如何在Java上从youtube下载视频？ 需要类（或代码片段）来描述如何做到这一点。 谢谢。
答案 0 :(得分：26)
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.logging.Formatter;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.Logger;
import java.util.regex.Pattern;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.CookieStore;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.ClientContext;
import org.apache.http.client.utils.URIUtils;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.BasicCookieStore;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.BasicHttpContext;
import org.apache.http.protocol.HttpContext;
public class JavaYoutubeDownloader {
public static String newline = System.getProperty("line.separator");
private static final Logger log = Logger.getLogger(JavaYoutubeDownloader.class.getCanonicalName());
private static final Level defaultLogLevelSelf = Level.FINER;
private static final Level defaultLogLevel = Level.WARNING;
private static final Logger rootlog = Logger.getLogger("");
private static final String scheme = "http";
private static final String host = "www.youtube.com";
private static final Pattern commaPattern = Pattern.compile(",");
private static final Pattern pipePattern = Pattern.compile("\\|");
private static final char[] ILLEGAL_FILENAME_CHARACTERS = { '/', '\n', '\r', '\t', '\0', '\f', '`', '?', '*', '\\', '<', '>', '|', '\"', ':' };
private static void usage(String error) {
if (error != null) {
System.err.println("Error: " + error);
}
System.err.println("usage: JavaYoutubeDownload VIDEO_ID DESTINATION_DIRECTORY");
System.exit(-1);
}
public static void main(String[] args) {
if (args == null || args.length == 0) {
usage("Missing video id. Extract from http://www.youtube.com/watch?v=VIDEO_ID");
}
try {
setupLogging();
log.fine("Starting");
String videoId = null;
String outdir = ".";
// TODO Ghetto command line parsing
if (args.length == 1) {
videoId = args[0];
} else if (args.length == 2) {
videoId = args[0];
outdir = args[1];
}
int format = 18; // http://en.wikipedia.org/wiki/YouTube#Quality_and_codecs
String encoding = "UTF-8";
String userAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13";
File outputDir = new File(outdir);
String extension = getExtension(format);
play(videoId, format, encoding, userAgent, outputDir, extension);
} catch (Throwable t) {
t.printStackTrace();
}
log.fine("Finished");
}
private static String getExtension(int format) {
// TODO
return "mp4";
}
private static void play(String videoId, int format, String encoding, String userAgent, File outputdir, String extension) throws Throwable {
log.fine("Retrieving " + videoId);
List<NameValuePair> qparams = new ArrayList<NameValuePair>();
qparams.add(new BasicNameValuePair("video_id", videoId));
qparams.add(new BasicNameValuePair("fmt", "" + format));
URI uri = getUri("get_video_info", qparams);
CookieStore cookieStore = new BasicCookieStore();
HttpContext localContext = new BasicHttpContext();
localContext.setAttribute(ClientContext.COOKIE_STORE, cookieStore);
HttpClient httpclient = new DefaultHttpClient();
HttpGet httpget = new HttpGet(uri);
httpget.setHeader("User-Agent", userAgent);
log.finer("Executing " + uri);
HttpResponse response = httpclient.execute(httpget, localContext);
HttpEntity entity = response.getEntity();
if (entity != null && response.getStatusLine().getStatusCode() == 200) {
InputStream instream = entity.getContent();
String videoInfo = getStringFromInputStream(encoding, instream);
if (videoInfo != null && videoInfo.length() > 0) {
List<NameValuePair> infoMap = new ArrayList<NameValuePair>();
URLEncodedUtils.parse(infoMap, new Scanner(videoInfo), encoding);
String token = null;
String downloadUrl = null;
String filename = videoId;
for (NameValuePair pair : infoMap) {
String key = pair.getName();
String val = pair.getValue();
log.finest(key + "=" + val);
if (key.equals("token")) {
token = val;
} else if (key.equals("title")) {
filename = val;
} else if (key.equals("fmt_url_map")) {
String[] formats = commaPattern.split(val);
for (String fmt : formats) {
String[] fmtPieces = pipePattern.split(fmt);
if (fmtPieces.length == 2) {
// in the end, download somethin!
