Failed to get final url

[a3d]

Hye, I want to know is there any way to get the "final url" before the video is download by server.
by using this command, the url is not finalize yet, I cant access directly to the video url. I think you understand what I means after youtube changed.

youtube-dl --get-url http://youtube.com/watch?v=Id

What I mean is after Downloading video webpage, Downloading video info webpage, Extracting video information..
is it possible to get the "final url" after extracting video information? Because I know with that final url, the server can download the video from youtube. using --get-url cant get that final url.

why I need this "final url" ?

Currently Im developing php script to download the mp3 from youtube instantly. yes instantly.
Of course it works fine on my pc because the access token is always created.
But on this program, Im stuck. I hope that you can show me how to get the final url.
Thanks.

[phihag]

The URL you get with --get-url is only valid for requests from the same IP(v4), and with the correct cookies (Use the --cookies option to store those). This is the final URL.

But for your application - as far as I understand, you want to convert on the fly without having to download the whole file - you can just use the -o option to either output to a pipe or stdout (with -o -), can't you?

If that doesn't work, you can also try to download with the cookies saved by --cookies.