Super High Definition Image (WHD: Wide/Double HD)Transmission System

Kenji Tanaka,1,* Kenji Suzuki,1 Masahito Sato,2 and Yoshiki Arakawa1

1Communications Research Laboratory, Koganei, 184-8795 Japan

2Victor Company of Japan, Ltd., Yokosuka, 239-8550 Japan

SUMMARY

This paper describes a WHD image transmissionsystem constructed from a display projector, CODECs, anda camera system imaging a super high definition image(WHD: Wide/Double HD) corresponding to two screenportions of common high-vision images. This system wasdeveloped as a transmission system to communicate withor transmit information giving a reality-enhanced feeling toa remote location by using images of super high definition.In addition, the correction processing for the distortions ofimages occurring due to the structure of the camera system,an outline of the transmission experiments using the pro-posed system, and subjective evaluation experiments usingWHD images are presented. © 2002 Wiley Periodicals, Inc.Syst Comp Jpn, 33(9): 41–49, 2002; Published online inWiley InterScience (www.interscience.wiley.com). DOI10.1002/scj.10063

Key words: HDTV; MPEG2; ATM; space sharing;reality-enhanced feeling.

1. Introduction

With the increased user needs for picture quality andthe improved computer processing capabilities in recentyears, efforts to decrease the cost and increase the accuracyof various display devices, such as CRT, LCD, and plasmadisplays, have progressed rapidly. In addition, BS digitalbroadcasting including HDTV broadcasting was initiatedin December 2000 after its implementation at the 27thOlympic Games (Sydney Games) of September 2000. Re-garding CS digital broadcasting, a transmission schemesimilar to that of BS digital broadcasting was adopted afterthe publication of a report of the Electrical Communica-tions Deliberative Council dated February 28, 2000. On thebasis of the above, it is expected that the spread of highdefinition images (or HDTV images) to ordinary house-holds will accelerate [1].

On the other hand, Independent Administrative Insti-tution, Communications Research Laboratory (CRL),started a multimedia virtual laboratory (MVL) project in1997 as a five-year plan. This laboratory has been conduct-ing research and development work on a virtual laboratoryfor performing joint research and experiments over high-speed networks constructed by connecting multiple re-search organizations. Using the Japan Gigabit Network(JGN) [2] which started in 1999 as a function of the Tele-communications Advancement Organization of Japan forR&D, or ATM services by carriers, the authors have con-ducted various studies: remote instructions of dance [3],

© 2002 Wiley Periodicals, Inc.

Systems and Computers in Japan, Vol. 33, No. 9, 2002Translated from Denshi Joho Tsushin Gakkai Ronbunshi, Vol. J84-D-II, No. 6, June 2001, pp. 1094–1101

*Graduate School of Engineering, University of Tokyo.

Contract grant sponsors: Supported in part by funding from the JapanGigabit Network for collaboration with the Telecommunications Ad-vancement Organization of Japan (JGN-G11028) and by scientific re-search aid from the Ministry of Education [Basic Research andDevelopment (B)(2)12558016].

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medical techniques (suturing techniques) [4], drilling workby remote operation robot [5], and sharing virtual spacesusing sounds and images of four points [6] and others [7–9]with the University of Tokyo/Tsukuba University/NationalInstitute of Multimedia Education.

In this paper, we describe a WHD image transmissionsystem constructed from a WHD projector, a low delayCODEC, and a WHD camera system for imaging highdefinition images (WHD: Wide/Double HD) correspond-ing to two screen portions of the usual HDTV images. Thissystem was developed as a transmission system for com-municating information with a reality-enhanced feeling,using images whose definition exceeds HDTV images,as part of the MVL project. In addition, the correctionprocessing method for distortions in imaged images dueto the structure of the WHD camera, an outline of thetransmission experiments using the proposed system,and subjective evaluation experiments using WHD im-ages are presented.

2. Configuration of WHD TransmissionSystem

The specifications of the WHD camera system, theWHD projector, and low delay CODEC for HDTV, whichcomprise the WHD transmission system, are discussedbelow.