downloadUrl = fmtPieces[1];
int pieceFormat = Integer.parseInt(fmtPieces[0]);
if (pieceFormat == format) {
// found what we want
downloadUrl = fmtPieces[1];
break;
}
}
}
}
}
filename = cleanFilename(filename);
if (filename.length() == 0) {
filename = videoId;
} else {
filename += "_" + videoId;
}
filename += "." + extension;
File outputfile = new File(outputdir, filename);
if (downloadUrl != null) {
downloadWithHttpClient(userAgent, downloadUrl, outputfile);
}
}
}
}
private static void downloadWithHttpClient(String userAgent, String downloadUrl, File outputfile) throws Throwable {
HttpGet httpget2 = new HttpGet(downloadUrl);
httpget2.setHeader("User-Agent", userAgent);
log.finer("Executing " + httpget2.getURI());
HttpClient httpclient2 = new DefaultHttpClient();
HttpResponse response2 = httpclient2.execute(httpget2);
HttpEntity entity2 = response2.getEntity();
if (entity2 != null && response2.getStatusLine().getStatusCode() == 200) {
long length = entity2.getContentLength();
InputStream instream2 = entity2.getContent();
log.finer("Writing " + length + " bytes to " + outputfile);
if (outputfile.exists()) {
outputfile.delete();
}
FileOutputStream outstream = new FileOutputStream(outputfile);
try {
byte[] buffer = new byte[2048];
int count = -1;
while ((count = instream2.read(buffer)) != -1) {
outstream.write(buffer, 0, count);
}
outstream.flush();
} finally {
outstream.close();
}
}
}
private static String cleanFilename(String filename) {
for (char c : ILLEGAL_FILENAME_CHARACTERS) {
filename = filename.replace(c, '_');
}
return filename;
}
private static URI getUri(String path, List<NameValuePair> qparams) throws URISyntaxException {
URI uri = URIUtils.createURI(scheme, host, -1, "/" + path, URLEncodedUtils.format(qparams, "UTF-8"), null);
return uri;
}
private static void setupLogging() {
changeFormatter(new Formatter() {
@Override
public String format(LogRecord arg0) {
return arg0.getMessage() + newline;
}
});
explicitlySetAllLogging(Level.FINER);
}
private static void changeFormatter(Formatter formatter) {
Handler[] handlers = rootlog.getHandlers();
for (Handler handler : handlers) {
handler.setFormatter(formatter);
}
}
private static void explicitlySetAllLogging(Level level) {
rootlog.setLevel(Level.ALL);
for (Handler handler : rootlog.getHandlers()) {
handler.setLevel(defaultLogLevelSelf);
}
log.setLevel(level);
rootlog.setLevel(defaultLogLevel);
}
private static String getStringFromInputStream(String encoding, InputStream instream) throws UnsupportedEncodingException, IOException {
Writer writer = new StringWriter();
char[] buffer = new char[1024];
try {
Reader reader = new BufferedReader(new InputStreamReader(instream, encoding));
int n;
while ((n = reader.read(buffer)) != -1) {
writer.write(buffer, 0, n);
}
} finally {
instream.close();
}
String result = writer.toString();
return result;
}
}
/**
* <pre>
* Exploded results from get_video_info:
*
* fexp=90...
* allow_embed=1
* fmt_stream_map=35|http://v9.lscache8...
* fmt_url_map=35|http://v9.lscache8...
* allow_ratings=1
* keywords=Stefan Molyneux,Luke Bessey,anarchy,stateless society,giant stone cow,the story of our unenslavement,market anarchy,voluntaryism,anarcho capitalism
* track_embed=0
* fmt_list=35/854x480/9/0/115,34/640x360/9/0/115,18/640x360/9/0/115,5/320x240/7/0/0
* author=lukebessey
* muted=0
* length_seconds=390
* plid=AA...
* ftoken=null
* status=ok
* watermark=http://s.ytimg.com/yt/swf/logo-vfl_bP6ud.swf,http://s.ytimg.com/yt/swf/hdlogo-vfloR6wva.swf
* timestamp=12...
