4　｜　NHK STRL ANNUAL REPORT 2017

1 8K Super Hi-Vision

NHK STRL is researching a wide range of tech-nologies in areas related to video, audio and transmission with an eye toward the start of new 4K/8K satellite broadcasting slated for Decem-ber 1, 2018, the future implementation of full-featured 8K Super Hi-Vision (SHV) and the terrestrial broadcasting of 4K/8K.

In our research on video formats, we standard-ized test signals for high-dynamic-range (HDR) program production and investigated the bright-ness of HDR video. We also developed 8K/120-Hz HDR live production equipment and conduct-ed demonstration experiments. In our work on cameras and recording systems, we developed a 1.25-inch 8K image sensor with 33 megapixels that supports high-speed imaging at a 240-Hz frame frequency (with a maximum of 480 Hz). We also prototyped an 8K/240-Hz single-chip color imaging system and a slow-motion player capable of simultaneous 240-Hz recording and 60-Hz reproduction. In addition, we implemented a video compression (ProRes) feature into our compression recorders, increased the speed of our compact memory package and developed a system that gives real-time previews of 8K ProRes fi les on a PC. In our work on displays, we increased the luminance of our 8K sheet-type display composed of four 4K organic light-emit-ting diode (OLED) panels that use thin glass sub-strates and made it operable at a 120-Hz frame rate. We also developed a high-luminance 8K HDR liquid crystal display with a peak luminance of 3,500 cd/m2, more than three times that of conventional displays. To improve the image quality and operability of our projector, we en-hanced a color shading correction processor and downsized the signal processors that drive the liquid crystal devices. Regarding video coding, we continued with our development of an 8K/120-Hz codec that uses High Effi ciency Video Coding (HEVC) and fabricated a prototype capa-ble of real-time operation. We also developed ad-vanced video coding technologies with higher ef-ficiency and proposed some of them at an international standardization meeting. Moreover, we studied the application of machine learning and super-resolution techniques to video coding.

In our work on audio, we improved the perfor-mance of our adaptive downmixing technique, which generates high-quality stereo or 5.1 ch sound signals from 22.2 ch audio signals for the simultaneous production of program audio. We also developed a real-time encoder/decoder for 22.2 ch sound using the MPEG-H 3D Audio LC profi le to investigate an audio coding scheme for next-generation terrestrial broadcasting. Regard-ing reproduction technologies, we studied a way of increasing the robustness of the binaural re-production method and developed a thin loud-speaker using a piezoelectric electroacoustic

transduction fi lm.In our work on transmission technologies, we

investigated the use of MPEG Media Transport (MMT) technology as a multiplexing transmission method for next-generation terrestrial broad-casting. We also continued with our research on an IP multicast delivery technology using MMT, including the demonstration of IP delivery tech-nologies for 4K/8K content and the development of a technology for synchronized presentation on multiple terminals. For the widespread use of satellite SHV broadcasting, we worked to im-prove the 12-GHz-band transmission perfor-mance and prepare the reception environment. We also investigated the next generation of sat-ellite broadcasting such as the 21-GHz band for a larger transmission capacity. Our work includ-ed research on a new transmission scheme, a 12/21-GHz-band dual-polarized antenna and satellite systems. For the terrestrial broadcasting of 4K/8K, we worked on the detailed design and performance improvement of a preliminary standard for next-generation terrestrial broad-casting. We also prepared the environment for main-station-scale experimental transmission stations in Tokyo and Nagoya for large-scale ex-periments to verify the preliminary standard. In addition, we researched the use of space-time coding for single-frequency network (SFN) tech-nology in order to reduce the deterioration of transmission performance, which occurs in an SFN area where radio waves arrive from multiple transmitting stations. Regarding wireless trans-mission technologies for program contributions, we researched a microwave-band field pick-up unit (FPU) with the aim of enabling SHV live broadcasting of emergency reports and sports coverage and worked on its standardization. We a l s o c o n t i n u e d w i t h o u r r e s e a r ch o n 1.2-GHz/2.3-GHz-band FPUs for the purpose of SHV mobile relay broadcasting such as road race coverage. We investigated a rate-matching tech-nique that adaptively controls the coding rate of error correction codes according to the variation in the channel response and demonstrated the mobile transmission of 8K video through field experiments. Regarding wired transmission tech-nologies, we developed 8K IP transmission equipment necessary for IP-based program pro-duction and program contribution systems and researched a technology for interconnection be-tween IP devices with different transmission for-mats and control methods. We also worked to-ward the practical retransmission of 4K/8K broadcasting over cable TV and investigated an in-building transmission system toward the de-velopment of a baseband transmission system, which is a future large-capacity transmission technology.

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1　8K Super Hi-Vision

1.2 Cameras

■ 8K 4X high-speed camera and slow-motion playerWe are developing a high-speed camera system and a

slow-motion player to achieve an 8K slow-motion system for sports programs.

For the high-speed camera, we made progress in our devel-opment of an image sensor and capture equipment that sup-port a 240-Hz frame frequency. We prototyped a 1.25-inch CMOS image sensor with 33 megapixels(1) (Figure 1-2). The im-age sensor contains a folding-integration analog-digital con-verter (ADC) with a three-stage pipelined ADC architecture and a digital correlated double sampling (CDS) circuit that sup-presses fl uctuations of the ADC circuit. This makes it possible to support both high-quality capture at a 120-Hz frame fre-quency and high-speed capture at 240-Hz or higher frame fre-quencies (up to 480 Hz). We fabricated an 8K/240-Hz sin-gle-chip color imaging system using the prototype image sensor. We also began developing a three-chip 8K high-speed camera using a color separation optical prism.

For the slow-motion player, we conducted experiments on 8K/240-Hz capturing of slow-motion video using a high-speed

monochrome imaging system and a compression recorder that uses 4:2:0 color sampling(2). We also upgraded a slow-motion system capable of simultaneously recording and reproducing video both at 60 Hz, which we prototyped in FY 2016, to make it able to simultaneously record video at 240 Hz and reproduce it at 60 Hz. This system has two U-SDI input interfaces to sup-port 4:4:4 color sampling. It also uses four signal processing boards, each of which can perform processing at 60 Hz, for the compression circuit and four SATA SSD recording units to sup-port recording at 240 Hz. This system can be externally con-trolled by a general-purpose controller.

Meanwhile, we built an 8K 2X slow-motion system using our previously developed full-featured 8K SHV equipment (i.e., a

1.1 Video systems

■High-dynamic-range televisionWe investigated the operational practice of the production of

high-dynamic-range television (HDR-TV) programs in coopera-tion with program production engineers. As the reference level for the Hybrid Log Gamma (HLG) system, we determined that objects with a refl ectance of 100% and white parts in characters and diagrams should be represented at 75% of the HLG signal level. We proposed a method for mapping SDR signals ranging from 0 to 100% to HLG signals ranging from 0 to 75% on the basis of the reference level to handle standard dynamic range (SDR) video materials in HDR programs. We also studied the luminance range which allows comfortable viewing of HDR-TV programs. The results of subjective evaluation experiments showed that viewers indicate the image on the display is too bright when its average luminance level exceeds 25% of the peak luminance of the display. We refl ected these research re-sults in Reports BT.2390(1) and BT.2408(2) issued by the Interna-tional Telecommunication Union Radiocommunication Sector (ITU-R) and also compiled them in ARIB Technical Report TR-B43(3). In addition, a color bar that we proposed for HDR-TV program production was specified in ITU-R Recommendation BT.2110(4) and ARIB Standard STD-B72(5). Regarding test signals (PLUGE signals) for adjusting the black level of displays, we in-vestigated signal levels suited for the adjustment of HDR-TV displays. Our fi ndings were incorporated into a revised version of ITU-R Recommendation BT.814(6).

We studied a metric for the color volume of HDR/wide-color-gamut displays. We demonstrated that the color volume can be estimated from a combination of the color gamut (the area) on the xy chromaticity diagram based on a conventional colorimetry method and the peak luminance of the display, without the need for complicated 3D volume calculations in a color space(7).

