IP Distribution Challenges SDI

ALEXANDRIA, VA.—In the broadcasting industry, two of the top favorable attributes are affordable cost and total reliability. In most facilities, reliability is king, as a failure can be both embarrassing and costly when commercials are on the line. Still, if something is both reliable and affordable, it’s a winner.

So it has been with routing and signal distribution for video systems. Once the industry transitioned to digital and switchers went from somewhat complex analog video/audio devices to SDI, routing switchers became less complex, more affordable and more reliable. Since SDI was a standard tailor-made for the television industry, it fit the needs of broadcasters perfectly.

So why are we now talking about routing and distributing television signals using IP technology? Didn’t the video industry already have a routing and distribution system designed specifically for it?

The reason we now discuss IP routing and distribution is because IP routing is less expensive than SDI (and analog audio/video) routing—in many instances by a considerable margin. In addition, IP routing is also considerably more flexible in its ability to send signals to/from places that would be difficult to reach with SDI. Finally, IP routing now has established standards for television distribution, which means that all vendors are on the same page when it comes to interoperability.

Lee Buchanan, senior director for networking at Grass Valley

Lee Buchanan, senior director for networking at Grass Valley

“Over the last couple of years, there has been a massive take-up in broadcasters moving towards IP-based solutions,” said Lee Buchanan, senior director for networking at Grass Valley. “Although there were challenges to bring the first systems online in 2016, we now have more than enough experience with such systems to ensure that they are designed and delivered in a way that we know will behave as expected.

“Although the suite of standards is continuing to evolve, the SMPTE ST 2110 standard has allowed the industry to standardize on a format for the transmission of video, audio and ancillary data in a very efficient manner,” Buchanan continued. “This standardization has allowed a much smoother deployment of multi-vendor systems.”


With the initial parts of the standard completed in 2017, the SMPTE ST 2110 video transport standard specifies how media-related data is described, carried and synchronized as it streams over IP networks in real-time for the purposes of live television production, playout, and other professional media applications. Television distribution has been drifting toward IP networks for years, and the ST 2110 standard makes it likely that the pace of this drift will increase.

John Mailhot, CTO for networking and infrastructure for Imagine Communications

John Mailhot, CTO for networking and infrastructure for Imagine Communications

Just so we’re all on the same page with the concept of IP routing, let’s take a look at how it differs from SDI routing with which we are all familiar.

“In IP, the ‘router’ is really a distributed concept—each device speaks IP and they are connected by Ethernet cabling to a network [or two for redundancy purposes],” said John Mailhot, CTO for networking and infrastructure for Imagine Communications. (Mailhot is also the drafting group editor for SMPTE’s ST 2110 standard.) “Devices that don’t speak IP need some kind of gateway, but those will become the exception over time. The ‘router’ is really now a control system that makes it all act like your traditional router acted.”

Two factors driving facilities toward IP routing are the proliferation of UHD signals and the sheer number of signals to route.

“IP makes the most sense in systems that need to scale to pretty large [greater than 1,000 HD signals, or greater than 256 UHD signals], and makes more sense the more devices have IP native signals available,” Mailhot said. “For small-to-medium systems composed of SDI equipment, and no need to evolve to UHD, SDI routing remains low-risk and cost-effective. Today is the ‘golden age’ of SDI routing—the products are fully debugged, audio embedding and dis-embedding and frame synchronizers and multiviewers are all built into the SDI routers, and the technology is familiar and therefore low-risk.”

Mailhot thinks that IP routing will eventually become standard for systems large and small, particularly as the need to move UHD signals grows.


For a video facility considering replacing an aging SDI plant with IP distribution, all the experts I talked to said this was now practical. However, they are two different beasts, so you need to ask the right questions.

“The most important question is: What devices are going to speak IP natively [and when] and which devices will still be SDI at the time of the upgrade?” Mailhot said. “This is essential for determining how many signals will require gateways, and how many are directly connected to the network.

“A second question is on the system’s overall scale: How big does the system need to grow in the reasonably-near term [12-18 months]?” he continued. “And will there also be changes in format [especially UHD]? This helps to establish the right network architecture to accommodate the near-term scale.”

It’s particularly important to note that audio is treated very differently for IP distribution than it is in an SDI system.

“SMPTE ST 2110 doesn’t just allow audio to be done separate from video, it actually always does it separately,” Mailhot said. “So the customer needs to make some decisions about how to organize the audio. How many channels to group into each stream and why? This is needed to find the right balance between ease-of-use and flexibility.”

Bob Caniglia, director of North America sales for Blackmagic Design

Bob Caniglia, director of North America sales for Blackmagic Design

In an SDI system, compression and latency are not part of the discussion when it comes to routing and distributing signals around a facility. SDI systems also are designed to send one signal per cable.

“With IP routers, you have to consider compression and network latency, but they provide multiple streams,” said Bob Caniglia, director of North America sales for Blackmagic Design. “With SDI routers, you have longer runs, direct connections and more reliability, but a 1:1 ratio for streams.”

Will IP distribution push SDI gear to the large-and-growing pile of intermediate technology that once was central to operations but has now been replaced by something better?

“Broadcasters need to evaluate IP and SDI routing with regard to their needs and what makes sense for their specific deployment,” Caniglia said. “While at present, the majority of broadcasters still rely on SDI routing for their day-to-day needs, IP is likely already a part of their overall workflow in some regard, [and] it’s definitely a consideration for the future.”


Grass Valley’s Buchanan pointed out the ever-increasing speeds of IP networks, and the inherent benefits of IP architecture.

“The rate of development in the IP industry far outstrips anything possible to achieve in broadcast,” he said. “On the back of this, 100GbE network speeds are now considered commonplace, with greater interface speeds just around the corner. As an industry, we are now in a position to leverage this fast pace of development and use it to our advantage in order to achieve significant advantages in terms of space, power, cabling and operational efficiency. With IP solutions, we also have the option to build the level of redundancy needed for any situation.”

Traditional routing switchers—both SDI and analog—have gotten more compact and affordable over the past two decades. As routing technology became mainstream in the past 30 years, reliability and performance have gone way up as well. If traditional routers had remained as large, complex and expensive as they were 30 years ago, there would be no contest—we would all be screaming for the relatively low-cost and flexible distribution provided by IP networks.

However, SDI routers got better in every regard in the past couple of decades, and that keeps them in the game today. Still, the days of traditional routers may be numbered.

“Over time, as more devices natively speak IP, the ability to connect them via IP will push IP technology into smaller systems and smaller deployments,” Mail-hut said. “And moving to UHD makes everything harder by a factor of four with SDI, so UHD also is a big driver of the need for scale and the movement to IP.”

Top photo: Jamie Oakford mans an Arena Television OB truck wired for IP distribution, with technology provided by Grass Valley.

Bob Kovacs

Bob Kovacs is the former Technology Editor for TV Tech and editor of Government Video. He is a long-time video engineer and writer, who now works as a video producer for a government agency. In 2020, Kovacs won several awards as the editor and co-producer of the short film "Rendezvous."