* has_cc=False
* fmt_map=35/854x480/9/0/115,34/640x360/9/0/115,18/640x360/9/0/115,5/320x240/7/0/0
* leanback_module=http://s.ytimg.com/yt/swfbin/leanback_module-vflJYyeZN.swf
* hl=en_US
* endscreen_module=http://s.ytimg.com/yt/swfbin/endscreen-vflk19iTq.swf
* vq=auto
* avg_rating=5.0
* video_id=S6IZP3yRJ9I
* token=vPpcFNh...
* thumbnail_url=http://i4.ytimg.com/vi/S6IZP3yRJ9I/default.jpg
* title=The Story of Our Unenslavement - Animated
* </pre>
*/
答案 1 :(得分：13)
我知道我迟到了。但是这段代码可能对某些人有用。所以我在这里附上它。
使用以下java代码从YouTube下载视频。
server <- function(input, output, session) {
updateSelectInput(session, "data1", "Select Region", choices = c(book3$Region))
}
在 POM.XML 文件
中添加以下依赖项package com.mycompany.ytd;
import java.io.File;
import java.net.URL;
import com.github.axet.vget.VGet;
/**
*
* @author Manindar
*/
public class YTD {
public static void main(String[] args) {
try {
String url = "https://www.youtube.com/watch?v=s10ARdfQUOY";
String path = "D:\\Manindar\\YTD\\";
VGet v = new VGet(new URL(url), new File(path));
v.download();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
希望这会有用。
答案 2 :(得分：4)
您可以查看公开的API here
答案 3 :(得分：4)
答案 4 :(得分：3)
ytd2是一款功能齐全的YouTube视频下载器。 Check out its source code如果你想看看它是如何完成的。
答案 5 :(得分：1)
参考：Youtube Video Download (Android/Java)
编辑3
您可以使用Lib：https://github.com/HaarigerHarald/android-youtubeExtractor
Ex：
String youtubeLink = "http://youtube.com/watch?v=xxxx";
new YouTubeExtractor(this) {
@Override
public void onExtractionComplete(SparseArray<YtFile> ytFiles, VideoMeta vMeta) {
if (ytFiles != null) {
int itag = 22;
String downloadUrl = ytFiles.get(itag).getUrl();
}
}
}.extract(youtubeLink, true, true);
他们使用：
解密签名。private boolean decipherSignature(final SparseArray<String> encSignatures) throws IOException {
// Assume the functions don't change that much
if (decipherFunctionName == null || decipherFunctions == null) {
String decipherFunctUrl = "https://s.ytimg.com/yts/jsbin/" + decipherJsFileName;
BufferedReader reader = null;
String javascriptFile;
URL url = new URL(decipherFunctUrl);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestProperty("User-Agent", USER_AGENT);
try {
reader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
StringBuilder sb = new StringBuilder("");
String line;
while ((line = reader.readLine()) != null) {
sb.append(line);
sb.append(" ");
}
javascriptFile = sb.toString();
} finally {
if (reader != null)
reader.close();
urlConnection.disconnect();
}
if (LOGGING)
Log.d(LOG_TAG, "Decipher FunctURL: " + decipherFunctUrl);
Matcher mat = patSignatureDecFunction.matcher(javascriptFile);
if (mat.find()) {
decipherFunctionName = mat.group(1);
if (LOGGING)
Log.d(LOG_TAG, "Decipher Functname: " + decipherFunctionName);
Pattern patMainVariable = Pattern.compile("(var |\\s|,|;)" + decipherFunctionName.replace("$", "\\$") +
"(=function\\((.{1,3})\\)\\{)");
String mainDecipherFunct;
mat = patMainVariable.matcher(javascriptFile);
if (mat.find()) {
mainDecipherFunct = "var " + decipherFunctionName + mat.group(2);
} else {
Pattern patMainFunction = Pattern.compile("function " + decipherFunctionName.replace("$", "\\$") +