2.1. WHD camera system

In imaging an object with a wide field of vision usingthree cameras, the configuration with three cameras ar-ranged in parallel as shown in Fig. 1(a) allows seamlessimaging of the object on line (II) of the same figure.However, object A on line (III) is not imaged by any camera.But object C on line (I) is imaged by two cameras, the leftcamera (Camera-1) and the center camera (Camera-2).

Thus, a method of dividing the imaged area usingprisms and mirrors [10] as shown in Figs. 1(b) and 1(c) isused. By this method, regardless of the distance betweenthe cameras and the imaged object and the location of theimaged object with respect to line (I), (II) or (III), an imagecan be obtained seamlessly without dead angles, duplica-tions, and the like.

Thus, by the one-lens–three-heads scheme shown inFig. 1(b), an image obtained by a special focus lens isdivided by the prism, and each area is imaged by threecamera heads. In this case, the image taken by the left andright camera heads (Head-1 and -3) are overlapped in thehorizontal direction with the image taken by the centralcamera head (Head-2) and this portion is taken as one imageby processing it through a seamless processor. Since the

lens part must be a special focusing lens, the system cost isincreased, while zoom operations or focus adjustments canbe performed easily. However, since three heads are re-quired, individual differences between the image pickupdevice must be adjusted for color.

Fig. 1. Configuration of multicamera.

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On the other hand, in the three-camera scheme shownin Fig. 1(c), the images taken by the left and right cameras(Camera-1 and -3) must be left-right rotated, since they areimages reflected by mirrors, and there are differences inimage quality from the image taken by the central camera,since only the image taken by the central camera is a directvision image. In addition, an imaged object is divided bythree independent cameras, and adjusting the focus, aper-ture, zoom, white-balance, location, direction, and so on ofeach camera is difficult. While an inexpensive camera sys-tem for commercial use can be constructed by this scheme,the location of the cameras must be adjusted, since theimage angle changes each time a zoom operation or a focusadjustment is made.

In addition, these two schemes comprise the systemproposed to the 2002 FIFA Japanese World Cup Organiza-tion Committee (JAWOC) for implementation of a virtualstadium during the world cup soccer games to be cospon-sored by Japan and Korea in 2002.

Figure 2 shows the configuration of the WHD camerasystem developed by the authors. The configuration is thetwo-camera scheme using two cameras and two mirrorssimilar to the three-camera scheme presented in Fig. 1(c).Two 2/3-inch three-panel HD cameras having image anglesof 36.5° are installed in the real camera positions (Real HDCamera-1 and -2 in the figure) and a virtual WHD camerataking images of 73° continuously by combining twoHDTV images in the vertical direction is constructed byadjusting the position, posture, and direction of each cam-era (pan-tilt-rotation), zoom, focus, aperture, white-bal-ance, and so on.

Figure 3(a) shows the image of a soccer game takenby placing the WHD camera on the fourth step of the mainstand of the National Kasumigaoka Stadium (Shinjuku-ku).

The image decreases as the distance from the camera in-creases (left and right ends of the same figure) since inaddition to adjustment errors in each adjusted parameter ofthe two cameras, the image is not symmetrical with respectto keystone distortion (the imaged body with respect to thetwo real cameras), or imaging is done with the grandstandin a slanted direction. Since the installation of the WHDcamera was to the right of center of the grandstand, the rightside is larger, with the left end decreasing more than theright end. In addition, since a broad angle lens is used, thereis little barrel distortion, but the above-mentioned keystonedistortions are dominant, and these effects can be ignored.However, the color tone and shape become noncontinuouswith the screen center, which connects the two HD cameraimages as the border.

Thus, the color tone and the image distortions havebeen adjusted and corrected by the editing studio of SonyPCL (Inc.). As a result, it has been confirmed that onecontinuous WHD image can be obtained as shown in Fig.3(b). However, this method cannot be applied to live broad-casting of an event. Thus, the following study was con-ducted.

UNIVERS (Unified Virtual Environment and RealOperation Space: a three-dimensional space sharing com-munications experimental facility) developed by theauthors is a display system formed by the three screens ofrear-projecting 100-inch projectors, in which the angleformed by the two left and right screens and the centralscreen can be varied from 180° to 90°. Thus, WHD imagesare taken by changing the angle formed by the left andcentral display surfaces by 180° (the display surface ofUNIVERS is formed at the position of straight line E-E′ inFig. 4; this corresponds to projection onto the plane screenfor WHD projector use), 90° (the display surface of UNI-VERS is formed at the position of straight lines A-A′ andB-B′), and 143.5° (the display surface of UNIVERS isFig. 2. Configuration of WHD camera.