■Full-featured 8K program production systemWe are conducting R&D on program production equipment

and systems that support a 120-Hz frame frequency with the goal of realizing full-featured 8K video production. At the NHK

STRL Open House 2017, we conducted video production exper-iments by connecting cameras, a production switcher, a re-corder, a display, time code equipment and a character super-imposer that we previously developed, and demonstrated the feasibility of live program production with the full-featured 8K video format (Figure 1-1)(8).

As full-featured 8K production equipment, we developed multiple-wavelength transmitting equipment that can transmit uncompressed video and general IP data and advanced devel-opment of a video editing system that can output 8K/120-Hz video and audio in real time.

[References](1) Report ITU-R BT.2390-3, “High dynamic range television for produc-

tion and international programme exchange” (2017)(2) Report ITU-R BT.2408-0, “Operational practices in HDR television

production” (2017)(3) ARIB Technical Report TR-B43 1.0, “Operational guidelines for high

dynamic range video programme production” (2018) (in Japanese)(4) Rec. ITU-R BT.2110-0, “Specification of colour bar test pattern for

high dynamic range television system” (2017)(5) ARIB Standard STD-B72, “Colour Bar Test Pattern for the Hybrid

Log-Gamma (HLG) High Dynamic Range Television (HDR-TV) System (1.0)” (2018)

(6) Rec. ITU-R BT.814-3, “Specifi cations of PLUGE test signals and align-ment procedures for setting of brightness and contrast of displays” (2017)

(7) K. Masaoka: “Rec. 2020 System Colorimetry and Display Gamut Me-trology,” Proc. IDW/AD’17 (2017)

(8) D. Koide et al.: “Full-Featured 8K-UHDTV Program Production Sys-tem -Demonstration Test of Live Program Production-,” ITE Techni-cal Report, vol.41, no.23, BCT2017-68 (2017) (in Japanese)

Figure 1-1. Live program production experiment and production system

Figure 1-2. Prototype 1.25-inch high-speed image sensor

6　｜　NHK STRL ANNUAL REPORT 2017

1　8K Super Hi-Vision

120-Hz compact single-chip camera and a compression record-er) and used the system for sports programs such as the NHK Trophy fi gure skating competition.

■Full-featured 8K compact cameraWith the aim of making a full-featured 8K SHV camera more

compact and practical, we are developing a prototype three-chip 8K camera using a 1.25-inch optical system. For effi cient development, we used the same components, such as a sensor drive board and a signal processing board, as those for our 4X high-speed camera.

As for a previously developed133-megapixel full-resolution single-chip camera that operates at a 60-Hz frame frequency, We applied inter-line scanning (interlaced scanning) to enable 120-Hz capture. In the scanning, the skipped lines were inter-polated by the adjoining lines when moving parts and by the prior frame when static pats in the image(3).

Using our previously developed full-featured 8K cameras and single-chip cameras, we recorded full-featured video outdoors, conducted live program production at the NHK STRL Open House 2017 and provided support for the production of NHK Special and other programs.

■Other camera-related technologiesWith the aim of developing a general-use 8K camcoder, we

developed prototype equipment for verifying basic functions that can compress 8K video to 1/80 the file size by using an AVC/H.264 encoder and record video for more than one hour into four SD cards. The compressed video achieved a peak sig-nal-to-noise ratio (PSNR) in excess of 48 dB(4).

To achieve autofocus (AF) capability, we developed an exper-imental imaging device using a hybrid AF system that com-bines phase-difference detection AF with contrast detection AF(5) and exhibited it at the NHK STRL Open House 2017.

We fabricated a dimming element using metal salt precipita-tion-type materials for an electronic neutral-density (ND) fi lter that can control incident light continuously. Reexamining the materials and modifying the drive circuit shortened the re-sponse time (i.e., the time in which the light transmission rate decreases to 1/8 of its original value) to three seconds(6).

We analyzed the principle of the problem of bit depth degra-dation, which occurs when high-chroma objects are captured.

Based on the analysis result, we demonstrated that bit depth reproduction can be improved by changing the processing or-der of the linear matrix and knee and clipping during signal processing within the camera(7).

We developed a system that can precisely measure the two-dimensional spatial resolution characteristics of a TV cam-era in real time and exhibited it at the NAB Show(8).

The research on image sensors was conducted in coopera-tion with Shizuoka University. The research on the electronic ND fi lter was conducted in cooperation with Murakami Corpo-ration.

[References](1) T. Yasue, K. Tomioka, R. Funatsu, T. Nakamura, T. Yamasaki, H.

Shimamoto, T. Kosugi, S. Jun, T. Watanabe, M. Nagase, T. Kitajima, S. Aoyama and S. Kawahito: “A 2.1μm 33Mpixel CMOS Imager with Multi-Functional 3-Stage Pipeline ADC for 480fps High-Speed Mode and 120fps Low-Noise Mode,” 2018 IEEE International Solid-State Circuits Conference (2018)

(2) K.kikuchi, T.Kajiyama, K.Ofura, T.Yamasaki, T.Yasue, R.Funatsu, E.M-iyashita and H.Shimamoto: “Development of 8K240fps compression recorder,” ITE annual Convention 2017, 33E-1 (2017) (in Japanese)

(3) T. Nakamura, T. Yamasaki, R. Funatsu and H. Shimamoto: “An 8K full-resolution 60-Hz/120-Hz multi-format portable camera system,” SMPTE 2017 Annual Technical Conference (2017)

(4) R. Funatsu, T. Kajiyama, T. Matsubara and H. Shimamoto: “Experi-mental Prototype of SD Memory Card Recordable 8K/60P Camcord-er,” IEEE ICCE 2018 (2018)

(5) T. Yamasaki, R. Funatsu, T. Nakamura and H. Shimamoto: “Hybrid Autofocus System by Using a Combination of the Sensor-Based Phase-Difference Detection and Focus-Aid Signal,” IEEE ICCE 2018 (2018)

(6) K.Kikuchi, K.Miyakawa, T.Yasue, H.Shimamoto, T.Mochizuki and M.Makita: “A gradation control method for metal salt precipitation type optical devices,” ITE Winter Annual Convention 2017, 12C-1 (2017) (in Japanese)

(7) K.Nomura, T.yasue, K.Masaoka and Y,Kusakabe: “Improvement of Color Reproduction for HDR/SDR Simultaneous Production Camera,” ITE Annual Convention 2017, 34E-2 (2017) (in Japanese)

(8) K. Masaoka, K. Arai, K. Nomura, T. Nakamura and Y. Takiguchi: “Re-al-Time Measurement of Ultra-High Definition Camera Modulation Transfer Function,” SMPTE 2017 Annual Technical Conference & Ex-hibition (2017)

1.3 Displays

We have made progress in our development of various dis-plays that can handle 8K SHV video and continued with our re-search on large sheet-type displays.

■SHV sheet-type display technologiesWe are developing lightweight, thin and sheet-type organic

light-emitting diode (OLED) displays for future large SHV dis-plays for home use. In FY 2017, we increased the luminance of our sheet-type display composed of four 65-inch 4K OLED pan-els that use thin glass substrates and made it operable at a 120-Hz frame rate. The display achieved high-quality 8K images (Figure 1-3). This display was demonstrated in cooperation with LG Display and ASTRODESIGN, Inc. We plan to develop a display that can show 8K images with a single panel and to re-search a fl exible display that uses a more lightweight and fl exi-ble plastic fi lm substrate.

■ 8K HDR liquid crystal displayWe developed an 8K HDR liquid crystal display that supports

more than three times the luminance of conventional displays

Figure 1-3. Sheet-type OLED display supporting high luminance and 120-Hz

frame rate

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1　8K Super Hi-Vision

1.4 Recording systems

We are developing compression recorders and peripheral equipment with the aim of developing full-featured 8K SHV re-cording equipment. In FY 2017, we added a video compression (ProRes) feature to our compression recorder, improved the re-cording and reproduction speed of our small memory package and developed a system that shows real-time previews of re-corded content on a PC(1).

