RealNetworks, AAC and DRM
CNet reports that RealNetworks will be launching a new download service with songs encoded in the MPEG4 Advanced Audio Coding (AAC) format.
However, the new service will pair RealNetworks' Helix Digital Rights Mangement (DRM) format with the open standard (AAC). As a result, these song files will be incompatible with Apple's iTunes and iPod (along with everything else). As the article explains, "For a song to play on a digital device, the gadget must both be able to play the underlying music format and to decode any proprietary content locks that protect against unauthorized copying."
Apple presently uses AAC + FairPlay Digital Rights Management (DRM) for their iTunes Music Store songs.