1、 Recommendation ITU-R BS. 1679-1 (10/2015) Subjective assessment of the quality of audio in large screen digital imagery applications intended for presentation in a theatrical environment BS Series Broadcasting service (sound) ii Rec. ITU-R BS.1679-1 Foreword The role of the Radiocommunication Secto
2、r is to ensure the rational, equitable, efficient and economical use 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 f
3、unctions of the Radiocommunication Sector are performed by World and 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 r
4、eferenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the 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 t
5、he ITU-R patent information database can also be found. Series of ITU-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 Broadcastin
6、g service (television) F Fixed service M Mobile, radiodetermination, 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-satelli
7、te and fixed service systems SM Spectrum management SNG Satellite news 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 Gene
8、va, 2015 ITU 2015 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R BS.1679-1 1 RECOMMENDATION ITU-R BS.1679-1 Subjective assessment of the quality of audio in large screen digital imagery applications intended
9、for presentation in a theatrical environment (Question ITU-R 15/6) (2004-2015) Scope This Recommendation is intended for use in the assessment of audio quality in large screen digital imagery applications intended for presentation in a theatrical environment. It may be used with theatrical speaker c
10、onfigurations as identified in Recommendation ITU-R BS.775 and Recommendation ITU-R BS.2051. The ITU Radiocommunication Assembly, considering a) that it will be necessary to verify the suitability of the technical solutions considered for members of that family of large screen digital imagery (LSDI)
11、 applications; b) that such verification will also need to include, when necessary, subjective assessment tests performed under rigorous scientific conditions; c) that Recommendation ITU-R BS.1284 specifies general requirements applicable to the subjective assessment of the quality or impairment of
12、program audio; d) that LSDI programs intended for presentation in a theatrical environment will be generally accompanied by multichannel audio, thus requiring a subjective assessment procedure designed for multichannel audio; e) that Recommendation ITU-R BS.775 and Recommendation ITU-R BS.2051 cover
13、 multichannel stereophonic audio signals and advanced sound systems with and without accompanying picture; f) that the subjective assessment of the quality of audio in LSDI applications intended for presentation in a theatrical environment requires a procedure in which the quality of the audio is as
14、sessed in the presence of the image component of the LSDI program, since perceptual interaction between audio and picture can affect the assessment of audio quality; g) that Recommendation ITU-R BS.1286 covers methods for the subjective assessment of audio systems with accompanying picture; h) that,
15、 the source-coding (if any) used for the delivery of LSDI program audio for presentation in a theatrical environment should be transparent or virtually transparent to the audio quality present on the program master, and the subjective assessment of source-coding transparency requires a procedure des
16、igned to assess small audio impairments; i) that Recommendation ITU-R BS.1116 covers methods for the subjective assessment of small impairments in audio systems including multichannel audio systems, recommends 1 that the subjective assessment of audio quality or audio impairments in LSDI application
17、s designed for program presentation in a theatrical environment should be based on a choice among the specifications contained in Recommendations ITU-R BS.1284, ITU-R BS.1286 and ITU-R BS.1116; 2 Rec. ITU-R BS.1679-1 2 that the listening environment used for those subjective assessments should be ba
18、sed on the universal multichannel stereophonic audio system specified in Recommendation ITU-R BS.775. If the subjective assessment uses a loudspeaker arrangement different from the reference one indicated in Recommendation ITU-R BS.775, the assessment report should describe it in detail; 3 that refe
19、rence should be made to Annex 1 for a summary indication of the provisions to be selected in the four Recommendations above, for implementation in the subjective assessment of audio of LSDI applications for presentation in a theatrical environment, and reference should be made to the four Recommenda
