ATSC 3.0 Will Mean Changes for Broadcast Audio
The standards developed by the Advanced Television Systems Committee (ATSC) are the bedrock of broadcasting, and the industry is awaiting the arrival of the next generation, known as ATSC 3.0, due to be announced in early 2017 after a series of evaluation and comment periods. ATSC 3.0 will take broadcast audio to the next level, one that will go well beyond the 5.1 environment and encompass increasing numbers of object-based channels as well as such issues as personalization and immersiveness, terms that may seem exotic today but will likely become as familiar as surround is now.
At NAB 2015, developers showcased what they hope will be core components of ATSC 3.0’s audio standards. For example, Dolby, whose Dolby Digital AC-3 is the sole audio codec for current broadcast-audio standards, is proposing its AC-4 next-generation emission codec for ATSC 3.0. An amalgamation known as the MPEG-H Audio Alliance — comprising Fraunhofer, Qualcomm, and Technicolor — backs the MPEG-H codec, which supports scene-based audio as well as objects. DTS had initially proposed its DTS:X object-based audio codec. However, the company reportedly has withdrawn its entry in the ATSC 3.0 audio sweepstakes for undisclosed reasons.
At the show, Fraunhofer demonstrated its system’s interactivity by presenting excerpts from field tests at live-broadcast events. The “Interactive 3D Audio System for TV” allowed viewers to customize sound broadcasts to suit personal preferences, such as switching dialog-language channels or creating a “home team” mix for sports broadcasts.
Dolby and MStar Semiconductor demonstrated the integration of Dolby AC-4 on an MStar reference TV, embedded with MStar’s latest HEVC-capable TV SoC (system on a chip). The demo ran on MStar Android-based reference TV software and supported real-time decoding of Dolby AC-4 — the very first such demonstration, according to Dolby. An adventure clip with 5.1 audio encode in AC-4 was played via the TV media player, with audio output on either the TV speaker or the headphone jack.
More recently, Dolby AC-4 was used, in conjunction with development partner Envivio’s HEVC (H.265) compression over DVB T-2, in a live 4K streaming demonstration at this year’s French Open tennis championship.
There Can Be More Than One?
What’s at stake are potentially huge sums, in the form of licensing fees for the winning supplier. Or could that be suppliers? Both Dolby’s and Fraunhofer’s current codecs coexist in European broadcasting, selected one at a time on a country-by-country basis by national broadcasters. (An earlier multiformat example: both Dolby and DTS audio codecs were specified when the DVD format arrived in 1997.)
That, says ATSC President Mark Richer, is a possibility. It’s up to the committee (ATSC S34-2) evaluating the new codecs and chaired by NBC director/Principal Audio Engineer Jim Starzynski. The committee’s list of requirements is extensive and includes adapting audio for a wide range of consumer speaker configurations and object-based control over audio-element placements.
“Our goal is generally to choose one,” says Richer, “but we could end up with both.”
Notes Robert Bleidt, GM, Audio and Multimedia Division, Fraunhofer USA Digital Media Technologies, “We live in a more complex world today. A television set today is a computer, and it can handle more than one codec. But what happens is strictly up to the ATSC.”
However, Dolby Senior Director, Sound Group, Jeff Riedmiller points out that other events may affect the outcome of the new standard, most notably the impending reallocation of RF spectrum, which will be in progress about the time the final ATSC 3.0 standards are announced.
“The efficiency of new codecs will be critical as we move further into a spectrum-challenged environment,” he cautions.
Dolby Broadcast Business Group SVP Giles Baker takes an even wider perspective, noting how the next set of standards will also have to address mobile platforms and global issues: “There are different timelines around the world to keep in mind. For instance, Europe is further ahead with 4K than we are here, but, so far, 4K has had little impact on the audio experience.”
The ATSC’s evaluation process for the 3.0 audio standard has been under way for nearly three years, Richer says. The proposed systems will be tested discretely and in their entirety over the summer, to establish the ATSC 3.0 Audio System Candidate Standard, which he characterizes as “one step above a working draft.” That’s expected to be announced this fall.
These tests, which involve both objective measurement and subjective listening, will be the first to examine immersive audio for a next-generation broadcast-television standard. Immersive-audio functionality enables high spatial resolution in sound-source localization in azimuth, elevation, and distance and provides an increased sense of sound envelopment throughout the listening area.
Audio “personalization” will include enhancements to the control of dialog, use of alternate audio tracks, and mixing of assistive audio services, other-language dialog, special commentary, and music and effects.
ATSC 3.0 audio also will support both normalization of content loudness and contouring of dynamic range, based on the specific capabilities of a user’s fixed or mobile devices and their unique sound environments.
What’s at stake, besides the financial aspects, says Richer, is “what the next-generation audio systems will be for broadcast for the U.S. and, hopefully, for other countries, perhaps even for cable and satellite transmissions; [their] benefits will be across all media” — including, ultimately, mobile devices, television’s next frontier.