1、Rec. ITU-R BT.1201 1RECOMMENDATION ITU-R BT.1201EXTREMELY HIGH RESOLUTION IMAGERY(Question ITU-R 226/11)(1995)Rec. ITU-R BT.1201The ITU Radiocommunication Assembly,consideringa) that extremely high resolution imagery could be used as future imaging systems in various fields, such ascomputer graphics
2、, printing, medical, motion pictures, television and so on;b) that for constructing such systems, it is necessary to consult with many experts in various related fields onimages;c) that studies and application experiments on extremely high resolution imagery are being conducted in variousparts of th
3、e world;d) that common usage of devices is preferable for economical implementation of the extremely high resolutionimagery systems;e) that bit-rate reduction technologies take a major role in transmission of the extremely high resolution imagery;f) that required spatial and temporal resolutions and
4、 aspect ratios may differ depending on the applications in themarket place;g) that conversion of spatial and temporal sampling lattices are becoming possible between different formatswithout introducing artifacts to the converted images;h) that Recommendation ITU-R BT.1200 “Target standard for digit
5、al video systems for the studio and forinternational programme exchange” defines an innovative approach to “resolution independent” TV systems over a widerange of applications,recommends1 that spatial and temporal resolution and picture aspect ratio should be flexible enough to meet a variety ofrequ
6、irements in different application fields. Annex 1 gives examples of current development work;2 that a header in the data stream should be used to define the parameters specified in 1 above;3 that commonality of colorimetry should be achieved in different formats.ANNEX 1Progress report on extremely h
7、igh resolution imagery (HRI)1 IntroductionBecause of the physical limitations in technologies which are available in the real world, most of the applicationsdescribed in this Recommendation are in non-real-time areas. To investigate realization issues in 2 a model has to beassumed. Because of the re
8、asons listed above, in spatial resolution hierarchy, the following conventions are used in thisRecommendation.2 Rec. ITU-R BT.1201A hierarchy of spatial resolution models are assumed in 2 as indicated in Table 1.TABLE 1A hierarchy of spatial resolution modelsHRI-0 HRI-1 HRI-2 HRI-3Spatial resolution
9、(number of samples)1 920 1 080 3 840 2 160 5 760 3 240 7 680 4 320The hierarchy is based on 16:9 screen aspect ratio but this is just for sake of discussion.HRI-0 to 3 are simple multiples of integers in horizontal and vertical directions.The HRI hierarchy is defined spatially and on the temporal ax
10、is the image is assumed to be stationary (or in non-realtime). In the real-time case it is classified by specifying the frame rate.2 Current situation2.1 Still and picture-by-picture image processing (currently in practice)It is reported that in recently released films digital film-optical effects a
11、re intensively used and this makes the films veryattractive to the majority of audiences. The digital film-optical effects, i.e., electronic processing on film, set a new stagefor film making, efficiently replacing the previous film optical processes by the cost-effective and well-establishedstudio
12、post-production techniques. These are compositing with computer-generated graphics, film matting andcompositing by blue-screen keyer, retouching of scenes to remove unwanted landscapes and colour and gradationchanges for old and decayed films. There are several such systems available in the market a
13、nd they are successfullyused. To compose the whole system, a CCD film scanner, an output film recorder and a signal processing facility areused. Workstations and relevant software packages are usually used to realize these effects. The equipment can handlefilm quality of extremely high resolutions;
14、that is more than 40 times of conventional TV signal resolutions.2.2 Computer graphics (CG)Images for graphics arts can be generated by computer graphics. The images are generated by off-line, and there are noserious technological problems involved. If the disk capacity used is large enough and a hi
15、gh-speed computer is used,parameters such as spatial resolution, screen aspect ratio, temporal resolution and others, can be set, in principleaccording to the demands. However, creation of moving images on a real-time basis is difficult to realize with currenttechnology. It depends on the complexity
16、 of the image to be produced and the CG technology used. Image generation bysimple CG technology, makes some applications, such as virtual reality systems, flight simulators and game machines,possible in real-time.For current HDTV programme production, approximately one hour is required using a 200
17、MIPS computer to generateone frame of a human image. If an HRI-3 level of image is to be produced with the same technology, 16 hours will beneeded to generate a 4 4 times higher resolution image. Availability of huge CPU power in terms of MIPS and anadoption of dedicated graphics engines are always