In our work on compression recorders, we implemented a video compression capability into our prototype compression recorder(1) to input/output recorded content via files to/from general-purpose editing software for direct editing. We also en-abled 40-Hz or higher real-time compression processing by us-ing the pipeline processing of three ProRes compression IP cores implemented into one FPGA. A ProRes compression IP core can perform 15-Hz processing of 8K resolution. We imple-mented this system into the three FPGAs on the compression signal processing board, which realized 120-Hz compression. To allow the simultaneous processing of 2K proxy video and 8K video, we incorporated a circuit that switches between 2K images and 8K images at high speed within the IP. The com-bined use of a decoder IP core that we implemented in FY 2016 and the compression IP core that we newly developed achieved the simultaneous recording of 8K video and 2K proxy video and 8K reproduction at 120 Hz. In addition, we implemented support for a general-purpose remote controller to enable op-eration on an outside broadcast (OB) van (Figure 1-5).

Regarding the small memory package, we increased the speed of the NVMe interface which we developed in FY 2016 and implemented support for two slots. We investigated a way of maximizing the device performance of a small memory package with the NVMe interface and found that it is necessary for the host interface to support the simultaneous issuance of multiple commands and a larger transfer data block size. We therefore modifi ed the host interface to support these capabili-ties, which enabled our compression recorder to achieve a re-cording speed in excess of 20 Gbps. We also equipped our small memory package with two slots and enabled it to record twice the number of hours of our prototype recorder fabricated in FY 2016. In addition, we developed backup software for small memory packages to enable data backup in raw data and video formats.

To allow easy previews of the content recorded in the com-pression recorder on a PC, we developed an 8K ProRes re-al-time preview board. Since the decoder IP core that we im-plemented into the compression recorder can operate at 8K/60 Hz if a suffi cient memory bandwidth is secured, we implement-

ed the decoder IP core into an FPGA evaluation board and de-veloped a PC driver. By installing these on a PC, we achieved the real-time preview of recorded video (Figure 1-6).

(Figure 1-4) in cooperation with Sharp Corporation. By employ-ing a technology for increasing the backlight luminance, the display achieved a peak luminance of 3,500 cd/m2 and a dy-namic range of 400,000:1 (both in measured values).

■Full-featured SHV projectorWe improved the image quality of our full-featured SHV pro-

jector that uses red, green and blue laser diodes as light sourc-es and supports a 120-Hz frame frequency. We reduced the lu-minance and color shadings on displayed images caused by the interference of laser beams by increasing the number of bright-ness correction points in the shading correction processor. We also improved the operability by downsizing the signal pro-cessing units that drives the liquid crystal device of the projec-tor and incorporating them into the projector head.

Figure 1-4. High-luminance 8K HDR liquid crystal display

Figure 1-5. Compression recorder and small memory package

Small memory package

Compression recorder

Figure 1-6. PC preview equipment

PC preview equipment

Preview video

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1.5 Sound systems providing a strong sense of presence

We are researching a 22.2 multichannel sound (22.2 ch sound) system for SHV and working on its standardization.

■SHV sound simultaneous production systemWe are studying technologies to produce high-quality 22.2 ch

sound efficiently and simultaneously while producing stereo and 5.1 ch sound.

In FY 2016, we studied an energy spectrum correction tech-nique for downmixing sound which focuses on the coherence between 22.2 ch audio signals. In FY 2017, we improved its performance and conducted subjective evaluations with sound engineers engaged in program production(1). As Table 1-1 shows, the sound obtained with the maximum amount of cor-rection, both in the suppression process and the amplifying process, was rated as the most appropriate downmixed sound. This demonstrated the sound quality improvement effect of the proposed technique.

We are also studying an upmixing technology for using sound materials recorded in stereo for 22.2 ch sound produc-tion. We developed a technique for separating components ac-cording to the mutual correlation of stereo signals by using an adaptive fi lter to generate 22.2 ch sound materials(2).

■Reproduction of converted SHV soundWe are researching technologies for the easy reproduction of

22.2 ch sound at home. We continued with our research on binaural reproduction using line array loudspeakers. In FY 2017, we devised a design method for a reproduction controller that increases the robustness against system perturbations and external disturbances(3) and implemented it into the signal pro-cessor that we are developing in cooperation with Sharp Cor-poration.

We also proposed a method for the low-order and high-ac-curacy modeling of head-related transfer functions including the characteristics of an expected reproduction environment and developed a signal processor for reproducing 22.2 ch sound with headphones using this method.

■Standard test materials for 3D multichannel stereophonic sound systemsIn FY 2017, the Institute of Image Information and Television

Engineers published Series A of standard test materials for 3D multichannel stereophonic sound systems. Toward this achievement, we contributed to the sound source production conducted by ARIB and prepared an explanatory document de-scribing evaluation items and recording conditions.

■Acoustic devicesWe exhibited the 22.2 ch sound single-unit microphone that

we developed in FY 2016 at the NHK STRL Open House 2017. We also contributed to the production of standard test materi-als for 3D multichannel stereophonic sound system. Using our microphone, we recorded various sounds such as the perfor-mance of octets by wind and string instruments and ambient sound at an amusement park. In addition, we studied beam forming method in order to improve the performance of sepa-ration between channels.

We developed a thin loudspeaker using a piezoelectric elec-troacoustic transduction film that could be applied to loud-speakers for fl at-panel TV and 22.2 ch sound loudspeakers for home use and exhibited it at the NHK STRL Open House 2017. This research was conducted in cooperation with Fujifi lm Cor-poration.

■Audio services for next-generation terrestrial broadcastingWe developed a real-time encoder/decoder for 22.2 ch

sound using the MPEG-H 3D Audio LC profi le(4) to study an au-dio coding scheme for next-generation terrestrial broadcasting. This research was conducted in cooperation with the Fraun-hofer Institute for Integrated Circuits.

We devised a serial form of audio definition model (ADM), which is metadata used for object-based audio, and a method to convey serial ADM. We also prototyped both transmitter and receiver of serial ADMs using a digital audio signal interface.

■StandardizationAt ITU-R, we prepared a Preliminary Draft New Recommen-

Table 1-1. Evaluation result of correction amount in suppression and

amplification processes

Selection rank 1 2 3 4

Suppression amount Max Medium Small None

Amplification amount Max Medium Small None

(A higher rank indicates a higher evaluation.)

Figure 1-7. Appearance of thin loudspeakers

[References](1) T. Kajiyama, K. Kikuchi, K. Ogura, E. Miyashita, M. Tecchikawahara,

H. Watase, Y. Nagai and H. Takashima: “Development of Compres-

sion Recorder for Full-featured 8K Super Hi-Vision,” ITE Journal, Vol.72, No.1, pp.J41-J46 (2018) (in Japanese)

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1　8K Super Hi-Vision

1.6 Video coding

We are researching video coding techniques for full-featured 8K SHV and SHV terrestrial broadcasting.

■ 8K 120-Hz HEVC encoderWe are developing an encoder that supports 8K/120-Hz vid-

eo (Figure 1-8). The encoder, which consists of twelve 4K/60-Hz encoding units, is capable of real-time coding of 8K/120-Hz input video by parallel processing. This system conforms to the Main 10 profile using the HEVC/H.265 scheme and supports 4:2:0 10-bit coding of 8K/120-Hz video.

Its bitstream is compliant with ARIB standard STD-B32 Ver-sion 3.9, which allows not only an 8K/120-Hz decoder but also a decoder for 8K test broadcasting (an 8K/60-Hz decoder com-pliant with ARIB standard STD-B32 Version 3.9) to partially de-code the 60-Hz sub-bitstream. The system also supports video usability information (VUI) parameters for HDR that are compli-ant with the above standard.