"(\\((.{1,3})\\)\\{)");
mat = patMainFunction.matcher(javascriptFile);
if (!mat.find())
return false;
mainDecipherFunct = "function " + decipherFunctionName + mat.group(2);
}
int startIndex = mat.end();
for (int braces = 1, i = startIndex; i < javascriptFile.length(); i++) {
if (braces == 0 && startIndex + 5 < i) {
mainDecipherFunct += javascriptFile.substring(startIndex, i) + ";";
break;
}
if (javascriptFile.charAt(i) == '{')
braces++;
else if (javascriptFile.charAt(i) == '}')
braces--;
}
decipherFunctions = mainDecipherFunct;
// Search the main function for extra functions and variables
// needed for deciphering
// Search for variables
mat = patVariableFunction.matcher(mainDecipherFunct);
while (mat.find()) {
String variableDef = "var " + mat.group(2) + "={";
if (decipherFunctions.contains(variableDef)) {
continue;
}
startIndex = javascriptFile.indexOf(variableDef) + variableDef.length();
for (int braces = 1, i = startIndex; i < javascriptFile.length(); i++) {
if (braces == 0) {
decipherFunctions += variableDef + javascriptFile.substring(startIndex, i) + ";";
break;
}
if (javascriptFile.charAt(i) == '{')
braces++;
else if (javascriptFile.charAt(i) == '}')
braces--;
}
}
// Search for functions
mat = patFunction.matcher(mainDecipherFunct);
while (mat.find()) {
String functionDef = "function " + mat.group(2) + "(";
if (decipherFunctions.contains(functionDef)) {
continue;
}
startIndex = javascriptFile.indexOf(functionDef) + functionDef.length();
for (int braces = 0, i = startIndex; i < javascriptFile.length(); i++) {
if (braces == 0 && startIndex + 5 < i) {
decipherFunctions += functionDef + javascriptFile.substring(startIndex, i) + ";";
break;
}
if (javascriptFile.charAt(i) == '{')
braces++;
else if (javascriptFile.charAt(i) == '}')
braces--;
}
}
if (LOGGING)
Log.d(LOG_TAG, "Decipher Function: " + decipherFunctions);
decipherViaWebView(encSignatures);
if (CACHING) {
writeDeciperFunctToChache();
}
} else {
return false;
}
} else {
decipherViaWebView(encSignatures);
}
return true;
}
现在使用该库高质量视频，音频丢失了，所以我将Murging Audio的{{3}}和最终输出的视频使用
编辑1
上一个答案为何无效
Pattern p2 = Pattern.compile("sig=(.*?)[&]");
Matcher m2 = p2.matcher(url);
String sig = null;
if (m2.find()) {
sig = m2.group(1);
}
截至2016年11月，边缘有些粗糙，但是 显示基本原理。今天的url_encoded_fmt_stream_map 冒号后没有空格（最好将此选项设为可选），并且 “
sig”已更改为“signature”在调试代码时，我发现了new关键字
signature&s在许多视频的网址中
此处编辑了答案
private static final HashMap<String, Meta> typeMap = new HashMap<String, Meta>();
initTypeMap（）;先致电
class Meta {
public String num;
public String type;
public String ext;
Meta(String num, String ext, String type) {
this.num = num;
this.ext = ext;
this.type = type;
}
}
class Video {
public String ext = "";
public String type = "";
public String url = "";
Video(String ext, String type, String url) {
this.ext = ext;
this.type = type;
this.url = url;
}
}
public ArrayList<Video> getStreamingUrisFromYouTubePage(String ytUrl)
throws IOException {
if (ytUrl == null) {
return null;
}
// Remove any query params in query string after the watch?v=<vid> in
// e.g.
