4.1 Networked program production systems

We are researching the use of Internet protocol (IP) commu-nications networks for transmitting video materials and dis-tributed server-based broadcasting systems to store program files permanently and to develop new services.

■ Improving reliability for real-time video transmissionThe transmission paths in IP networks are shared and si-

multaneously used by multiple users and applications, so when the traffic of other users or applications (cross-traffic) increases, the available bandwidth may decrease and/or the transmission delay may suddenly increase, which causes qual-ity degradation and/or interruption of video transmissions. To counter these effects, we developed delay management tech-nology for multiple paths that analyzes the conditions of each path before allocating data to them (Figure 1).

First, the available bandwidth on each path is estimated using the transmission delay and the decrease in the trans-mission rate at the receiving end (these values increase when the input data including cross-traffic exceeds the capacity of observed path). The data allocated to each path is limited to this estimated value, and it should be adjusted according to changes in cross-traffic. To avoid temporary fluctuations, this adjustment is deferred until the maximum allowable delay is reached (1).

Wireless LAN used to transmit real-time video face prob-lems because of transmission speed variations and signal in-terruptions. We collaborated with NHK ITEC Inc. to improve the rate controller of a video codec so that it could better deal with the transmitting conditions of wireless LANs, and we de-veloped wireless LAN switching devices which switch wireless LAN systems when a signal interruption occurs.

We are researching advanced program-pro-duction technology for producing high-quality, attractive content efficiently, creating new forms of video expression, and supporting emergency news reports.

IP networks are expanding rapidly, and we are researching ways to use them for transmitting video materials for program production and dis-tribution. IP networks carry other traffic, which can limit the available transmission bandwidth and cause long delays. In particular, communica-tion over wireless LANs can be impeded by radio propagation conditions. We have developed tech-nology for transmitting video materials without interruption by estimating the available band-width, and we have begun field trials on it.

Working toward future tapeless program pro-duction systems, we developed a wide-area dis-tributed file system and a cloud-based content processing system to manage content use effi-ciently.

In research on high-quality speech synthesis, we are studying automatic read-out weather reports and developing methods to synthesize speech for a new speaker from a small amount of speech data on the speaker, augmented with a lot of speech data on other speakers that is stored in a database.

In research on audio devices, we improved the efficiency of light-weight loudspeakers using polymer films. We also developed a microphone that can handle high sound pressure and used it to record sound for Super Hi-Vision (SHV) video of a space shuttle launch. We are also looking for-ward to a practical implementation of our silicon electret condenser microphone; in particular, we estimated the lifetime of the charge stored in the dielectric inside the microphone at ordinary tem-peratures. The study showed that it is stable and can be used over long periods of time.

We continued our research on a “field pickup

unit” (FPU) for wireless contribution links in the 120-GHz-band that uses cross polarization for wireless transmission of uncompressed SHV sig-nals. At present, we are looking into the feasi-bility of using the 1.2-GHz and 2.3-GHz-bands as a replacement for the 700-MHz-band current-ly used by FPUs to cover road races and other events. We prototyped transmitters and receiv-ers using these bands. We also made progress in our research on a microwave-band FPU. We improved our macro-diversity reception adapter and used it for coverage of road races and golf events. We also studied schemes for a bi-di-rectional FPU and a frequency-domain channel equalization technique.

We improved the performance and functional-ity of our millimeter-wave mobile camera, which can transmit video wirelessly from a Hi-Vision camera with low delay and high quality, and used it in productions of many programs including the 62nd annual “Kohaku Utagassen” year-end song festival program. We are also interested in changing the 700-MHz-band frequency of our ra-dio microphones. To this end, we conducted re-search on a digital radio microphone that trans-mits uncompressed audio signals that are stable and low delay.

In our work on mobile and portable antennas, we evaluated the effects of the human body on the emission characteristics of walkie-talkie antennas in the VHF band and conducted field transmission tests using a 14-GHz-band SNG mesh reflector antenna.

We continued our research on a millimeter-wave TV camera that takes images of objects ob-structed by smoke, wood, and other materials. We improved its display functions so it could dis-play 3D images and detect slight movements in objects, and we used it in imaging tests through fog, smoke, and flames.

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4 Advanced contents production technology

■ Distributed server-based broadcasting systemThe distributed server-based broadcasting system consists

of a wide-area distributed file system for storing and search-ing program files, a cloud-based content processing system for high-speed video processing, and a program content distribu-tion system.

