12 Gb SDI Cost, Cables and Capabilities

How it stacks up against GbE standards
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LOS ANGELES—As a follow-up to last month’s double dose of SDI vs. IP (and all the follow-up comments; thank you kind readers), I thought I’d focus a bit more on the future of live video signal distribution.

In my last post, I stuck to currently deployed technologies, 3G SDI and 10 Gb Ethernet. I compared and contrasted the use of these transmission and distribution technologies for live video and audio production. The key take away was that while it is possible to use 10 Gb IP for live video, the design of such IP gear and systems is not as straightforward as designing a facility with SDI. SDI being the older, more mature technology, has the advantage of simplicity and ease of use, including test and debugging, although restricted to just carriage of serial digital video with embedded audio.

Last month, my belief was that 12 Gb SDI (SMPTE 2082) was still nascent in the market. Surely, I thought with 10 Gb Ethernet now and 25 Gb standards to be delivered in 2016, the future may well be an all-IP world. At the SMPTE Annual Technical Conference in late October, I walked around the exhibits and found 12 Gb SDI product on the stands, working and very much available. Talking to the primary suppliers of SDI chip sets, Semtech (Gennum) and Macom, I learned that they are sourcing the critical chipsets for SMPTE ST 2082—which became a standard earlier this year—and have been working with their customers to integrate into the products, both at the SMPTE show as well as products to come on the market in the next year.

So let’s look at what 12 Gb SDI can do today. 12 Gb SDI uses regular 75 ohm coax cable—e.g., Belden 1694—and fiber. Distance on coax is the usual 100 meters or about 300 feet, while single-mode optical fiber is rated in kilometers. Further, ST 2082 is flexible in how it can be used, given that it multiplexes eight 1.5 Gbps SDI links across the coax. Thus any signal in the SDI hierarchy is supported, including 270 Mbps, 1.5, 6, and 12 Gbps. Keep in mind that 12Gbps supports video signals up to UHD-1 (2160x3840, 10-bit, 4:2:2) at 60 fps.

I asked both Semetch and Macom about the cost of 12 Gb SDI versus 3G SDI. The chipset cost is 1.5 to two times the cost of 3Gbps chips, partly due to low volume but also because the 12 Gb chipset combines both the receive and equalization modules. I inquired about system costs for 12 Gb SDI products from vendors such as Ross and Black Magic Design. They reported that while the cost is higher for 12 Gb SDI because of the increase of internal bandwidths and processing, greater functionality is available for multiviewers, MADI audio routing, audio embedding/de-embedding, as well as grouping of multiple SDIs into one 12 Gb SDI output. The resulting total cost of 12 Gb products compared to standard 1.5 Gb/3Gb products using outboard gear to accomplish these functions is the same or less.

Oh, and if you need a SMPTE ST 2022 IP connection, sure enough, there are SFP ports that can convert from SDI to IP.

Where’s 25 Gb Ethernet? Still in committee; standardization early to mid-2016. The physical layer consists of twin-axial cables with two lengths: 3 and 5 meters or 100 meters on multimode fiber-optic. The target design is for data center intra- and inter-rack wiring to reduce the number of top-of-the-rack switches. Cost to be determined.

So to summarize, 12 Gb SDI is ready today, costs in line with other SDI solutions, can carry multiple SDI signals, as well as support UHDTV 1 signals (up to 60 fps); 25 Gb Ethernet—to be determined.

Oh, one thing you can’t do with 12 Gb SDI is update your Facebook, Tweet or post a selfie on Instagram.