Since the encoder divides the video frame into four vertical slices for parallel processing, a degradation in image quality tends to appear around the boundaries between divided slices of video, especially when the video has vertical motion. To suppress the degradation, we employed a design that reduces 8K/120-Hz video to 4K/60-Hz video and analyzes the reduced video in advance to control the entire coding. We developed technologies for increasing the image quality, which include a technique to control the quantization value of the boundary ar-eas based on the amount of motion predicted by preliminary analysis. We conducted subjective evaluations using a software simulator to verify the effectiveness of these technologies and confirm the coding quality(1). This research was conducted in cooperation with Fujitsu Laboratories Ltd.

As part of R&D on 120-Hz video coding, we produced evalu-ation images that are helpful for evaluating the performance of the processing of fast-moving images and coding control in co-operation with NTT (Nippon Telegraph and Telephone Corpora-tion).

■ 8K 120-Hz HEVC decoderWe are developing a decoder in parallel with the encoder.

Our decoder consists of a software decoder that operates on a general-purpose workstation and an interface converter. In FY 2016, we implemented a video decoder unit of the software de-coder. In FY 2017, we implemented its audio decoder unit and TS input unit. This enabled the real-time decoding of TS signals of 8K/120-Hz video and 22.2 ch sound. Decoded 8K/120-Hz

video is generated from eight spatiotemporally divided Display-Port outputs and converted by the interface converter to signals for a single U-SDI. Decoded audio signals are multiplexed with video signals for output.

■Development and standardization of next-generation video coding technologiesWe are developing advanced high-efficiency video coding

technologies for next-generation terrestrial broadcasting. For intra-frame prediction technology, we developed a method for the high-precision prediction of chroma signals using decoded luma samples in intra prediction and a method for improving entropy coding for chroma intra prediction modes(2). For in-ter-frame prediction technology, we developed a motion com-pensation method considering the continuity with the motion vector of neighboring blocks and a method for predicting the motion vector adaptively according to the shape of partitioned coding blocks. We also developed a way to improve the entro-py coding of transform coeffi cients by estimating the residual signal energy and a deblocking filter control method that re-duces signifi cant coding degradation in HDR-format video. We confirmed that these technologies improve coding efficiency and proposed some of them to an international standardization conference on next-generation video coding as prospective el-emental technologies for advanced video coding.

To promote the performance improvement of future video coding schemes for HDR video, we provided the JCT-VC and JVET international standardization conferences with test se-

dation on serial ADMs on the basis of a joint proposal by Japan, the US and the UK. At the Society of Motion Picture and Televi-sion Engineers (SMPTE), we proposed a draft of the standard for conveying serial ADMs using AES3 digital audio signal in-terface. At ARIB, we set up a group to study the requirements for next-generation audio services and began activities.

At the Japan Electronics and Information Technology Associ-ation (JEITA) and the International Electrotechnical Commis-sion (IEC), we produced a committee draft for a vote on a standard for transmitting a 22.2 ch sound signal stream encod-ed by MPEG-4 AAC using an optical interface to reproduce 22.2 ch sound at home. Additionally, we contributed to the revision of a standard for transmitting 22.2 ch sound signal stream en-coded by MPEG-4 AAC using an HDMI specified by the Con-sumer Technology Association (CTA).

At JEITA and IEC, we continued with our works to revise a standard for the general channel allocation including 22.2 ch sound system to add channel labels for various multichannel sound systems.

At AES, we contributed to the publication of technical guide-lines which prescribe that each country’s broadcasting rules (i.e., -24LKFS for Japan) should be followed in principle for the target loudness of over-the-top television programs(5).

[References](1) T. Sugimoto and T. Komori: “Tone compensation method for down-

mixing of 22.2 ch sound,” ITE Winter Annual Convention 2017, 12C-5 (2017) (in Japanese)

(2) Y. Sasaki, T. Komori and T. Nishiguchi: “A study of upmix algorithm from stereo to 22.2ch audio,” ITE Winter Annual Convention 2017, 31B-3 (2017) (in Japanese)

(3) K. Matsui, A. Ito, S. Mori, M. Inoue and S. Adachi: “A method to re-lieve the binaural reproduction controller applying output tracking control,” Autumn meeting of the Acoustical Society of Japan, 1-P-31 (2017)(in Japanese)

(4) ISO/IEC 23008-3:2015/AMD3:2017 (2017)(5) “Loudness Guidelines for OTT and OVD Content,” Technical Docu-

ment AESTE1006.1.17-10 (2017)

Figure 1-8. Appearance of 8K/120-Hz encoder

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quences of the HLG format and also jointly proposed effi cient coding settings for using HEVC as comparative criteria with the BBC. These settings were adopted as the criteria for the perfor-mance comparison of future video coding schemes. They were also refl ected in HEVC video coding guidelines for HDR coding (ISO/IEC TR 23008-15 | ITU-T H. Sup.18)(3)-(5).

As an overseas research effort, we developed HDR tone-mapping nonlinear functions suited for video coding in cooperation with Universitat Pompeu Fabra and demonstrated the improvement in coding effi ciency(6).

■Application of machine learning to coding toolsAs an initial study to explore the feasibility of applying ma-

chine-learning-based coding tools to video coding, we con-ducted a basic evaluation on post-fi lters and intra prediction. We built a post-fi lter using a machine learning method based on convolutional neural networks and demonstrated that it can reduce mosquito noise and improve the PSNR. We also devel-oped an intra prediction tool based on a multilayer perceptron, which is a type of neural network. The results of training and evaluation showed that it is possible to develop a single predic-tor that behaves as if it is equipped with multidirectional and planar prediction modes, indicating the feasibility of a new, effi -cient intra prediction tool.

Also, in cooperative research with Meiji University, we devel-oped an intra prediction process using a neural network con-sisting of two convolutional layers and two fully connected lay-ers and confi rmed that it can increase the speed of a prediction mode that uses prediction samples and adjacent reference samples as an input(7).

■Enhancement of super-resolution technology and its application to video codingIn our research for enhancing super-resolution technologies,

we developed a technique for super-resolution reconstruction from 2K to 8K that uses an alignment and assignment method considering the frequency band by a registration process be-tween wavelet multiscale components. The new technique achieved a higher speed and higher image quality than conven-tional methods(8)(9).

We are also studying a way of applying super-resolution re-construction to video coding technology. As inter-frame predic-tion images, we newly introduced blurred prediction images and super-resolved prediction images that use registration su-per-resolution between wavelet multiscale components and observed improvements(10).

■Noise reduction and band limitation equipmentWe developed noise reduction and band limitation equip-

ment that performs a pre-coding process to increase coding ef-fi ciency. The equipment applies shrinkage functions in each el-ement position after the wavelet-packet decomposition of each frame and controls the amount of shrinkage according to the band limitation frequency and the pixel level, enabling a high-precision noise reduction and band limitation process(11). This research was conducted as a government-commissioned project from the Ministry of Internal Affairs and Communica-tions titled “R&D on Advanced Technologies for Terrestrial Tel-evision Broadcasting.”