The wide-area distributed file system does not have a cen-tralized management structure and has the advantages of be-ing a permanent storage for the ever-expanding trove of files at broadcasting stations a way to share these files with mul-tiple users. In FY2011, we developed a scheme to manage and search files stored with continuous ID indexes, giving a data-base functionality to the wide-area distributed file system(2). By using on-air time as a continuous ID, files containing video, audio, text and other data stored on the wide-area distributed file system can be accessed in frame units on a common time line and can be synchronized and used easily. We also im-proved the performance of an algorithm to equalize the num-ber of data items stored in each node of the distributed hash table used to manage the files.

The cloud-based content processing system distributes video processing work to multiple servers over the network, and its advantage is that parallelization and video processing speed can be increased simply by increasing the number of

servers(3). In FY2011, we examined the amount of transmission buffers used by the pull-based file transfer protocol developed earlier, developed methods for identifying bottlenecks in video processing, prototyped equipment, and verified their perfor-mance.

We are studying a Time Zapping Service of a distributed server-based broadcasting system in which user can access past broadcasting programs by inputting their on-air times. To provide large numbers of program scenes to many viewers, we developed a caching algorithm to coordinate cache control among edge servers to save on storage. We also studied and implemented a user interface for the service.

[References](1) T. Koyama, S. Oda, M. Kurozumi, K. Aoki and M. Yamamoto: “A

Study on Delay Control Method for Real-time Video Streaming Using Multiple Paths,” IEICE Technical Report, Vol. 111, No. 278, CQ2011-46, pp. 13-18 (2011) (in Japanese)

(2) Y. Kaneko, M. Hwang, S. Takeuchi and Y. Izumi: “File Management Method by Mapping into Continuous Identifier for Distributed File System,” ITE Annual Convention, 11-1 (2011) (in Japanese)

(3) M. Hwang, Y. Kaneko, S. Takeuchi and Y. Izumi: “A Case Study on the Parallel Distributed Video Processing Method that Guarantees the Throughput,” IEICE Society Conference, B-7-60 (2011) (in Japa-nese)

4.2 High-quality speech synthesis

We are researching high-quality speech synthesis technol-ogy that can read out manuscripts for broadcast and automati-cally read out data broadcasts for visually impaired persons.

We have already developed a high-quality text-to-speech synthesis method that uses a large amount of recorded an-nouncer’s speech in news programs and built equipment to automatically read out Radio 2’s “Kabushiki Shikyo” (State of the Markets) broadcast(1). In FY2011, we built equipment to read out weather reports and began studying its operational issues. Using the speech synthesis system developed in FY2010 and the results of a study on classifying sentence structure(2), we generated synthesized speech from six-months worth of weather report data to verify the generality and robustness of the system. This test confirmed that the equipment could syn-thesize the required speech without difficulty. Also, in antici-

pation of its use in real broadcasts, we made improvements to the equipment and its database, making it easier to update the names of maritime regions, etc., and to add new announcers’ voices.

To enable speech synthesis with a wide range of expres-sions, we began developing a method to synthesize speech for a new speaker from a small amount of speech data on that speaker, augmented with speech of other speakers that has been stored in a database. In FY2011, we introduced speech conversion rules for using a speech training database loaded with associated acoustic and linguistic data. We also devel-oped a method to complement speech sequences with missing sounds with small amounts of data on new speakers.

We promoted our speech-rate conversion technology for language-learning applications on smart-phones (Figure 1).

Cross-traffic

Limits to available bandwidth

Allocate to other path

Transmit dataOverflow data is delayed

Transmission path

[Delay]

[Time]

Maximum allowable delay

Reporting site

Channel no. 1

Channel no. 2

Channel no. N Broadcast station

Current time Time limit

Delay in received data

Estimate available bandwidth of each path and allocate data Estimate delay of each path and avoid excessive control

　・・・

Without any control

With allocation control

Estimate delay, derive time limit,

and adjust control timing.

Figure 1. Procedure for switching transmission channels

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4　Advanced contents production technology　｜　4.2 High-quality speech synthesis

To enhance the fast playback function used for education and recitation, we developed a scheme to control the speech rate according to the part-of-speech, as a supplement to the con-trol using voice pitch and intensity. Control by part-of-speech would be especially useful when the text of an utterance is available. Finally, we improved the synthesis and announcer training equipment by adding functions for changing intona-tion in order to synthesize and edit speech for new words such as place names.

