Happy Birthday to ST 2110!
The switch from analog technologies to digital often ends up meaning that you are now dealing with ‘simply bits’ which quickly end up being moved around standard ethernet networks. However, in audio and video, time is of paramount importance and ethernet was not built around the idea that timing was critical. In the professional broadcast space, rather than jumping straight from analog to networking, there has been another phase, that of Serial Digital Interface (SDI) technology.
SDI Appears
In the early days of digital processing of video data, networking protocols simply could not cope with the high level of bandwidth needed for digital transmission of uncompressed high quality video. For this reason, in 1989 SMPTE introduced the 259M standard which was aimed at standard definition applications with 10 bit color support and operating at up to 360 Mbps (for 960 x 486 60i signals – and contrasting with a typical network at that time of 10Mbps). The signal was to be transmitted over a coax cable with BNC connectors and the interface was optimized for low latency, a critical feature in live broadcasting. SDI uses a point-to-point topology although switchers and other devices can be used for routing.
In 1998, SMPTE published the SMPTE 372M standard that upgraded the interface to just under 3Gbps using two cables and this was superseded by 3G-SDI (SMPTE 424M) which allowed a single cable to be used for that bit rate and supporting 1080P60 video. 3G-SDI has been very, very widely adopted and there are is a huge range of cameras, routers, switches and monitors that support that standard.
Moving to Higher Speeds
In the early days of 4K broadcasting, four 3G-SDI connections were used to connect systems as the four 1080P signals were the equivalent of a single 4K image (as 16 would be for 8K).
To meet the demand for higher resolutions, in 2015 6G-SDI and 12G-SDI were introduced. 6G supports up to 2160P30 while 12G goes up to 2160P60, making 4K UltraHD possible with a single cable. A survey from the IABM in 2024 found only around 7% of broadcasters that were intending to support UltraHD were planning to use 12G-SDI and there was little to no adoption planned of quad 3G-SDI and 6G-SDI. The market effectively jumped from 3G-SDI to 12G-SDI.
Meanwhile in the Network Ecosystem….
While SDI was mainly confined to broadcast applications, the world of ethernet networks was developing very fast and with the advantage of massive scale. The idea of using off-the-shelf networking components was very attractive, so SMPTE developed the ST 2110 suite of standards that allowed the transmission of high quality video over standard network components. The standard was published just 10 years ago in November 2015.
As well as being able to exploit the cost benefits of networking components, moving video onto networks with switching and routing options also means that it becomes possible for many more people in a broadcast environment to get access to the content. The author has spoken to broadcasters who have highlighted the huge cultural change in broadcast environments when executives can see broadcast content and that quality at their desks.
The standard allows uncompressed (ST 2110-20) or compressed video (ST 2110-22) to be used and the most popular codec for compressed video over ST 2110 is JPEG XS which was designed at the same time as ST 2110 to be visually lossless and very low latency. JPEG XS also maintains its quality over at least 10 encoding-decoding cycles, a key feature in a studio environment.
ST.2110 is Intended to be Flexible
Unlike SDI, ST 2110 is intended to be very flexible, so any video format is supported and the limit is just the bandwidth of the system at the chosen compression ratio. That it is stark contrast to SDI where formats are strictly defined. Whereas 8K video needs four 12G-SDI cables, ST 2110 can carry 8K over a single ethernet (or optical) cable of sufficient bandwidth.
The idea of ST 2110 is attractive, but the pace of adoption has really been impacted by the cost of changing the equipment. The new standard makes a lot of sense if you are building a new facility but its not always worthwhile to change or update existing studios. Given the pressure on broadcasters recently, it’s not hard to understand a reluctance to make an investment in new infrastructure. Meanwhile, equipment makers have been adding standard support for ST 2110 into their devices. At recent IBC and NAB shows, a very common refrain from exhibitors is ‘and we’ve now added ST 2110 support’.
The value of ST 2110 was recognized just a few weeks ago when SMPTE, the EBU and the VSF were jointly awarded a technical Emmy for Outstanding Achievement in Engineering, Science & Technology for the work they did in developing the standard. The award was given by the Television Academy.
There Are Alternatives
ST.2110 is not the only game in town when it comes to digital video distribution systems. There is a variation on the ST.2110 theme that is called IPMX and is aimed at ProAV installations, avoiding some of the more expensive components of ST.2110. There’s an interesting short comparison of the two here.
There are also proprietary systems, often developed before ST.2110 was created, such as Sony NMI, Grass Valley DirectIP and Evertz ASPEN. They typically have been developed to interoperate with ST.2110.
NDI was developed by NewTek and has three flavors, and Audinate has adopted its Dante audio networking technology to include video as Dante AV. NDI is particularly used in applications such as education, security and in cloud-based systems. It is also used by broadcasters outside the studio environment. Wikipedia has a great comparison table of different IP-based protocols for video production.
Just as we were finalizing this article, we heard of a new partnership between Matrox Video and tvONE combining the tvONE processors with Matrox converters to allow integration and connectivity with ST.2110 and IPMX.
