Recently we've made some improvements to the Rdio web service. The documentation is now up to date.
Until recently Rdio allowed users to embed albums, tracks and playlists by copy-and-pasting and <object>/<embed> tag. We've just moved to using an <iframe> based embedding approach, partly to fix some bugs and partly to give us more flexibility in the future. Things that can be embedded (Tracks, Albums and Playlists) now have an optional iframeUrl field that can be requested through extras from any method that returns those types.
You can embed with code like:
<iframe width="width" height="height" src="iframeUrl" frameborder="0"></iframe>
UPCs and ISRCs
UPCs are Universal Product Codes, like CD bar codes. There's one for each musical release (like an album or a single). ISRCs are International Standard Recording Codes, they're like that but for musical recordings. Each recording should have the same ISRC, even if a recording is shared across multiple releases (for example a single, an album track and a best-of compilation track). Rdio now exposes UPCs on albums and ISRCs on tracks through the optional upcs and isrcs fields on Album and Track objects.
There are now getAlbumsByUPC and getTracksByISRC methods to search the Rdio catalog based on these identifiers. These are quite useful for mashups since other music services and databases expose these.
More extras and cleanup
More methods now take extras including getObjectFromUrl, getObjectFromShortCode and getActivityStream. getObjectFromUrl andgetObjectFromShortCode no longer require authentication. getHeavyRotation takes start and count so it's possible to page through results.
Track now has an optional isInCollection field that indicates if the track is in the calling user's collection. Playlists have an optional trackKeysarray field. Users have artistCount and albumCount to complement the existing trackCount, these indicate the user's collection size.