Fig. 3. Correction of WHD images.

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formed at the position of straight lines C-C′ and D-D′). Theresults of displaying at various angles are shown in Fig. 5.In the cases of 90° and 143.5°, images are taken by install-ing a digital camera at the intersection point of the normallines of each display screen, and, in the case of 180°, withthe height at the center of the display screen and with the

digital camera at a position 4 m from the screen. As a resultit has been confirmed that natural shapes of the imagedobjects can be obtained by eliminating the effects of key-stone distortions by making the angle formed by the screen143.5°, which is the angle formed by the intersection of twovertical lines with respect to the screen center lines of thetwo high-vision cameras of the WHD camera system, asshown in Fig. 5(c). In addition, the black-lined part in thecenter of the result represents the frames of the screens usedby UNIVERS.

The color tone is adjusted frequently since the imag-ing environment including the sunlight or the position ofthe sun changes frequently in outdoor imaging. Color tone-adjusting work may be avoided in imaging during the nightor under a certain level of illumination indoors, by makingadjustments at the beginning of an event, since the illumi-nation conditions are constant in these cases. This adjust-ment work is performed by the usual broadcasting work,but becomes difficult due to the existence of two cameras.

2.2. WHD projector

This projector is constructed from three display de-vices which are 1.3 inch of 3,950,000 pixels (1028 × 3840pixels) corresponding to the RGB colors with the structureof the D-ILA (direct image light amplifier), an opticalsystem which projects in magnification by pixel aspecttransformations, and 243.5 inch (of a height of 1.5 m and awidth of 6 m) and 165 inch (of a height of 1 m and a widthof 4 m) front side projecting-type screens.

The D-ILA structure, unlike the general TFT (ThinFilm Transistor) structure, is constructed by coupling anactive matrix-type board built inside a driver with a single-crystal silicon board/CMOS structure, and displays an im-age by writing input image signals into each pixel by aninternal driver and modulating the vertically oriented liquidcrystals by the individual pixel voltages. In this way, thesuper high-density pixel structure shown in Table 1 can berealized while achieving a high-speed response charac-

Fig. 5. Images on UNIVERS.

Fig. 4. Relation between structure of WHD camera andangle of screens.

Table 1. Specifications of LCD

Effective pixel number 3840 (H)* 1028 (V)

Pixel arrangement pitch 7.6* 14.8 µm

Effective display area 29.1840* 15.2144 mm

diagonal 1.30 inches

aspect ratio 16:9

Electrode interval of adjacent pixel

0.5 µm

Aperture ratio 90.3%

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teristic and a high aperture rate, reflection factor, and con-trast.

A 750-W xenon lamp is used as light source, the lightfrom which is focused by an optical system and is decom-posed into RGB by an incident-side dichroic mirror. Eachcolor of light is reflected by a steering mirror and directedonto the associated display device via a PBS (deflectingbeam splitter). The light of each color reflected and modu-lated by each display device is transformed in luminanceby the PBS, synthesized by a dichroic mirror on the ejectingside, and projected onto a screen by a projecting lens. Asshown in Fig. 6, an anamorphic lens is used as the projectinglens and the pixel aspect ratio in the screen displayed imageis made to be 1:1 by converting the aspect ratio of thedisplay device from 16:9 to 4:1 on the screen.

As shown in Fig. 7, the interval of each pixel on thescreen becomes 1.5 mm when an image is projected onto a243.5-type screen. In this case, the vision angle per pixel isabout 1′ by Eq. (1) when an image on the screen is viewed

from 5 m away. This value corresponds to the visual senselimits of a still image for a vision of 0.7 to 1.0 [11]:

Using this projector, a high-vision image 2 ch with ahorizontal size of 1920 pixels and vertical size of 1024pixels as a dynamic image is taken as an input image in 30Hz interlaced mode, and is projected as a progressive imagewith a horizontal size of 3840 pixels and a vertical size of1024 pixels. In addition to left–right rotation for convertinga WHD camera image (which is a mirror image) into acorrect image, upper–lower rotation or left–right upper–lower rotation is performed in real time. For a still image,an input image of the dynamic image is preserved as a stillpicture file and a still image accumulated in a still picturedatabase is read out and displayed within 10 seconds.

