Sign Google Music API

Hi there,

im actually trying to get the google music api to work...i want to write a little mini player for windows, caus i hate their browser thing. I managed it to get the authorisation key, playlists and tracks. But my problem is to get a streamURL.

Im trying it with this URL:

Code:
https://android.clients.google.com/music/mplay?songid=1bb2a665-da01-3bcd-a642-56cea7f5e141&pt=e&dt=pc&targetkbps=128&start=0
it seems the headers must contain the headers (GoogleLogin auth) and (X-Device-ID), i send them both, but i get only 403 errors. Somebody has experience with this and can help?