[References](1) H. Segi, R. Tako, N. Seiyama, T. Takagi, H. Saito and S. Ozawa: “Sen-

tence-Generating System for Speech Synthesis Using Templates and Application for the ‘Weather Report’ Radio Program,” ITE Jour-nal, Vol. 65, No. 1, pp. 76-83 (2011)

(2) H. Segi, R. Tako, N. Seiyama, and T. Takagi: “Template-based Meth-ods for Sentence Generation and Speech Synthesis,” IEEE Interna-tional Conference on Acoustics, Speech and Signal Processing 2011, ITT-L1.6 (2011)

4.3 Acoustic devicesWe are developing loudspeakers based on new principles of

sound generation and microphones with new functionalities to be used for producing content for next-generation broadcast media.

■ Lightweight loudspeakers using polymer filmIn FY2011, we studied the efficiency of loudspeakers in terms

of three parameters: ratio of direct current voltage to alternat-ing current voltage, film thickness, and ratio of relative dielec-tric constant to Young’s modulus. As a result, we found that

efficiency can be increased by decreasing the AC voltage (Fig-ure 1) and using thinner film(1). This research was conducted in cooperation with Foster Electric Co. Ltd.

■ High-pressure microphoneTo produce Super Hi-Vision programs with a strong sense

of “being there”, we developed a microphone capable of re-cording high-pressure sounds such as from a space shuttle or rocket launch, and recorded a space shuttle launch with a mi-crophone set up near the launch pad. The resulting sound was of sufficient quality for broadcast.

■ Silicon microphoneIn FY2011, we measured the lifetime of the charge stored

within the dielectric of our silicon electret condenser micro-phone. Specifically, we tested charge loss under accelerated discharge conditions by heating the dielectric storing the charge and used the results to estimate the charge lifetime at ordinary temperatures. The results confirmed that the charge lifetime would be ten years or more and that in normal op-eration, the silicon electric condenser microphone would be stable and could be used over long periods of times.

[References](1) T. Sugimoto, K. Ono, A. Ando, Y. Morita, K. Hosoda and D. Ishii:

“Semicylindrical Acoustic Transducer From a Dielectric Elastomer Film with Compliant Electrodes,” Journal of the Acoustical Society of America, Vol. 130, No. 2, pp. 744-752 (2011)

Figure 1. Language learning application with speech rate conversion function

AC voltage (V)

Effic

ienc

y (d

B/W

/m)

40 80 120 160 20063

69

75

81

Figure 1. AC voltage vs. efficiency

32　｜　NHK STRL ANNUAL REPORT 2011　

4　Advanced contents production technology　｜　4.3　Acoustic devices

4.4 Contribution transmission technology

We have made progress in R&D on various wireless trans-mission equipment used at broadcast program production sites to transmit program contributions.　

■ 120-GHz-band FPU for uncompressed SHVWe advanced with our research on a 120-GHz-band Field

Pick-up Unit (FPU) using cross-polarization multiplexing, for wireless transmission of uncompressed Super Hi-Vision sig-nals. In FY2011, we prototyped a transmitter (receiver) and dig-ital baseband signal processing modules for a compact, reli-able FPU that was based on the performance requirements set out by the Ministry of Internal Affairs and Communications’ “Study Group on spectrum-sharing technologies and other is-sues for next-generation broadcasting systems” in FY2010. We also conducted field tests of cross-polarization multiplexing for approximately one month and studied transmission char-acteristics in rainy and other conditions (Figure 1).

■ 700-MHz-band FPUThe Ministry of Internal Affairs and Communications (MIC)

is considering reallocating the frequencies used by the current FPU for coverage of road races and other events from the 700-MHz band to the 1.2-GHz and 2.3-GHz-bands. In anticipation of this change, we built transmitters and receivers operating in these bands(1) (Figure 2). This effort entailed making modi-

fications to the demodulation algorithms, including noise nor-malization and channel estimation, in the space-time trellis coded multiple-input multiple-output (STTC-MIMO) modula-tor-demodulator, and it reduced degradation in the equipment to below 0.5 dB. This equipment was field tested on running-relay courses in Kyoto and Hakone, under the auspices of the MIC in their project titled “Investigation and working group for technical requirements related to reallocating 700-MHz-band FPU frequencies”.

We conducted a survey of the conditions in the 1.2GHz and 2.3GHz bands by using wideband prototype antennas based on a log-periodic antenna.

We also continued to improve the performance of the trans-mitter antenna for the 700 MHz band. From the analysis of reception data, we confirmed that the antenna gain could be increased by choosing the proper height of the antenna. We confirmed the improvements by computer simulations, and we used the modified antenna to cover road races.