2.3. Low-delay CODEC for HDTV

In coding and decoding a WHD image, the low-delayCODEC for HDTV developed by CRL in 1998 was usedin a pair. The specifications of this CODEC are shown inTable 2. In addition, regarding sound, transmission of up to4 ch is possible with one CODEC, and sound of twomicrophones is transmitted using only 2 ch in the experi-ments described in the following section.

3. WHD Transmission Experiments

3.1. Basic experiments

The configuration of the basic experiments with theWHD image transmission system conducted between

Fig. 6. Aspect transfer by anamorphic lens.

(1)

Fig. 7. Ability of eyesight.

Table 2. Specifications of HD CODEC

Input signal BTA S-001/002 (analog/digital)SMPTE 240 M/260 M/274 Mspecifications

Degree of resolution 1920/1440 pixels 1080/1035 lines

Field frequency 60.0 Hz/59.94 Hz

Color signal ratio 4:2:0/4:2:2

Coding scheme MPEG2 MP@HL

Motion compensation prediction of both directions, halfpixel accuracy

Information rate 21.6/58.3/117.0 Mbit/s

Delay time minimum 180 ms (P pictureinterval: when M = 1)

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NIME and CRL in early 1999 is shown in Fig. 8. Here, ascenery image around NIME taken by a WHD camerasystem installed on the fifth floor of an NIME researchbuilding is coded by a low-delay HDTV encoder and trans-mitted about 60 km over an ATM public network (the circuitcontract band was 75 Mbit/s, and the information transmis-sion rate per coding device was 22 Mbit/s based on thespecifications of the CODEC and the band of the transmis-sion path), decoded at CRL, and then output to the WHDprojector.

It has been confirmed by the experiments that aseamless image can be taken by adjusting various parame-ters of the cameras as discussed in Section 2.1, that syn-chrony can be ensured by inputting a synchronous signal ofone of the two cameras installed at NIME to the othercamera, and that synchrony within the frames can be com-pensated by inputting two image signals obtained afterdecoding at CRL into the frame synchronizer.

3.2. Verification experiments

The configuration of the verification experimentswith sports events such as rugby or soccer played in astadium beginning in 2000 is shown in Fig. 9. Here, animage of the WHD camera system installed in the televisionbroadcasting booth on the fourth step of the main stand ofthe stadium is transmitted about 30 km by the HDTVtransmission service, which has the specifications shown inTable 3, to the University of Tokyo Intelligent ModelingLaboratory (IML), coded by two low-delay HDTV encod-

ers installed within the IML, transmitted about 30 km viaan ATM public network and the JGN run by the Telecom-munications Advancement Organization of Japan (theminimum bandwidth on the transmission path is 135 Mbit/sand the information rate per coding device is 22 and 60Mbit/s from the constraints of the specifications of theCODEC), decoded at CRL, and output to the WHD projec-tor.

The measures against keystone distortions of imagesdiscussed in Section 2.1 and the associated methods havebeen verified by experiments. In addition, subjective evalu-

Fig. 8. Experiments with NIME.

Fig. 9. Experiments with national stadium.

Table 3. Specifications of HDTV Tx. service

Signal form BTA S-001

Field frequency 60.0 Hz

Band limits (luminance signal: Y)

60 Hz ~ 24 MHz

Band limits (colordifferential signal: Pb, Pr)

60 Hz ~ 8 MHz

Standardized frequency (luminance signal: Y)

55.6875 MHz

Standardized frequency (luminance signals: Pb,Pr)

18.5625 MHz

Coding scheme scramble binary NRZ

Quantization 8 bit

Transmission rate 622.08 Mbit/s

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ation experiments discussed in the next section were per-formed using the images collected in the experiments.Regarding the effects of the coding information rate, differ-ences between 22 and 60 Mbit/s were not observed, prob-ably because the objective images of the players, referees,ball, and upper screen part change only partially in theimages evaluated, without camera work involving panning,tilt, zoom, and so on. Thus, evaluation experiments bytransmission at lower rates using other evaluation imagesand other CODECs remain as future tasks.

