The 4K Revolution
When the Federal Communications Commission approved the ATSC digital broadcast standard in December 1996, most consumers shrugged as the pundits (us at Home Theater included) heralded the greatest advance in television since the introduction of color in the 1950s. Time has proven us right. With six times the detail of standard-definition video, HDTV has been both a revelation and a revolution. For those who care about picture quality, one quick look was enough to know the world had changed, and we were never going back.
The birth of HDTV forever altered home theater, too, especially the viewing of movies on a big screen. Cineasts with fat wallets and great determination had earlier discovered the wonders of blowing up 480-line images from Laserdiscs using bulky CRT-based front projectors, but to what effect? Even the best line doublers of the day couldn’t fully hide the softness and scan lines. But with HD came a startling and indeed film-like movie experience. And it only got better (or at least more affordable) with the growth of digital projection. When we finally got a highdefinition disc format in Blu-ray, we knew we had reached the pinnacle.
Or had we? What went unnoticed about the rollout of digital video in the home is that it set the stage for a digital revolution in the movie world, one that promised to replace a 100-year-old chemical-based medium—film—with giant data files. The benefits of digital cinema, both for image capture and exhibition, have been written about extensively and are covered briefly in our accompanying article “Hollywood, the 4K Way” on page 34. What’s important is that, in the years since HDTV took us by storm at home, digital has marched slowly into Hollywood, following a grand master plan that let it unfold itself with ever-improving image quality. The current digital cinema standard-bearer is a format called 4K that delivers more than four times the detail of an HDTV image for any given screen size. Today, 4K is making its first push into the consumer video market. Whether its impact at home will rival what it has already done and threatens to do in the film industry remains to be seen. What is clear, however, is that its arrival at our doorsteps is historical and promises a new, even more immersive home theater experience.
What Is 4K?
Digital cinema first came into the broad public eye in early 1999 as a high-profile experiment of George Lucas, who was fascinated by how the technology might improve both the filmmaking and moviegoing experience. Just as he had championed cinema sound through his THX program, Lucas became enamored of the idea that moviegoers would see a less adulterated and more faithful rendition of his final product if he could capture and display it digitally. To that end, he worked with Sony and Panavision on parameters for their first 1080p/24-frame-per-second digital camera and shot portions of Star Wars: Episode I—The Phantom Menace in digital. More critically, he took a high-definition digital master of the final film and did a limited run using prototype digital cinema projectors at four theaters—two in New York and two in Los Angeles. One theater in each market used a Texas Instruments DLP model, the other a JVC Image Light Amplifier (ILA) projector with high-def CRT tubes as the imaging devices. I saw both projections and was impressed each time by how difficult it was to distinguish the result from film. Indeed, when I saw the movie again a few days later, projected from a worn, dirty film print, it was easy to see where the digital projections excelled. They had their subtle flaws, no doubt. But none of the people who paid full ticket price to see the movie digitally asked for their money back.
Following this successful proof of concept, seven major movie studios banded together in 2002 to form Digital Cinema Initiative (DCI), LLC, whose purpose was to map out Hollywood’s digital future for movie distribution and exhibition. The need to establish common standards for image formats, projection equipment, and digital encryption technology was obvious if the film industry could ever hope to eliminate the vast costs associated with manufacturing and shipping film prints. The initial DCI specification, released in 2005, dictated a primary minimum resolution of 2K, where the K represents the binary version of a thousand pixels, or 1024. The 2K format calls for a 2048-horizontal x 1080vertical pixel grid, just slightly more than the 1920 x 1080 full HDTV standard.
But in the course of those early discussions at DCI, much attention was being paid to how movie theaters were evolving. According to Chris Cookson, president of Sony Pictures Technologies and an early supporter of a higher-resolution 4K format, stadium seating had already started to take hold in some high-end multiplex venues, suggesting that the rectangular movie palaces built in decades past were giving way to squarer, boxier auditoriums. Smaller screens that used to be on the short wall of a deep, sloping theater were becoming larger screens situated on the long wall, and moviegoers were being pushed much closer to the screen as exhibitors sought to create a dramatically more engaging experience than close-distance HDTV viewing at home could provide.
The precise acuity of human eyes seeing with 20/20 vision is an established scientific fact based on our common physiology. So theater designers have always known how distance from the screen affects our ability to resolve detail. This can be expressed as a function of screen height, commonly called picture height. And from this relationship, Cookson and others inside DCI surmised that 2K, which was already establishing itself as a de facto standard for digital cinema, wasn’t going to cut it for the long term in these newer theaters. They advocated another option for the future, one that amounted to a full doubling of pixels in both the horizontal and vertical planes to bring the grid to 4096 x 2160. That’s 4K.