18、the key for generating high resolution images in CG.In present graphic workstations, the most common display parameters are 4:3 screen aspect ratio, square pixels,60 frames progressive scanning, 1 280 1 024 pixels, and a total 32 bits gradation in colour and in grey scale. In recentmodels, 1 600 1 0
19、24 pixels and a total 48 bits gradation are adopted.Rec. ITU-R BT.1201 33 Realization issues3.1 Display technology3.1.1 CRT (cathode ray tube)In CRT displays with an image size of about 20 in, a resolution of about 1000 lines can be achieved at a shadow maskpitch of about 0.3 mm. In high-level works
20、tations, a 0.15 mm pitch has already been realized. The mask pitch dependson many technical factors, like the thickness of the mask and manufacturing conditions. With the present technologylevel the limit is estimated to be about 0.16 mm in the 40 in size of CRT. Current spot size of the electron be
21、am is around1-2 mm. To have higher resolution it is necessary to reduce the size of the spot to around 0.5-1 mm.It is also necessary to increase the driving speed of CRT deflection circuitry. This is achieved by reducing the width ofthe deflection yoke wire and by lowering the loss at the core. To r
22、educe deflection errors a digital compensation circuitwill be necessary.3.1.2 LCD (liquid crystal display)There are two alternative applications of LCD technology to the display of high resolution imagery. For direct-viewtype LCD the availability of a larger size liquid crystal panel will be a poten
23、tially large problem in terms of technologyand cost involved. For high resolution image display, a larger size screen is always requested by viewers. In this regard,projection type LCD has a problem of tradeoff between expensive optical systems for a larger size liquid crystal paneland the lower bri
24、ghtness gained from a small size liquid crystal panel.3.2 Acquisition technology3.2.1 TV cameraThe marginal resolution of a lens system for practical use is assumed to be about 100 lines/mm. Therefore, theachievable vertical resolution by a 1 in lens system (CCD scanning area of 14 7.8 mm) is 7.8 10
25、0 2 = 1560 TVlines, and it is considered that an optical system that is larger than 1 in would be necessary in a system above HRI-1 level(3 840 2 160).When a higher resolution is required, the pixel size of image pick-up devices tends to decrease. The low sensitivity isalleviated by such measures as
26、 enlarging the light-receiving surface, adopting a high sensitivity element, and reducingthe noise level.Regarding the number and the size of pixels, a prototype of a 2 million-pixel (2/3 in optical system) CCD has beenannounced as a two-dimensional CCD for television. Not the reduction of size but
27、expanding the surface of the chipdevices which can cover up to HRI-1 is considered achievable within several years. A new technology would benecessary for further increase of resolution.The reduction of the S / N ratio of a camera lowers the compression rate. Thus, lowering the noise level is a prim
28、eimportance.3.2.2 TelecineThree different image pick-up methods are currently adopted in telecine. Those are image pick-up tube camera or CCDimage pick-up area sensor, flying spot scanner, and laser scanner. Most of the problems originating in the high resolutionimagery with those techniques come in
29、 real-time telecine operations. If the applications are in non-real-time, almost allthe problems disappear in its slow speed scanning operations.3.2.3 Electronic still cameraThe image quality of silver salt photography using 35 mm film is almost equivalent to that of the HRI-1 class. Handlingof much
30、 higher resolution is possible by enlarging the size of the film used.Presently, for exclusive use for still images, a 2 in 2 in CCD with 4 million pixels, which correspond to the resolutionbetween HRI-1 and HRI-2, has been realized. Much higher resolution is to be accomplished by a new device torep
31、lace CCD.4 Rec. ITU-R BT.12013.3 Transmission technology3.3.1 Optical transmissionWith the use of the 1.55 m wavelength, a transmission rate of more than 2.5 Gbit/s and a relay interval of 100 km hasbeen realized. As the optical transmission system has a very large transmission capacity compared to
32、other systems, it isassumed that it will be the basic transmission system in any future use of advanced digital images.Table 2 shows several potentially important fields in development of optical transmission technology to convey thefuture high bit-rate signals in HRI real-time applications. It can
33、be easily seen that some innovative break-throughtechnologies are indispensable.TABLE 2Issues on technology development of optical relay transmissionIn the case where 150 Mbit/sis the applied transmission ratiofor real-time HRI-0 and 1(1)In the case where 600 Mbit/sis the applied transmission ratiof