// http://www.youtube.com/watch?v=0RUPACpf8Vs&feature=youtube_gdata_player
int andIdx = ytUrl.indexOf('&');
if (andIdx >= 0) {
ytUrl = ytUrl.substring(0, andIdx);
}
// Get the HTML response
/* String userAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:8.0.1)";*/
/* HttpClient client = new DefaultHttpClient();
client.getParams().setParameter(CoreProtocolPNames.USER_AGENT,
userAgent);
HttpGet request = new HttpGet(ytUrl);
HttpResponse response = client.execute(request);*/
String html = "";
HttpsURLConnection c = (HttpsURLConnection) new URL(ytUrl).openConnection();
c.setRequestMethod("GET");
c.setDoOutput(true);
c.connect();
InputStream in = c.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
StringBuilder str = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
str.append(line.replace("\\u0026", "&"));
}
in.close();
html = str.toString();
// Parse the HTML response and extract the streaming URIs
if (html.contains("verify-age-thumb")) {
Log.e("Downloader", "YouTube is asking for age verification. We can't handle that sorry.");
return null;
}
if (html.contains("das_captcha")) {
Log.e("Downloader", "Captcha found, please try with different IP address.");
return null;
}
Pattern p = Pattern.compile("stream_map\":\"(.*?)?\"");
// Pattern p = Pattern.compile("/stream_map=(.[^&]*?)\"/");
Matcher m = p.matcher(html);
List<String> matches = new ArrayList<String>();
while (m.find()) {
matches.add(m.group());
}
if (matches.size() != 1) {
Log.e("Downloader", "Found zero or too many stream maps.");
return null;
}
String urls[] = matches.get(0).split(",");
HashMap<String, String> foundArray = new HashMap<String, String>();
for (String ppUrl : urls) {
String url = URLDecoder.decode(ppUrl, "UTF-8");
Log.e("URL","URL : "+url);
Pattern p1 = Pattern.compile("itag=([0-9]+?)[&]");
Matcher m1 = p1.matcher(url);
String itag = null;
if (m1.find()) {
itag = m1.group(1);
}
Pattern p2 = Pattern.compile("signature=(.*?)[&]");
Matcher m2 = p2.matcher(url);
String sig = null;
if (m2.find()) {
sig = m2.group(1);
} else {
Pattern p23 = Pattern.compile("signature&s=(.*?)[&]");
Matcher m23 = p23.matcher(url);
if (m23.find()) {
sig = m23.group(1);
}
}
Pattern p3 = Pattern.compile("url=(.*?)[&]");
Matcher m3 = p3.matcher(ppUrl);
String um = null;
if (m3.find()) {
um = m3.group(1);
}
if (itag != null && sig != null && um != null) {
Log.e("foundArray","Adding Value");
foundArray.put(itag, URLDecoder.decode(um, "UTF-8") + "&"
+ "signature=" + sig);
}
}
Log.e("foundArray","Size : "+foundArray.size());
if (foundArray.size() == 0) {
Log.e("Downloader", "Couldn't find any URLs and corresponding signatures");
return null;
}
ArrayList<Video> videos = new ArrayList<Video>();
for (String format : typeMap.keySet()) {
Meta meta = typeMap.get(format);
if (foundArray.containsKey(format)) {
Video newVideo = new Video(meta.ext, meta.type,
foundArray.get(format));
videos.add(newVideo);
Log.d("Downloader", "YouTube Video streaming details: ext:" + newVideo.ext
+ ", type:" + newVideo.type + ", url:" + newVideo.url);
}
}
return videos;
}
private class YouTubePageStreamUriGetter extends AsyncTask<String, String, ArrayList<Video>> {
ProgressDialog progressDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
progressDialog = ProgressDialog.show(webViewActivity.this, "",
"Connecting to YouTube...", true);
}
@Override
protected ArrayList<Video> doInBackground(String... params) {
ArrayList<Video> fVideos = new ArrayList<>();
String url = params[0];
try {
ArrayList<Video> videos = getStreamingUrisFromYouTubePage(url);
/* Log.e("Downloader","Size of Video : "+videos.size());*/
if (videos != null && !videos.isEmpty()) {
for (Video video : videos)
{
Log.e("Downloader", "ext : " + video.ext);
