BBC Reports On Object-Based Broadcast Audio

HOLLYWOOD, CA—A presentation by Frank Melchior, lead technologist with BBC Research & Development in the U.K., during the AES 57th International Conference in Hollywood, CA, at the beginning of March offered a glimpse into the potential of object-based audio.
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HOLLYWOOD, CA—A presentation by Frank Melchior, lead technologist with BBC Research & Development in the U.K., during the AES 57th International Conference in Hollywood, CA, at the beginning of March offered a glimpse into the potential of object-based audio. As Melchior observed at the conclusion to his presentation, “Object-based broadcasting is the future of audio.”

Frank Melchior, lead technologist with BBC Research & Development, discusses the BBC’s forays into object-based broadcast audio during the AES 57th International Conference on “The Future of Audio Entertainment Technology.” The BBC, a public-service broadcaster funded by license fees levied on U.K. residents, has been experimenting with object-based audio for some time, as Melchior revealed. For example, the 5 live Football Experiment streamed audio over the web that allowed listeners to adjust the relative levels of the commentary and the sound of the soccer stadium. The audience was encouraged to complete a survey, which revealed that listeners were not particularly interested in altering the level of the atmosphere, but 30 percent chose to raise the level of the commentary while 30 percent lowered it.

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“If we do immersive audio, we can’t do separate mixes for separate outputs,” said Melchior, as such a workflow would be cost-prohibitive. Beginning in 2012 the BBC experimented with radio dramas produced with a 24-speaker layout automatically rendered to 5.0 and, for the broadcast, to stereo. Subsequently, the focus has been on binaural production: “It’s most easily accessible to the BBC radio audience.”

The BBC has developed its own binaural production system rather than using commercially available tools—“Because we want to understand what is going on,” said Melchior—that utilizes three methods: dry HTRF (head-related transfer function), virtualization and a version for stereo headphone reproduction. “From experience, there’s room for all of them; the BBC’s mixing tools offers all options,” he reported. For example, a show featuring famed naturalist David Attenborough might include his commentary in stereo but the jungle atmospheres in binaural, he said. “There’s room for combinations.”

But, he also noted, “Object-based broadcasting is not just about immersive audio; there’s so much more.” The R&D department has been thinking hard about the potential for personalization, for example. “Mainly it means clever algorithms are selecting content for you based on what you have heard before,” he said.

The BBC’s Responsive Radio project goes beyond that. “The audio content should be responsive to the listeners and their environment. It could modify speech and background balances,” he suggested. Delving deeper into the possibilities, there might be a pause function during a radio drama, for instance, that allows the background music to continue, keeping the listener in the mood of the program while they do something like make a cup of tea. Implementing such features has required the BBC to develop rendering and distribution techniques, which it did using a standard web browser. Chrome and Firefox are both well supported, he said.

“Wouldn’t it be great if you could adjust the length of the program without producing different versions?” he asked. Using object-based audio it’s possible to adjust a 30-minute program to play back in, say, 22 minutes—not by altering the speed, but the content. “You leave out the less important bits, but the essence is always there. The content creator decides what the essence is,” he explained.

“It’s a way to represent the program so that you can make a choice of how long it should be, and you always get a great story,” he added. In the future, he imagined, that functionality could be tied to a vehicle’s GPS, lengthening or shortening a program based on road conditions and expected arrival time.

These and other experiments are available on a web platform, Taster, which was launched at the start of the year, he said, where the BBC can get immediate feedback from listeners. The site is geo-restricted, but there are workarounds for audiences outside the U.K. who wish to experience it.

The ITU is recommending object- based audio for the Advanced Sound System, its term for next-gen audio. The BBC is contributing to the creation of standards, Melchior noted, such as recommendations for an extension to BWF that can handle object-based audio data. The R&D department is also working with other standards bodies and has published its recommendations as an Open Source document, enabling others to participate in ongoing developments.

To enable the format to develop, said Melchior, “We need the equivalent of PCM in the object-based world to make it successful and allow us, as broadcasters, to exchange content. We also need agreement on the production environment; for example, how to monitor. And we need tools.” The workflow needs to scale, he also pointed out, as experiments thus far been produced as one-offs.

“Object-based audio is definitely an enabler for great new experiences,” he concluded. New technology and standards are emerging, “But an open dialogue about the needs and the problems and the challenges is the most helpful thing now. There’s no point saying everything is solved; it’s not solved—but it will be.”

The effort will be worth it: “It has the potential to be transformational,” he said.

BBC Research & Development
bbc.co.uk/rd

BBC Taster
bbc.co.uk/taster