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 21-GHz satellite-relayed transmission) and output (display technology and a projector system).
• Input: A 33-megapixel image sensor to take full 8K x 4K-resolution images was jointly developed with a United States 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 24-Gbit/s 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 128 Mbits/s, 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 21-GHz-band satellite transmission path to deliver programs to homes. The 21-GHz 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 500-Mbit/s signal in 300-MHz bandwidth in the 21.85-GHz 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, which is expected to be launched by next March.
• 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 0.3 mm x 0.3 mm--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 81 pixels, each 0.3 mm x 0.3 mm, developed by NHK , Pioneer, Noritake and NBC. With the small pixels, the display achieved luminous efficiency of 1.1 lumen/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 target is to display 8K x 4K images with one system.
• Production: For smooth transmission of programming to a broadcasting station from a variety of locations, NHK developed a fiber-optic transmission system that conveys a baseband 24-Gbit/s Super Hi-Vision signal without the need for compression.
In the transmission system, the data is converted to three 10-Gbit/s signals of different wavelengths and multiplexed using dense wavelength division multiplexing for transmission over a single fiber-optic cable. Using two amplifiers for relays, the system was reported to have transmitted the Super Hi-Vision signal over 300 km or 186 miles.
NHK is working to build an ecosystem for Super Hi-Vision in global standardization bodies. It scored a victory last year when its video format (7,680 x 4,320 pixels) was included as one of the International Telecommunication Union's large-screen formats in the ITU-R BT.1769 standard. The large-screen standard includes 4K x 2K (3,820 x 2,160) and 8K x 4K (7,680 x 4,320).
NHK is also working at the Society of Motion Picture and Television Engineers (SMPTE), a powerful technical society in the area of standardization for broadcasting equipment. It is proposing that Super Hi-Vision should be included in SMPTE's discussion agenda.
NHK's lab has also been working with partners from related industries. In most cases, the labs' researchers selected candidates and asked them to co-develop necessary technologies. Thus far, the partners have been mostly Japanese companies.
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