3.3. Subjective evaluation experiments

The WHD projector was displayed at the “Reality-Enhanced Display Forum 2000” held at Tokyo Institute ofTechnology in November 2000. Subjective evaluation ex-periments were conducted with the participants, and re-sponses were obtained from 68 subjects. Three kinds of stillimages (images obtained by scanning pictures of the scen-ery of Harajuku or Furano, aerial picture of CRL) anddynamic images (images obtained after adjusting the colortone and correcting the distortions of soccer images col-lected in March 2000 for a round of verification experi-ments) were used as evaluation images, and five evaluationcategories—“very poor,” “poor,” “average,” “good,” and“very good”—were used for ordinary television images(SDTV) and HDTV images. Regarding the dynamic im-ages, scoring evaluations were also performed while watch-ing the soccer game at the stadium (viewing of a soccergame by an inexperienced subject based on the experienceof viewing other games, plays, and the like). In addition, inorder to extract the factors governing the evaluations, freerecords for each evaluation item written by the subjectswere obtained. A 165-inch screen (height 1 m, width 4 m)was used as the projection screen and a maximum of 10subjects were seated about 5 m from the screen.

The experimental results are shown in Table 4. Theresponse rates do not reach 100% except for the comparisonof a dynamic image with SDTV, for reasons such as lack ofviewing experience with HDTV, which was an object ofcomparison, inability to image game viewing in a stadiumbecause of lack of experience, inability to view until thedisplay of a still picture because of time constraints, and soon.

Regarding still images, numerous subjects com-mented on the broad field of vision, such that the proposedsystem can display a number of pixels far exceeding that ofthe NTSC and has wide visual field, and high evaluationresults of 4.1 for SDTV and 3.4 for HDTV were obtained.With regard to dynamic images, many similar commentswere made and a high evaluation result of 3.8 was obtainedwhen compared with SDTV, while comments on the prob-lem of color tone and the degree of resolution were numer-

ous and an evaluation result of 2.9, which is inferior toHDTV, was obtained in a comparison with HDTV. Inaddition, the effects of television broadcasting of SDTVand HDTV, such as the zoom-up function or slow motionreplay of scoring scenes, the display of the game clock, andthe like, have been requested.

Here, the color tone and the degree of resolution,which have been commented on frequently in evaluationsof dynamic images, are discussed. Few subjects have madesimilar comments even in evaluations of still images. Thus,the variance when comparing a still image with HDTV islarger than in other cases. These problems are attributed tothe decrease in resolution and the occurrence of ghostingcaused by the fact that imaging is done through glass, thatan imaged object reflected on the structural mirrors of thecameras is imaged, and so on. The insufficient contrast ratioof the projector or the insufficient brightness due to agingof the lamps are also contributing factors. Regarding these,improvements in the contrast ratio (from 500:1 to 2500:1)and the brightness (from 400 lm to 550 lm) have beenachieved by improving the display elements (reducingspacer balls and defects, improving shading, improving theaperture ratio by reducing the pixel electrode interval, andimproving the orientation film) and changing the lampsafter the evaluation experiments. Subjective evaluationswith these improvements are to be made in the near future.

Table 4. MOS

Evaluationimage

Object ofcomparison

Mean value(variance)

Responserate (%)

Still image SDTV 4.05 (0.64) 86.8

HDTV 3.35 (1.15) 72.1

Dynamicimage

SDTV 3.84 (0.94) 100.0

stadiumgamewatching

3.21 (0.97) 92.6

HDTV 2.91 (0.88) 82.4

Fig. 10. WHD still Image: at Harajuku.

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However, a comparison with game watching in astadium yielded an evaluation result of 3.2. Hence, theproposed system is considered to faithfully transmit theenvironment of watching a soccer game in a stadium withhigh reality-enhanced feeling.

4. Conclusions

As part of the MVL project, this paper presents aWHD image transmission system constructed from a dis-play projector, CODECs, and a camera system for high-definit ion images (WHD: Wide/Double HD)corresponding to two screen portions of the usual HDTVimages, which has been developed to transmit informationwith reality-enhanced feeling by means of images whosedefinition exceeds that of HDTV images. It also presentsan outline of transmission experiments using the system, astudy of the corrective processing of image keystone dis-tortions due to the structure of the WHD camera system,and the results of experiments on subjective evaluation ofthe WHD images.

