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YouTube Live の遅延を自動的に最小化します
// ==UserScript==
// @name YouTube Live minimum latency
// @description YouTube Live の遅延を自動的に最小化します
// @namespace https://gitlab.com/sigsign
// @version 0.2.3
// @author Sigsign
// @license MIT or Apache-2.0
// @match https://www.youtube.com/*
// @run-at document-start
// @noframes
// @grant none
// ==/UserScript==
(function () {
'use strict';
function loadPage(fn) {
/**
* YouTube は SPA になっているため load だけではページ遷移を捕捉できない。
* load と yt-page-data-updated を併用するか yt-navigate-finish を使う。
*
* See: https://stackoverflow.com/questions/24297929/
*/
document.addEventListener('yt-navigate-finish', fn, false);
}
function getPlayer() {
return document.querySelector('#movie_player');
}
function getLiveLatency(player) {
const current = Date.now() / 1000;
const time = player.getMediaReferenceTime();
return time ? current - time : 0;
}
function getBufferHealth(player) {
const stats = player.getVideoStats();
if (!stats) {
return 0;
}
const bufferRange = stats.vbu;
if (!bufferRange) {
return 0;
}
const buffer = bufferRange.split('-');
if (buffer.length < 2) {
return 0;
}
const bufferTime = Number(buffer.slice(-1)[0]);
const currentTime = Number(stats.vct);
if (isNaN(bufferTime) || isNaN(currentTime)) {
return 0;
}
return bufferTime - currentTime;
}
const thresholds = {
NORMAL: {
latency: 10.0,
buffer: 2.0,
},
LOW: {
latency: 5.0,
buffer: 1.5,
},
ULTRALOW: {
latency: 2.0,
buffer: 1.0,
},
};
function getThresold(key) {
if (typeof key !== 'string') {
return null;
}
return key in thresholds ? thresholds[key] : null;
}
loadPage(() => {
const player = getPlayer();
if (!player) {
return;
}
const stats = player.getVideoStats() || {};
if (stats.live !== 'live' && stats.live !== 'dvr' && stats.live !== 'lp') {
return;
}
const availableRates = player.getAvailablePlaybackRates() || [];
if (!availableRates.includes(1.25)) {
return;
}
const video = document.querySelector('video');
if (!video) {
return;
}
const startAcceleration = () => {
const rate = player.getPlaybackRate();
if (rate !== 1.0) {
return;
}
const stats = player.getVideoStats() || {};
const latency = getLiveLatency(player);
if (stats.live !== 'live' && latency > 120) {
/**
* DVR or プレミア公開、かつ遅延が 2 分以上ある場合、
* ユーザーが自分の意思でシークしていると想定して対象から外す。
*/
return;
}
const threshold = getThresold(stats.latency_class);
if (!threshold) {
return;
}
if (stats.live === 'lp') {
// プレミア公開は 11 秒程度の Live Latency が必ず発生するため 15 秒を閾値とする。
threshold.latency = 15;
}
const buffer = getBufferHealth(player);
if (buffer > threshold.buffer && latency > threshold.latency) {
player.setPlaybackRate(1.25);
setTimeout(stopAcceleration, 50);
}
};
const stopAcceleration = () => {
const rate = player.getPlaybackRate();
if (rate !== 1.25) {
return;
}
const stats = player.getVideoStats() || {};
const buffer = getBufferHealth(player);
const threshold = getThresold(stats.latency_class);
if (!threshold || buffer < threshold.buffer) {
player.setPlaybackRate(1.0);
}
else {
setTimeout(stopAcceleration, 50);
}
};
video.addEventListener('playing', startAcceleration);
const timer = setInterval(startAcceleration, 60 * 1000);
const eventCleaner = () => {
video.removeEventListener('playing', startAcceleration);
clearInterval(timer);
};
document.addEventListener('yt-navigate-start', eventCleaner, { once: true });
});
})();