■ Macro-diversity receiver systemFor the 16-input base-station receiver prototyped in FY2010,

we built a new macro-diversity receiver adapter that add the Half mode whose occupied bandwidth is 8.5 MHz or lower, im-proves signal synchronization, and has better input and output interfaces(2). This equipment provides stable video transmis-sions for coverage of road races and golf and is easy to use (Figure 3).

■ Bidirectional FPUIn FY2010, we prototyped basic test equipment for studying

time division duplex (TDD) methods. This year, we studied the transmission efficiency of the FPU when varying the ratio of uplink to downlink capacity(3). We made progress on design-ing packetized OFDM transmission scheme, studied the basic functions for a hardware implementation, including the signal synchronization scheme, and built prototype program mod-ules.

■ New wireless transmission technologiesWe are studying application of single carrier frequency do-

main equalization (SC-FDE) to our millimeter-wave-band FPU. In FY2011, we conducted a simulation comparing the trans-mission characteristics of OFDM and SC-FDE in a static multi-

Figure 1. View of cross-polarization multiplexing field transmission tests

16-input base-station receiver

Macro-diversity receiver adapter

Figure 3. Macro-diversity receiver adapter used in the road-race relay

STTC-MIMOModulator

Transmitter

2.3GHz U/C2.3GHz D/C: 2 units

2.3 GHz-band PA: 2 units STTC-MIMODemodulator

Control/instrumentation PC

Receiver

Oscilloscopemonitor, etc.

Synchronization signal generator, encoder, etc.

Figure 2. Prototype 2.3 GHz-band FPU

NHK STRL ANNUAL REPORT 2011　｜　33

4　Advanced contents production technology　｜　4.4 Contribution transmission technology

path environment. The results suggested that in the millime-ter-wave-band, where amplifier linearity is poor, the SC-FDE method will be able to extend transmission distances more than OFDM can. Also, with the goal of developing wireless transmission technology of the Gbps class and a means to transmit compressed SHV or uncompressed HDTV video, we based the simulations on a 4x4 MIMO transmission technol-ogy using four transmitting antennas instead of the conven-tional system which uses two antennas.

■ Millimeter-wave mobile cameraOur millimeter-wave mobile camera can transmit HDTV

video wirelessly with low delay and high image quality. In FY2011, we improved the performance and functionality to make it more practical. We made improvements to synchro-nize the radio frequency in all base stations by transmitting a common reference signal using optical lines. We also added an automatic gain control (AGC) function to the optical-elec-trical converter for the return-link IF signal in order to keep the transmitting power constant. Also, to improve operability on site, we developed a demodulator with a link-quality monitor that displays and records the quality of the radio channel in real time, and added an auxiliary channel carrier transmission function that allows the reception conditions of the return link at the camera, such as return signal error rate and received C/N, to be monitored at the sub-video control room (Figure 4). We also prototyped a return video transmission system that sends four return video signals simultaneously and allows the camera-person to select any of them. The millimeter-wave mobile camera with these improvements was used for many programs including the 62nd “Kohaku Utagassen” year-end song festival program.

■ Radio microphone transmission technologyThe action plan for spectrum reallocation of the Ministry

of Internal Affairs and Communications calls for the frequen-cies of specified radio microphones to be changed from the 700-MHz-band to TV white space and 1.2-GHz-band. At pres-ent, we are studying how to implement this plan. In addition, to transmit a radio microphone signal stably with low delay on these reallocated frequencies, we are researching a digital ra-dio microphone able to transmit uncompressed audio signals.

In FY2011, we studied the transmission schemes using OFDM and error correcting code. We optimized transmission parameters to the requirements of the radio microphone, in-cluding the carrier interval and pilot arrangement, and studied schemes that are tolerant to interference from reflected waves, etc. We also reduced the transmission delay by selecting an er-ror correcting code length and OFDM symbol length that would be suited to the length of the uncompressed audio sample. We incorporated the results of this study into prototype test equip-ment for digital radio microphone transmissions with diversity reception (Figure 5), and achieved a transmission delay of 1 ms, which is less than 1/3 that of conventional digital radio microphones transmitting compressed audio signals.

We also studied the effect the human body has on the emis-sion characteristics of a 700-MHz-band radio microphone when it is near a person. We examined two types of micro-

phone, a hand-held type, which has the microphone and trans-mitter as one unit, and a two-piece type, which has a separate microphone and transmitter. We used our numerical human body model and human body phantom to perform the evalu-ations. As a result, we found that screening and reflection due to the human body can result in losses of antenna gain of ap-proximately 10 dB for the handheld unit and 20 dB for the two-piece unit. These values are very close to the values known from experience(4).

