1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T P.834.1 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2015) SERIES P: TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Methods for objective and subjective assessment of speech quality Extension of the method
2、ology for the derivation of equipment impairment factors from instrumental models for wideband speech codecs Recommendation ITU-T P.834.1 ITU-T P-SERIES RECOMMENDATIONS TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Vocabulary and effects of transmission parameters on customer opinion of
3、transmission quality Series P.10 Voice terminal characteristics Series P.30 P.300 Reference systems Series P.40 Objective measuring apparatus Series P.50 P.500 Objective electro-acoustical measurements Series P.60 Measurements related to speech loudness Series P.70 Methods for objective and subjecti
4、ve assessment of speech quality Series P.80 P.800 Audiovisual quality in multimedia services Series P.900 Transmission performance and QoS aspects of IP end-points Series P.1000 Communications involving vehicles Series P.1100 Models and tools for quality assessment of streamed media Series P.1200 Te
5、lemeeting assessment Series P.1300 Statistical analysis, evaluation and reporting guidelines of quality measurements Series P.1400 Methods for objective and subjective assessment of quality of services other than voice services Series P.1500 For further details, please refer to the list of ITU-T Rec
6、ommendations. Rec. ITU-T P.834.1 (06/2015) i Recommendation ITU-T P.834.1 Extension of the methodology for the derivation of equipment impairment factors from instrumental models for wideband speech codecs Summary Recommendation ITU-T P.834.1 describes an extension of the methodology for deriving eq
7、uipment impairment factors from instrumental models of Recommendation ITU-T P.834. It is intended that it be primarily applied to determine wideband equipment impairment factors Ie,wb, capturing the degradation introduced by wideband speech codecs. The resulting wideband equipment impairment factors
8、 derived by this methodology are intended to be used on the extended transmission rating scale underlying the E-model (see Appendix II of Recommendation ITU-T G.107). They reflect the auditory impairments of the corresponding equipment in a listening-only mode. The methodology of Recommendation ITU-
9、T P.834.1 makes use of instrumental models (so called “objective methods“), e.g., the model defined in Recommendation ITU-T P.862.2. It is to be considered as supplementary to the methodology based on auditory listening-only tests, described in Recommendation ITU-T P.833.1. It provides valid Ie,wb v
10、alues only for those codecs for which the instrumental model used produces meaningful estimations. Speech material associated with Recommendation ITU-T P.834.1 is freely available on the test signal database at www.itu.int/net/ITU-T/sigdb. History Edition Recommendation Approval Study Group Unique I
11、D* 1.0 ITU-T P.834.1 2009-04-29 12 11.1002/1000/9729 2.0 ITU-T P.834.1 2015-06-29 12 11.1002/1000/12517 Keywords Codec, E-model, equipment impairment factor, impairment factor method, objective method, wideband speech transmission. _ * To access the Recommendation, type the URL http:/handle.itu.int/
12、 in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T P.834.1 (06/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommuni
13、cations, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunica
14、tions on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure
15、 laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommu
16、nication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these
17、mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU dra
18、ws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members o
19、r others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not rep
20、resent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2015 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T P.834.1 (06
21、/2015) iii Table of Contents Page 1 Scope . 1 2 References . 2 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 3 5 Conventions 3 6 Experimental set-up and data processing . 3 6.1 Input speech material 3 6.2 Reference conditions
22、4 6.3 Processing of speech material 5 6.4 Calculation of MOS estimations using the instrumental model . 5 7 Derivation of wideband equipment impairment factors . 6 8 Limitations of the instrumentally derived wideband equipment impairment factor values 7 Annex A Speech material . 8 Appendix I Calcula
23、tion of equipment impairment factors from scores provided by the instrumental model described in ITU-T P.862.2 10 Bibliography. 11 iv Rec. ITU-T P.834.1 (06/2015) Introduction ITU-T has introduced the impairment factor method in order to describe the joint effect of different types of degradations o
24、n the overall transmission quality. According to this method, transmission impairments can be transformed into so-called “psychological factors“, which are assumed to be additive on a psychological scale. The transmission rating scale (R scale) underlying the E-model (see ITU-T G.107) is assumed to