[References](1) S. Iwasaki, Y. Sugito, K. Chida, K. Iguchi, K. Kanda et al.: “Subjective

Evaluation of 8K120Hz Encoder Simulator,” Proceedings of the 2017 IEICE General Conference, D-11-7 (2018) (in Japanese)

(2) S. Iwamura, S. Nemoto and A. Ichigaya: “Redundant fl ag removal on chroma intra mode coding,” JVET-H0071 (2017)

(3) S. Iwamura, S. Nemoto, A. Ichigaya and M. Naccari: “Analysis of 4K Hybrid Log-Gamma test sequences,” JVET-F0094 (2017)

(4) S. Iwamura, S. Nemoto and A. Ichigaya: “Candidate rate points of HLG material for anchor generation,” JVET-G0103 (2017)

(5) S. Iwamura, S. Nemoto, A. Ichigaya and M. Naccari: “On the need of luma delta QP for BT.2100 HLG content,” JVET-G0059 (2017)

(6) Y. Sugito et al.: “Improved High Dynamic Range Video Coding with a Nonlinearity based on Natural Image Statistics,” International Journal of Signal Processing Systems, Vol.5, No.3, pp.100-105 (2017)

(7) T. Toyozaki, Y. Shishikui and S. Iwamura: “A Study on intra predic-tion mode decision method using deep learning,” Proceedings of the 2017 IEICE General Conference, D-11-56 (2017) (in Japanese)

(8) Y. Matsuo and S. Sakaida: “Super-Resolution for 2K/8K Television by Wavelet-Based Image Registration,” Proceedings of IEEE GlobalSIP, GS IVM-P.1.4, pp. 378-382 (2017)

(9) Y. Matsuo, A. Ichigaya and K. Kanda: “Super-Resolution from 2K to 8K by Registration of Wavelet Multi-Scale Components,” Picture Coding Symposium of Japan 2017 (PCSJ2017), P-2-15, pp. 86-87, (2017) (in Japanese)

(10) Y. Matsuo and S. Sakaida: “Coding Efficiency Improvement by Wavelet Super-Resolution Restoration for 8K UHDTV Broadcasting,” Proceedings of IEEE ISSPIT (2017)

(11) Y. Matsuo, K. Iguchi and K. Kanda: “Coding Effi ciency Improvement by Band-Limitation Equipment for Advanced Digital Terrestrial TV Broadcasting System,” Proceedings of the 2017 ITE Winter Conven-tion, 14C-4, (2017) (in Japanese)

1.7 Media transport technologies

We are conducting R&D on the use of MPEG Media Trans-port (MMT) technology as a multiplexing transmission method for next-generation terrestrial broadcasting. We are also con-ducting research on IP multicast delivery technology using MMT, in which we demonstrated the IP delivery of 4K/8K live content and presented a new viewing experience using in-ter-terminal synchronization technology.

■Multiplexing transmission method for next-generation terrestrial broadcastingAiming for next-generation terrestrial broadcasting, we re-

searched a multiplexing scheme for IP packets that conforms to the channel coding system for terrestrial broadcasting and an IP transmission system used over studio to transmitter links (STLs) and transmitter to transmitter links (TTLs) to enable a single-frequency network (SFN). We compiled our fi ndings into specifications and conducted verifications with a prototype

remux(1). More specifically, we performed experiments at the Hitoyoshi and Mizukami experimental stations in Kumamoto Prefecture on transmitting output signals from the remux to multiple modulators over commercial IP networks. The results demonstrated that an IP transmission-based SFN can be built by using signaling information in the signals for synchroniza-tion control. To improve the quality of mobile services in next-generation terrestrial broadcasting, we proposed a broad-cast signal complementary system that allows continuous pro-gram viewing even when broadcast waves are interrupted dur-ing travel by seamlessly switching to the reception by mobile communications. The results of fi eld experiments (Figure 1-9) demonstrated the feasibility of the system(2)(3).

Part of this research was conducted as a government-com-missioned project from the Ministry of Internal Affairs and Communications titled “Research and Development for Ad-vanced Digital Terrestrial Television Broadcasting System.”

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1.8 Satellite broadcasting technology

We are researching 12-GHz-band satellite broadcasting sys-tem to improve the transmission performance for 8K UHDTV broadcasting, and researching next-generation satellite broad-casting systems such as 21-GHz-band satellite broadcasting for future broadcasting services.

■Advanced transmission system for satellite broadcastingWe are researching 64APSK (Amplitude Phase Shift Keying)

coded modulation using set partitioning in order to further in-crease the capacity of satellite transmission. As a way of im-

proving the transmission performance through a channel with nonlinear distortion caused by the satellite transponder, we de-signed 64APSK coded modulation that considered the charac-teristics of the nonlinear distortion on the satellite and the per-formance of an adaptive equalizer using the LMS (Least Mean Squares) algorithm on the receiver side. Using the number of constellation points on the circles of 64APSK modulation as parameters, we designed the number of the points, bit alloca-tion to signal points and LDPC(Low Density Parity Check) cod-ing that obtain the best required carrier-to-noise ratio (C/N) af-ter error correction under the condition of an output back-off of 5 dB, which is the optimum operation point of a 12-GHz-band satellite transponder during 64APSK transmission. Com-puter simulations showed that the designed 64APSK coded modulation (our proposed method)(1) improved the required C/N by approximately 0.4 dB compared with the conventional method optimized by considering only AWGN (Additive White Gaussian Noise), when the output back-off was 5 dB (Figure 1-10).

We prototyped a cross-polarization interference cancellation device equipped with a negative-phase synthesized algorithm that reduced the deterioration in transmission performance caused by the simultaneous reception of right- and left-hand circularly polarized waves. We demonstrated that this interfer-ence cancellation function improved the required C/N by 0.2 dB when the cross-polarization discrimination was 25 dB and the modulation scheme of the desired waves was 32APSK (3/4).

■Advanced satellite broadcasting systemsWith the aim of increasing the capacity of 12-GHz-band sat-

ellite broadcasting by using multilevel coded modulation, we

■MMT-based IP multicast delivery technologyTo promote 8K SHV broadcasting, we verifi ed MMT-based IP

multicast delivery technology that could be used for the IP re-transmission of broadcasting in closed networks of cable TV

stations and other service providers and for the IP delivery of the relevant content linked with broadcasting. We conducted a delivery experiment using live content from the ISU Grand Prix of Figure Skating 2017/2018, NHK Trophy, and demonstrated that 4K/8K content can be delivered to multiple content deliv-ery service providers simultaneously with low latency. As an example of the application of a high-accuracy synchronization scheme using an absolute time stamp, which is a feature of MMT, we developed an inter-terminal synchronization technol-ogy that allows multiple content delivered by IP multicast dis-tribution to be displayed in synchronization without delay by adjusting the timing to display video at the same time with clock synchronization among multiple reception terminals. We exhibited interactive content, “Domo’s Slapstick Race,” using this technology at the NHK STRL Open House 2017, CEATEC JAPAN 2017 and NHK Science Stadium 2017, demonstrating the feasibility of a new viewing experience(4).

[References](1) S. Aoki et al.: “A Study on IP Multiplexing Scheme in Next-generation

Terrestrial Broadcasting System,” ITE Annual Convention, 14C-1 (2017) (in Japanese)

(2) Y. Kawamura et al.: “Field Experiment of Hybrid Video Delivery Using Next-Generation Terrestrial Broadcasting and a Cellular Network,” IEEE International Conference on Consumer Electronics 2018, pp.173-174 (2018)

(3) Y. Kawamura et al.: “An Implementation of a Cooperative Broadcast and Cellular Network System for Mobile Reception of Next-Genera-tion Terrestrial Broadcasting,” ITE Annual Convention, 14C-4 (2017) (in Japanese)

(4) Y. Kawamura: “Inter-Terminal Synchronization Technology Using MMT,” Cable New Era, vol.4, no.7, p.47 (2017) (in Japanese)

Image: Google

A

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Figure 1-9. Field experiment using an complementary system

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Figure 1-10. Transmission performance of 64APSK coded modulation

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1.9 Terrestrial broadcasting transmission technology

For the terrestrial broadcasting of SHV, we made progress in our R&D on a next-generation terrestrial broadcasting system, the establishment of a large-scale experiment environment, channel planning and next-generation single-frequency net-work (SFN) technology. Part of this research was being per-formed under the auspices of the Ministry of Internal Affairs and Communications, Japan as part of its program titled “Re-search and Development for Advanced Digital Terrestrial Tele-vision Broadcasting System,” in cooperation with Sony Corpo-ration, Panasonic Corporation, Tokyo University of Science and NHK Integrated Technology Inc.

■Next-generation terrestrial broadcasting systemWe worked on the detailed design and performance im-

provement of a preliminary standard for next-generation ter-restrial broadcasting. In FY 2017, we designed low-density par-i ty-check (LDPC) codes, investigated a hierarchical transmission method, reexamined the transmission and multi-plexing confi guration and control (TMCC) transmission scheme and evaluated transmission characteristics of the preliminary standard through computer simulations.

