The languishing state of digital audio broadcasting in the United States following its introduction more than two years ago has spurred the nation’s largest broadcast conglomerates to form an “HD Digital Radio Alliance” to facilitate the bona-fide rollout of digital service. Key to this campaign is the coming of what the Alliance calls “HD2 multicast sidechannels.”

The ability to broadcast multiple program streams on a single radio channel is relatively new to the U.S. digital radio environment. As initially developed over the last 15 years (!) the dominant U.S. digital radio protocol, now known as “HD Radio,” did not accommodate a multicasting feature: National Public Radio spearheaded its creation less than three years ago.

Expect an HD radio station’s “main program” to reflect its analog equivalent and the “sidechannel” to be some variant of the main program format. For example, in May, Infinity’s WUSN-FM in Chicago became the first commercial station to digitally multicast. The station’s primary format is country and its sidechannel is “Future Country,” described as an offshoot that skews younger than the station’s traditional demographic. As encoding algorithms get more efficient the Alliance predicts stations will carve up available bandwidth to serve up additional program streams.

Notably, one of the HD Digital Radio Alliance’s main functions is “to fairly and equitably coordinate local market ‘format allocations,’ so that companies aren’t stepping on each other as they launch what amount to scores of brand new radio stations.” Nothing would seem to squelch an innovation’s inherent competitiveness more than dictating the bounds of its release, which is what the nation’s largest broadcast companies will do by deploying multicast capability first.

Digital radio broadcasting in the United States has a long history of technical and quality-of-service shortcomings, much of which remains to be written. But what is worst is the turkey’s blatantly proprietary nature. Not only must radio transmitter and receiver manufacturers give a fraction of every sale to Ibiquity, the developer of the HD Radio protocol, but stations themselves must pay both an up-front fee and recurring royalties to Ibiquity for the privilege of broadcasting.

This de facto requirement of a second, private license to broadcast in the digital future, and its attendant implications for access to the airwaves, is not yet a subject of any meaningful discussion. Alternative digital broadcast frameworks exist, but market momentum is leading regulatory momentum, meaning none are being taken seriously. The HD Digital Radio Alliance initiative is designed to make sure momentum continues in that direction.

That the major players in the HD Radio Alliance are also major investors in Ibiquity and just happen to control so many radio stations as to give them unmatched nationwide audience penetration for their technology of choice smacks of a cornered market. Think again: they are getting anxious to recoup the conservatively-estimated quarter billion dollars they’ve sunk into digital radio development over the years (and the Alliance proposes to nearly double this investment). Especially in the face of increasing audience erosion from satellite radio, webcasting, and podcasting. How best to sell the technology of choice? Perhaps the HD Radio Playbook, a new industry eyes-only enclave of information, holds clues.

There’s lots more research to be done on digital radio in the U.S., because it stinks on so many levels. After an extended absence from the subject I’m just re-warming to it. Stay tuned.