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
17、-line systemsRec. ITU-R BT.1128-2 3A number of organizations have already developed test still pictures and sequences. The test material listed in Annex 2of this Recommendation should be preferred to assess the quality achieved by the system under evaluation, in regard tothe type of degradation cons
18、idered. The list given in Annex 2 includes critical material which may be used followingRecommendation ITU-R BT.500. According to Recommendation ITU-R BT.500, test material is chosen according tothe following criteria: to be representative of variety of typical programming and current production tec
19、hniques; to cover a wide range of criticality levels; to include still pictures.To ensure the optimum quality of source signals, and therefore avoid any biasing in the evaluation, digitally storedpictures and sequences are the preferred type. The D-1 4:2:2 tape format (Recommendation ITU-R BR.657) s
20、houldprovide a basis for the exchange of source pictures and sequences between laboratories, to make comparison betweensystems more meaningful. Computer tape formats are also possible.Further studies are necessary to determine the criticality of the test pictures and sequences listed in Annex 2.ANNE
21、X 2This Annex provides lists of available test pictures and sequences for the assessment of conventional picture quality,together with information concerning their characteristics and formats.TABLE 2Conventional television test pictures and sequencesTitle Contents Representative of AttributesAvailab
22、ility(o: available) Criti-to be examined525 625calityStillsFormal pond LuminanceresolutionooBoats with lighthouse Luminanceand colourresolutionooClown Clown making up HorizontalresolutionooBoy with toys Boy playing with severalcoloured toysSkin and colouredgesooGirl with toys Girl playing with sever
23、alcoloured toysSkin and colouredgesooYoung couple Man and woman with stripedclothesFine detail LuminanceresolutionooToys and blackboards Colour, verti-cal resolutionooTree Luminance patterns o oMale headKiel harbour Detailed view of the KielharbourFine resolution SpatialresolutionooLatin textGraphTe
24、st cardZone plate4 Rec. ITU-R BT.1128-2TABLE 2 (continued)Title Contents Representative of AttributesAvailability(o: available) Criti-to be examined525 625calityStills Chroma keyComb and pencilTwigs and ribbonOld master Foreground Chroma key FG oOld master Background Chroma key BG oDummy with combMo
25、ving sequencesBBC disc 1 Rotating disc with severalfeatures attached on it.The axis of rotation is parallelto the viewing axisCircular motion oBBC disc 2 Idem. Increased speed Circular motionBBC disc 3 Idem. Increased speed Circular motionBBC drum 1 Rotating drum with shoppictures attached on it. Th
26、e axisof rotation is verticalCircular motionBBC drum 2 Idem. Increased speed Circular motionClown Clown making up. Artificiallymoving slidePan (H, V) oBoy with toys Boy playing with severalcoloured toys. Artificiallymoving slidePan (H, V) oKiel harbour View on the detailed harbour Rapid rocking o oT
27、able tennis Play and detailed background Pan/zoom/cut o oMobile and calendar Miniature train circulating infront of a coloured settingSlow motion o oRenata and scarf Young woman moving slowly infront of detailed settingCircular motionRenata and butterflies Young woman moving slowly infront of a deta
28、iled setting and cuton coloured drawing ofbutterfliesCircular motionSailboat Old four-masted ship alongsidethe quaySlow motion o oFlower garden Panning on detailed colouredflowers and housesSlow pan o oSusie Young woman telephoning Slow o oDiva with titles Diva singing in a church withtitlesCuts oDi
29、va with noise Diva singing in a church withincreasing noise areaProd. wipe o oCommercialFamily portrait Old fashion dressed family Wipe o Tempest Wind on a miniature garden Random motion o oTempest with noise Wind on a miniature garden withadded noiseRandom motion o oTitlesCruising Frozen dancing sc
30、enes 2-10 freezes o oRec. ITU-R BT.1128-2 5TABLE 2 (continued)Title Contents Representative of AttributesAvailability(o: available) Criti-to be examined525 625calityMoving sequences Chroma keyBalls of wool Moving ball of wool Medium Colour motion o oPopple Pan/rotate MotionrenditionooCactus and comb
31、CactusOld master Foreground Chroma key Foreground Slow pan oOld master Background Chroma key Background Slow pan oCiao Foreground CK, FG, luminance, colourdetailsSlow pan/zoom o oCiao Background CK, BG, luminance, colourdetailsSlow pan/zoom o oCiao, foreword via PALcode/decodeCross luminance colour
32、Slow pan/zoom oNOTE 1 Contents of the EBU library tape. The duration of each sequence is 30 s.NOTE 2 The content of the library list will be updated from time to time; the tape is available in the D1 digital format(Recommendation ITU-R BR.657), all segments of the library tape are in the public domain and may be used freely for evaluationsand demonstrations. Requests should be addressed to the European Broadcasting Union (EBU) through the RadiocommunicationBureau of the ITU.
