The humble BNC connector
has been around for so long that most broadcast engineers don’t even
know what the letters “BNC” mean. Ask around the workshop:
“What do the letters B-N-C stand for?” I’ve yet
to find someone who knows the answer off the top of their head.
I had to Google it myself. “Bayonet
Neill-Concelman” is the correct answer. We can thank Paul Neill and
Carl Concelman for designing that compact, quick, easy and reliable coaxial
cable interface that faithfully transports our real time synchronous television
content between pretty much every piece of broadcast baseband video equipment—and
a lot of audio content too.
Neill and Concelman had military applications in mind when they
designed this ubiquitous signal interface for the ends of coaxial cables. The
military aspect of their design objective makes for an interesting coincidence
when you consider that the patent application on which they based their
collaborative effort was filed with the US Patent Office just a couple of weeks
after World War II ended in Europe in 1945. As the tired, hungry and
demoralized soldiers laid down their weapons across Europe, Octavio Salati was
in his lab at Hazeltine Corporation in springtime America, enthusiastically
writing his patent application, complete with meticulously hand-drawn
crosssectional images for his “electrical connector.” He
filed his patent on May 19, 1945. His patent protection was awarded to him on
January 30, 1951. (The patent approval process took about the same amount of
time as World War II.)
The idea behind the BNC connector is older than the author of this article. But
not by much. That the BNC connector is still so thoroughly entrenched in our
daily lives in 2014 is quite remarkable. Its longevity is testimony to the
success of its design. But, there are forces at work to end the 60-year reign
of our small round shiny friend.
The inevitable replacement for your old faithful BNC/coax combo is
the cheap but rather unsatisfying plastic 8P8C connector on dual unshielded
twisted pair (UTP). After 60 years of saying “BNC on coax,”
we’re supposed to soon be saying “8P8C on UTP.”
It’s not quite the same, is it? “8P8C on UTP”
doesn’t roll off the tongue particularly well.
That’s why nearly everyone calls it “Ethernet
cable.” Even “Ethernet cable” is too much of a
mouthful for some people, so you’ll typically hear them say
“Cat 5,” “Cat 5e” or “Cat
6” instead—referring to the relatively inexpensive category 5 or
category 6 unshielded twisted pair copper cables for Gigabit Ethernet
applications. “8P8C” is rather lacking in aesthetic appeal
as far as names go. Why didn’t they ask George Lucas for suggestions?
He came up with C3PO and R2D2 for the Star Wars movie. He could have done much
better for us than “8P8C.”
And that’s why we all prefer to call it a modular
connector, or perhaps more commonly and somewhat inaccurately, the RJ45
It goes to prove one thing—that the IT and telco industries are definitely at
the upper limit of their creativity with three letter acronyms (TLAs).They
can’t do four. They need help from someone like George Lucas for
that, but he charges too much. Cost is important. Cost is the basic motivation
behind the effort to replace all of the broadcaster’s BNC/coax
infrastructure with Ethernet cables. It’s already a fait accompli for
non-real time asynchronous video transfer.
Relocating or replicating broadcast MXF files around a TV station
or production house and even around the planet through Ethernet cables and
IT/telco packet switching infrastructure is already the done thing. It makes
sense to do that now. Enough bandwidth is available at the right price, and for
simple file relocation and replication, we can accept some degree of variable
transfer speeds, interruptions and latencies.
But streaming synchronous live uncompressed high definition video as a playout
signal or pass-through signal or a live camera source back to the studio,
remains a very tall order for a TCP/IP network. It isn’t only a
matter of having enough bandwidth and not too much latency. It’s also
a matter of having a whole ecosystem of IP friendly devices that support all
the operational functions of television production and broadcasting—and all the
devices in that ecosystem need to obey the network protocol rules so that
traffic flows smoothly—without bottlenecks, hiccups or crashes.
THE AVB EXAMPLE
An ecosystem of IP-friendly streaming video devices can only come about if
three things exist. First, there has to be the will to do things entirely in
the IP domain. Second, there has to be a set of standards to follow for the bit
streams and electrical interfaces and network protocols. And third, we need a
marketplace of manufacturers to invest in the launching of a whole new family
of products that conform to the new standards, and those manufacturers must
have some hope of selling gazillions of said products.
So far, in May 2014, enough of a will has existed for a long enough
duration to have brought about a set of standards. The standards can be found
under the umbrella term “AVB” - Audio Video Bridging. The
AVB set of four IEEE standards is comprised of the following: IEEE 802.1AS
(precise time synchronization), 802.1Qat (Stream Reservation Protocol),
802.1Qav (“traffic shaping” to prevent bottlenecks and
packet clogging in queues) and 802.1BA (identifying which devices on the
network are AVB-capable and which ones are not).
