有许多非常相似的问题，但到目前为止，我找不到任何可以直接回答这个问题的问题。很多回复包括“查看这个的源代码”并包含一个链接，不幸的是我正在努力分析这些链接中的源代码，所以我希望有人可以一步一步地给我一些东西。
这是我到目前为止所做的：
我已经完成了第1,2,5步，它们都完全符合我的要求，但似乎对如何进行第3步缺乏明确性。有人可以请打破这进一步下降了吗？例如：
这对我来说非常有用，如果可能的话，我会喜欢在C＃或PHP中提取链接的步骤或非常简单的应用程序。
答案 0 :(得分：4)
以下是基于Pafy的更简洁的实现：
using System;
using System.Linq;
using HttpUtility = System.Web.HttpUtility;
using NameValueCollection = System.Collections.Specialized.NameValueCollection;
using WebClient = System.Net.WebClient;
class Program {
public static void Main(string[] args) {
string videoID = "2FlgVN03fNM";
string[] itagByPriority = {"5", "6", "34", "35"};
string videoUrl = "https://www.youtube.com/get_video_info?asv=3&el=detailpage&hl=en_US&video_id=" + videoID;
string encodedVideo = null;
using (var client = new WebClient()) {
encodedVideo = client.DownloadString(videoUrl);
}
NameValueCollection video = HttpUtility.ParseQueryString(encodedVideo);
string encodedStreamsCommaDelimited = video["url_encoded_fmt_stream_map"];
string[] encodedStreams = encodedStreamsCommaDelimited.Split(new char[]{','});
var streams = encodedStreams.Select(s => HttpUtility.ParseQueryString(s));
var streamsByPriority = streams.OrderBy(s => Array.IndexOf(itagByPriority, s["itag"]));
NameValueCollection preferredStream = streamsByPriority.LastOrDefault();
if (preferredStream != null) {
Console.WriteLine("{0}&signature={1}", preferredStream["url"], preferredStream["sig"]);
}
}
}
答案 1 :(得分：2)
如果您想跳过一个简单的代码示例，可以在GitHub上看到完整的源代码：https://github.com/XtrmJosh/YouTubeDownloader
我的假设非常正确，虽然花了我10个小时左右，但我终于实现了我的目标。这是一个粗略的细分：
以下是我用来获取HTML文档中所有视频网址的代码（仅适用于YouTube - 目前为止）
public static List<string> ExtractUrls(string html)
{
string title = GetTitle(html);
List<string> urls = new List<string>();
string DataBlockStart = "\"url_encoded_fmt_stream_map\":\\s+\"(.+?)&"; // Marks start of Javascript Data Block
html = Uri.UnescapeDataString(Regex.Match(html, DataBlockStart, RegexOptions.Singleline).Groups[1].ToString());
string firstPatren = html.Substring(0, html.IndexOf('=') + 1);
var matchs = Regex.Split(html, firstPatren);
for (int i = 0; i < matchs.Length; i++)
matchs[i] = firstPatren + matchs[i];
foreach (var match in matchs)
{
if (!match.Contains("url=")) continue;
string url = GetTxtBtwn(match, "url=", "\\u0026", 0, false);
if (url == "") url = GetTxtBtwn(match, "url=", ",url", 0, false);
if (url == "") url = GetTxtBtwn(match, "url=", "\",", 0, false);
string sig = GetTxtBtwn(match, "sig=", "\\u0026", 0, false);
if (sig == "") sig = GetTxtBtwn(match, "sig=", ",sig", 0, false);
if (sig == "") sig = GetTxtBtwn(match, "sig=", "\",", 0, false);
while ((url.EndsWith(",")) || (url.EndsWith(".")) || (url.EndsWith("\"")))
url = url.Remove(url.Length - 1, 1);
while ((sig.EndsWith(",")) || (sig.EndsWith(".")) || (sig.EndsWith("\"")))
sig = sig.Remove(sig.Length - 1, 1);
if (string.IsNullOrEmpty(url)) continue;
if (!string.IsNullOrEmpty(sig))
url += "&signature=" + sig;
urls.Add(url);
}
