1、 Recommendation ITU-R BT.500-13(01/2012)Methodology for the subjective assessment of the qualityof television picturesBT SeriesBroadcasting service(television)ii Rec. ITU-R BT.500-13 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use
2、 of the radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and
3、 Regional Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the
4、 submission of patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of IT
5、U-R Recommendations (Also available online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination,
6、 amateur and related satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite ne
7、ws gathering TF Time signals and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2012 ITU 2012 All rights reserved. No part of this publication m
8、ay be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R BT.500-13 1 RECOMMENDATION ITU-R BT.500-13 Methodology for the subjective assessment of the quality of television pictures (Question ITU-R 81/6) (1974-1978-1982-1986-1990-1992-1994-1995-1998-1998-2000-2002-2009-
9、2012) Scope This Recommendation provides methodologies for the assessment of picture quality including general methods of test, the grading scales and the viewing conditions. It recommends the double-stimulus impairment scale (DSIS) method and the double-stimulus continuous quality-scale (DSCQS) met
10、hod as well as alternative assessment methods such as single-stimulus (SS) methods, stimulus-comparison methods, single stimulus continuous quality evaluation (SSCQE) and simultaneous double stimulus for continuous evaluation (SDSCE) method. The ITU Radiocommunication Assembly, considering a) that a
11、 large amount of information has been collected about the methods used in various laboratories for the assessment of picture quality; b) that examination of these methods shows that there exists a considerable measure of agreement between the different laboratories about a number of aspects of the t
12、ests; c) that the adoption of standardized methods is of importance in the exchange of information between various laboratories; d) that routine or operational assessments of picture quality and/or impairments using a five-grade quality and impairment scale made during routine or special operations
13、by certain supervisory engineers, can also make some use of certain aspects of the methods recommended for laboratory assessments; e) that the introduction of new kinds of television signal processing such as digital coding and bit-rate reduction, new kinds of television signals using time-multiplex
14、ed components and, possibly, new services such as enhanced television and HDTV may require changes in the methods of making subjective assessments; f) that the introduction of such processing, signals and services, will increase the likelihood that the performance of each section of the signal chain
15、 will be conditioned by processes carried out in previous parts of the chain, recommends 1 that the general methods of test, the grading scales and the viewing conditions for the assessment of picture quality, described in the following Annexes should be used for laboratory experiments and whenever
16、possible for operational assessments; 2 that, in the near future and notwithstanding the existence of alternative methods and the development of new methods, those described in 4 and 5 of Annex 1 to this Recommendation should be used when possible; and 2 Rec. ITU-R BT.500-13 3 that, in view of the i
17、mportance of establishing the basis of subjective assessments, the fullest descriptions possible of test configurations, test materials, observers, and methods should be provided in all test reports; 4 that, in order to facilitate the exchange of information between different laboratories, the colle
18、cted data should be processed in accordance with the statistical techniques detailed in Annex 2 to this Recommendation. NOTE 1 Information on subjective assessment methods for establishing the performance of television systems is given in Annex 1. NOTE 2 Description of statistical techniques for the
19、 processing of the data collected during the subjective tests is given in Annex 2. Annex 1 Description of assessment methods 1 Introduction Subjective assessment methods are used to establish the performance of television systems using measurements that more directly anticipate the reactions of thos
20、e who might view the systems tested. In this regard, it is understood that it may not be possible to fully characterize system performance by objective means; consequently, it is necessary to supplement objective measurements with subjective measurements. In general, there are two classes of subject
21、ive assessments. First, there are assessments that establish the performance of systems under optimum conditions. These typically are called quality assessments. Second, there are assessments that establish the ability of systems to retain quality under non-optimum conditions that relate to transmis
22、sion or emission. These typically are called impairment assessments. To conduct appropriate subjective assessments, it is first necessary to select from the different options available those that best suit the objectives and circumstances of the assessment problem at hand. To help in this task, afte
23、r the general features reported in 2, some information is given in 3 on the assessment problems addressed by each method. Then, the two main recommended methods are detailed in 4 and 5. Finally, general information on alternative methods under study is reported in 6. The purpose of this Annex is lim
24、ited to the detailed description of the assessment methods. The choice of the most appropriate method is nevertheless dependent on the service objectives the system under test aims at. The complete evaluation procedures of specific applications are therefore reported in other ITU-R Recommendations.
