Dolby AC-4 and MPEG-H Vie for ATSC 3.0 Adoption

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Dolby AC-4 and MPEG-H Vie for ATSC 3.0 Adoption


In the ATSC 3.0 audio format battle, Dolby AC-4 seems to hold a clear lead over MPEG-H, especially when it comes to support in the United States. However, with many countries yet to commit to either of the two codecs, it's still too soon to count out MPEG-H.

Both formats were touted at the recent Audio Engineering Society (AES) New York convention that was held at the Javits Center, where exhibitors included both Dolby and German company Fraunhofer, which developed MPEG-H with Qualcomm and Technicolor. The convention provided one of the best opportunities yet to get a clear picture of what benefits both audio compression and delivery formats stand to provide to consumers--whether they're watching movies, TV shows, or other video content, and whether that viewing is being done on a large-screen UHD TV, a tablet, or even a tiny smartphone.

The Benefits of ATSC 3.0 Audio
By now, at least some of you have probably heard that ATSC 3.0 offers a wide range of features, including enhanced audio. Beyond just the promise of improved sound quality, the various benefits of ATSC 3.0 audio have largely taken a back seat to other aspects of the ATSC 3.0 story, including its support for UHD, High Dynamic Range, Wide Color Gamut, and higher frame rates. (Editor's note: Just two weeks ago, the FCC officially authorized the ATSC 3.0 standard for use by broadcasters.)

MPEH-H-trademark.jpgFor starters, ATSC 3.0 allows for the inclusion of more immersive 3D audio formats--up to 7.1.4 audio (with the .4 referring to home theater support for four height speakers: top front left, top front right, top rear left, and top rear right). Of course, most consumers don't have height speakers to take advantage of that capability. Most consumers likely don't even have a 5.1-channel surround system in their home, and many folks are perfectly satisfied with either the mediocre sound that comes out of their TVs or a cheap soundbar.

"That's why we're working with soundbar manufacturers," said Fraunhofer Audio's Technology Specialist Jan Plogsties. At CES in January, "we will most likely announce [a] collaboration" with one of the soundbar manufacturers "where we basically say, 'You can do a lot with [this new] format when you have good rendering in your soundbar'"--even if you don't have a 5.1, 7.1, or 7.1.4 setup.

Fraunhofer demonstrated a soundbar using MPEG-H at the International Broadcasting Convention (IBC) in Amsterdam in September but didn't say what speaker company manufactured it. Plogsties noted that Fraunhofer is also talking with TV makers in South Korea that also make soundbars--which was a clear reference to LG and Samsung (neither company immediately responded to a request for comment). The soundbar can be connected via HDMI, or "you can do the decoding directly in the soundbar" using MPEG-H, he said.

Headphones also represent a "huge opportunity to use next-generation codecs," said Roger Charlesworth, executive director of the DTV Audio Group, after the AES convention. Object-based audio systems "allow you to render [an immersive] listening experience more easily on a range of devices," including headphones, he explained. Therefore, viewers of a movie or TV show on a smartphone or tablet can get a simulation of the height and depth that would be provided in a traditional home theater setting with surround sound speakers.

Audio Personalization Is Another Part of the Story
Plogsties gave me an MPEG-H demonstration at AES New York to show how the codec can provide a wide range of audio personalization features. For example, somebody watching a movie with MPEG-H can choose between multiple languages or listen to director's commentary instead of the main soundtrack, much like what viewers of DVD and Blu-ray Disc movies are able to do with the click of a button on the remote.

Of course, it's no secret that traditional linear TV viewing and optical-disc-based viewing of movies and other video content are both on the decline as more viewers shift to on-demand streaming via Netflix and other over-the-the-top services. But, Charlesworth noted, "the one thing we've lost in streaming" is the director's commentary, a feature that many of us had come to love on Blu-ray and DVD discs. For broadcasters, content creators, and all the people who work on the delivery and distribution side of the equation, "if you want to do any of those things in streaming now, you have to have a whole different soundtrack--and that's a giant pain in the ass," he explained. Netflix alone might need dozens of versions of the same program, including stereo and 5.1 versions, along with versions in multiple languages, he pointed out, adding: "The complexity of it is just absurd."

But MPEG-H and AC-4, which offer most of the same main capabilities, make that process a whole lot easier. Charlesworth predicts that each ATSC 3.0 audio codec is "going to get traction," and each one will have certain advantages over the other in each market.

Brian Markwalter, CTA Senior Vice President-Research & Standards, said much the same thing. "The two audio systems chosen for ATSC 3.0 have the obvious benefit of bringing consumers the latest generation of compression technology, offering better quality and more flexibility at lower data rates. One example of the flexibility that will appeal to content creators and distributors is the ability to separate, for example, the music and effects--i.e., all of the sounds you hear in a TV program minus the spoken dialogue--from the English language dialogue, the Spanish dialogue, and the video description vocal track so that they can be selected and mixed at the receiver. Although it is possible in theory to do this with current systems, in practice the broadcaster has to create a complete audio program for English and an equivalent one in Spanish and broadcast them both, using more precious bandwidth than is necessary. These systems are also more forward-looking, accommodating traditional multichannel audio and newer object audio, so that consumers will get the best possible experience regardless of whether they use a soundbar or a decked-out multichannel speaker system."

