Mediaplay缓存优化

Optimize media playback by caching video segments to minimize user waiting time and maximize cache efficiency.
Wrap lines
// ==UserScript==
// @name         Mediaplay缓存优化
// @namespace    http://tampermonkey.net/
// @version      1.7
// @description  Optimize media playback by caching video segments to minimize user waiting time and maximize cache efficiency.
// @author       KiwiFruit
// @match        *://*/*
// @grant        none
// @license MIT
// ==/UserScript==

(function() {
    'use strict';

    // 检查网络信息API是否可用
    if (navigator.connection && navigator.connection.downlink) {
        const networkSpeed = navigator.connection.downlink;
        console.log(`Estimated download speed: ${networkSpeed} Mbps`);
    } else {
        console.log('Network Information API not supported or downlink property not available.');

        // 尝试动态加载Speedtest by Ookla库
        const script = document.createElement('script');
        script.src = 'https://cdn.jsdelivr.net/npm/speedtest-net'; // Speedtest by Ookla的CDN地址
        script.onload = function() {
            console.log('Speedtest by Ookla library loaded successfully.');

            // 创建Speedtest实例并开始测试
            const speedtest = new window.SpeedTest({
                upload: true, // 是否测试上传速度
                download: true, // 是否测试下载速度
                ping: true // 是否测试延迟
            });

            speedtest.on('data', data => {
                console.log('Speedtest Data:', data);
            });

            speedtest.on('error', err => {
                console.error('Speedtest Error:', err);
            });

            speedtest.start();
        };
        script.onerror = function() {
            console.error('Failed to load Speedtest by Ookla library.');
        };
        document.head.appendChild(script);
    }

    // 初始化参数
    const N = 10; // 假设每个视频有10个片段
    const d = Array.from({ length: N }, () => Math.random()); // 下载时延模拟
    const videoQuality = 720; // 假设视频分辨率为720p
    const userPreferences = { quality: true }; // 假设用户偏好高清视频
    const D = 5; // 最大允许总时延
    const C = 3; // 缓存容量限制
    let lambda_val = 0;
    let mu_val = 0;
    const alpha = 0.1;
    const beta = 0.1;
    const tolerance = 1e-6;
    const max_iterations = 1000;

    // 效用函数
    function u(x, di, videoQuality, userPreferences) {
        const qualityFactor = userPreferences.quality ? videoQuality : 1;
        return x === 1 ? (qualityFactor / Math.max(di, 0.06)) : 0; // Assuming 60ms as 0.06 seconds
    }

    // 下载时延
    function getDownloadDelay(segmentSize) {
        const networkSpeed = navigator.connection ? navigator.connection.downlink : 15; // Default to 15Mbps if not available
        const bandwidth = networkSpeed * 1024 * 1024; // Convert Mbps to bytes per second
        return segmentSize / bandwidth; // Calculate download delay
    }

    // 优化算法 (梯度下降法)
    function optimizeCache(d, D, C, alpha, beta, max_iterations, tolerance) {
        let x = new Array(N).fill(0);
        let iteration = 0;

        while (iteration < max_iterations) {
            // 梯度下降更新
            const gradLambda = d.reduce((sum, di, idx) => sum + di * x[idx], 0) - D;
            const gradMu = x.reduce((sum, xi) => sum + xi, 0) - C;

            lambda_val -= alpha * gradLambda;
            mu_val -= beta * gradMu;

            // 更新决策变量
            for (let i = 0; i < N; i++) {
                const utility = u(x[i], d[i], videoQuality, userPreferences) - lambda_val * d[i] - mu_val;
                x[i] = utility > 0 ? 1 : 0;
            }

            // 检查收敛条件
            if (Math.abs(gradLambda) < tolerance && Math.abs(gradMu) < tolerance) {
                break;
            }

            iteration++;
        }

        return x;
    }

    // 缓存策略
    function cacheSegments(mediaElement, optimalSolution) {
        const sources = mediaElement.querySelectorAll('source');
        sources.forEach((source, index) => {
            if (optimalSolution[index] === 1) {
                const segmentUrl = source.src;
                fetch(segmentUrl)
                    .then(response => response.blob())
                    .then(blob => {
                    // 将片段存储在内存或本地存储中
                    console.log(`Cached segment ${index}:`, blob);
                })
                    .catch(error => console.error(`Failed to cache segment ${index}:`, error));
            }
        });
    }

    // 获取页面上的所有媒体元素（视频和音频）
    const mediaElements = document.querySelectorAll('video, audio');

    // 对每个媒体元素进行处理
    mediaElements.forEach(mediaElement => {
        // 监听播放事件
        mediaElement.addEventListener('play', function() {
            console.log('Media element started playing:', mediaElement);

            // 启动缓存逻辑
            const optimalSolution = optimizeCache(d, D, C, alpha, beta, max_iterations, tolerance);
            cacheSegments(mediaElement, optimalSolution);
        });

        // 监听暂停事件
        mediaElement.addEventListener('pause', function() {
            console.log('Media element paused:', mediaElement);
            // 在这里可以添加一些暂停时的处理逻辑，例如停止缓存或释放资源
        });

        // 监听结束事件
        mediaElement.addEventListener('ended', function() {
            console.log('Media element ended:', mediaElement);
            // 在这里可以添加一些播放结束时的处理逻辑，例如清理缓存或重置状态
        });
    });
})();
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