25、2 Common features General viewing conditions for subjective assessments are given. Specific viewing conditions, for subjective assessments of specific systems, are given in the related Recommendations. 2.1 General viewing conditions Different environments with different viewing conditions are descri
26、bed. Rec. ITU-R BT.500-13 3 The laboratory viewing environment is intended to provide critical conditions to check systems. General viewing conditions for subjective assessments in the laboratory environment are given in 2.1.1. The home viewing environment is intended to provide a means to evaluate
27、quality at the consumer side of the TV chain. General viewing conditions in 2.1.2 reproduce a near to home environment. These parameters have been selected to define an environment slightly more critical than the typical home viewing situations. Some aspects relating to the monitors resolution and c
28、ontrast are discussed. 2.1.1 Laboratory environment 2.1.1.1 General viewing conditions for subjective assessments in laboratory environment The assessors viewing conditions should be arranged as follows: a) Ratio of luminance of inactive screen to peak luminance: 0.02 b) Ratio of the luminance of th
29、e screen, when displaying only black level in a completely dark room, to that corresponding to peak white: 0.01 c) Display brightness and contrast: set up via PLUGE (see Recommendations ITU-R BT.814 and ITU-R BT.815) d) Maximum observation angle relative to the normal (this number applies to CRT dis
30、plays, whereas the appropriate numbers for other displays are under study): 30 e) Ratio of luminance of background behind picture monitor to peak luminance of picture: 0.15 f) Chromaticity of background: D65g) Other room illumination: low 2.1.2 Home environment 2.1.2.1 General viewing conditions for
31、 subjective assessments in home environment a) Ratio of luminance of inactive screen to peak luminance: 0.02 (see 2.1.4) b) Display brightness and contrast: set up via PLUGE (see Recommendations ITU-R BT.818 and ITU-R BT.815) c) Maximum observation angle relative to the normal (this number applies t
32、o CRT displays, whereas the appropriate numbers for other displays are under study): 30 d) Screen size for a 4/3 format ratio: This screen size should satisfy rules of preferred viewing distance (PVD) e) Screen size for a 16/9 format ratio: This screen size should satisfy PVD rules 4 Rec. ITU-R BT.5
33、00-13 f) Monitor processing: Without digital processing g) Monitor resolution: See 2.1.3 h) Peak luminance: 200 cd/m2i) Environmental illuminance on the screen (Incident light from the environment falling on the screen, should be measured perpendicularly to the screen): 200 lux The viewing distance
34、and the screen sizes are to be selected in order to satisfy the PVD. The PVD (in function of the screen sizes) is shown in the following table and graph. Figures could be valid both for SDTV and HDTV as very little difference was found. 1514131211109876543210PVD for moving imagesPVD()Ratio ofviewing
35、 distance(m)topicture height(m)H0 0.5 1 1.5 2Screen height (m)This table and graph are intended to give information on the PVD and related screen sizes to be adopted in the Recommendations for specific applications. Screen diagonal (in) Screen height (H ) PVD 4/3 ratio 16/9 ratio (m) (H ) 12 15 0.18
36、 9 15 18 0.23 8 20 24 0.30 7 29 36 0.45 6 60 73 0.91 5 100 120 1.53 3-4 Rec. ITU-R BT.500-13 5 2.1.3 Monitor resolution The resolution of professional monitors, equipped with professional CRTs, usually complies with the required standards for subjective assessments in their luminance operating range
37、. Not all monitors can reach a 200 cd/m2peak luminance. To check and report the maximum and minimum resolutions (centre and corners of the screen) at the used luminance value might be suggested. If consumer TV sets with consumer CRTs are used for subjective assessments, the resolution could be inade
38、quate, depending on the luminance value. In this case it is strongly recommended to check and report the maximum and minimum resolutions (centre and corners of the screen) at the used luminance value. At present the most practical system available to subjective assessments performers, in order to ch
39、eck monitors or consumer TV sets resolution, is the use of a swept test pattern electronically generated. A visual analysis allows to check the resolution. The visual threshold is estimated to be 12/20 dB. The main drawback of this system is the aliasing created by the shadow mask that makes the vis
40、ual evaluation hard, but, on the other hand, the aliasing presence indicates that the video frequency signal exceeds the limits given by the shadow mask, which under samples the video signal. Further studies on CRTs definition testing could be recommended. 2.1.4 Monitor contrast Contrast could be st
41、rongly influenced by the environment illuminance. Professional monitors CRTs seldom use technologies to improve their contrast in a high illuminance environment, so it is possible they do not comply with the requested contrast standard if used in a high illuminance environment. Consumer CRTs use tec
42、hnologies to get a better contrast in a high illuminance environment. To calculate the contrast of a given CRT, the screen reflection coefficient, K, of such CRT is needed. In the best case the screen reflection coefficient is approximately K = 6%. With a diffused environment I illuminance of 200 lu
43、x and a K = 6%, a 3.82 cd/m2, luminance reflection of inactive screen areas is calculated with the following formula: KILreflected= With the given values, the reflected luminance (cd/m2) is nearly 2% of the incident illuminance (lux). The CRT is considered not to have mirror like reflections on the
44、front glass, whose exact influence on contrast is difficult to quantify because it is very dependant on lighting conditions. In 2.1.1 and 2.1.2, the contrast ratio CR is expressed as: maxminLLCR / = 6 Rec. ITU-R BT.500-13 where: Lmin: luminance of inactive areas under ambient illumination (cd/m2) (w
45、ith the given values Lmin= Linactive areas+ Lreflected= 3.82 cd/m2) Lmax: luminance of white areas under ambient illumination (cd/m2) (with the given values Lmax= Lwhite+ Lreflected= 200 + 3.82 cd/m2). With such values a CR = 0.018 is computed, strictly close to the 0.02 value stated in 2.1.1.1 and
46、2.1.2.1, a). 2.2 Source signals The source signal provides the reference picture directly, and the input for the system under test. It should be of optimum quality for the television standard used. The absence of defects in the reference part of the presentation pair is crucial to obtain stable resu
47、lts. Digitally stored pictures and sequences are the most reproducible source signals, and these are therefore the preferred type. They can be exchanged between laboratories, to make system comparisons more meaningful. Video or computer tapes are possible formats. In the short term, 35 mm slide-scan
48、ners provide a preferred source for still pictures. The resolution available is adequate for evaluation of conventional television. The colorimetry and other characteristics of film may give a different subjective appearance to studio camera pictures. If this affects the results, direct studio sourc
49、es should be used, although this is often much less convenient. As a general rule, slide-scanners should be adjusted picture by picture for best possible subjective picture quality, since this would be the situation in practice. Assessments of downstream processing capacity are often made with colour-matte. In studio operations, colour-matte is very sensitive to studio lighting. Assessments should therefore preferably use a special colour-matte slide pair, which will consistently give high-quality results. Movement can be introduced into the fo
