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OPINION – SDI: The known quantity

IP transport infrastructure needs time to mature and overcome broadcast timing requirements and latency expectations, says David Ackroyd, vice president business development, Omnitek

One of the key opportunities for customers in the current market environment is to seize on the standardisation of 4K SDI transport enabling them to develop products that address customer demand for 4K production technology. SDI continues to be the known quantity for 4K systems design and is growing in use, mainly in the production environment. This is supported with the recent introduction of high-speed 6G and 12G-SDI standards.

At the emergence of transformational technologies such as UHD, equipment manufacturers and early broadcast adopters have a need for new test equipment that measures and generates signals to test designs and systems. The major enabling technologies for this transformation are the speed increases of 28nm FPGA and line driver/receiver devices, that allow SDI data rates at 12Gbps.

Omnitek has identified three main requirements for a successful UHD-1 workflow: connectivity, data division and data integrity:

The first of these – how to transfer uncompressed signals from camera, to router, to switcher, to editor, to storage, to transmission — is possible at present over SDI using quad-link 3G, 6G, dual link 6G and single-link 12G-SDI standards. Display connections are also possible via DisplayPort 1.2 and HDMI 1.4 & 2.0. With no clear preferences yet being adopted there is a need for equipment to manage signals from all of these standards.

To maintain compatibility with legacy SDI infrastructure, 4K material can be transported using either ‘2-Sample Interleave’ or ‘Square Division’ formats (the former being officially adopted as an SMPTE standard) which need to be automatically handled by products and systems. Each has its merits and the combination of these data-packing formats in systems, alongside the single and multi-link transport standards make it necessary to check and test the formats throughout the signal chain. So we can see how important it is for equipment to be able to handle both SQ and 2SI formats.

Thirdly, when designers are dealing with new high-speed SDI standards eg. 12Gbps, the issue of signal integrity presents itself. On a given system, SDI waveform timebase jitter needs to be four times lower at 12Gbps than 3Gbps when measured in picoseconds. This presents a considerable challenge for receiver chips to be able to lock to a signal and for transmitter chips to generate low-Jitter output.The challenge in overcoming this issue is to understand where output jitter sources lie and to be vigilant in removing them.

Omnitek’s deep experience in these engineering issues led to the design of the Ultra 4K Tool Box which provides an SD-SDI up to 12G-SDI toolset to help with these challenges and offer a rapid development route for broadcast engineers and systems integrators to build, test and commission UHD and 4K systems.

At IBC, Omnitek is seeing an increasing number of manufacturers announcing 4K SDI products and therefore an increase in demand for our high speed test equipment both from manufacturers and system designers as well as a clearer indication of the direction customers are moving with regard to SDI vs. IP debate through the maturity of related products and infrastructure. This gives us a reference point for what’s real and what’s virtual.