Regarding the LDPC codes, we redesigned some of the 69,120-bit-length codes (long codes) that we designed in FY 2016 for the preliminary standard and also newly designed 17,280-bit-length codes (short codes). By using an appropriate

(multiedge type: MET) structure for codes with a low coding rate, we demonstrated that both long codes and short codes with any coding rate (2/16 to 14/16) can achieve the same or better performance than ATSC 3.0 (Figure 1-12).

For the hierarchical transmission method, we investigated

are investigating a way of increasing the output power of the broadcasting satellite transmission. If the output power is in-creased, the side lobes of an on-board antenna need to be sup-pressed to keep radio wave interference to other countries be-low the level agreed by international adjustment. To develop an on-board 12-GHz dual-polarized refl ector antenna with low side lobes, which is capable of separately receiving right- and left-hand circularly polarized waves, we selected and proto-typed a corrugated horn antenna to be used as the feeder. The radiation patterns of our prototype feeder agreed with the de-signed values and a cross-polarization discrimination of 30 dB or more was obtained in the 300-MHz bandwidth. We plan to design a dual refl ector antenna using two noncircular aperture reflectors based on the designed feeder to further reduce the side lobes of an on-board antenna.

We designed a 12/21-GHz-band dual-polarized feeder that allows a single antenna to receive both 12-GHz-band and 21-GHz-band satellite broadcasting by right- and left-hand cir-cular polarization. The feeder has a multilayer structure of four-element microstrip array antennas, which enables the si-multaneous arrangement of the focal point of the refl ector (Fig-ure 1-11). The feeder obtained a VSWR (Voltage Standing Wave Ratio) of 1.1 or less for both frequency bands. An evaluation using the feeder design values showed that an offset parabolic refl ector antenna with 50 cm aperture diameter achieves gains more than 34 dBi for the 12-GHz band and 38 dBi for the 21-GHz band as well as a cross-polarization discrimination more than 25 dB.

Weak signals in the intermediate-frequency range (2.2 GHz to 3.2 GHz) for left-hand circular polarization leak from a re-ception system for 12-GHz-band 4K/8K satellite broadcasting. To measure these signals, we devised a method for improving the C/N of the measured signals (leaked signals) by correlation processing of the leaked signals and received signals, and we prototyped and evaluated a measurement tool capable of the high-precision measurement of the leaked power. We con-fi rmed by the prototype that the C/N can be improved by 40 dB or more by limiting the band of correlation output signals with a narrow-band pass fi lter.

As a feeder that increases the output satellite transmission

power by spatial synthesis using a 21-GHz-band array-fed re-fl ector antenna, we prototyped a three-element partial model using a sequential array structure in which horn antennas are arranged with rotational symmetry. We confirmed that a cross-polarization discrimination 30 dB or more is obtained by reducing radio waves reflected inside the neighboring ele-ments.

To conduct a wide-band transmission experiment using a 21-GHz-band experimental transponder of the BSAT-4a broad-casting satellite and evaluate rain attenuation characteristics in the 21GHz band, we set up 21-GHz-band reception equipment that combines a parabolic antenna with 1.5 m aperture diame-ter (48 dBi gain) and an automatic satellite-tracking system.

[References](1) Y. Koizumi, Y. Suzuki, M. Kojima, H. Sujikai and S. Tanaka: “Study on

the optimization of 64APSK coded modulation design under the nonlinear transmission path simulating the satellite transponder characteristics,” Proceedings of the 2018 IEICE General Conference, B-3-10 (2018) (in Japanese)

50mm

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21-GHz-band MSA20-GHz-band MSA

21-GHz-band feed circuit

12-GHz-band 0.6 wavelength (14.7 mm)

21-GHz-band 0.5 wavelength (6.9 mm)

Figure 1-11. Structure of 12/21-GHz-band dual-polarized feed antenna

ATSC3.0

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Figure 1-12. Relationship between required C/N and transmission rate

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layered division multiplexing (LDM) that transmits two signals with different transmission robustness after mapping and add-ing them(1). We implemented a system to apply LDM to the whole signal bandwidth and a system to apply LDM only to the partial reception band into our modulator and demodulator. We also prototyped a demodulator for mobile reception that re-ceives only the partial reception band (1.5-MHz bandwidth) and uses a sampling rate reduced to 1/4 that of a conventional de-vice with the aim of reducing the power consumption of a fre-quency-division multiplexing (FDM) receiver. Moreover, as a technology for improving the characteristics, we implemented the TMCC transmission scheme using differential space fre-quency block codes (DSFBCs) and a frequency interleaver that performs a cyclic shift in segment units for each OFDM symbol to increase the frequency diversity gain.

Using a modulator and demodulator that we developed in FY 2016, we evaluated the reception characteristics of the partial reception band through laboratory experiments and fi eld exper-iments with an STRL experimental station(2). As a result of vari-ous modifications including the use of LDPC codes for er-ror-correcting codes, the expansion of the partial reception bandwidth to approximately 3.5 times that of One-Seg for ter-restrial TV broadcasting and the provision of a longer time-in-terleave length option, the required fi eld strength was reduced by 2.6 dB and the transmission effi ciency was improved by 60% compared with those of One-Seg (Figure 1-13). We reflected this partial reception capability compliant with the preliminary standard in a channel coding system for sponsored research.

■Construction of large-scale experimental environment for next-generation terrestrial broadcastingAs part of the program titled “Research and Development for

Advanced Digital Terrestrial Television Broadcasting System,” we prepared for setting up experimental transmission stations

in Tokyo and Nagoya. In FY 2017, we designed a transmitter and developed a transmission antenna that will be used at the experimental station in Tokyo. For Nagoya, we designed two experimental transmission stations (one with the size of a main station and the other with the size of a relay station) and devel-oped a transmission antenna for the main station and a trans-mitter for the relay station.

In large-scale experiments to be conducted in both areas, we plan to use signals with an extended bandwidth than that of the current terrestrial TV broadcasting. We conducted laborato-ry experiments to confi rm the permissible values of co-channel interference and adjacent channel interference for the signals with the extended bandwidth. We investigated the co-channel and the adjacent channel protection ratios for the extended bandwidth signal through laboratory experiments. We assessed the protection ratios for the current terrestrial TV broadcasting signals interfered with by the extended bandwidth signal using 15 kinds of terrestrial TV receivers(3).

To obtain licenses in both areas, we provided the relevant broadcasters with a prior explanation of the transmission spec-ifi cations of the experimental stations and their possible impact on terrestrial TV broadcasting and gained approval for the transmission specifi cations (Table 1-2). We applied to the Re-gional Bureaus of Telecommunications for an experimental station license with the goal of starting radio emission in the autumn of 2018.

■Channel planningSince FY 2016, we have been engaging in channel planning

in cooperation with the Engineering Administration Depart-ment with the aim of enabling terrestrial SHV broadcasting that uses the same UHF band as current terrestrial TV broadcasting. In FY 2017, we studied new channels for terrestrial SHV broad-casting and frequency reallocation of existing digital terrestrial broadcasting. We reviewed selection criteria for determining the availability of channels and increased the number of calcu-lation points, which improved the accuracy of the repacking scale estimation.

