Taking legacy content into the 4K world

Josef Marc

Author: Josef Marc

Published 1st January 2014

by Josef Marc
Issue 84 - December 2013 There are 780,000 UHDTVs already manufactured and poised to hit the marketplace, and the effects of those devices (and the factories that continue to make them) are unstoppable. UHDTV and 4K will be everywhere, sponsored by UHDTV manufacturers and content owners. 4K tablets are shipping as well. As the drumbeat for 4K grows ever louder and consumers embrace the trend, 4K content distribution will become the norm, and broadcast engineers will be called upon to convert all manner of existing content to the new format. There are some critical things broadcast engineers should know as they prepare that legacy content for the next generation of consumer devices.
First of all, why is 4K so important, and why now? Whats the urgency?
With last years explosion of mobile viewing, the introduction of 1920 x 1080 resolution tablets and hand-held devices, and this years shipments of hundreds of thousands of UHDTVs, were going to see a transformation in what people demand from video archives.
In order to contribute to the 4K experience, content distributors will need to pull a lot of content from their archives, and that content will need to be processed to look good in 4K according to a slough of new standards and methods, many of which are still evolving. So radical is the difference with 4K that the NHK, EBU, and other standards bodies around the world asked SMPTE to review all the standards that we have been using in television and revise them for 4K. For example, theres a new color-space standard called ITU-R BT.2020, which is much more appropriate for 4K than existing standards, and standards bodies are working hard to achieve it in time for the Winter games in Sochi, Russia, and the FIFA World Cup in Brazil.
Even some companies that rely on more traditional means of delivery, such as Digital Cinema and HDTV, have been asking for 4K standards. Those companies dont deliver in 4K right now, but they still benefit from 4K production because it simply makes their content look better. The directors artistic intent (or in the case of sports, the detail in the live action) comes across better if the content is produced in 4K, even if someone is only watching in HDTV or Digital Cinema.
Whats the urgency? By virtue of creating the aforementioned 780,000 UHDTVs, we have already committed to broadcasting in 4K. Those TVs wont be fed by over-the-air broadcast for a few years, but they will be fed in 2014 by satellite, over-the-top services, and Blu-ray H.265. People are buying the TVs and will expect to be able to watch those rapidly approaching world sports events in 4K, so we have to deliver.
Is all 4K the same? In a word, no.
There are already two common screen resolutions that are very close to each other. To the naked eye, they look the same, but to an engineer, they are very different. One has slightly fewer than 4,000 pixels across, and one has slightly more. Both are the same height, and both are called 4K. For an engineer, UHD-1 refers to the 4K technology that is already available, and UHD-2 refers to 8K technology, which is still under development.
Another wild card is the frame rate, which can range from 24 fps up to 300 fps. There are also two color spaces in the current 4K ecosystem BT Rec. 709 and BT Rec. 2020.
To make matters even more complicated, content shot with the popular RED 5K camera adds another variable to the mix. Producers often shoot in 5K for content that will be played on large outdoor screens, such as on the side of a building at an outdoor venue like the World Cup. Its not uncommon, though, for that same outdoor video to be played on smaller indoor screens as well, so people often mix output from the RED camera into their 4K workflow, making the work even more challenging for the engineer.
Given all those variables, its easy to see why all 4K is not the same. A director might say he or she wants something in 4K, but there are endless combinations of variables that could go into it. Its up to the engineer to figure out what the artistic intent is, and whats going to look best for the given production. So whats an engineer to do? What should an engineer look for?
The cats out of the bag forever. Motion pictures and TV will never again be as simple as film and HDTV. While all of the standards, methods, and jargon shake out over the next few years, there are some things engineers should keep in mind when starting any new 4K project: Determine the frame rate first because that detail will affect the rest of the infrastructure. There is a five-fold difference between 24 fps and 120 fps, soframe rate has a huge impact on everything else.
Be clear of the specifi c expectations at the outset. Which of the 4Ks does the director want? The one thats under or the one thats over? Or do they really mean 5K?
Know which standards are at play. Even though the fi le or signal you receive is following standards, the question is, which standards is it following? Because no combination of standards, frame rates, color spaces, and audio maps is set in stone, you can expect a lot of trial and error, and some combinations simply wont work. So ask people which standards they are using, and be specifi c. They might say UHDTV, but that could mean UHD-1/Rec. 709 color/5.1 audio at 50 fps, or another of an endless combination of specs.
Even after clarifying standards and expectations, what other engineering challenges are in store?
There are a few.
The fi rst has to do with the color spaces. Right now you have to convert the color among Rec. 709, BT.2020, and XYZ (which is not a standard but is part of the mix). While they are expected to improve, at this point color volume conversions only proceed with 16 percent accuracy. That inaccuracy is a problem because it interferes with the artistic intent of the material and can result in lost detail, such as the variations in color that allow you to see the textural difference between a piece of burlap and a piece of cardboard.
Second, the displays themselves whether a TV, a computer screen, or a projector aimed at the side of a building must be told whats coming at them so that they know what to do with the information, and that happens via metadata. Were still experimenting with which metadata schemas work best with which screens. Not only that, but screens that play 4K video are just now being invented, so its an ongoing process.
Finally, there are economics to consider. For one thing, there is the cost of displays. Before 4K, much of an engineers work could be done using an affordable HDTV available at any appliance store, but with 4K and all of its variables, sometimes a more sophisticated display is required. A high-quality 4K display can cost as much as an expensive car. In many cases, the less expensive display would suffi ce, but how do you know which one to use when?
What can we expect in the near future?
Given the evolving nature of the medium, there will be a lot of experimentation in the next couple of years. Well see continued experimentation with frame rates and other variables from major broadcasters such as Sky in the UK and NHK in Japan, from display manufacturers, camera makers everyone up and down the chain. In the near future well also see the results of some experiments, such as the Sochi games and updates to the SMPTE standards, which should help us move closer to establishing best practices for 4K.
Engineers can also look forward to the end of interlacing, which is a very good thing because interlacing complicates everything, especially the second/multiscreen experience.
Finally, theres a trend toward high dynamic range (HDR), which means consumers will be able to make adjustments to their displays within much broader limits. To put it in context, since the 1930s, dynamic range (measured in nits) has been limited to 100 nits, but now we can expect it to go up to as much as 100,000 nits in some applications. Todays HDTVs already offer a range of nearly 1,000 nits. If HDR goes up on the displays, then it has to go up everywhere else to feed the displays. That means engineers must become familiar with dynamic range and how to accommodate it.
The good news is, my company is working to overcome all the variables and uncertainty in 4K, with affordable workstations equipped with a unique software player and specialized test patterns that make engineering for 4K much less expensive and much more precise. The Archimedia 4K/UHDTV Workstation, for example, is confi gured to be a complete reference system for all master formats, including 4K uncompressed and JPEG 2000, and includes the Archimedia Master Player software, 4K HDMI output, loads of storage, and all the CPU power necessary to play, QC, verify, and manipulate master fi le formats

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