ITU-R BT 1128-2-1997 Subjective Assessment of Conventional Television Systems《普通电视系统的主观评定》.pdf
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1、Rec. ITU-R BT.1128-2 1RECOMMENDATION ITU-R BT.1128-2SUBJECTIVE ASSESSMENT OF CONVENTIONAL TELEVISION SYSTEMS(Question ITU-R 211/11)(1994-1995-1997)Rec. ITU-R BT.1128-2The ITU Radiocommunication Assembly,consideringa) that a number of administrations and organizations throughout the world are current
2、ly using analogueconventional television systems (NTSC, PAL, SECAM);b) that subjective assessments are a vital element in analogue and conventional quality television system designand selection;c) that Recommendation ITU-R BT.500 outlines a number of recommended subjective assessment methods,many of
3、 the methodological details of which are appropriate for assessing conventional television quality;d) that conventional television systems may be used as a reference for comparison with the newly developedsystems;e) that the results of subjective tests can be analysed, presented and interpreted in m
4、any different ways andtherefore it is highly desirable to increase the degree of standardization in the methods of analysis, presentation andinterpretation of the results of subjective tests so that comparison may be made between results obtained by differentworkers;f) that Recommendation ITU-R BT.5
5、00 has been modified to provide only general information on methodologyfor the subjective assessment of the quality of television pictures,recommends1 that subjective assessment of image quality of conventional television systems should be made following thegeneral methodology given in Recommendatio
6、n ITU-R BT.500;2 that subjective assessments of the overall quality and of the failure characteristics of conventional systemsshould use the specific viewing conditions and the subjective assessment methods described in Annex 1.ANNEX 1The subjective quality of conventional television systems:Paramet
7、ers for application of Recommendation ITU-R BT.5001 Viewing conditionsThe assessors viewing conditions should be arranged as follows:1.1 Selection of viewing conditionsOne particular set of viewing conditions should be used in assessments of conventional television. However, differentviewing distanc
8、es may be used for normal and critical assessments (see Table 1).2 Rec. ITU-R BT.1128-2TABLE 11.2 Specific conditions for conventional televisionThese viewing conditions are specific to conventional systems. Supplementary more general viewing conditions aregiven in Recommendation ITU-R BT.500.a) Rat
9、io of viewing distance to picture height 4 H and 6 H (see Note 1)b) Peak luminance 70 cd/m2c) Monitor (see Note 2) High quality 22 inscreen size ( 56 cm)d) Viewing angle subtended by that part of the 43 high 57 widebackground that satisfies specificationsNOTE 1 A distance of six times the height of
10、the picture (6 H) is the preferred distance for assessments ofconventional systems (625/50, 525/60), however using assessors at 4 H also is acceptable, provided the results are givenseparately.NOTE 2 Where more than one viewing room is used, monitors should be carefully matched. Because there is som
11、eevidence that display size may influence the results of subjective assessments experimenters are requested to explicitlyreport the screen size and make, and model of displays used in any experiments.2 Assessment methodsSubjective assessments of the overall quality of an image of conventional qualit
12、y delivered by an emission systemshould be made using a double-stimulus continuous quality-scale method (Recommendation ITU-R BT.500) with studioquality images as reference.Assessments of the failure characteristics of an emission system delivering conventional quality should be made using adouble-s
13、timulus impairment scale method (Recommendation ITU-R BT.500) with either a studio quality image orunimpaired image from an emission system as reference.When performance over the range of programme content and transmission conditions likely to be encountered inpractice is of issue, it is recommended
14、 that the description of failure characteristics as in Appendices 1 and 2 to Annex 1of Recommendation ITU-R BT.500 be considered.Using these methods, care must be taken to distinguish the influence of the display format from that of the basic systemformat (e.g. display of a 4:3 image on a 16:9 monit
15、or). Assessments may be performed in order to take account of thedifferent display formats if applicable and appropriate.3 Test materialA number of approaches have been taken into account in establishing the kinds of test material required in televisionassessments. A survey of typical assessment pro
16、blems and of test materials used to address these problems is given inTable 2 of Recommendation ITU-R BT.500.Assessment problem Viewing conditionsAssess conventional systems Viewing at 6 HAssess conventional systems under criticalconditionsViewing at 4 H for 625-line systemsand at 4 H or 5 H for 525
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