for (int i = 0; i < urls.Count; i++)
{
urls[i] += "&title=";
urls[i] += title;
}
return urls;
}
public static string GetTitle(string RssDoc)
{
string str14 = GetTxtBtwn(RssDoc, "'VIDEO_TITLE': '", "'", 0, false);
if (str14 == "") str14 = GetTxtBtwn(RssDoc, "\"title\" content=\"", "\"", 0, false);
if (str14 == "") str14 = GetTxtBtwn(RssDoc, "&title=", "&", 0, false);
str14 = str14.Replace(@"\", "").Replace("'", "'").Replace("\"", """).Replace("<", "<").Replace(">", ">").Replace("+", " ");
return str14;
}
public static string GetTxtBtwn(string input, string start, string end, int startIndex, bool UseLastIndexOf)
{
int index1 = UseLastIndexOf ? input.LastIndexOf(start, startIndex) :
input.IndexOf(start, startIndex);
if (index1 == -1) return "";
index1 += start.Length;
int index2 = input.IndexOf(end, index1);
if (index2 == -1) return input.Substring(index1);
return input.Substring(index1, index2 - index1);
}
此代码（使用当前的YouTube格式）提供指向FLV文件的链接，您可以下载该文件并执行您喜欢的操作（在YouTube的服务条款中）。然后，我使用它来查找此代码提供的最高质量链接：
public static string GetFLV(List<string> urls)
{
// Acquire a list of links which match the criteria for being FLV files
List<string> flvurls = new List<string>();
foreach (string url in urls)
{
string itag = Regex.Match(url, @"itag=([1-9]?[0-9]?[0-9])", RegexOptions.Singleline).Groups[1].ToString();
int itagint;
int.TryParse(itag, out itagint);
if (itagint == 5 || itagint == 6 || itagint == 34 || itagint == 35)
{
flvurls.Add(url);
}
}
// If we didn't find any FLVs, we return a fatal error and cause a bug later on
if (flvurls.Count == 0)
{
MessageBox.Show("Fatal error | iTag could not be found for FLV filetype. Please contact software vendor for assistance.");
return "";
}
// If we did find some FLVs, we need to find the highest quality FLV
else
{
#region findBestFLV
foreach (string url in flvurls)
{
string itag = Regex.Match(url, @"itag=([1-9]?[0-9]?[0-9])", RegexOptions.Singleline).Groups[1].ToString();
int itagint;
int.TryParse(itag, out itagint);
if (itagint == 35)
{
return url;
}
}
foreach (string url in flvurls)
{
string itag = Regex.Match(url, @"itag=([1-9]?[0-9]?[0-9])", RegexOptions.Singleline).Groups[1].ToString();
int itagint;
int.TryParse(itag, out itagint);
if (itagint == 34)
{
return url;
}
}
foreach (string url in flvurls)
{
string itag = Regex.Match(url, @"itag=([1-9]?[0-9]?[0-9])", RegexOptions.Singleline).Groups[1].ToString();
int itagint;
int.TryParse(itag, out itagint);
if (itagint == 6)
{
return url;
}
}
foreach (string url in flvurls)
{
string itag = Regex.Match(url, @"itag=([1-9]?[0-9]?[0-9])", RegexOptions.Singleline).Groups[1].ToString();
int itagint;
int.TryParse(itag, out itagint);
if (itagint == 5)
{
return url;
}
}
#endregion
}
MessageBox.Show("Fatal error | Something has gone horrible wrong whilst finding the best FLV to use. Run, brave warrior, for the end is near.");
return "";
}
请注意，这一刻非常糟糕，剩下的代码主要是我借用并略微编辑的片段，但是这一点我从头脑中写下了一些匆忙的尝试，为SOF得到了一些东西。< / p>
希望这有助于其他人：）