We have advanced with our R&D and standardization activities related to the Super Hi-Vision（8K/SHV）video system.
■ Video format standardization
We continued our work on standardization of the SHV video format （called UHDTV in standardization terminology）with ITU-R. In FY2011, we reached an agreement on a preliminary draft new Recommendation, including a wide-gamut colorimetry and a frame frequency of 120 Hz, but the formats for the luminance and color-difference signals were outstanding issues. We did a comparative study of constant luminance and nonconstant luminance（the conventional format）and obtained results showing that there is less degradation when converting to a constant luminance from an RGB source image but that there is no subjective difference in quality between the two. Moreover, we found that there are differences when processing the luminance and color-difference signals with constant luminance compared with the results when processing RGB signals.
In FY2012, we worked at ITU-R to standardize UHDTV based on these results. This resulted in agreement that both constant luminance and non-constant luminance have advantages and disadvantages and the draft new Recommendation would include both methods. The approval process resulted in the establishment of Recommendation ITU-R BT. 2020, ” Parameter values for ultra-high definition television systems for production and international programme exchange,”（1）in August 2012.
The SMPTE standard 2036-1 was revised and ARIB standardSTD-B56（2）（Table 1）was established in light of the ITU-R Recommendation. Among the formats specified in the ITU-R Recommendation, ARIB STD-B56 specifies the formats that will be used for UHDTV broadcasting in Japan.
We also contributed to creating standard test materials at ARIB for UHDTV still-images and HDTV-resolution still-images conforming to the UHDTV wide-gamut system colorimetry.
Table 1. Main parameters of UHDTV and HDTV image formats
We developed equipment to convert the colors of the SHV wide-gamut system colorimetry to colors in the HDTV color space, while maintaining image quality. We increased the performance of computations by using a 3D Look-Up Table（LUT）. The conversion provides better image quality than those based on RGB values by maintaining the luminance and hue of colors falling outside of the HDTV color gamut and only decreasing the chroma when mapping into the HDTV color gamut.
To clarify the resolution requirements for SHV cameras, we studied the Modulation Transfer Functions（MTF）of various HDTV broadcast and 4K digital cinema cameras and drew up guidelines for the required resolution characteristics.
Earlier UHDTV interfaces were based on HD-SDI standards and assume a field frequency of 60 Hz（frame frequency of 30Hz）, with a 4:2:2 format and 10 bits. In contrast, the SHV signal format includes a frame frequency of 120 Hz, formats from 4:2:0 to 4:4:4, and 12 bits. We developed a new 10-Gbps multi-link interface capable of handling various UHDTV signals in a unified way, including full-spec SHV signals（7680 × 4320 pixels, 120-Hz frame frequency, 4:4:4 format, 12 bit）and others such as 3840 × 2160 pixels, 60 Hz frame frequency, and formats including 4:2:2 and 4:2:0. We also prototyped a transmitter and receiver to verify the effectiveness and practicality of this interface.
（1）Recommendation ITU-R BT.2020, “Parameter values for ultra-high definition television systems for production and international programme exchange”（2012）
（2）ARIB Standard STD-B56, “Ultra-high definition television format studio standards”（2013）（Japanese）