■Next-generation SFN technologyThe remux equipment that we developed in FY 2016 has the

capability of sending eXtensible Modulator Interface (XMI) sig-nals that will be entered into an OFDM modulator. It therefore can control the signal output timing of the modulator according to each transmitting station’s transmission timing information,

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Timing informationHitoyoshi experimental station Mizukami experimental station

Figure 1-14. System diagram of SFN transmission experiment

Table 1-2. Transmission specifications of experimental stations

Tokyo Nagoya

Type Main station Main station Relay station

Location Minato Ward, Tokyo Nagoya City, Aichi Yatomi City, Aichi

Transmission channel UHF ch28 UHF ch35 UHF ch35

Polarization Horizontal and vertical (Dual-polarized MIMO)

Transmission PowerHorizontal 1 kW

Vertical 1 kWHorizontal 1 kW

Vertical 1 kWHorizontal 10 W

Vertical 10 W

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which is multiplexed with XMI packets, to enable an SFN.In FY 2017, we conducted an SFN fi eld experiment over an

optical IP network in Hitoyoshi City, Kumamoto Prefecture. In the experiment, XMI packets sent from a remux installed at the Hitoyoshi experimental station were delivered to the Mizukami experimental station over the optical IP network. Then, OFDM signals generated by the modulators at the Hitoyoshi and Miz-ukami stations were transmitted from the two stations using the same frequency (UHF ch46). We confi rmed at a reception point set up in a place where radio waves from the two sta-tions arrive that video was successfully transmitted without er-rors in an SFN environment. We also observed the difference in the arrival time of radio waves from the two stations and con-fi rmed the operation of the transmission timing control func-tion (Figure 1-14).

We researched the use of space-time coding (STC) for SFN technology (coded SFN) to reduce the deterioration of trans-mission characteristics, which occurs when radio waves arrive from multiple transmitting stations in an SFN area. Computer simulations using channel characteristics collected in areas where an SFN is formed for terrestrial digital broadcasting showed that using the coded SFN technology can improve transmission characteristics by up to 4.8 dB even in cases where the characteristics degrade with a conventional SFN (Figure 1-15)(4).

■ International collaborationITU-R WP6A (Terrestrial broadcasting delivery) is preparing a

report titled “Collection of fi eld trials of UHDTV over DTT net-works.” In FY 2017, we proposed adding new information about terrestrial transmission experiments using a non-uniform constellation and 8K transmission experiments in an SFN envi-ronment using HEVC/H.265 compression.

As part of research toward next-generation terrestrial broad-casting, we enrolled in the 3rd Generation Partnership Project (3GPP), which standardizes mobile communication systems, and began investigating the standardization trend of 5G. We also began a study on the use of 5G systems for broadcasting in cooperation with the European Broadcasting Union (EBU).

We visited KBS and ETRI of South Korea to investigate the situation of terrestrial 4K broadcasting, which was started on May 31, 2017, and future mobile services.

We conducted a questionnaire-based survey about emergen-cy warning broadcasting at the Future of Broadcast Television (FOBTV), where broadcasters around the world gather, and re-ported the collected results at meetings of the NAB Show in April and IBC 2017 in September.

As part of activities at the Digital Broadcasting Experts Group (DiBEG), we exchanged opinions about next-generation terres-trial broadcasting with SBTVD-Forum, a standardization organ-ization in Brazil.

[References](1) A. Sato et al. (NHK): “A Study on Applying Layered Division Multi-

plexing for Next Generation Digital Terrestrial Broadcasting,” ITE Tech. Rep., Vol.41, No.6, BCT2016-34, pp.45-48 (2017) (in Japanese)

(2) H. Miyasaka et al. (NHK): “A Study on the Partial Reception for the Proposed Specifi cation of the Next Generation Terrestrial Broadcast-ing,” ITE Annual Convention 2017, 14C-3 (2017) (in Japanese)

(3) N. Shirai et al. (NHK): “A study on Bandwidth Extension for the Pro-posed Specifi cation of the Next Generation Terrestrial Broadcasting,” ITE Tech. Rep., Vol. 42, No. 11, BCT2018-48, pp.43-46 (2018) (in Japa-nese)

(4) A. Sato et al. (NHK): “Transmission Performance Evaluation of SFN Technology with Space Time Coding,” ITE Tech. Rep., Vol. 41, No. 43, BCT2017-92, pp.37-42 (2017) (in Japanese)

1.10 Wireless transmission technology for program contributions (FPU)

With the goal of realizing SHV live broadcasting of emergen-cy reports and sports coverage, we are conducting R&D on fi eld pick-up units (FPUs) for transmitting video and sound ma-terials. In FY 2017, we researched a microwave-band FPU and a 1.2-GHz/2.3-GHz-band FPU.

■Microwave-band FPUWe researched a microwave-band (6/6.4/7/10/10.5/

13-GHz-band) FPU that can transmit SHV video signals over a distance of 50 km, which is the same as the transmission dis-tance of current FPUs for Hi-Vision, and worked toward its standardization.

We previously employed dual-polarized multiple-input multi-

Received power ratio CA/CB of waves from two stations (Stations A and B) constituting an SFN [dB]

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Coded SFN (Collected channel characteristics)

Figure 1-15. Comparison of transmission characteristics between coded SFN and conventional SFN

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ple-output (MIMO) technology and orthogonal frequency-divi-sion multiplexing (OFDM) with a higher-order modulation scheme to expand the transmission capacity(1). Additionally, in FY 2017, we quadrupled the FFT size from 2,048 points to 8,192 points to increase the ratio of the effective symbol duration to the guard interval. We also introduced a non-uniform constel-lation, optimized the OFDM pilot signal level(2) and improved the bit interleave and also used LDPC codes for error correction to reduce the required C/N. These improvements resulted in a maximum transmission capacity of 312 Mbps, 5.7 times that of current FPUs (55 Mbps), and a transmission capacity of 200 Mbps, 3.6 times that of current FPUs, under the same required C/N (Figure 1-16).

At ARIB, we contributed to the establishment of a new standard incorporating the above technologies, ARIB STD-B71 “Portable Microwave Band OFDM Digital Transmission System for Ultra High Defi nition Television Program Contribution.”

■ 1.2-GHz/2.3-GHz-band FPUTo enable the mobile relay broadcasting of SHV signals by

using the 1.2-GHz/2.3-GHz-band, we are researching a MIMO system with adaptive transmission control using the time divi-sion duplex (TDD) scheme.

In FY 2017, we improved functions to expand the transmis-sion rate. For uplinks that transmit SHV video signals from a

mobile station to a base station, we increased the amount of information that can be transmitted per OFDM carrier symbol from 14 bits to 16 bits and improved the time ratio of uplinks to downlinks that transmit signaling information from a base sta-tion. This achieved wireless transfer at a maximum rate of about 140 Mbps. We also developed a function for supporting multiple base stations to expand the transmission service area for a road race relay. This function selects four antennas hav-ing a good reception quality out of many antennas and uses them for demodulation.

In our work on rate matching, which controls the coding rate of error correction codes adaptively according to the varying channel quality to prevent transmission errors, we implement-ed a function to control the coding bit rate of 8K video accord-ing to the variation in the error correction coding rates into a prototype system. We connected the system with an HEVC/H.265 codec with a variable rate and demonstrated that it can transmit SHV video signals at a rate varying in the range from 50 Mbps to 140 Mbps.

Using this prototype system (Figure 1-17), we conducted fi eld transmission experiments with assumed marathon courses around our laboratory and in urban areas. The experiments evaluated the mobile transmission characteristics of a MIMO system with adaptive transmission control, which dynamically changes the number of MIMO streams to be multiplexed, the modulation scheme and the error correction coding rate ac-cording to the channel status, and demonstrated the mobile transmission of SHV video signals in excess of 100 Mbps by the system connected with an 8K codec with a variable rate(3).

Part of this research was conducted as a government-com-missioned project from the Ministry of Internal Affairs and Communications titled “R&D on Highly Effi cient Frequency Us-age for the Next-Generation Program Contribution Transmis-sion.”