Acknowledgments. The authors are grateful tovarious people affiliated with the Victor Company of Japan,Canon Sales, NTT Communications, Mitsubishi Electrical,and Sony-PCL for their assistance in the construction andtransmission experiments, and to various people affiliatedwith the National Institute of Multimedia Education, Na-tional Kasumigaoka Stadium, the University of Tokyo In-telligent Modeling Laboratory, the TelecommunicationsAdvanced Organization of Japan, the Japanese Rugby andFootball Association, the Japanese Professional SoccerLeague, J League Imaging (Ltd.), and the Japanese SoccerAssociation for providing the experimental environment. In addition, the authors express their gratitude to Sen-ior Researcher Machizawa, Team Leader Nakagawa, andother people of the Next Generation Internet Group, Infor-mation and Network Systems Division, CommunicationsResearch Laboratory, for their support in constructing thenetwork. We also acknowledge our obligation to variouspeople, beginning with Research Associate T. Aoki andProfessor H. Yasuda of the University of Tokyo, ResearchCenter for Advanced Science and Technology, for theircontinuing valuable suggestions and guidance. Part of this study was supported by funding from theJapan Gigabit Network for collaboration with the Telecom-munications Advancement Organization of Japan (JGN-G11028) and by scientific research aid from the Ministry

of Education [Basic Research and Development(B)(2)12558016].

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AUTHORS (from left to right)

Kenji Tanaka (member) received his B.S. degree from the Department of Electronic Engineering of Fukuoka Universityin 1989 and joined the Communications Research Laboratory, Ministry of Posts and Telecommunications (now the Communi-cations Research Laboratory). He was engaged in research on electric wave propagation and mobile satellite communicationssystems using the experimental satellite V at the Space Communications Technology Laboratory, Kashima Space Communica-tions Center, Kanto Branch of the Communications Research Laboratory. In 1995 he became a research associate in the Researchand Development Department, National Institute of Multimedia Education, where he performed R&D related to the intercol-legiate satellite network (SCS: Space Collaboration System). In 1998 he became a research officer in the EmergencyCommunications Research Laboratory, Communications Systems Division, Communications Research Laboratory, and par-ticipated in construction of the Japan Gigabit Network (JGN) for research and development. He is currently a senior researcherwith the Next Generation Internet Group, Information Communications Division, Communications Research Laboratory, anda doctoral candidate at the University of Tokyo. He is a member of the Japan Educational Engineering Society.

Kenji Suzuki (member) received his B.S. degree from the Department of Electronic Engineering, College of VocationalTraining (currently the University of Vocational Ability Development) in 1983. He then joined the Radio Research Laboratory,Ministry of Posts and Telecommunications (now the Communications Research Laboratory), and has been involved in researchon satellite control technology, mobile satellite communications, and the MVL (multimedia virtual laboratory). He is currentlya technical member of the Space Communications Group, Wireless Communications Division, Communications ResearchLaboratory. He is a member of the Japanese VR Society and HIS Society.

Masahito Sato (member) received his B.S. degree from the Department of Electrical Engineering of Meisei Universityin 1976. He joined Victor Company of Japan in 1981, and has been involved in research and development in the fields of computerapplication systems, MPEG and other image compression, LSI development, and superhigh-definition image processing anddisplay systems. He is currently lead technical member, Task Development Cluster, Technology Development Headquarters,Victor Company of Japan.

Yoshiki Arakawa (member) received his B.S. degree from the Department of Engineering Management of WasedaUniversity in 1978 and his M.S. degree in mechanical engineering in 1980. He then joined Matsushita Electrical Industries. Hemoved to the Communications Research Laboratory, Ministry of Posts and Telecommunications (now the CommunicationsResearch Laboratory) in 1990, and currently is the leader of the Image Group, Information Communications Division,Communications Research Laboratory. His research areas include graph and image processing by hypergeometric graphs(hypertriangular/hypertetrahedral). He is a member of the Information Processing Society and the Precision Engineering Society.

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