if (video.ext.toLowerCase().contains("mp4") || video.ext.toLowerCase().contains("3gp") || video.ext.toLowerCase().contains("flv") || video.ext.toLowerCase().contains("webm")) {
ext = video.ext.toLowerCase();
fVideos.add(new Video(video.ext,video.type,video.url));
}
}
return fVideos;
}
} catch (Exception e) {
e.printStackTrace();
Log.e("Downloader", "Couldn't get YouTube streaming URL", e);
}
Log.e("Downloader", "Couldn't get stream URI for " + url);
return null;
}
@Override
protected void onPostExecute(ArrayList<Video> streamingUrl) {
super.onPostExecute(streamingUrl);
progressDialog.dismiss();
if (streamingUrl != null) {
if (!streamingUrl.isEmpty()) {
//Log.e("Steaming Url", "Value : " + streamingUrl);
for (int i = 0; i < streamingUrl.size(); i++) {
Video fX = streamingUrl.get(i);
Log.e("Founded Video", "URL : " + fX.url);
Log.e("Founded Video", "TYPE : " + fX.type);
Log.e("Founded Video", "EXT : " + fX.ext);
}
//new ProgressBack().execute(new String[]{streamingUrl, filename + "." + ext});
}
}
}
}
public void initTypeMap()
{
typeMap.put("13", new Meta("13", "3GP", "Low Quality - 176x144"));
typeMap.put("17", new Meta("17", "3GP", "Medium Quality - 176x144"));
typeMap.put("36", new Meta("36", "3GP", "High Quality - 320x240"));
typeMap.put("5", new Meta("5", "FLV", "Low Quality - 400x226"));
typeMap.put("6", new Meta("6", "FLV", "Medium Quality - 640x360"));
typeMap.put("34", new Meta("34", "FLV", "Medium Quality - 640x360"));
typeMap.put("35", new Meta("35", "FLV", "High Quality - 854x480"));
typeMap.put("43", new Meta("43", "WEBM", "Low Quality - 640x360"));
typeMap.put("44", new Meta("44", "WEBM", "Medium Quality - 854x480"));
typeMap.put("45", new Meta("45", "WEBM", "High Quality - 1280x720"));
typeMap.put("18", new Meta("18", "MP4", "Medium Quality - 480x360"));
typeMap.put("22", new Meta("22", "MP4", "High Quality - 1280x720"));
typeMap.put("37", new Meta("37", "MP4", "High Quality - 1920x1080"));
typeMap.put("33", new Meta("38", "MP4", "High Quality - 4096x230"));
}
编辑2：
有时此代码无法正常工作
同源政策
https://stackoverflow.com/a/15240012/9909365
https://en.wikipedia.org/wiki/Same-origin_policy
problem of Same-origin policy. Essentially, you cannot download this file from www.youtube.com because they are different domains. A workaround of this problem is [CORS][1].
Ref：https://en.wikipedia.org/wiki/Cross-origin_resource_sharing
url_encoded_fmt_stream_map // traditional: contains video and audio stream
adaptive_fmts // DASH: contains video or audio stream
每个都是逗号分隔的数组，我称之为“流对象”。每个“流对象”将包含这样的值
url // direct HTTP link to a video
itag // code specifying the quality
s // signature, security measure to counter downloading
每个URL都会被编码，因此您需要对其进行解码。现在是棘手的部分。
YouTube的视频至少具有3个安全级别
unsecured // as expected, you can download these with just the unencoded URL
s // see below
RTMPE // uses "rtmpe://" protocol, no known method for these
RTMPE视频通常用于官方全长电影，并受SWF验证类型2的保护。这自2011年以来一直存在，并且尚未进行反向工程。
实际上很难下载类型为“ s”的视频。您通常会在VEVO视频等中看到这些内容。它们以诸如
的签名开头AA5D05FA7771AD4868BA4C977C3DEAAC620DE020E.0F421820F42978A1F8EAFCDAC4EF507DB5 然后使用这样的函数对签名进行加扰
function mo(a) {
a = a.split("");
a = lo.rw(a, 1);
a = lo.rw(a, 32);
a = lo.IC(a, 1);
a = lo.wS(a, 77);
a = lo.IC(a, 3);
a = lo.wS(a, 77);
a = lo.IC(a, 3);
a = lo.wS(a, 44);
return a.join("")
}
此功能是动态的，通常每天都会更改。为了使该功能更加困难，该功能托管在URL中，例如
这引入了同源策略的问题。本质上，您不能从www.youtube.com下载此文件，因为它们是不同的域。解决此问题的方法是CORS。使用CORS，s.ytimg.com可以添加此标头
Access-Control-Allow-Origin: http://www.youtube.com
，它将允许JavaScript从www.youtube.com下载。当然他们不这样做。此解决方法的一种解决方法是使用CORS代理。这是一个代理，它使用以下标头响应所有请求
Access-Control-Allow-Origin: *
因此，既然您已经代理了JS文件，并使用该函数对签名进行加扰，则可以在查询字符串中使用它来下载视频。
答案 6 :(得分：-3)
有youtube数据api https://developers.google.com/youtube/v3/code_samples/java
您可以通过java，php和更多技术下载YouTube视频。