[References](1) K. Murase, H. Kamoda, K. Shibuya, N. Iai and H. Hamazumi: “Micro-

wave Link for 4K and 8K Broadcasting Program Contribution”, ITE Annual Convention 2017, 32E-1 (2017) (in Japanese)

(2) K. Murase, H. Kamoda, K. Shibuya, N. Iai, K. Imamura and H. Hama-zumi: “A Study on OFDM Pilot Symbol Level for 4K and 8K Micro-wave Link for Program Production”, ITE Technical Report, Vol. 42, No. 5, BCT2018-34, pp. 41-44 (2018) (in Japanese)

(3) K. Mitsuyama, F. Uzawa, F. Ito and N. Iai: “Outdoor Field Trial of 4×4 TDD-SVD-MIMO System with Adaptive Transmission Control,” ITE Technical Report, Vol.41, No.35, BCT2017-84, pp.13-16 (2017) (in Jap-anese)

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Figure 1-16. Transmission capacity and required C/N of microwave-band FPU

Equipment on the mobile station side Equipment on the base station side

Power amplifierPower amplifier Channel emulator

Transmission and reception control unit Transmission and reception control unit

Transmission and reception radio frequency unit

Transmission and reception radio frequency unit

Figure 1-17. Prototype MIMO system with adaptive transmission control

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1.11 Wired transmission technology

We are researching a program production and program con-tribution system using Internet Protocol (IP) technology that can be used for 8K programs. We are also studying a channel bonding technology for transmitting 8K programs over cable TV networks and the FTTH (Fiber to the Home) digital base-band transmission system.

■ IP-based program production and program contribution systemApplying IP technology to program production and program

transmission allows signals of various formats for video, sound, synchronization and control to be temporally multi-plexed and transmitted over a shared network at a low cost. In FY 2017, we worked on the following three R&D areas:

(1) Experiment on remote audio mixing using 8K IP transmis-sion

While conventional live program production requires a con-version process to synchronize signals received from a venue with the broadcast station’s master clock, an IP-based program production system can use the same clock for the venue and the broadcast station by exchanging clock synchronization in-formation between them using Precision Time Protocol (PTP). We verifi ed the synchronization performance in the ISU Grand Prix of Figure Skating 2017/2018, NHK Trophy, by time-multi-plexing and transmitting 8K video packets, 128 ch sound pack-ets and PTP packets over commercial IP networks between Osaka and Tokyo. The results showed that sound from a live coverage venue in Osaka can be mixed at the NHK Broadcast Center in Tokyo if the jitter of PTP packets is about one micro-second(1). Meanwhile, some production devices failed in clock synchronization. We plan to improve the synchronization algo-rithm and consider a way of reducing the PTP jitter, which var-ies with the network structure.

(2) Development of IP transmission equipment for mezza-nine-compressed 8K signals

8K program contributions used for program production need to be transmitted with high quality and low latency. However, transmitting a large amount of uncompressed signals incurs a higher network cost. We therefore developed equipment that applies mezzanine compression to 8K signals and transmits them over IP networks. This equipment can transmit 8K video at a reduced bandwidth with low latency while maintaining a high image quality comparable to that of uncompressed sig-nals. For example, 8K program contribution signals (4:2:2 sam-pling, 60-Hz frame rate, 40-Gb/s video bandwidth) that are mezzanine-compressed to 1/5 (post-compression video band-width of 8 Gb/s) can be transmitted over a single cable for general 10 Gb Ethernet. Laboratory experiments demonstrated that the equipment can transmit mezzanine-compressed 8K signals stably with high image quality and low latency (Figure 1-18). We plan to conduct fi eld transmission experiments, sup-port a 120-Hz frame rate and implement an error correction function(2).

(3) Development of an IP transmission system converterFor the interconnection between devices that use different

signal transmission formats and equipment control methods in an IP-based program production system, we developed a mechanism for converting the format and control method and fabricated a prototype converter.

The IP video router (IPVR) system being developed in NHK as a network matrix uses a different transmission format and control method from those of devices for IP-based program production systems. Using our prototype converter, we con-ducted a connection test between the IPVR and an IP program production system that we prototyped in FY 2017. The results demonstrated that the control device of the IP program produc-tion system can control the IPVR and that IPVR video signals can be transmitted to the IP program production system.

■Cable TV transmission of SHV signalsWe continued with our R&D on a channel bonding technolo-

gy to transmit partitioned 8K signals over multiple channels so that 8K programs can be distributed through existing coaxial cable television networks. In FY 2016, we developed a compact receiver equipped with a demodulator LSI that supports chan-nel bonding technology. In FY 2017, we conducted experiments on the retransmission of 8K satellite broadcasting over com-mercial cable networks using this receiver. The results showed that our compact receiver can receive retransmitted 8K signals stably. We also helped Japan Cable Laboratories compile re-quirements for a demonstration experiment on the retransmis-sion operation specifications for new 4K/8K satellite broad-casting and prepare experimental procedures with the aim of realizing a 4K/8K retransmission service on cable TV.

■Digital baseband transmission system for FTTHAs a way of distributing broadcasts to homes using FTTH, we

are studying a 10-Gbps-class digital baseband transmission system that divides multichannel streams of 8K and Hi-Vision broadcasting into IP packets and multiplexes them with base-band signals by using time-division multiplexing. In FY 2017, we studied an intra-building transmission system for condo-minium buildings installed only with coaxial cables, which can-not transmit baseband signals. The intra-building transmission system selects IP packets in response to a viewer request and converts them to radio frequency (RF) signals so that they can be transmitted over an existing coaxial cable. We prototyped a transmitter and receiver which comply with Data Over Cable Service Interface Specifi cation (DOCSIS) used for internet com-munications on cable TV and added a function to improve the frequency usage effi ciency and demonstrated the effectiveness of the system. We also investigated a way of migrating the ex-isting FTTH equipment for RF signal transmission to the digital baseband transmission system in stages(3).

[References](1) M. Kawaragi, T. Koyama, J. Kawamoto, S. Kitajima and T. Kurakake:

“Study on Synchronization Method for IP Remote Production,” Vol. 42, No. 11, BCT2018-39, pp. 5-8 (2018) (in Japanese)

(2) J. Kawamoto and T. Kurakake: “XOR-based FEC to Improve Burst-Loss Tolerance for 8K Ultra-High Definition TV over IP Transmis-sion,” IEEE GLOBECOM2017, CSSMA. 4-05 (2017)

(3) T. Kusunoki, Y. Hakamada and T. Kurakake: “A study for coexistence transmission of SCM and 10Gbps baseband video signals over FTTH networks,” BCT2017-90, pp. 45-48 (2017) (in Japanese)

Transmitter

Receiver

8K video after IP transmission with mezzanine compression

Figure 1-18. Laboratory experiment on the IP transmission of mezza-

nine-compressed 8K signals

NHK STRL ANNUAL REPORT 2017　｜　17

1　8K Super Hi-Vision

1.12 Domestic standardization of broadcasting systems

We are engaged in domestic standardization activities relat-ed to 4K and 8K ultra-high-defi nition television satellite broad-casting systems.

For the start of new 4K/8K satellite broadcasting in 2018, the Association for Promotion of Advanced Broadcasting Services (A-PAB) has been preparing operational guidelines(1). ARIB worked on revisions of its technical standards that specify the television systems in cooperation with A-PAB (Table 1-3). Members of NHK STRL contributed to these standardization ef-

forts for ultra-high-defi nition television broadcasting by partici-pating as committee chairperson of an ARIB development sec-tion and managers and members of the relevant ARIB working groups.

[References](1) ARIB Technical Report TR-B39 1.7, “Operational guidelines for ad-

vanced digital satellite broadcasting” (2018)(in Japanese)

Table 1-3. Major revisions of the ARIB standards for ultra-high-definition television satellite broadcasting systems

Domain ARIB Standard Major revisions

Multiplexing (MMT/TLV)

STD-B60 (ver. 1.12) Change in the specification for an HEVC video descriptors supporting HDR/wide color gamut and clarification of MMT specifications

Conditional access STD-B61 (ver. 1.4) Specification of the number of components (e.g., video, audio and data) and scramble keys that can be simultaneously processed by a receiver

Multimedia coding STD-B62 (ver. 1.9) Addition of the specification for handling ideographic variants, clarification of the receiver reference model, and clarification of the communication capability

Receiver STD-B63 (ver. 1.7) Addition of the specification for digital video and audio output supporting HDMI 1.4b and 2.1, and specification of performance requirements such as the number of components (e.g., video, audio and data) and scramble keys that can be simultaneously processed by a receiv-er and