Question: I used <http://www.youtube.com/get_video?video_id=ID&t=SIGNATURE&fmt=18> replaced

ID and SIGNATURE with the proper values. But I don't get see any save or download window, 

instead A blank window.

I am in Macintosh platform with Safari browser. Help Appreciated.

Answer: 
The internet is full of not working examples so here's a script for anyone who needs. Something is wrong with the flv files. Their links deliver .txt files but it's good with webm and mp4. I need that for the pr0n sites too hehehe

```
<?php

//$debug = true;

if(empty($debug))
    $debug = false;

if(empty($_GET['id']))
    die('no id');
if(!preg_match('/^[A-Z0-9-_]+$/i', $_GET['id']))
    die('invalid character in id');
else
    $id = $_GET['id'];

if(empty($_GET['type']))
    $type = 'mp4';
else
if(!preg_match('/^[A-Z]+$/i', $_GET['type']))
    die('invalid character in type');
else
    $type = strtolower($_GET['type']);

$url = 'http://youtube.com/get_video_info?video_id=';
$key = 'url_encoded_fmt_stream_map';
$content = file_get_contents($url.$id);
parse_str($content, $result);

if($debug)
    {
    echo $url.$id.'<br/>';
    echo $key.'<br/>';
    echo $type.'<br/>';
    echo '<pre>';
    print_r($result);
    echo '</pre>';
    }
else
    {
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="videofile.'.$type.'"');
    }

$type = 'type=video/'.$type;
$files = explode(',url=', $result[$key]);
$files[0] = substr($files[0], 4);

for($i=0; $i<count($files); $i++)
    {
    $file = urldecode($files[$i]);
    $found = strpos($file, $type) > -1;

    if ($debug)
        {
        if ($found) 
            echo '[THIS]';
        echo '<a href="'.$file.'">'.$file.'</a><br/><br/>';
        }
    else
        {
        if ($found) 
            {
            $file = explode('; codecs=', $file);
            @readfile($file[0]);
            break;
            }
        }   
    }
?>  

```
youtube changed the request used to get the flv file.
Now it looks like

<http://v2.lscache3.c.youtube.com/videoplayback?ip=0.0.0.0&sparams=id%2Cexpire%2Cip%2Cipbits%2Citag%2Calgorithm%2Cburst%2Cfactor%2Coc%3AU0dYSVZMTl9FSkNNOF9ORlJF&fexp=903816&fexp=903813%2C908400&algorithm=throttle-factor&itag=34&ipbits=0&burst=40&sver=3&expire=1294610400&key=yt1&signature=9C4D194A7F85F0171771486714D3F061ED2924F6.98D10BB190123CADCA3CDF993174D47F8932895F&factor=1.25&id=10af5a6280e42a28>

you can grab easily all the parameters except oc parameter i.e %2Coc%3AU0dYSVZMTl9FSkNNOF9ORlJF
from the response, still searching a way to get it.

youtube locks the link to the browser, so you cannot use it on the server.
if you look in the source code of the youtube page you will find something like the above address but without the oc parameter, if you copy it from firebug net panel or chrome resources it will download the flv movie as "videoplayback".