20、tions themselves for full details of the selected provisions. Annex 1 Summary of provisions for the subjective assessment of LSDI audio quality 1 Introduction This Annex provides a summary of the provisions that should be implemented when performing subjective assessment tests of audio quality or au
21、dio impairment for LSDI applications designed for program presentation in a theatrical environment. These provisions have been taken from those contained in Recommendations ITU-R BS.775, ITU-R BS.1116, ITU-R BS.1284 and ITU-R BS.1286. They apply to the case of the indicated LSDI applications, which
22、can be characterized as follows: The audio to be assessed is a multichannel program audio. The audio accompanies program images presented on a large screen in a theatrical environment. The expected impairment is small with respect to the subjective audio quality present on the program master. Refere
23、nce should be made to the Recommendations listed above for full details of the selected provisions. 2 General provisions related to the assessment of program audio Recommendation ITU-R BS.1284 specifies general requirements for the subjective assessment of audio quality. Several provisions apply to
24、the specific case of the subjective assessment of small impairments in multichannel program audio with accompanying picture. This particularly applies to the following elements. Listening panel Expert listeners are preferred to non-expert listeners. It has been argued that non-experts may be represe
25、ntative of the general population, and that experts may be excessively critical. However, with long-term exposure to artefacts, in time some non-experts become experts. Therefore, tests using experts give a better and quicker indication of the likely results in the long term. Rec. ITU-R BS.1679-1 3
26、Grading scales The following five-grade scale is recommended for the subjective assessment of “basic audio quality”1. Due to the fact that LSDI applications focus on high quality the five-grade quality scale is not appropriate. For comparison tests, either a method based on the following seven-grade
27、 comparison scale or one based on numerical differences using the above five-grade scales may be used. In general, these are not equivalent and may not give the same results. Taking into account that LSDI is focusing on high quality comparison tests in general are not adequate. NOTE 1 The scales sho
28、uld be treated as continuous, with a recommended resolution of 1 decimal place. NOTE 2 It has been shown that the use of pre-defined intermediate anchor points may introduce bias. It is possible to use the number scales without descriptions of anchor points. In such cases, the intended orientation o
29、f the scales must be indicated. This may help to overcome translation problems when comparing the results of tests written in different languages. If intermediate anchor points are not used it is essential that the results for individual subjects are normalized with respect to mean and standard devi
30、ation. Recommendation ITU-R BS.1284 provides the normalization algorithm that can be used. Test procedures Tests may be of single presentations, paired comparisons (one of which may be the reference) or multiple comparisons, with or without references. The presentations may be repeated as required.
31、Short-term human memory limitations may dictate that each program excerpt should not last longer than 15 to 20s.; excerpts may be very short (a few seconds) for some tests. In the case where the sequence is a musical item, the phrase should not appear to be interrupted. When the test sequence is not
32、 under the control of the subject, it is necessary to provide a clear indication of the current presentation. 1 Basic audio quality is used here in the same way as it is used in Recommendation ITU-R BS.1116. Impairment 5 Imperceptible 4 Perceptible, but not annoying 3 Slightly annoying 2 Annoying 1
33、Very annoying Comparison 3 Much better 2 Better 1 Slightly better 0 The same 1 Slightly worse 2 Worse 3 Much worse 4 Rec. ITU-R BS.1679-1 No session with any one listener should last longer than about 15 to 20 min without interruption. If the sessions must be consecutive, they should be separated by
34、 rest periods of at least the same duration. Program material When the system is intended to carry high quality audio, as it is the case of LSDI applications, the test material should be chosen for its highly critical behavior with respect to the impairments introduced by the system being tested. To
35、 ensure the comparability of test data obtained in different places and/or at different times, some program sequences should be the same in all the tests to be compared. Statistical testing on the common test items must be performed to check whether it is allowed to compare the results of two tests.