■ Effects of the human body on commercial broad-caster walkie-talkie link emissionsWe investigated the effect of human body on the radiation

patterns of the antenna for handheld transceivers with a nu-merical simulation of a human-body and identified a safe loca-tion for the antennas in terms of the specific absorption rate (SAR). The results are described in ARIB STD-B54,where the SAR values are given as guidelines.

■ Mesh reflector antenna for satellite news gatheringWe conducted field transmission tests using our 14-GHz-

band satellite news gathering (SNG) mesh reflector antenna and a practical transmitter (Figure 6) and succeeded in stable transmission of video signals. The gain and cross-polarization characteristics of the antenna were very nearly as designed.

[References](1) T. Nakagawa and T. Ikeda: “Performance Improvement of 2x2

STTC-MIMO-OFDM System,” ITE Technical Report, Vol. 36, No. 10,

Figure 4. Link quality monitor and loopback BER display

Meshreflectorantenna

Practical transmitter

Figure 6. Mesh reflector antenna transmitting video signal

Receiver

Delay time: 1ms

Transmitter

Figure 5. Digital radio microphone transmission test equipment

34　｜　NHK STRL ANNUAL REPORT 2011　

4　Advanced contents production technology　｜　4.4 Contribution transmission technology

BCT2012-48, pp. 69-72 (2012) (in Japanese)(2) K. Mitsuyama, F. Uzawa, T. Ikeda and T. Ohtsuki: “Field Experiment

of Macrodiversity Reception on Road Race Course,” IEICE Technical Report, Vol. 111, No. 12, RCS2011-14, pp. 77-82 (2011) (in Japanese)

(3) F. Uzawa, K. Mitsuyama and T. Ikeda: “A Study on Duplexing Meth-

od for Bi-directional FPU,” ITE Technical Report, Vol. 35, No. 34, BCT2011-63, CE2011-25, pp. 41-46 (2011) (in Japanese)

(4) N. Kogo and H. Hamazumi: “Effect of Human Body on Radiation Pat-tern of Wireless Microphone,” ITE Technical Report, BCT2011-90, Vol. 35, No. 54, pp. 111-116 (2011) (in Japanese)

4.5 Millimeter-wave TV camera

We are continuing with our research on a millimeter-wave TV camera that obtains an image by transmitting 60-GHz-band radio waves toward the subject and receiving the reflect-ed waves.

In FY2011, we focused on improving the image display meth-ods for broadcasting applications. We decided to use perspec-tive projection to draw pixels on the screen, because the cam-era can measure the objects in three dimensions; elevation, azimuth and depth. This enables viewers to get an intuitive understanding of the 3D space being imaged(1)(2) (Figure 1). We also made the camera detect slight movements in objects on a per-pixel basis, using the fact that the phase of reflected waves changes significantly for even very small movements. These pixels are displayed in a different color(1)(3) (red pixels in Fig-ure 1). This makes it possible for the camera to distinguish be-tween living and non-living objects, and consequently, it holds promise for a wide range of applications.

We conducted tests showing that objects, such as man-nequins and humans, can be captured using the millimeter-wave camera at distances of up to 10 m when they are com-pletely hidden from the naked eye or ordinary cameras by fog, smoke or flames. The camera also could distinguish between the mannequins and the human in the test by detecting small movements that the human made even when standing still.

[References](1) H. Kamoda, J. Tsumochi and F. Suginoshita: “Millimetre-wave Active

Imaging System Using 60-GHz Band,” IBC2011 Conference (2011)(2) J. Tsumochi, H. Kamoda and F. Suginoshita: “Evaluating Perfor-

mance of Monostatic Millimeter-wave Imaging Radar,” 2011 Korea-Japan Microwave Conference, FR1-5-5 (2011)

(3) J. Tsumochi, H. Kamoda and F. Suginoshita: “Detection of Slight Variation in Distance Using Millimeter-wave Imaging System,” IE-ICE Society Conference, C-2-97 (2011) (in Japanese)

Mannequins

ElevationDepth

Azimuth

human

The many red pixels indicate that small movements were detected.

Figure 1. Image captured by the millimeter-wave camera

NHK STRL ANNUAL REPORT 2011　｜　35

4　Advanced contents production technology　｜　4.5　Millimeter-wave TV camera