I was trying to get a track ID from a Rdio's URL (http://rd.io/x/QekWETcvG5k/), but it looks like it can't be done. Rdio have a method for this in their own API (getObjectFromUrl) and another method to get it from the Shortcode (getObjectFromShortCode), which is that code in the end of their URLs.
I need this so the user can share a track from Rdio app in Android directly for my app.
Of course I could use Rdio API, but I would like to be able to use only Echo Nest API for now.
Spotify and Deezer, for example, have their song's ID on their URLs, so it's very easy to parse it, but it's not the case of Rdio, and maybe it's not the case for others.