“If you pace off a modern theater, you find that the sweet spot where most of the paying customers sit first is between one-and-a-half and two screen heights back from the screen, and the back wall will typically be about three screen heights,” Cookson explains. “At one-and-a-half screen heights away from the picture, when the picture has 2000 pixels in height, it turns out, the smallest thing you can see is one of those pixels. If you have 20/20 vision and the ability to see that level of detail, the structure of a 2K picture is actually too coarse to really get the best experience out of it. So when we were doing the DCI specification and looked at what modern theaters had evolved into, we really saw 4K as being the optimal resolution.”
4K Comes Home
A 4K resolution image presents 8.8 million pixels on the screen versus the 2.2 million attributable to 2K or the 2,073,600 pixels in a 1080p HDTV image. That’s more than a quadrupling of picture detail over what you’re watching now. As some of us at Home Theater discovered recently on a visit to Sony Pictures’ Colorworks post-production facility, the benefits of native 4K content projected with a native 4K projector are immediately obvious on a 20-foot or larger screen. But do you really want 4K on a smaller screen at home?
Cookson argues that you will, suggesting that the television experience has always taken its lead from your local cinema. At the advent of TV broadcasting, theaters were projecting black-and-white images on a 4:3 aspect ratio screen, so television followed suit. Movies, and therefore the theaters, added color, so TV added color. The same pattern was followed with surround sound and eventually widescreen.
“Now the theaters have moved the image closer and made the screen bigger,” Cookson says, “so that raises the question of whether we want the home entertainment experience to create an image that has the same relationship to your eye. It’s not that you’ll have a 40-foot screen in your house. But if you have a 10foot screen and sit one-and-a-half screen heights back to have the same kind of viewing experience you have in the theater, you’ll want the same 4K image the theater needs to make the best use of that relationship between the viewer’s eyeball and the screen.”
Joel Silver, president and founder of the Imaging Science Foundation (ISF), agrees that the advance to 4K in the home is “the natural evolution of the business. It’s inevitable. We’ve been going that way since we started with John Logie Baird’s 28-line system in the 1930s.” But Silver is guardedly skeptical about what 4K might bring in its earliest incarnations. The added resolution, he says, “will be a godsend” for viewers who sit close to their projection screens and now see pixel structure and stairstepping on their 1080p systems. But in the absence of native 4K content to play on these projectors, Silver worries about the potentially degrading effects of upscaling 1080p content to fill out a 4K screen.
Although scaling techniques have improved through the years, the algorithms used to add extra pixels to each frame can and do often run into difficulties on challenging content, such as angles, circles, motion, etc. This can result in noticeable artifacts or subtle softness that may be introduced to help hide them.
“The only good upscaling is no upscaling,” he says bluntly. “There is upscaling that is dramatically less bad, but any scaling, no matter what the quality is, will lose to no scaling. The beauty of the era we’re in right now is that I take home my Blu-ray Disc that has 1080p content on it, I plug it into my 1080p display, and the pixels talk directly to each other on a one-to-one, dot-to-dot basis. The only time you won’t have compromises is when your bitmap of the hardware matches that of the software. The ultimate benefit of 4K will come with 4K content.”
Gary Klasmeier, project engineer manager for D-ILA Systems at JVC Professional Division, also sees the potential for introducing problems in the upconversion to native 4K. But he suggests there’s a much lesser likelihood of that if the scaling from full HD is done to the 3840 x 2160 Quad HD version of 4K—essentially a perfect quadrupling of full HD—rather than to the full DCI 4K spec of 4096 lines. “If you’re working from a 1920 x 1080 signal, it probably makes sense to scale it only up to 3840 x 2160,” he observes. “Otherwise, you’re going to get some really crazy math and roundoff just to fill that difference between 3840 and 4096. You could end up with some scaling artifacts that are pretty ugly.”
For his part, Cookson acknowledges that “there are cheap and easy ways to upscale pictures that don’t work particularly well.” Doing it right, he says, “takes a detailed understanding of image structures and image science. Some of the software systems I’ve seen are extremely exciting because of the way they approach it and the intelligence they use in creating an image analysis that yields something that blends well and enhances the apparent resolution. And then there are others that just look god awful.” Sony’s goal, he adds, is to make the good technology available in a way that allows cost-effective integration in a consumer projector like the new 4K VPL-VW1000ES.
Meanwhile, at least one other forward-thinking manufacturer is paying attention to these challenges. Onkyo has introduced 4K upscaling in several audio components. Six Onkyo AVRs—starting with the affordable TX-NR609 at $600 list—offer the respected Marvell Qdeo video processor for 4K upscaling, while five A/V receivers in the custom-oriented Integra brand (beginning with the DTR-50.3) and the DHC-80.3 surround processor (reviewed on page 68) boast this feature.
Why include this now when there are virtually no 4K displays available? “They’re on the horizon,” explains Onkyo national marketing and product planning manager Paul Wasek. “Onkyo has always been an early adopter of technology, so this is just another example of that. We think the Qdeo chipset is one of the finest in the world for 4K scaling, so incorporating it provides the consumer with the ability to send a quality signal directly to the display without having to rely on the display to do that.”