NHK’s Research Labs Serves as Breeding Ground for 8K Innovation

This year, Japanese public broadcaster NHK announced that it will speed development of its 8K Super Hi-Vision, which offers 16 times the resolution of HD, and begin broadcasting tests in 2016 with the goal of starting a commercial terrestrial service as early as 2018 — two years before the Tokyo 2020 Olympics. Although there is still a tremendous amount of development needed to create a full 8K ecosystem, SVG’s visit to NHK’s Science & Technology Research Laboratories (STRL) in Tokyo suggests that the broadcaster may be closer than many industry observers think.

The trio of cameras used for NHK’s 8K productions were supplied by (from left) Ikegami, Hitachi, and ASTRODESIGN, respectively.

NHK’s highest-profile live 8K production to date took place over the summer at the FIFA World Cup in Brazil, following testing and demonstrations at the London 2012 Olympics and this year’s Games in Sochi. Since the World Cup, NHK has also produced a sumo-wrestling event in Tokyo and has plans to further expand its production at the 2016 Olympics in Rio de Janeiro. All this is leading up to the largest sports event to hit Japan in decades, the 2020 Olympics, when NHK believes it will already be transmitting 8K Super Hi-Vision to the home. However, there is still a lot to do — technologically and otherwise — before that becomes a reality.

Inside the CUBE 8K Camera
Although NHK used three 8K Ikegami SHV8000 60-fps cameras (plus two FOR-A FT-ONE 4K cameras for slo-mo replay and one Sony F65 4K camera for features) for its World Cup coverage in Brazil, it aims to build a full 120-fps 8K Super Hi-Vision video-production system to more clearly capture the fast-moving action of sports.

NHK’s Hiroshi Shimamoto at the NHK Science & Technology Research Labs facility

“60 fps is okay for a still image,” says Hiroshi Shimamoto, Ph.D, senior research engineer, Advanced Television Systems Research Division, NHK Labs. “But, when the object is moving fast, there is motion blur, so double the frame rate is ideal for fast-moving [action].”

The broadcaster has worked with ASTRODESIGN to develop the CUBE, a compact 120-fps 8K camera that uses a new 120-fps single-chip CMOS sensor (Shizuoka University is also collaborating on the CMOS-image-sensor research). The CUBE camera, which was tested in Brazil but not used in the actual production, weighs just 2 kg and can easily be used for handheld and robotic positions. When the camera head is connected to a dedicated optical transmission unit, it can be operated using the same hybrid fiber cable as conventional HD cameras. This also allows additional functionality, such as lens control, intercom, return inputs, and tally inputs. NHK says it will continue to research and develop full-spec single-chip cameras with full 8K-pixel count, 120 fps, and a wide color gamut.

A side-by-side comparison of NHK’s 8K World Cup footage illustrates the motion blur at 60 fps compared with 120 fps.

While the cameras continue to improve for 8K production, lensing continues to pose a major challenge for NHK.

“We have measured several kinds of lenses. Some are good and some are not, but the latest cinema lenses are very good,” says Shimamoto. “[Lenses] are the most important thing for us because resolution and frame rate are good, but the problem is sensitivity. The depth of focus is very thin, so the higher sensitivity, the better it is to shoot in 8K.”

Terrestrial 8K Transmission Becoming Reality
NHK has also continued to develop a large-capacity terrestrial transmission technology for 8K broadcasting to the home.

After successfully completing the first-ever terrestrial 8K-transmission test (over a distance of 4.2 km) in May 2012, NHK pushed the boundaries further last February by transmitting an 8K signal over a distance of 27 km  (the same distance that can be achieved by current terrestrial digital broadcasting). In this case, a compressed 8K signal was transmitted on UHF channel 46 (6-MHz bandwidth) at 98.1 Mbps, from an NHK TV relay station in Hitoyoshi City, Kumamoto Prefecture, to a receiving station 27 km away.

To transmit the 4K signal, NHK deployed H.264 compression; ultra-multilevel OFDM (orthogonal frequency division multiplexing), which encodes digital data on multiple carrier frequencies (also used in WiFi); and dual-polarized MIMO (multiple-input, multiple-output) technology, in which multiple antennas are used at the points of transmission and reception to enhance performance.

The transmission/modulation kit used by NHK for its test broadcasts

Ultra–multi-level OFDM technology increases the number of signal points in the modulation of each carrier that constitutes an OFDM signal, greatly expanding transmission capacity. By increasing the number of signal points in the carrier modulation to 4,096, NHK was able to transmit 12 bits of data per carrier symbol. In addition, by simultaneously using horizontally and vertically polarized waves within the same channel to send information, the dual-polarized MIMO technology doubled the transmission capacity.

According to Susumu Saito, of NHK Labs’ Advanced Transmission Systems Research Division, the expected maturation of the H.265/HEVC (High Efficiency Video Coding) compression standard is likely to simplify this extremely complicated transmission scheme in the future. NHK continues to develop HEVC encoding and decoding tools and demonstrated 8K video at 120 fps using HEVC compression at IBC2014 in Amsterdam in September.

22.2 Multichannel Surround Sound Rocks the House
Although crisp resolution of 8K video is plenty appetizing to the eye, it’s the audio side that may be the most impressive aspect of Super Hi-Vision. NHK’s 22.2-multichannel 3D surround-sound system truly puts the viewer in the front row of a stadium, concert hall, or parade like nothing else. NHK’s theater located at STRL features a 300-in. 8K screen and 22.2-channel system. The system features nine speakers across the top layer, 10 speakers in the middle layer, and three speakers on the bottom layer, along with two LFEs (low frequency effects).

Although the sound system is truly an experience, NHK is currently researching and developing alternative ways for people to experience the 22.2-channel system in limited audio environments, including those with fewer speakers, displays with built-in speakers, and headphones.