1、 Rec. ITU-R BT.1769 1 RECOMMENDATION ITU-R BT.1769 Parameter values for an expanded hierarchy of LSDI*image formats for production and international programme exchange (Question ITU-R 15/6) (2006) Scope Some LSDI applications require certain resolution and scanning formats that go beyond HDTV in ord
2、er to give viewers enhanced visual experiences. This Recommendation specifies an expanded hierarchy of LSDI image formats for production and international programme exchange while retaining the tiered relationship with the formats in existing Recommendations. The ITU Radiocommunication Assembly, con
3、sidering a) that LSDI (large screen digital imagery) is a family of digital imagery systems which can be used in a wide variety of applications including programme presentations such as dramas, plays, sporting events, concerts, etc.; b) that hierarchical image formats for LSDI are required in order
4、to cover the various applications; c) that ITU-R Recommendations cover three levels of image formats, namely 0.5 Mega pixels, 1 Mega pixels and 2 Mega pixels and that the 2 Mega pixels systems specified in Recommendation ITU-R BT.709 is the highest picture quality which ITU has ever standardized; d)
5、 that parameter values for an expanded hierarchy of LSDI image formats should provide conformity with Recommendation ITU-R BT.709; e) that Recommendation ITU-R BT.1201 Extremely high resolution imagery, recommends image resolutions related to 1 920 1 080 based on Recommendation ITU-R BT.709 by simpl
6、e integer ratios; f) that Recommendation ITU-R BT.1680 Baseband imaging format for distribution of large screen digital imagery (LSDI) applications intended for presentation in a theatrical environment, recommends image formats up to HDTV resolution as members of a hierarchy of LSDI digital image fo
7、rmats; g) that some LSDI applications will require resolutions beyond that specified in Recommendation ITU-R BT.1680, since viewing angles determine the required level of image resolution and visual experiences with wider viewing angle give viewers a higher sensation of *LSDI is a family of digital
8、imagery systems applicable to programmes such as dramas, plays, sporting events, concerts, cultural events, etc., from capture to large screen presentation in high-resolution quality in appropriately equipped theatres, halls, and other venues. 2 Rec. ITU-R BT.1769 reality. For example, some televisi
9、on productions intended for very large venues may require such higher resolutions; h) that LSDI image formats are different from motion picture image formats; j) that parameters for the network transport of the expanded hierarchy of LSDI image formats are contained in ITU-T Recommendation J.601, rec
10、ommends 1 that in order to expand the hierarchy of LSDI image formats for production and international programme exchange, beyond the image formats recalled in considerings c) and h) and excluding motion picture image formats, image formats based on Table 1 characteristics should be used when requir
11、ed. TABLE 1 Picture characteristics Values Item Parameter 3 840 2 160 LSDI system 7 680 4 320 LSDI system 1.1 Picture aspect ratio 16:9 1.2 Samples per active line 3 840 7 680 1.3 Active lines per picture 2 160 4 320 1.4 Sampling lattice Orthogonal 1.5 Order of samples Left to right, top to bottom 1
12、.6 Pixel aspect ratio 1:1 (square pixels) 1.7 Sampling structure 4:2:0, 4:2:2, 4:4:4 1.8 Frame rate (Hz) 24(1), 25, 30(1), 50, 60(1)1.9 Image structure Progressive 1.10 Bit/pixel 10, 12 1.11 Colorimetry See Recommendation ITU-R BT.1361 (1)For the 24, 30 and 60 Hz systems, frame rates having values d
13、ivided by 1.001 are also included. NOTE 1 An example of LSDI system that gives viewers visual experiences of a high-sensation of reality is explained in Appendix 1. NOTE 2 Viewing angles for the hierarchy of LSDI image formats are shown in Appendix 2. NOTE 3 A study result on psychological effects o
14、f wide-screen video system for LSDI applications is shown in Appendix 3. Rec. ITU-R BT.1769 3 Appendix 1 An example of LSDI system that gives viewers visual experiences of a high-sensation of reality FIGURE 1 Horizontal viewing angle of LSDI system Appendix 2 Viewing angles for the hierarchy of LSDI
15、 image formats TABLE 2 Horizontal viewing angle for the hierarchy of LSDI image formats LSDI system 1 920 1 080 3 840 2 160 7 680 4 320 Viewing distance (relative to picture height) 3 1.5 0.75 Viewing angle (degrees) 31 58 96 These values are calculated, assuming the distance at which scanning lines
