McAdams On: What HDMI 2.0 Means for 4KTV
THE TRENCHES The
HDMI forum this week released version 2.0 of what has become the common
interface standard for HDTV screens. Among its notable capabilities, 2.0 is
said to be able to transport uncompressed 60 frame-per-second 4K video at 18
gigabits per second.
This means full 4K to the TV is achievable at 2,160 progressive scan lines per
frame versus the 720 that comprise an HDTV picture. What that means is that under no circumstance will you want your video calls
to be viewed on a TV set. It also may have implications for professional
facilities—from hardly a nit to the Holy Grail single-format workflow—depending
upon whom you ask.
Take Chuck Pagano, executive vice president and chief technology officer for
ESPN, for one. ESPN is building a new 195,000-square-foot digital production
center (next to the “old” 120,000-square-foot digital production center).
“Sports Center” is set to become the inaugural telecast next spring.
“The only place we’ll use HDMI is feeds to TV sets,” Pagano said of the new
facility. “Our cardiopulmonary system is moving toward AVB HD-based IEEE
1722—enterprisewide for our facility. It’s video streaming over Ethernet fabric
for broadcast quality. There isn’t a limitation. We’re putting it in to handle
4K if we need to.
“HDMI is purely a consumer entity,” he said. “You may see us use it on TV sets, but if we can
have them on Ethernet, we’ll probably do that for robustness.”
Others saw more potential for HDMI 2.0’s use in media facilities. Amberfin’s
Bruce Devlin envisioned it making inroads beyond connecting TV sets.
“It’s pretty important because we now have a cheap, reliable interconnect for
displays at virtually any resolution,” he said. “It goes further that many
consumer-generation devices have HDMI out, so a neat way of capturing video at
varying, non-HD-SDI resolutions is to use HDMI to capture the data. It will
find its way as an ingest format.”
Mark Schubin, engineer in charge at the Metropolitan Opera, wasn’t sold on
“I don’t see it. It
was never intended as a professional connection, so it doesn’t have locking,
which is what you want on a professional connector,” he said.
Media workflow consultant Mark Darlow took a long view. What if one could use HDMI 2.0 to start devising
glass-to-glass 4KTV with a single format, versus the dozen spawned by the
digital transition? Although the necessary equipment does not exist now, HDMI
2.0 could be an impetus for development.
“Say you’re out doing
news… instead of docking on a network location, which is historically what they
do, using Cat-5 or Cat-6, they would use HDMI,” he said. “The point is—fewer
standards to support; less investment in competing standards; lower price of
development for vendors and thus equipment costs for operators. A professional
industry starts to take advantage of high-end consumer price points.”
Clyde Smith, senior vice president of new technologies at Fox Network Engineering
and Operations, said HDMI 2.0 feasibly could be used in “small islands for
certain professional apps, such as editing and graphics.” Fox, however, is
going with fiber.
“The 18 Gbps over twisted pair copper means it is length-limited,” Smith said.
That length-limit is about one-fourth of what HD-SDI can do, said Mike
Tsinberg, president and CEO of Key Digital Systems.
“HD-SDI can reach about 300 feet while pure HDMI cables can be no more then 75
feet.,” he said. “To extend HDMI to 300 feet, you need to deploy HDbaseT
technology that runs over CAT5e/6 with RJ45 connectors. So the difference is
not only in format capabilities but also physical. To replace the physical
infrastructure of today’s studio will be very expensive. So the reason has to be extremely good for that.”
HDMI 2.0 has other
limitations as well, SMPTE Fellow Peter Ludé said.
“As I understand it, HDMI
2.0 will only support UHDTV-1—2160 x 3840—at 10-bit 4:2:0 or 4:2:2. Professional
use will often call for 12-bit 4:2:2 or even 4:4:4, thereby exceeding the
capability of HDMI 2.0. It’s also worthwhile to note that various
standards groups are including consideration for 120 fps [for 4K], not just the
50/60 fps supported by the new HDMI.”
One more major barrier for HDMI’s adoption in professional facilities—HDCP.
High-Bandwidth Digital Content Protection. It’s a bane for systems integrators,
one veteran said.
professional A/V world and broadcast systems perspective, the HDMI battle
continues to be a struggle,” he said. “Between HMDI versions, physical
connector and cabling limitations, prominent use of consumer displays for
monitoring in broadcast facilities, and signal-restricting issues with HDCP
when converting between HDMI and broadcast SDI formats, you end up with a huge
can of worms.”
So what is HDMI 2.0 good for on the
professional front? Schubin, who is intrigued by very little, was intrigued by
one particular spec: Dynamic synchronization of video and audio streams.
“What you need to do is always take the same amount of time to process audio and video,” he said. “But if you go into a
switcher, a frame-rate converter, a standards converter, etc. You keep delaying
the video and not the audio, so you have video leading audio—lip sync error.”
The classic “Godzilla” effect.
“There’s a second issue,” he said. “In MPEG, there’s a presentation time-stamp,
or PTS, that stamps video and audio frequently so receiver can bring everything
into sync, but there’s no decent requirement in the standard for how often you
have to do that. It’s data and it takes up data rate. Maybe it’s not something
you want to do so much. So the home user has to change channels to get audio
and video back into sync.”
Not good. Something less annoying might be on that other channel, so HDMI 2.0
does hold promise in that regard. The other potential upside is collateral to
professional facilities—4KTV adoption by the public, which would then drive 4K
“I’m glad it finally got
announced, because it may give a bit of a steroid to 4K’s potential,” ESPN’s
Pagano said. “4K’s been limited in terms of frames per second. HDMI 1.4b is
limited to 24 or 30 fps. You’re seeing 3:2 pulldown down in the TV set. You
don’t see a minimal 60 frame-per-second 4K.”
Indeed, Panasonic just announced the first 60 fps, HDMI 2.0 4KTV set, a 65-incher
for $6,000, on deck to ship next month. That’s $14,000 less than the first 4KTV set introduced in the U.S. market a year ago.
Whether or not the public embraces 4KTV remains to be seen, however. A viewer has to sit within cellular-frying
proximity to the screen to visually discern the difference between 4K and HD—technically.
Marketing is a powerful mind-altering
tool. Big box retailers will display 4KTV sets in the most flattering of wall-mounted
logistics while passé HD sets will reside in the dreaded aisles.
Dudes—sincerest apologies, but you know who you are—will bite like striped bass
before a thunderstorm.
Because a viewer has to sit so close to a 4KTV set—1.5 times screen height—the
format may give rise to a new out-of-home venue, Pagano said.
“I look at it from the perspective of a sports fan. Normally, its done with
friends, colleagues, etc.,” he said. “I think there’s a benefit to 4K, but maybe
not in the home. Maybe it creates a subculture of man caves.”
And so it goes.