Dolby-AC4.jpgDolby's U.S. Lead
AC-4 scored a major win last year when the ATSC's audio group recommended it over MPEG-H for U.S. broadcasters. In the ATSC 3.0 A/300 document that ATSC released on October 19, it pointed out that "all ATSC 3.0 terrestrial and hybrid television services emitted within a given region shall use one audio system selected for that region," and "broadcast organizations in North America have selected the audio system defined in A/342, Part 2 as the audio system for use in Mexico, Canada, and the U.S." And that audio system was ... drum roll, please ... Dolby AC-4.

Nobody really should be all that surprised that AC-4 was selected by North American broadcasters over MPEG-H. After all, Dolby is a publicly traded U.S. company with a well-established presence in the market. "What's happened here is that there are different verticals and different international markets where Fraunhofer or Dolby will hold sway," Charlesworth explained. He added: "I think that both will be successful in certain markets or in certain verticals. For instance, I think there's sort of an anti-American bias a little bit in Germany," where Fraunhofer is "the home team, so [we may] see more implementations of MPEG-H in" that market or another one "where Fraunhofer is more dominant."

As for the U.S., Charlesworth said, "when we talk about immersive audio, I think there's no question that Dolby is already making huge progress here, and I think that there is a trust level" already among industry professionals in Hollywood with Dolby audio technology, including the Atmos surround sound system. "With Dolby, people are already mixing film in Atmos now. We're seeing premium episodic TV. Starz has multiple shows that are available in Atmos currently. And we'll be seeing more Atmos content from Netflix and from Amazon and from people like that, and HBO's Game of Thrones is available in Atmos. So, I think that Hollywood has a kind of a pipeline that's already Atmos, and so what we're seeing--what we saw a long time ago with 5.1--we're seeing that with Atmos. It becomes sort of the standard" for mixing sound now.

Charlesworth predicts that AC-4 support will soon appear in a wide range of set-top boxes and TV sets and, presumably, into future Roku set-top boxes, game consoles, Apple TV and other devices for the U.S. market.

Following the NAB Show in Las Vegas earlier this year, Dolby CEO and President Kevin Yeaman said on his company's second-quarter earnings call that AC-4 was "gaining early traction." He said AC-4 was "twice as efficient as Dolby Digital Plus and offers compelling new features." Although "implementation takes time, key partners like Samsung, LG, Sony, and VIZIO have already announced the adoption" of AC-4 in their TVs. We may hear more announcements on that front at the next CES in January.

Like Charlesworth, CTA's Markwalter predicts that both AC-4 and MPEG-H "will be used widely." So far, Dolby AC-4 has apparently nabbed the U.S. and the rest of North America, while MPEG-H has nabbed South Korea. But there have been signs that AC-4 also holds an advantage in Europe, despite Fraunhofer's presence. For one thing, the first Dolby AC-4-equipped TVs are already in the market "today from LG and Samsung in North America and Europe," according to Mathias Bendull, vice president of Multi-Screen Services Audio at Dolby. There have also been "several successful live Dolby AC-4 broadcasts, including a live transmission" of the Roland-Garros French Open tennis tournament this year by France Television--a transmission in Atmos, delivered via AC-4, he said.

Bendull also pointed to the fact that the European Telecommunications Standards Institute (ETSI) published the AC-4 standard. That was back in 2014. At the time, ETSI called AC-4 a "flexible, cost effective and enhanced experience for industry and end-users." ETSI didn't go to bat for MPEG-H and publish that standard, which certainly on the face of it appeared to mean that ETSI favored AC-4 over MPEG-H. Despite that, however, ETSI spokeswoman Claire Boyer told me, "ETSI does not recommend any specific standard over another, but we let the industry make them and adopt and use them if they find it beneficial."

Even assuming that AC-4 wins the battle for Europe, however, there would still be plenty of countries left. So, it remains to be seen which format will have the upper hand overall in one year's time. For now, though, AC-4 appears to be in the driver's seat when it comes to the living room--especially when you factor in the advantage it enjoys thanks to it being the only one of the two codecs that already supports the increasingly omnipresent Atmos surround sound technology.

Additional Resources
HDMI 2.1 Is Coming Soon to AV Gear Near You at HomeTheaterReview.com.
Promising Signs for Broadcast UHD TV at the NAB Show at HomeTheaterReview.com.
CEDIA 2017 Show Wrap-up at HomeTheaterReview.com.



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