16、 just cannot be perceived by people with visual acuity of 1.0. 4 Rec. ITU-R BT.1769 Appendix 3 A study on psychological effects of wide-screen video system for LSDI applications 1 Introduction This Appendix describes the psychological evaluation results of “sensation of reality” of LSDI covering fro
17、m HDTV format to expanded format. The results would contribute toward determining system parameter values such as display size, viewing distance and spatial resolution. 2 Subjective evaluation experiments A single stimulus method with seven-categorical scale (1 = no presence at all; 7 = very strong
18、presence) was used for evaluating the “sensation of reality” of images projected on a screen. The size of images was varied by changing the number of scanning lines from 1 000 to 4 000. The viewing distance was determined to be the point at which viewers with normal vision could no longer discern th
19、e scanning line structure. This corresponds to three times the picture height when the image size is 1 920 1 080. The viewing angle varies between 33 and 100 according to the image size. Table 3 lists the experimental conditions. Forty-one non-expert subjects evaluated five still landscape pictures
20、listed in Table 4. They were shot with two different camera angles of 60 and 100 to see the effect of spatial distortion resulting from the mismatch between the screen-viewing angle and camera angle, and it can result in a reduced “sensation of reality”. The display sub-system of ultra-high definiti
21、on video system with 4 000 scanning lines (8k 4k display system) was used for an experiment apparatus. The system is reported in Report ITU-R BT.2053 Large screen digital imagery. The display is equipped with four 8-million-pixel liquid crystal on silicon devices, and a pixel offset method enhances
22、the resolution as equivalent to 32 million pixels. The screen size is approximately 7 m horizontally and 4 m vertically (320-inch diagonally). Screen brightness is 50 cd/m2and contrast ratio is more than 700:1. Table 5 lists the major items of the systems signal format. 3 Results “Sensation of reali
23、ty” evaluated in seven-grade categorical scale was converted to interval scale to perform a multivariate analysis of variance (MANOVA) with a three-factor within-subject design (screen-viewing angle, camera angle and picture content). Significant values were obtained for the main effect of the scree
24、n-viewing angle, the main effect of the picture content, and for screen-viewing angle camera angle interactions. The main effect of the picture content was significant because picture 1 was rated higher than the other pictures. If MANOVA is performed without the results for picture 2, then significa
25、nt results are not obtained for the main effect of the picture content. Figure 2 shows the relationship between the average score of pictures 1-5 and the screen-viewing angle for different camera angles. “Sensation of reality” increases monotonously with viewing angle, although the results for camer
26、a angle of 60 slightly levels off at the viewing angle above 90. 4 Conclusion The results confirm that wider viewing angle generates higher “sensation of reality”. It also implies that LSDI with higher resolution than HDTV would be needed for applications that require higher Rec. ITU-R BT.1769 5 “se
27、nsation of reality”. On the other hand, it is known that decreases of comfortableness would arise when the viewing position is too close to wide-screen images. In order to facilitate a wide variety of LSDI applications, study of expanded hierarchy of LSDI systems should be advanced. TABLE 3 Experime
28、ntal conditions Scanning lines 1 000 1 143 1 333 1 600 2 000 2 667 3 200 3 556 4 000 Picture aspect ratio 16:9 Picture size diagonally (inch) 75 86 100 120 150 200 240 267 300 (m) 2.8 Viewing distance (H) 3.0 2.6 2.2 1.9 1.5 1.1 0.93 0.84 0.75 Horizontal viewing angle (degrees) 33.2 37.6 43.3 51.0 6
29、1.6 76.9 87.3 93.3 100.0 TABLE 4 Test pictures Camera angle 60 (degrees) 1 2 3 4 5Camera angle 100 (degrees) 1 2 3 4 5TABLE 5 Signal format of 8k 4k display system Parameter Value Picture rate 60 frames per second Image structure Progressive Sample per active line 7 680 Active lines per picture 4 320 Picture aspect ratio 16:9 6 Rec. ITU-R BT.1769 FIGURE 2 Sensation of reality vs. viewing angle
