What is 12G-SDI? A guide to the standard

While the serial digital interface (SDI) has been the professional standard for AV interfaces since the 90s, with 4K and UHD becoming much more prevalent video formats for broadcasters (and requiring a massive four times the bandwidth of HD), moving it around isn't as simple as pushing it through your beloved SDI cables. Step in 12G-SDI... 

What is 12G?

12G is an SDI standard developed to support greater resolution, frame rates and colour fidelity. It provides four times the bandwidth of HD, carrying 12Gbps, making it ideal for the 4Kp60 format. It's not new as such, with 6G/12G being in development since 2012 for UHD, but has not yet been ratified by the SMPTE (Society of Motion Picture and Television Engineers), the governing body of standards, with the draft name of SMPTE ST-2082.

For a bit of historical perspective, the original SDI standard 259M (introduced way back in 1989) could carry about 270Mbps of data. As broadcasters transitioned from 480i to 480p to 720p to 1080i to 1080P, and from copper to fibre, the SDI specification was updated, with 292 (for 1080i) carrying about 1.5Gbps and 424 upped this to about 3Gbps (for 1080p).

Who's using it?

12G is available to any manufacturer but not many have stepped in yet to support the unratified SMTPE standard in their products. One manufacturer who has done so is Blackmagic Design. Their DeckLink 4K range of capture and playback cards all support 12G, as well as their Teranex Mini and Teranex Express (the world's first broadcast convertor to include multi-rate 12G SDI connections).

Simon Westland, director of sales, Blackmagic Design EMEA, said that as a manufacturer they've always championed the use of common, open standards and non-proprietary connectivity and codecs. "What a customer wants to do is plug anything into anything and for it to work," he said. "Fast action production has required the use of high frame rates for many years now, but while HD formats up to 1080p60 are very common, a lack of support for the same high frame rates in Ultra HD has hampered adoption of the format.

"With that in mind, we have been through nearly every aspect of our product range and added 12G-SDI, which supports single cable connectivity for the 2160p60 format. Customers can instantly see the benefits of not only the higher frame rates that 12G-SDI can offer in Ultra HD production, but also the simplicity that single cable connectivity offers. So while other technologies might be able to offer the necessary bandwidth, they will add unnecessary weight and cost, and will increase the overall risk of image degradation and signal dropout."

Within broadcast and production, facilities are still built on 3G SDI standards, as 6G and 12G will not work over long distances and not many 'end points' have 6G or 12G inputs yet. We'll probably see more 12G-enabled products at the next NAB show, but the more interesting development will be 12G over fibre, as this gives both the distance and the bandwidth to provide 4K and UHD signals around facilities.

Want to know more about 12G and Blackmagic Design video products? Give us a call on 03332 409 306 or email broadcast@Jigsaw24.com. For all the latest news, follow @Jigsaw24Video on Twitter or 'Like' us on Facebook.