If SDI is to be replaced with a network-based mode of transport, broadcasters and television producers are going to need a way of perfecting timing and syncronisation that matches genlock, and that means the introduction of a new standard.
Ever since it was standardized in the late 1980s, studios, facilities, OB trucks and many other professional broadcast set-ups have relied on SDI (Serial Digital Interface), the video glue that has held television, especially live television, together.
Using SDI and its familiar coaxial cables with their easy-to-use BNC connectors it has been possible to happily construct a reliable, error-free, plug-and-play, real-time video operation capable of successfully getting a show to air.
But while it still works well, it is not perfect. SDI only allows for one-way, single-purpose and point-to-point infrastructures and is usually expensive, is certainly exclusive (requiring engineers) and has limitations for future developments like high frame rates.
As a result, there are moves that will eventually see SDI and other professional studio interfaces/signals and equipment like AES and MADI, replaced by generic IT technology and packetized networks using Ethernet, IP, etc.
While these networks won’t immediately provide the guaranteed bandwidth or real-time transfer that SDI does they do have the potential to make the design and build of a studio or facility easier, more flexible and more cost-effective.
The various flavours of IP-based network will also have the ability to move content from anywhere to anywhere, across longer distances, and have one connection that can carry multiple audio and video streams, control and metadata. As you will know, if you’ve ever seen the ‘spaghetti’ underneath a TV facility, SDI-based infrastructures requires many cables.
IT-based operations can even be remotely or centrally managed or have additional security provisions put in place. And, let’s be honest, IP touches most equipment these days anyway.
It’s a potential game changer.
Before we start yanking out our coaxial cables, however, certain technical developments are still required to make a network-based broadcast infrastructure work in the way that television requires. One of these is the ability to synchronize video and time. Otherwise it will be impossible to coordinate cameras, routers, displays and lots of other equipment.
Currently the industry uses Genlock signals for switching and mixing and Timecode for, well, timing.
These references are, as the SMPTE puts it ‘ancient technologies’ from a ‘simpler time.’ A mix of analogue and digital, they don’t support high frame rates and they require nailed down architectures.
Therefore, a new standard is required.
The proposed solution to this is the upcoming ST 2059 suite of standards. Based around the IEEE 1588 PTP (Precision Time Protocol) the new benchmarks will allow the TV industry to deliver precision time with sub-nanosecond granularity over an IP network.
Officially named “Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems,” IEE 1588 PTP was originally designed for industrial automation systems. Now it is being adapted for TV too.
It works like this: to synchronize clocks distributed across a network, dedicated hardware is added to Ethernet interface chips in order to make highly accurate data timing measurements. These chips measure the time at which an Ethernet data frame moves from the Media Access Control circuitry to the physical interface on an interface chip that is 1588-compliant.
In turn, these time stamp values then allow software inside the connected devices to determine if there is offset between clocks and if any delay exists between any two interfaces on a network.
Although still in development, the ST 2059 standard will play a key role if the industry moves away from SDI.
But don’t think this is some futuristic ‘Tomorrow’s World’-style fantasy.
This technology is already used by StageBox on the Net Caddie, the camera-mounted device that allows an HD-SDI output to be injected directly into a standard IP network environment, taking with it the (compressed) high-definition video, associated sound channels, talkback, tally lights, timecode and a genlock signal.
Net Caddie is completely synchronized, providing the IP equivalent to a genlocked SDI system, using timing and control based on IEEE 1588 and SMPTE ST 2059.
It is a great example of how technology is already being developed to work across networks, rather than using SDI coaxial cables
It may not yet be quite time to rip up our TV studios and start again, but the day is certainly coming where IP will do more than just provide access to the worldwide web.