.connect(filter);


		let getLoudness = function(){
			let array = new Float32Array(analyser.fftSize);
			analyser.getFloatTimeDomainData(array);

			let max = 0;
			for (let i = 0; i < array.length; i++){
				let a = Math.abs(array[i]);
				max = Math.max(max, a);
			}

			let dB = 10 * Math.log10(max);
			return dB;
		}


		let lastLoudness = unsafeWindow.threshold;

		let timeOffset = undefined;

		let changeSpeed = function(newSpeed){
			document.getElementById("playButton").click(); //pause the video in an attempt to prevent desync
			videoElement.playbackRate = newSpeed;
			videoElement1.playbackRate = newSpeed;
			document.getElementById("playButton").click();
		}

		let silenceDetector = function(){
			if(videoElement.paused || unsafeWindow.disableScript){
				setTimeout(silenceDetector, 20);
				return;
			}
			let loudness = getLoudness();
			if(loudness < unsafeWindow.threshold){
				if(lastLoudness > unsafeWindow.threshold){
					lastSilence = videoElement.currentTime;
				}
				else{
					if(videoElement.currentTime - lastSilence >= unsafeWindow.maxGap){
						if(videoElement.playbackRate != unsafeWindow.fastSpeed){
							changeSpeed(unsafeWindow.fastSpeed);
						}
						if(unsafeWindow.verboseScript){
							console.log("forwarding");
						}
					}
				}
			}
			else{
				if(videoElement.playbackRate != unsafeWindow.normalSpeed){
					changeSpeed(unsafeWindow.normalSpeed);
				}
			}
			lastLoudness = loudness;
			setTimeout(silenceDetector, 20);
		}

		let lastSilence = videoElement.currentTime;
		silenceDetector();
	}

	let waitForSpeedButtons = function(){
		if(document.getElementsByClassName("play-speed").length < 1){
			setTimeout(waitForSpeedButtons, 100);
			return;
		}

		for(let speedButton of document.getElementsByClassName("play-speed")){
			speedButton.onclick = function(e){
				unsafeWindow.normalSpeed = unsafeWindow.PanoptoViewer.PlaySpeed[e.target.id];
			}
		}
	}

	waitForVideo();
	waitForSpeedButtons();

	GM_registerMenuCommand("Enable noise suppression", function(){filter.Q.value = unsafeWindow.filterQ; filter.frequency.value = unsafeWindow.filterFrequency;});
	GM_registerMenuCommand("Disable noise suppression", function(){filter.Q.value = 0;});

	GM_registerMenuCommand("Enable silence skipper", function(){unsafeWindow.disableScript = false;});
	GM_registerMenuCommand("Disable silence skipper", function(){unsafeWindow.disableScript = true;});
})();