NHK bets on Super Hi-Vision as future TV

The people at the Japan Broadcasting Corp. (NHK) see their 8K x 4K ultrahigh-resolution broadcasting, which they have labeled Super Hi-Vision, as the next generation of consumer TV. Now they have taken a step toward realizing that vision by demonstrating working prototypes of key component systems.

But don't start saving up for a new set yet. It might be a few decades, give or take several years, before the technology makes it to market. And the breakneck pace at which communications, broadcasting and information technologies are transforming themselves leaves a question hanging over the whole enterprise: Twenty or more years from now, will consumers want it?

Still, the specs are impressive. Super Hi-Vision's resolution is 7,680 x 4,320pixels—16 times that of today's 1,920 x 1,080pixel HDTV. NHK, Japan's public broadcaster, has demonstrated it at several venues over the past two years using large screens—on the order of 450- and 600-inch diagonal.

"We've been demonstrating Super Hi-Vision on large screens to show its high image quality, so people might have thought that the system is to be used at a big public event only. No, it isn't," said Kenkichi Tanioka, director general of NHK Science and Technical Research Laboratories. "NHK is a TV broadcaster. Our real challenge is how to deliver this wonderful quality content to each and every home."

Based on their experience with HDTV, NHK officials said it takes about 30 years for a broadcasting system to be developed and accepted. NHK began working on HDTV in 1969, and it was the first to start HDTV broadcasting in 1989—in analog. It took 31 years, until 2000, for NHK to start satellite digital HDTV broadcasting in Japan. Terrestrial digital TV broadcasting, in collaboration with some private TV stations, followed in 2003. And by last December, coverage of the terrestrial digital HDTV service had spread to all corners of Japan.

Based on that 30-year-cycle theory, since NHK started working on Super Hi-Vision in 1995, the technology should be ready around 2025.

"We believe that Super Hi-Vision is the ultimate 2D broadcasting system. But it is not our final target. What comes next will probably be 3-D TV broadcasting. We want to realize natural, eye-friendly 3D after we realize Super Hi-Vision broadcasting," said Tanioka.

NHK's R&D plan is based on the strong faith in broadcasting. Even two decades ahead. "We believe that TV broadcasting will continue serving," said Hideki Suganami, director of planning and general affairs of the labs. "Quality and reliability are always required for broadcasting, especially for a public broadcaster, and we've been satisfying the requirement. We don't expect that something else can easily replace broadcasting."

A closer look
Super Hi-Vision delivers 8K x 4K images at a 16:9 aspect ratio, scanned 60fps in progressive mode with 22.2 multichannel sound. The transmission method has not been nailed down yet. It is designed to give the viewer a strong sensation of reality. So to give the viewer the sensation of being engulfed in images on a display, the desirable horizontal viewing angle was set at 100°. This means that with the standard recommended viewing distance 0.75 times the display height, NHK calculates that the standard size for a Super Hi-Vision display in the home would be 100 inches. Therefore, the viewer would have to be about 1m from the display.

Under those conditions, 8K x 4K was the resolution at which the viewer would not see individual pixels. "The specifications were defined as the ultimate resolution from the viewpoint of the human factor. And the number of pixels is the integral multiplication of the present HD specification, four times both horizontally and vertically. This makes format conversion, maintaining backward compatibility, and building hardware easy," said Suganami.

To give viewers the 'ultimate' sensation of reality, Super Hi-Vision was designed to have a 100° viewing angle.

Showing off
To display the potential of the technology, the NHK lab demonstrated at its open house in May the core technologies required to broadcast Super Hi-Vision TV programs from input (a camera and an image sensor), data processing (H.264 encoder and decoder system), transmission (simulated 21GHz satellite-relayed transmission) and output (display technology and a projector system).

Input—A 33Mpixel image sensor to take full 8K x 4K-resolution images was jointly developed with a U.S. venture company, which is apparently affiliated with the former Photobit Corp. This year's prototype captures only monochrome video images. Next, researchers plan to set a prism on the sensor to capture images in red, green and blue to build a color camera using the three imagers.

Compression/decompression—With Fujitsu Laboratories Ltd, NHK developed MPEG-4 AVC/H.264-based real-time encoding and decoding prototype systems. The encoder and the decoder have 16 processing units each. For quick algorithm alternation, an FPGA is used for the processing unit.

The original 24Gbps Super Hi-Vision signal is divided into 16 streams at the parallelization unit in the encoder and passed to each of 16 coding units. The signal is compressed 1/200, to 128Mbps, in real-time; then it can be handled in a broadcasting system.

In actual broadcasting, the signal would be transmitted to a satellite and sent back to the decoding system at home. In the demonstration, the signal was sent to a simulated satellite system and sent to the prototype decoder system, which has the mirror structure with 16 processing units. The 16 streams decoded at 16 processing units are then restored to one Super Hi-Vision signal.

Transmission—NHK intends to use a 21GHz-band satellite transmission path to deliver programs to homes. The 21GHz band is allocated for broadcasting and reserved for future use. NHK researchers prepared prototype units for the simulated satellite transmission. The wideband modulator prototype can handle multiple Super Hi-Vision channels. It can transmit a 500Mbps signal in 300MHz bandwidth in the 21.85GHz band to a satellite. A prototype traveling wave tube, which is mounted on a satellite, amplifies the signal and sends it back via a satellite-mounted antenna. The signal is received in the home via an approximately two-foot parabolic antenna; then it is demodulated at the wideband demodulator. Quadrature phase shift keying was used for the modulation. "The signal is actually transmitted and received through a simulated satellite path, but there is no home-use upper Hi-Vision display yet," said a spokesman.

To experiment with the transmission via an actual satellite, NHK and the National Institute of Information and Communications Technology will use the WINDS satellite, a satellite for superhigh-speed data transmission, expected to be launched by March.

NHK intends to use the 21GHz band for the satellite broadcasting system at introduction. That band is allocated for broadcasting but is not yet used.

Display—Home displays, even experimental ones, that can deliver 8K x 4K resolution are not yet available. To achieve that high resolution in a 100-inch display, one pixel should be as small as 0.3mm x 0.3mm—or half the size of a pixel in today's 50-inch HD panel. The smallest at present is in a 6.5-inch plasma display panel with 144 x 81pixels, each 0.3mm x 0.3mm, developed by NHK, Pioneer, Noritake and NBC. With the small pixels, the display achieved luminous efficiency of 1.1lumen/watt by using Ne-Xe gas in the panel.

Victor Co. of Japan Ltd (JVC) is working with NHK to develop a Super Hi-Vision front projector with high dynamic range. The prototype projector processes image data in two stages using three I-DLA devices, for R, G and B in the first stage, and a device for luminance processing in the second stage. Compared with contrast ratios of present front projectors at several thousand to one, the prototype achieved 1 million to one. Tone reproduction in dark areas has especially been improved.

The prototype projector consists of two systems to generate Super Hi-Vision resolution. The next goal is to display 8K x 4K images with one system.

Production—For smooth transmission of programming to a broadcasting station from various locations, NHK developed a fiber-optic transmission system that conveys a baseband 24Gbps Super Hi-Vision signal without the need for compression.

In the transmission system, the data is converted into three 10Gbps signals of different wavelengths and multiplexed using dense wavelength division multiplexing for transmission over one fiber-optic cable. Using two amplifiers for relays, the system was reported to have transmitted the Super Hi-Vision signal over 186miles.

- Yoshiko Hara
EE Times