Surround 2004: 5.1 FM Radio Broadcasts with HD Radio and Coded Discrete Technology

Surround 2004: One of the more interesting sessions at Surround 2004 was a presentation by Frank Foti of Omnia Audio of a new “coded discrete” system which provides a way to broadcast 5.1 Surround Sound over FM Radio stations.

In his presentation at the conference, Foti explained that iBiquity’s new HD Radio System provides a way for AM and FM Radio Stations to compete with the satellite broadcasters such as Sirius and XM Radio. HD Radio was shown at the Consumer Electronics Show (CES) this January to good reviews. It uses a codec with 20-32kbps bandwith to deliver AM Stereo and a similar technology with 96kbs to deliver FM Stereo.

Omnia Audio is a maker of audio processing products for AM and FM radio stations. They have been working with the Fraunhofer Institute in Germany (one of the developers of MP3 and MPEG AAC perceptual audio codecs) and Agere Systems on a new “coded discrete” system. The system takes 5.1 music and converts it into a form that can be broadcast within the 96kbps bandwidth of HD Radio’s FM system. It does this by generating a stereo compatible downmix of the 5.1 audio as well as a “surround side channel” that contains the information necessary to convert the stereo downmix back to a 5.1 Surround Sound broadcast.

Comparing the Source and Coded Discrete
Foti argues that his 5.1 coded discrete system is much more effective than using a 2 channel matrix system for surround sound playback with HD Radio. To illustrate his point, Foti played a selection by R.E.M. and “Layla” from the Eric Clapton Unplugged album. Each song was A/B’d between a WAV file of the original 5.1 material and a 96kbps coded discrete version using a small 5.1 audio setup in the conference room.

In both cases, listeners could tell the two apart. The original offered better definition, detail and separation than the 96kbps coded discrete version. However, the coded discrete version of each song did preserve the 5.1 surround sound soundfield on playback. The demonstration illustrated how such a system could help stimulate interest in today’s 5.1 high resolution SACD and DVD-A Surround Sound audio systems, even though the emphasis here is clearly on the Surround Sound feature of these systems rather than their full fidelity.

Next Steps
The folks at iBiquity have stayed out of the discussion of whether a 2 channel matrix approach or Omni’s coded discrete approach is the best way to go to bring Surround Sound to their HD Radio for FM Broadcasters system. In light of that, Omni is taking their technology on the road with demonstrations at events including the recent NAB and Radio Broadcasters conferences.

Next up is a planned simulated closed ciruit HD Radio broadcast of the system which could occur as soon as next month at a Radio Broadcasters conference to be held in San Diego in October. For that event, DVD Audio source material would be featured in the demonstration.

The Omnia System is an interesting development to watch. It could be part of the puzzle in bringing 5.1 Surround Sound to the attention of more members of the public in the months ahead. We’ll watch the Omni demonstrations and progress with interest.