A surprising discovery when one looks for information on these
standards is the fact that the family of four standards was finalized and
published about three years ago. It begs these questions: “Why is it
taking so long? Why hasn’t AVB taken the television world by
storm?” The answers to questions like those are rarely simple. But
there is an important side note.
There was one more important standard required, and that standard
wasn’t ratified until August last year: IEEE Std 1722.1-2013.
That’s the one that provides a kind of intelligence for a sort of
plug and play AVB device to just work when you connect it to the bridge.
Without that, a lot of manual configuration on setup menus would be required
before you could plug an AVB device into the bridge. In reality, the AVB
standards were not really a complete set until about nine months ago. That
could partly explain why AVB systems aren’t all around us yet.
As part of our further analysis for the purpose of finding more
answers, let’s compare the upcoming rollout of AVB to the rollout of
digital video over coaxial cable 25 years earlier. The Serial Digital Interface
(SDI) first saw the light of day when Sony and Ampex launched their D2 format
19mm composite video tape recorders. To make D2 VTRs simpler to install within
the existing TV station cabling infrastructure, the parallel data streams on
the cumbersome and distance-challenged parallel digital interface used on the
early D1 VTRs had to be serialised by the inclusion of a new dedicated chipset
behind the male BNC connectors on the D2 VTR. It was that humble pair of
serializer and deserializer LSI chips that allowed a standard BNC connector on
75 ohm coaxial cable to pass SD digital video streams at 270 Mbps.
Sony had the market for that SDI chipset very much to themselves in
the early days. They sold the serializer/deserializer chipset to all the other
broadcast video equipment manufacturers. That low-cost chipset was a major
contributing factor that allowed the whole broadcast industry to quickly and
cheaply adopt the new SDI digital video interface.
Today there are many semiconductor manufacturers producing HD-SDI
transceiver chipsets. Within a very short span of time, video monitors, audio
monitors, audio recorders and players, CGs, still stores, test equipment,
switchers, routers and every other video-related device was “in the
game.” SDI was adopted with great enthusiasm because the SDI
ecosystem was quick and easy to create. And that SDI chipset remains, with its
BNC-oncoax bedfellow, in wide and stable use today.
WRITING THE SCRIPT
That story of SDI is a hard act to follow. But follow it AVB must. Writing the
script of the AVB story is a group called the AVnu Alliance (www.avnu.org). The
AVnu Alliance is the AV industry body responsible for certifying products for
compliance to the AVB standards. Passing all
the compliance tests permits the manufacturer to attach the
“AVnu Certified” logo to their product. That logo is what
you look for when you’re shopping for the parts to build yourself a
BNC-free AVB zone.
The first question on my mind as I navigated my way to the AVnu
Alliance web site was “If I’m building an AVB facility
today, how many components of the system can I buy that are already AVB
certified?” The answer surprised me. The answer is
“one.” Uno. Un. Ichi. To be fair, the official list of AVnu
Certified products as of May, 2014, has 14 items on it. But those 14 items are
the various models of one product line: the Extreme Networks “Summit
X440” series of Gigabit Ethernet Switch. It’s appropriate
that the first item to pop out of the AVnu certification process is the switch.
Without a switch, there’s no AVB. And in the Audio Video Bridge
world, the whole system revolves around the bridge. In AVnu language the
certified Gigabit Ethernet switch falls under the product category called
Okay, we’ve bought ourselves a bridge, thanks to the good
work of Extreme Networks and AVnu Alliance. What do we start saving our pennies
for now? What will be the next products to earn their AVnu Certified logo? How
long will it take us to build our BNC-free AVB platform? What other products
are coming down the AVnu certification lab’s pipeline?
At NAB this year, Arista Networks was making noises about the upcoming AVB
certification for their Ethernet switches. They gave a very convincing
demonstration of frame accurate real time glitch-free switching of live HD
streams. That demo was in partnership with Fox Networks Engineering &
Operations. So this isn’t just marketing smoke and mirrors. This is a
real world practical demonstration—of an AVB bridge, with a real broadcaster.
So we have another bridge coming for sure when Arista’s products get
their AVnu logo.
We can cross “bridge” off the shopping list.
What about cameras, microphones, monitors, test equipment, amplifiers,
loudspeakers, legacy videotape players, audio mixers, real time digital
effects, realtime graphics, video mixers with keyers, and etc.? When will they
come out with an 8P8C socket and AVB compatibility? Sennheiser demonstrated a
prototype of an AVB microphone in 2012. There’s no more recent news
than that on their web site.