34、or real-time HRI-2 and 3(1)Optical relay transmissiontechnologyOptical transmission techniqueup to 100 Gbit/sOptical transmission techniqueup to Tbit/s bit levelCoherent light wave transmissiontechnologyCoherent light wave transmissiontechnologyLight modulation technology Light modulation technology
35、FDM (10 waves) FDM (100 waves)Light amplification technology (1)See Table 9 for definitions of the real-time HRI-0 -1 -2 -3.3.3.2 Satellite broadcastingAs for broadband satellite broadcasting, frequencies from 21.4-22 GHz (600 MHz) assigned by the World Adminis-trative Radio Conference for Dealing w
36、ith Frequency Allocations in Certain Parts of the Spectrum (Malaga-Torremolinos, 1992) (WARC-92) may be used. In this case, from the viewpoint of the bandwidth in the travelling-wavetube (TWT), etc., it is possible to realize broadcasting satellite repeaters at about a 300 MHz bandwidth. However, in
37、actual broadcasting, from the aspects of electric power generation and the scale of the satellite, attenuation andatmosphere absorption attenuation of the 21 GHz band radio wave must be overcome by changing the radiation poweraccording to the amount of rainfall of each region. The following technica
38、l developments are necessary for this purpose: highly efficient, lightweight, and high-output TWT, space synthetic antenna, electric power synthetic technology, radiation power control technology.3.3.3 CATVRegarding CATV, compared with the present analogue transmission, real-time transmission of HRI
39、 signals requires thefollowing measures: the use of multichannels, realization of better quality transmission, higher speed and broader bands, use of digital and optical technology.Rec. ITU-R BT.1201 5Table 3 lists an example of a combination between a bandwidth and modulation levels for each member
40、 of the real-timeHRI transmission hierarchy.TABLE 3Bandwidth and modulation levels for HRI transmissionReal-time HRI transmission hierarchy(1)(After compression)Combination between a bandwidth and modulation levelsHRI-0 (50 Mbit/s) 12 MHz/64-QAMHRI-0 and 1 (65-130 Mbit/s) 24-36 MHz/64-QAM18 MHz/256-
41、QAMHRI-2 and 3 (500 Mbit/s) 100 MHz/256-QAM (optical fibre cable required)(1)See Table 9 for definition of the real-time transmission hierarchy.3.4 Storage technology3.4.1 VTRsThe technology trend extrapolated from home use VTRs (8 mm, VHS) shows that 1.0-2.5 bit/m2by the year 2000 canbe expected. T
42、able 4 indicates available recording surface areas for each type of cassette on the market.TABLE 4Recording surface areas for cassette tapesTape 8 mm cassette VHS cassetteTapes in the markets(width, length, thickness)(8 mm, 106 m, 10 m) (12.7 mm, 246 m, 19 m)Tapes to appear in 2000(width, length, th
43、ickness)(8 mm, 212 m, 5 m) (12.7 mm, 467 m, 10 m)Effective recording area of the tape(90% of the width used)1.52 1012 m25.33 1012m2To record the real-time HRI signals an application of some form of compression algorithms to input recording signals isconsidered mandatory. Table 5 shows estimated reco
44、rding capacity for each VTR format under consideration.From Table 5, it is considered that a ratio higher than 1/60 is required for real-time HRI-3 signal recording.The calculations below are estimates based on the assumptions made from the current surface recording trend. In orderto realize a recor
45、der for each HRI hierarchy in the real world some other considerations have to be taken into account.6 Rec. ITU-R BT.1201TABLE 5Estimated recording capacity of VTRs by the year 2000Real-time Original signalMoving picture(h)Still picture(No. of sheets)HRI hierarchy(1)bit rate(Gbit/s)Cassette typeComp
46、ression ratioCompressionratio1/60 1/30 1/4 1/10HRI-02 million pixels2.5 8 mmVHS8274140.523 1051 106HRI-18 million pixels10 8 mmVHS27130.10.57 1043 105HRI-219 million pixels40 8 mmVHS0.520.20.90.030.112 1046 104HRI-333 million pixels72 8 mmVHS0.31.00.10.50.020.061 1043 104(1)See Table 9 for definitio
47、n of the real-time hierarchy.3.4.2 DisksThe technology trend, extrapolated from the current disk technologies, shows that 4 to 9 times of increase in recordingcapacity by the year 2000 can be expected. Table 6 indicates available recording capacity for each size of disk currentlyon the market.TABLE
48、6Recording capacity to be achieved by the year 2000Storage mediaSize(mm)Recording capacity(Mbyte)MD 64 600-1 350CD-ROM 120 2 720-6 120LD 300 18 200-41 000To record real-time HRI signals an application of some form of compression algorithms to input recording signals isconsidered mandatory. Table 7 s
49、hows estimated recording capacity for each disk format under consideration.Rec. ITU-R BT.1201 7TABLE 7Estimated recording capacity of video disks by the year 2000Moving picture(h)Still picture(No. of sheets)Real-timeHRI hierarchy(1)Original signalbit rate(Gbit/s)Storage mediaCompression ratioCompressionratio1/60 1/30 1/4 1/10HRI-02 million pixels2.5 MDCD-ROMLD0.060.31.70.030.10.80.020.12 1039 1036 104HRI-18 million pixels10 MDCD-ROMLD0.010.060.40.010.030.20.035 1022 1032 104HRI-219 million pixels40 MDCD-ROMLD0.0
