1、Rec. ITU-R BT.710-4 1RECOMMENDATION ITU-R BT.710-4SUBJECTIVE ASSESSMENT METHODS FOR IMAGEQUALITY IN HIGH-DEFINITION TELEVISION(Question 211/11)(1990-1992-1994-1997-1998)Rec. ITU-R BT.710-4The ITU Radiocommunication Assembly,consideringa) that a number of administrations and organizations throughout
2、the world are currently using and/or evaluatinghigh-definition television systems, and that in many parts of the world HDTV broadcasting is likely to become theprimary medium of the next century;b) that subjective assessments are a vital element in HDTV system design and selection;c) that Recommenda
3、tion ITU-R BT.500 outlines general subjective assessment methods, many of themethodological details of which are also appropriate in the context of HDTV;d) that Recommendation ITU-R BT.500 has been modified to provide only general information on methodologyfor the subjective assessment of the qualit
4、y of television pictures,recommends1 that subjective assessment of image quality of high-definition television systems should be made following thegeneral methodology given in Recommendation ITU-R BT.500;2 that subjective assessments of the overall quality and of the failure characteristics of HDTV
5、systems shoulduse the specific viewing conditions and the subjective assessment methods described in Annex 1.ANNEX 11 Viewing conditionsTABLE 1Viewing conditions for the subjective assessment of HDTV image qualityCondition Item Values1)a Ratio of viewing distance to picture height 3b Peak luminance
6、on the screen (cd/m2)2)150-250c Ratio of luminance of inactive tube screen (beams cut off) to peakluminance3) 0.02d Ratio of the luminance of the screen when displaying only black level in acompletely dark room, to that corresponding to peak white4)approximately 0.01e Ratio of luminance of backgroun
7、d behind picture monitor to peakluminance of pictureapproximately 0.15f Illumination from other sources5)lowg Chromaticity of background D65h Angle subtended by that part of the background which satisfies thespecification above6). This should be preserved for all observers53 high x 83 wide2 Rec. ITU
8、-R BT.710-4TABLE 1 (end)2 Assessment methodsSubjective assessments of the overall quality of an HDTV image delivered by an emission system should be made usinga double-stimulus continuous quality-scale method (Recommendation ITU-R BT.500) with the HDTV studio qualityimage as reference.Assessment of
9、the failure characteristics of an HDTV emission system should be made using a double-stimulusimpairment scale method (Recommendation ITU-R BT.500) with either the HDTV studio image or the unimpairedemission image as reference.When performance over the range of program content and transmission condit
10、ions likely to be encountered in practice isof issue, the description of composite failure characteristics as in Appendix 2 to Annex 1 of Recommendation ITU-RBT.500 should be considered.Using these methods, care must be taken to distinguish the influence of the display format from that of the basic
11、systemformat (e.g. any up-conversion). If it is felt to be applicable and appropriate, supplementary assessments may beperformed using different displays in order to take into account different display formats.Some of the HDTV emission systems may include an embedded conventional television format (
12、backwardscompatibility). Thus, there is a need to evaluate, in terms of picture quality, the adequacy of conventional televisionpictures embedded in HDTV emissions. For these systems, the viewing conditions and assessment methods given inRecommendations ITU-R BT.1128 and BT.1129 should be applied.Ba
13、sic concepts and procedures described in Recommendation ITU-R BT.1129 should be applied to digital HDTVemission systems that employ bit-rate reduction schemes.3 Test materialsRecommendation ITU-R BT.1210 lists a wide range of still pictures and moving sequences. These should preferably beused as the
14、 common test materials for HDTV quality assessments.Condition Item Values1)i Arrangement of observers Within 30 horizontallyfrom the centre of thedisplay. The vertical limit isunder studyj Display size7)1.4 m (55 in)1)As it currently may not be possible to achieve these conditions fully for tests, a
15、lternative values are given on an interimbasis. It should be recognized, however, that the results of tests conducted under the interim conditions may not be, ingeneral, comparable to those obtained in situations in which lower presentation objectives apply.2)Peak luminance on the screen correspondi
16、ng to the video signal with 100% amplitude. Values 70 cd/m2should be useduntil the specified level becomes technically feasible.3)This item could be influenced by the room illumination, as well as the contrast range of the display.4)Black level corresponds to the video signal with 0% amplitude.5)Room illumination should be adjusted such that it is possible to satisfy the conditions c and e.6)A minimum of 28 high x 48 wide is recommended.7)Values 76.2 cm (30 in) should be used if displays of the specified size are not available.
