Five years after pubcasters switched off the last of their analog TV transmitters and advanced into an all-digital world, planning is underway for the next generation of digital TV.
The ATSC 3.0 standard has been years in the making, and years of work and many questions remain before pubcasters are ready to put it on the air.
ATSC is the Advanced Television Standards Committee, an international nonprofit comprising broadcasters, regulators, consumer electronics manufacturers, broadcast equipment companies and other experts. It developed the ATSC 1.0 standard that was adopted for broadcast digital TV in the early 2000s and is now charged with replacing that standard to keep up with rapid advances in the technologies used in broadcast TV.
ATSC is working on two sets of standards. ATSC 2.0, which was on display at the National Association of Broadcasters Show in Las Vegas in April, is closer to fruition but less revolutionary. As an enhancement to the existing DTV standard, ATSC 2.0 promises to help broadcasters add interactive features and improve integration with “second-screen” devices (that tablet or smartphone that’s in your hand while you’re watching TV) without requiring major changes to digital TV as we know it. ATSC 2.0 is rapidly approaching “candidate standard” status before final adoption.
ATSC 3.0, on the other hand, promises bigger opportunities, more flexibility for broadcasters and potentially much more disruption to the existing broadcast infrastructure.
The ATSC 1.0 standard carried over the analog TV concept that each TV station gets 6 MHz of radio frequency spectrum, primarily intended for delivering its own video content to a viewer at a fixed location.
When the standard was being developed, around the turn of the millennium, the state of the art allowed for 19.39 megabytes per second (Mbps) to be delivered over those 6 MHz — enough data to support one high-definition and two, or at most three, standard-definition video services. Advances in encoding have pushed that envelope, making it possible to serve up two HD video streams, with some compromises in quality.
Improving on that, as ATSC 3.0 promises to do, will mean a break from current standards. Instead of the MPEG-2 video compression now used for DTV, ATSC 3.0 will move ahead, likely to the H.265 HEVC (High Efficiency Video Coding) codec that can pack much more video data into fewer bits.
In addition to improved coding that allows more video to be transmitted with fewer bits, ATSC 3.0 envisions a new “physical layer” — the technology that turns that bitstream into a signal that can be transmitted over the airwaves. Instead of the 19.39 Mbps of ATSC 1.0 and 2.0, an ATSC 3.0 station is expected to be able to transmit at least 25 Mbps within its 6 MHz of RF spectrum.
“It’s going to have all these new technical features that are going to enable evolution and revolution of the business,” says Eric Wolf, PBS’s v.p. of technology strategy and planning. That includes ultra–high-definition video, more capacity for additional HD and SD video, and the ability to reach the mobile devices where so many viewers now want to watch their television.
Beyond the relatively modest enhancements of the upcoming ATSC 2.0 system, ATSC 3.0 is also being designed to include a host of emerging technologies. Those include two-way capability that enables broadcasters to track who’s watching their programming and interact with viewers. It also provides better support for single-frequency networks that can use multiple transmitter sites to provide stronger signals over more parts of a market.
Along with these advances, ATSC 3.0 also opens the possibility that the entire TV broadcast transmission system in the U.S. will be rendered obsolete for the second time in a decade. None of the tens of millions of DTV receivers now in use will be able to decode the new video codec that ends up being part of the finished ATSC 3.0 standard, if they’re even capable of receiving signals transmitted in the new system’s physical layer.
At the other end, thousands of TV transmitters will need new encoders, and possibly much more in the way of new equipment, to be able to transmit it.
Working out details
“The media industry is moving quickly,” Wolf says, “and broadcasters have no interest in hanging around with 20-year-old technology if we can avoid it.” But working out the intricate details of a new broadcast standard takes time, and the ATSC 3.0 standard is a work in progress.
“There are myriad working teams within the ATSC process,” Wolf notes. “Standards-defining organizations have particular ways of working, partly because those are effective means of reaching an industry consensus, partly because it keeps you legal — there are lots of very interesting intellectual property and other kinds of issues that can come up.”
But that regimented process takes time. The ATSC 3.0 proceeding began in 2011, and the selection of a “candidate standard” — a preliminary version of the system that can be tested and evaluated before winning regulatory approval — is not expected until at least early 2016.
Actual implementation of the standard will likely take at least several more years, as broadcasters and regulators work out a transition plan and manufacturers begin producing transmission equipment. The manufacturers will equip new TVs to pick up the new standard and develop a converter, likely to take the form of a Chromecast-style USB or HDMI stick, to allow existing sets to receive signals transmitted in the new standard.
Wolf expects that by next April’s PBS TechCon and the NAB Show, “there will be a lot of detail on the ATSC table” so that pubcasters can develop a better understanding of what the transition will mean for them. In the meantime, he encourages PBS member stations to become involved in the standards-setting process led by Chris Homer, v.p. of operations and engineering. Homer hopes to involve as many engineers from local stations as possible, giving them the opportunity to get an early look at what awaits them in the ATSC 3.0 conversion.
“The stations are involved in the standards process in some ways even more than PBS is, because they’re the people that obviously operate the transmitters,” Wolf says. “We’re really delighted to support people, and we’ll buddy up so that they’re not swimming in the deep waters all on their own.”
At the station end, the transition to ATSC 3.0 brings with it plenty of unanswered questions. That goes beyond the obvious issues of cost and logistics of equipment upgrades to the parallel process that’s already underway for some pubcasters: deciding how to proceed across the uncertain terrain of the FCC’s spectrum auction and repacking proceeding, now tentatively set for 2016.
There instead should be an “ATSC 4.0” standard, which does what ATSC 3.0 does, but is compatible with current TV sets and cable boxes.
That would be wonderful, but you can’t defy the laws of physics, captain. Or of digital electronics. That said, I’d sure like to see mp4-like codecs (3.0) take over from DVD-era codecs (MPEG-2).