Beyerdynamic has partnered with XMOS to utilize an external AVB gateway for the
microphones in their wireless conference room systems. So yes, we can now get a
microphone signal into an AVB bridge, thanks to the XMOS “mic in to
AVB out” box. But that’s a conference room microphone
network. What about a high quality voice-over booth microphone? Or a studio
shotgun boom mic? “To be confirmed,” is the current reply.
Wohler announced an AVB interface card for their AMP2 series of
video/audio monitor just before NAB this year. This gives us the ability to
monitor, mix, level adjust and remux the audio channels in an AVB stream. Now
we can cross “audio monitor/level adjuster” off the
shopping list. That’s about it. A bridge, some conference room
microphones and an audio/video monitor/adjuster are what we can easily find
today. That’s not much. AVB promises to save us so much money. Why is
the television world not overtly beating a path to the AVB door? If we look at
the list of AVnu members on the AVnu web site, the most familiar names to us
television people are Avid and Dolby. Sony isn’t there. Neither is
Panasonic, nor Grass Valley, nor Imagine Communications (nee Harris), nor
Miranda, nor Blackmagic Design, nor JVC. Yamaha is there, but broadcast
television is only a small part of their total business.
Avid is on the AVnu membership list, mostly it appears, with their
audio hat on. Avid’s ProTools and SC48 mixing console are definitely
candidates for a place in an AVB world. Shure, Sennheiser, Bose, Harman and
Beyerdynamic are AVnu Alliance members. So it appears that the audio world
shows more interest in networking their real-time baseband payload over
Ethernet than the video world does.
Barco is an AVnu Alliance member. Barco’s presence among all the
audio names in the list is a hint that AVB might have more relevance in
non-broadcast AV applications like auditoriums, concert halls, stadiums, houses
of worship, and the like. But somewhat like a fox in a flock of sheep, appears
the name of Audinate in the list of AVnu members. Audinate has already
established a market for their Dante product line, which is a credible
Ethernet-based near-enough-realtime audio networking solution over standard
commodity Ethernet switches. Audinate is surely wise to be in the AVB group so
their current headline product, Dante, can take advantage of the new
capabilities offered by AVB bridges.
But the success of Dante on existing non-AVB Ethernet network infrastructure
is, one might expect, also a factor that could be taking some shine off the
whole AVB concept. The audio world already has a solution of sorts in Dante.
Why do they need AVB?
AVB FOR CONSUMERS
To make matters worse for AVB, when we look at the consumer AV
device market, it appears to be far ahead of AVB with their own networking
solutions as part of a quite mature ecosystem nurtured by the HDBaseT Alliance
(www.hdbaset.org). The HDBaseT Alliance was founded by LG Electronics, Samsung
Electronics, Sony Pictures Entertainment and Valens in 2010. Their secret
weapon is what they call “5Play on a Single Cable”, which means
they can carry all of the following on a single Gigabit Ethernet cable: Up to
4K video (one way) PLUS digital audio (one way) PLUS 100BaseT Ethernet (two
way) PLUS control signals (two way) PLUS up to 100W of DC power (to the
The Ethernet cable for HDBaseT is a standard commodity 8P8C on
Cat5e/6 UTP cable from your local computer store. And up to 100 metres in a
single run is feasible. But the HDBaseT switch and data transport method on the
cable is proprietary. It isn’t based on packet switching like
Ethernet. It’s based on a superset of HDMI. There are already enough
HDBaseT devices to build a system. The reason the HDBaseT Alliance could
establish an ecosystem of devices so effectively is because the whole ecosystem
is based on an extension to the HDMI chipset. In other words, it’s
just like 25 years ago when SDI easily established a foothold in our business
thanks to the SDI chipset.
The HDMI chipset already handles high bit-rate video and audio. And
most importantly, it already handles the HDCP copy protection protocols for
Hollywood HD content. By combining the HDMI chipset with the new Valens HDBaseT
chipset, the “5Play” killer app could be realized. That
brings us to AVB’s Achilles heel. They don’t have a chipset
that makes a microphone or other AV device connect easily to an AVB bridge.
It’s going to take a long time to write all the device AVB driver
software and have every device AVnu certified. A chipset negates the need for
all that time. AVB doesn’t have a chipset. They only own a set of
IEEE standards. They really need a chipset.
So it looks like we might be in for a long wait for a BNC-free zone
from AVB. The good news is, if you buy that Extreme Networks X440 switch today,
you can still get value from it today as a normal Ethernet switch, and take
comfort in the fact of being “AVB ready” for when those AVB
devices eventually do come out of the certification pipeline.