Test Gear Meets Challenge of UHD, ATSC 3.0

Wide color gamut and high dynamic range now in the mix
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ALEXANDRIA, VA.—Evolution toward new standards is inevitable, and the pace of change seems to increase even as we watch. As the television industry prepares for next-gen TV, test equipment vendors are working fast to have the necessary gear available to monitor and maintain video quality. Still, there remain many questions about the eventual implementation of an ATSC 3.0 standard, as well as working with 4K, high dynamic range, wide color gamut and other image enhancements.

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Omnitek’s Ultra XR presents measurements based on the original, full 4K/UHD signal without any loss of data. Support for 12-bit 4:4:4 SDI input formats in YCbCr, RGB, and XYZ, wide color gamut RGB [ITU-R BT.2020], high dynamic range inputs [ST2084/PQ] and Hybrid Log Gamma is a necessity, according to Rob Arnold, vice president of worldwide sales for U.K.-based test equipment manufacturer Omnitek.

“To see all the high-frequency detail present in a 4K image, it is essential a ‘true’ 4K UHD analysis solution is used such as Omnitek’s Ultra XR, which presents measurements based on the original, full 4K UHD signal without any loss of data,” Arnold said. “It’s also worth noting that 4K UHD can be delivered over quad 3G-SDI, dual 6G-SDI and 12G-SDI, in square division and two-sample interleave modes, so a solution... should be able to accommodate all these configurations.”

START AT THE BEGINNING
Test and measurement for video includes familiar waveform monitors, vector-scopes and other visual aids such as audio level displays. However, getting the signals correct starts right at the point they enter the plant, and that’s still true with 4K video.

“Two key questions production companies and broadcasters should be asking themselves when moving high-quality video and audio through their facilities [whether it’s a production truck or a bricks and mortar TV station] are: Is the content all synchronized and is it compliant and at the quality level I need it to be?” said Ian Valentine, director of marketing for video products at Tektronix in Beaverton, Ore. “To address this challenge, production and broadcast staff need two types of equipment: a sync pulse generator and waveform monitor or media processor. The former is used to accurately synchronize the facility, the latter provides visualization, QC and measurement capability.

“For 4K specifically, the required bandwidth [12 Gbps] introduces another element to the puzzle,” Valentine added. “There are three ways that this can be done. The first is to take advantage of existing infrastructure and split the signal over four 3G SDI links. The second and rapidly evolving solution for this is the use of an IP physical layer.

“The advantages of this approach are the flexibility of a network architecture as different or higher resolution formats are introduced and the potential cost savings associated with being able to use widely available IT switching technologies,” Valentine continued. “The third technology is 12G-SDI, and it’s seen mainly in the acquisition [component] of the production chain. With many broadcasters opting to use quad 3G links to handle 4K as part of the transition to an IP environment, they need to be able to measure link timing and to check video/audio levels and gamut including ITU-R BT.2020 for extended color gamut on 4K content.”

For typical waveform/vector displays, there are both standalone waveform/vector monitors as well as rasterizers that place the same display onto a large-screen monitor. The former are dedicated devices that do one thing: display video waveforms with maybe a small window for a video confidence monitor. Rasterizers are terrific in rooms where you need to see across the room at a glance what the signals look like, such as production and master control rooms.

Rasterizers came on strong 10 years ago in the test and measurement space but standalone units have plenty of adherents.

“Rasterizers are still very popular,” said Pete Anderson, director of sales for the U.S office of Japan-based Leader Instruments. “More customers are asking about rasterizers than 10 years ago but it all depends on the customer’s needs and preference. We are finding that many customers in Latin America still have a preference for a conventional waveform monitor, while in the U.S. it varies from more rasterizers at times to more conventional waveform monitors at other times.”

For 4K UHD monitoring, the song—or waveform monitor, in this case—remains the same, except for a couple new twists.

“4K video uses the same graticule scales as HD for luminance [waveform] and chrominance [vector] and measurements are still in percentage or digital values,” Anderson said. “What is new are the measurement scales for high dynamic range, which can be in cd/m2 or higher percentage values and CIE chromaticity displays that show if content falls under BT.709 or BT.2020 wide color gamut color space.”

ATSC 3.0 STANDARDIZATION
With a final ATSC 3.0 standard expected later this year, there are two potential streams of 4K UHD video that broadcasters need to accommodate—an uncompressed (or lightly compressed) high-datarate signal inside the plant and a highly compressed feed sent to the exciter for broadcasting. It goes without saying that both these streams have test and measurement requirements.

“While the majority of 4K content is encoded via HEVC, it’s important for broadcasters to be aware that they will likely begin delivering HEVC video over an MPEG-2 transport stream and may have other equipment in the workflow that abides by previous standards,” said Ralph Bachofen, vice president of sales and marketing at Triveni Digital in Princeton Junction, N.J. “Having a transport-stream analysis and troubleshooting tool that supports a broad range of video compression schemes, from HEVC to H.264 and MPEG-2, will streamline this process.”

Once the video has been modulated onto an ATSC 3.0 data stream, there is a need to monitor the video for errors and signal quality. Of course, without a final standard for ATSC 3.0, this part of the test and measurement process is still evolving. That’s not the same as saying there are no choices, however.

“Triveni Digital is one of the few vendors today that offers a solution for detailed analysis of ATSC 3.0 streams and data structures,” Bachofen said. “Using an ATSC 3.0 quality assurance system during the trial phase of the new standard, broadcasters can analyze their services and quickly detect, isolate and resolve issues to launch early deployments and trials of ATSC 3.0.”