36、 In any event, the content of a program sequence in general should be neither so interesting nor so disagreeable or boring that the listener is distracted. However a few program sequences designed to stress the systems under test might also sound unpleasant. Statistical treatment of data The subject
37、ive scores should be processed to derive the mean values and confidence intervals. This will describe the data and, if the resulting discrimination is inadequate to satisfy the objectives of the test, further processing should be carried out, as detailed in Recommendation ITU-R BS.1116. The overall
38、value of the test will be enhanced if the data is further analysed to verify the underlying assumptions of the test and to evaluate subject reliability. Presentation of test results Specifications for the presentation of the test results are given in Recommendation ITU-R BS.1116. In general, all asp
39、ects of the test should be reported, as per Recommendation ITU-R BS.1116, even if some of the aspects were not implemented or controlled. 3 Provisions related to the assessment of multichannel program audio Recommendation ITU-R BS.775 specifies a reference loudspeaker arrangement for multichannel pr
40、ogram audio, and the use of five reference recording/transmission signals for left (L), right (R), centre (C), channels for the front, and left surround (LS) and right surround (RS) channels for the side/rear. Additionally the system may include a low frequency extension signal for a low frequency e
41、ffects (LFE) channel. The Figure that details the reference loudspeaker arrangement in Recommendation ITU-R BS.775 is reproduced in Fig. 1 for memory and reference. An example of the loudspeaker arrangement in a typical theatre environment is shown in Fig. 2; in this case (see Note 1), in order to o
42、btain coverage over a larger seating area, the surround channels are reproduced by two arrays of loudspeakers. Depending on the LSDI application for which the subjective assessment test is designed, the loudspeaker configuration that best fits the investigated application should be chosen. 4 Provisi
43、ons related to the assessment of advanced sound system program audio Recommendation ITU-R BS.2051 specifies a reference loudspeaker arrangement for advanced sound system program audio. In the event that a loudspeaker layout used is specified in Recommendation ITU-R BS.2051 rather the ITU-R BS.775 ad
44、ditional reporting and measurement of the listening environment should be captured. For clarification of the experimental conditions and listening environment, all loudspeaker positions (distances and angles) used in the test, as well as their relative Rec. ITU-R BS.1679-1 5 placements to the listen
45、ing position, must be described in detail in the test report. This description must follow the form and the content details commensurate with the loudspeaker layouts and the listening positions as specified in Recommendation ITU-R BS.775. It will also be necessary to identify and describe all loudsp
46、eaker positions in the vertical dimension for the layouts of advanced sound systems that include the loudspeakers at different positions in height. 1 6 7 9 - 0 110 010 012 012 060 RLLS2 1CB1RS2CL , RL S, R S03010 0 . . . 12 000FI G U R E 1R ef er enc e l o ud s p eak er ar rang em en t as s ho w n i
47、 n R e c. I T U - R B S. 775L ou ds p ea kerH or i z ont al ang l ef r om ce nt r e( deg r ee s )H ei gh t( m )I ncl i n at i o n( deg r ee s )0 . . . 1 5 d ow n1. 21. 2 1. 2Sc re en 1 H D T V R e fe re nce d is ta nceSc r e en 2H : h ei ght o f s c r e enB : l oud s pe ak er ba s e w i dt h= 3 H (2
48、 = 2 H (2 6 Rec. ITU-R BS.1679-1 5 Provisions related to the assessment of programme audio with accompanying picture Recommendation ITU-R BS.1286 specifies methods for the subjective assessment of audio with accompanying picture. Recommendation ITU-R BS.1116 specifies methods for the subjective asse
49、ssment of audio systems including those specified in Recommendation ITU-R BS.775 and advanced sound systems specified in Recommendation ITU-R BS.2051. It identifies the four areas of assessment below as requiring the presentation of the visual component of the programme, namely: 1 6 7 9 - 0 2FI G U R E 2E xa m p l e o f a l o uds p e ak e r ar r ang e m e n t i n a n L S D I t he at r i c al ve nu eL e f t C e n t r e R i ghtPe r f or a t e ds c r e e nL e f ts u r r oun da r r a yR i ghts u r r oun da r r a yRec. ITU-R BS.1679-1 7 correlation
