YouTube 720p

change default YouTube video quality to 720p or highest available below 720p. can be used for other video qualities by changing preferredQuality in the code below.

您需要先安装一个扩展,例如 篡改猴Greasemonkey暴力猴,之后才能安装此脚本。

您需要先安装一个扩展,例如 篡改猴暴力猴,之后才能安装此脚本。

您需要先安装一个扩展,例如 篡改猴暴力猴,之后才能安装此脚本。

您需要先安装一个扩展,例如 篡改猴Userscripts ,之后才能安装此脚本。

您需要先安装一款用户脚本管理器扩展,例如 Tampermonkey,才能安装此脚本。

您需要先安装用户脚本管理器扩展后才能安装此脚本。

(我已经安装了用户脚本管理器,让我安装!)

您需要先安装一款用户样式管理器扩展,比如 Stylus,才能安装此样式。

您需要先安装一款用户样式管理器扩展,比如 Stylus,才能安装此样式。

您需要先安装一款用户样式管理器扩展,比如 Stylus,才能安装此样式。

您需要先安装一款用户样式管理器扩展后才能安装此样式。

您需要先安装一款用户样式管理器扩展后才能安装此样式。

您需要先安装一款用户样式管理器扩展后才能安装此样式。

(我已经安装了用户样式管理器,让我安装!)

// ==UserScript==
// @name         YouTube 720p
// @namespace    http://www.youtube.com/
// @version      1.4.3
// @description  change default YouTube video quality to 720p or highest available below 720p. can be used for other video qualities by changing preferredQuality in the code below.
// @match        http://youtube.com/*
// @match        https://youtube.com/*
// @match        http://www.youtube.com/*
// @match        https://www.youtube.com/*
// @grant        none
// @run-at       document-end
// ==/UserScript==


youtubeOverride = function (unsafeWindow) {
    
    // qualities = ['auto', 'hd1080', 'hd720', 'large', 'medium', 'small', 'tiny'];
    // set the quality desired here:
    preferredQuality = 'hd720';
    // overrideMaxAttempts = 30;
    overrideTryDelay = 1000;
    
    console.log('override script starting');
    if (location.pathname.indexOf("/embed/") === 0) {
        var player = unsafeWindow.yt.player.getPlayerByElement(unsafeWindow.document.getElementById("player"));
        if (player != null) {
            overridePlayer(player);
        } else {
            console.log('cannot get player api');
        }
    } else {
        tryToOverride();
        
        var target = document.getElementById('player');
        var MutationObserver = window.MutationObserver;
        var observer = new MutationObserver(function (mutations) {
            mutations.forEach(function (mutation) {
                if (mutation.target.id === 'player-unavailable')  {
                    console.log('player mutation detected');
                    var player = unsafeWindow.document.getElementById('movie_player');
                    if (player != null) {
                        overridePlayer(player);
                    } else {
                        console.log('cannot get player api2');
                    }
                }
            });
        });
        observer.observe(target, { childList: true, subtree: true });
    }
    
    function getPlayerApi() {
        if (location.pathname.indexOf("/embed/") === 0) {
            var player = unsafeWindow.yt.player.getPlayerByElement(unsafeWindow.document.getElementById("player"));
            return player;
        } else {
        	return unsafeWindow.document.getElementById('movie_player');
        }
    }
        
    function tryToOverride(player) {
        console.log('quality override starting');

        player = player != null ? player : getPlayerApi();

        if (player == null || !('setPlaybackQuality' in player)) {
            console.log('error: setPlaybackQuality not available');
            return false;
        }

        var qualityLevels = player.getAvailableQualityLevels();
        var qualityToSet = null;
        for (var i = 0; i < qualityLevels.length; i++) {
            if (qualityLevels[i].trim().toLowerCase() === preferredQuality) {
                qualityToSet = qualityLevels[i];
                break;
            }
        }
        if (qualityToSet == null) {
            qualityToSet = qualityLevels[0];
        }
        if (qualityToSet == null) {
            console.log('error: no quality levels available');
            return false;
        }
        player.setPlaybackQuality(qualityToSet);
        console.log('set quality to ' + qualityToSet);
        return qualityToSet == player.getPlaybackQuality();
    }
    
    function overridePlayer(player) {
        if (overridePlayer.running) {
            return;
        }
        overridePlayer.running = true;
        
        overrideTimeoutFunc.attempts = 0;
        overrideTimeoutFunc();
        
        function overrideTimeoutFunc() {
            overrideTimeoutFunc.attempts++;
            var success = tryToOverride(player);
            if (!success /*&& overrideTimeoutFunc.attempts < overrideMaxAttempts*/) {
                setTimeout(overrideTimeoutFunc, overrideTryDelay)
            } else {
                overridePlayer.running = false;
            }
        }
    }
};

(function () {
    // inject script into page
    if (this.unsafeWindow != null) {
        youtubeOverride(unsafeWindow);
    } else {
        var scriptElem = document.createElement('script');
        scriptElem.setAttribute('type', 'text/javascript');
        scriptElem.text = '(' + youtubeOverride.toString() + ')(window);';
        
        document.documentElement.appendChild(scriptElem);
        document.documentElement.removeChild(scriptElem);
    }
})();