Deploying 12G SDI

As new media technologies such as 4K/ultra HD (UHD) are being introduced or planned in Asia, underlying storage infrastructures must effectively scale to keep up with expanding performance requirements. The broadcast and media industries are also under pressure to manage the exponential growth of content, demand for multiplatform content delivery, rigorous global production schedules, and transition to all-IP media operations.

With the emergence of 4K and HDR production, remote production companies and studios have been struggling to make sense of the additional requirements for more cabling and native equipment that supports it. Where the highest quality HD signal uses a single 3 Gbps SDI cable to connect point A to point B – for example, a camera to a production truck – the same workflow in 4K or UHD requires four separate 3 Gbps cables, often referred to as a quad link or four-wire infrastructure.

Looking to reduce weight and system complexity, production companies and master control suites are demanding a single-cable solution, and the industry is responding with a 12 Gbps cable and connections on key pieces of gear to make it a reality. So far, not many customers have implemented true 12 Gbps systems, but a trend is emerging for all obvious reasons.

A single 12 Gbps SDI cable is roughly 30 percent lighter than four 3 Gbps cables, allowing a remote production truck to carry less weight, eliminate dozens of cables, and still produce beautiful 4K or UHD pictures.

With 12G, there is a bandwidth to handle high-resolution requirements like 4K, UHD, high frame rates, and deep color depth, over one 12G-SDI cable. Simplifying everything down to a single cable is a massive time, routing, and resource benefit for these types of productions.

Connecting 4K
Companies that are already providing 10 Gbps fiber and connectors for them, moving up extra 20 percent to 12 Gbps is not that big a deal. There are few 4K cameras that have SMPTE fiber connectors, and that most output via four 3 Gbps SDI cables that are then converted to hybrid fiber. In 4K for SMPTE 304 camera cables, the first change in connector was a design for fiber optics. Equipment makers switched over to single-mode optical fiber, and bandwidth limits went away. They are not worried about 12 Gbps; they can run a tremendous amount of data over a distance of 10–20 km.

In addition to upping the electronic performance of their new cable, manufacturers targeted 8 mm as the maximum diameter for the cable to allow more of it to be wound on a reel. The finished product came in at 7.7 mm, a cable that is more flexible and lighter. In order to avoid confusion over the new 24 Gbps patchbay, several companies modified the color of it. For traditional SDI connectors Neutrik created the UHD BNC connector, which includes improvements that allow signal transmission at 12 Gbps SDI and beyond for 4K or even 8K.

Benefits of a single-cable, native 12 Gbps environment also include less connectivity headaches. 12G switcher or router saves logistical resources all across the workflow. This can also save physical space, taking up a smaller footprint when constructing video infrastructure. Many 4K cameras are now offering at least 6G, and since 12G-SDI can also handle 6G-SDI, a single cable can handle all the way from 1.5G to 12G and everything in-between.

Canare rolled out a 12G coax solution that consists of cables and connectors specifically designed to maximize 4K camera transmission, with superior performance at distances up to 100 m. Canare’s 12G solutions also support 3G and 6G signals.

AJA Video Systems exhibited a new 12GM mini-converter that allows users to convert different SDI sources to and from 12G-SDI. The company also offers the 12GDA, a 1×6
re-clocking distribution amplifier, which distributes a single 12 Gbps source to six different outputs. It also works on 6G, 3G, and 1.5G-SDI signals as well.

Transition to 12 Gbps
Industry experts are not only talking about 12G, but also 24G, 50 Gbps, and 100 Gbps. The latter high-capacity connections could be used for bidirectional signal flow, connecting multiple routers together or for supporting an entire production and playout facility that handles lots of data. Belden recently announced a smaller and lighter 12 Gbps-SDI coaxial cable, which can accommodate to any type of 4K or UHD production environment. The attraction of 12G is that it has less points of failure; some users get a little concerned about the timing and synchronization with a lot of four-wire around a facility. The biggest advantage is that 12G-SDI provides a comfortable interface that people are used to.

Evertz has sold a considerable amount of 12G-SDI equipment to Korean and Japanese broadcasters and production studios preparing for the 2018 Winter Olympics in Seoul, South Korea and the 2020 Summer Olympics in Japan, which will both feature 4K and 8K signal acquisition and distribution.

Distance Limitations
Another factor in the decision to migrate to a 12 Gbps infrastructure is how far the user needs a signal to travel. Broadcast cable and SDI connector suppliers are offering a series of products that support 12 Gbps signal flow. Featuring advanced attenuation characteristics that are optimized for 12 Gbps signal transport, Canare’s L-3.3CUHD cable is rated for up to 60 m (about 200 feet), its L-5.5CUHD up to 100 m (330 feet), and its L-8CUHD up to 140 m. These distances can be extended through the use of fiber-optic transceivers on the back of a camera which convert the SDI signal to light for transport over miles of fiber cable.

The demand for 12G cable is gradually increasing, but customers are still at the inquiry and evaluation stage of upgrading their cabling system from their current
SD/HD/3G applications. Cost is a big issue in deciding when to move to 4K production and distribution.

Production companies should begin their migration plans by implementing 4K SDI islands with products – such as 12G routers– and build from there as the need arises.

No one is going to rip their whole facility out and start new. The first step of any move is to decide between four-wire or native 12G technology; suppliers are making conversion cards to support this move. These up/down/cross converter cards can be used to up convert to either 4-wire 4K or 12G-SDI. Once the 4K signal counts in any facility will increase significantly, then the consideration of moving to an IP-based environment becomes very real. With its packet-based delivery scheme, IP is agnostic to format or signal count. In this case it is all just data. With 12G-SDI you need two cables, one to go in and one out, versus a single IP cable that is bidirectional.

With IP, service providers are not constrained to one cable, one signal. They have lots of flexibility. IP provides a lot more flexibility in infrastructure set up and where resources can be allocated. However, 12G works same as SDI cabling, so there is an argument to be made to stay in the SDI world, at least for the short term. IP will not replace SDI cable soon due to the cost involved in making a totally new investment. Additionally, there is no standardized IP system like SMPTE. Therefore, no one is anxious to make the commitment to move to an IP system.

On the progressive side manufacturers of cameras, video production switchers, servers, and other key pieces of production equipment including fiber-optic transceivers and conversion cards have shown solutions to support all forms of 12 Gbps signal acquisition and delivery.

Way Forward
Broadcast and production equipment manufacturers have a short window to promote and sell 12G technology. Companies are seeing great potential in 12G-SDI, at least in the short term, for mobile production companies looking to shed weight and simplify their onsite production activities. Customers can realistically deploy an end-to-end 12G-SDI workflow today. With many new technologies, the benefits of a 12G-SDI infrastructure are attractive, but cost is the main hurdle that many are not ready to overcome. Also, as signal counts increase, eventually the laws of physics will not be able to keep up with that copper cable and the industry will have to move to IP. For now, 12 Gbps transport over a single cable is a technology in search of a market.