如何解密 Youtube 视频 URL 密码

Question

我想知道某些网站如何获得可以下载的 youtube 视频链接，例如 https://en.savefrom.net/387/ 或其他网站 实际上我想获得一个可下载的 mp3 的 youtube 视频链接，我所能得到的只是没有被下面的代码包裹的 url

function getYouTubeVideo(Request $request)
    {
        $videoId = $request->query('videoId');

        $client = new Client(['http_errors' => false]);
        $response = $client->request('GET', 'https://www.youtube.com/watch?v='. $videoId, [
            'headers' => [
                'Referer' => 'https://www.youtube.com/'
            ]
        ]);
        // $body =  $response->getBody()->getContents();



        // Find the script tag that contains ytInitialPlayerResponse variable
        $pattern = '/<script nonce=".*?">.*?var ytInitialPlayerResponse = ({.*?});<\/script>/s';
        preg_match($pattern,  $response->getBody()->getContents(), $matches);

        // Extract the value of ytInitialPlayerResponse
        $ytInitialPlayerResponse = json_decode($matches[1]);
        // dd($ytInitialPlayerResponse);
        // Now you can access the properties of ytInitialPlayerResponse
      
        if (isset($ytInitialPlayerResponse->streamingData->adaptiveFormats)) {
            $key = $ytInitialPlayerResponse->streamingData->adaptiveFormats;

            // Filter the array based on the conditions
            $result = array_filter($key, function ($item) {
                if (isset($item->audioQuality)) {
                    if ($item->audioQuality == "AUDIO_QUALITY_MEDIUM" && $item->mimeType == "audio/webm; codecs=\"opus\"") {
                        return true;
                    }
                }
            });

            // Output the filtered result
            $urlmp3 = [];
            $signatureCipher = [];

            if (isset(reset($result)->signatureCipher)) {
                $song = reset($result)->signatureCipher;
            }

            if (isset(reset($result)->url)) {
                $song = reset($result)->url;
            }

            $duration = reset($result)->approxDurationMs;
            $artist_name =   $ytInitialPlayerResponse->videoDetails->author;
            $cover =   $ytInitialPlayerResponse->videoDetails->thumbnail->thumbnails[0]->url;
            $song_title =   $ytInitialPlayerResponse->videoDetails->title;

            // Return the response as JSON
            return response()->json([
               
                'song' => $song,
                'duration' => $duration,
                'artist_name' => $artist_name,
                'cover' => $cover,
                'song_title' => $song_title,
            ]);
        } else {
            return response()->json([
                'message' => 'Not a video',
            ]);
        }
    }

但是那些用密码加密的链接就像

s=cMM%3D%3DwYxRgPQP2sS79i%3DBHLQRVW0p8GFbTdLE-H0ivHw9m5VBiAx67RKqfY%3Dwv1fLXd6pZCwK2uQQlfZ9wBUT3AAv9lQoKAhIQRw8JQ0qOA&sp=sig&url=https ://rr5---sn-......

问题很简单，解密这个url的过程是怎样的， 我希望我能解释一下这个问题