25、reflect such a psychological scale. The impairment factor method allocates a value of impairment to each parameter describing the transmission channel, and then allows the simple addition of these impairments to determine the overall impairment. The overall transmission rating, R, is finally calcula
26、ted by subtracting the overall impairment from the maximum value Rmax. Whereas the R scale and the E-model were originally formulated for narrowband (300-3400 Hz) speech transmission only, Appendix II of ITU-T G.107 presents an extension of this scale to wideband (50-7000 Hz) speech transmission. Al
27、though a complete wideband version of the E-model is not yet available, Appendix IV to ITU-T G.113 provides values for wideband equipment impairment factors Ie,wb, which describe the degradation resulting from selected wideband speech codecs on the extended R scale. This Recommendation describes a m
28、ethodology for the derivation of Ie,wb values for other wideband speech codecs, based on the results of so-called “objective methods“. Rec. ITU-T P.834.1 (06/2015) 1 Recommendation ITU-T P.834.1 Extension of the methodology for the derivation of equipment impairment factors from instrumental models
29、for wideband speech codecs1 1 Scope This Recommendation describes an extension of the ITU-T P.834 methodology and is intended to derive wideband equipment impairment factors Ie,wb quantifying the impairment introduced by wideband (50-7000 Hz) speech codecs. It is assumed that the reader is familiar
30、with ITU-T P.834. Such wideband equipment impairment factors have been introduced as a simplified measure of the degradation introduced by wideband speech codecs on the integral transmission quality from mouth to ear. They are in no way an exact description of the effects related to each individual
31、codec or codec tandem, which may be very diverse in their perceptual nature. Instead, they represent the relative degradation in comparison to other impairments occurring in a connection. In order to provide guidance on the quantitative amount of impairment introduced by such codecs, a framework of
32、wideband equipment impairment factor values for several wideband speech codecs has been derived by ITU-T; see Appendix IV to ITU-T G.113. The derivation of these values is based on many subjective listening-only tests carried out in different test laboratories, so as to guarantee stable values for a
33、ll the codecs under investigation so far, as well as their relationship to each other. If new equipment impairment factor values for different codecs require derivation, then the overall consistency with the established framework is of primary importance if results are to be obtained that are valid
34、for network planning. The methodology described in this Recommendation has been designed to fulfil this requirement. So far, wideband speech codecs are the only wideband elements for which impairment factors have been derived. For asynchronous tandems of multiple codecs of the same type or of multip
35、le codecs of different types, it is assumed that individual equipment impairment factors are additive. The overall equipment impairment factor for the chain of codecs is then calculated as a simple sum of all the individual Ie,wbs. Experimental test data collected provide evidence that this simple a
36、dditivity is not satisfied for all the potential combinations of codecs. These deviations from the pure additivity property are an item for further study. Impairment factor values for other wideband network elements, resulting in other types of degradations and to be used in a wideband version of th
37、e E-model, have not yet been defined and are also for further study. ITU-T currently recommends two methodologies for the derivation of wideband equipment impairment factors: this Recommendation and ITU-T P.833.1. The methodology described in ITU-T P.833.1 is based on the results of auditory listeni
38、ng-only tests. The approach in this Recommendation, which is based on instrumental models (so-called “objective methods“), requires that the models used provide valid estimations of auditory judgements. Only in this case will the derived wideband equipment impairment factors be valid. The methodolog
39、y described has been tested with the model defined in ITU-T P.862.2 and results have been found to be satisfactory in most cases. _ 1 This Recommendation includes speech material which is freely available on the test signal database at www.itu.int/net/ITU-T/sigdb. The speech material is also availab
40、le in a zipped file associated with this Recommendation. 2 Rec. ITU-T P.834.1 (06/2015) 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editio
41、ns indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid
42、ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.107 Recommendation ITU-T G.107 (2015), The E-model: A computational model for use in transmission planning. ITU-T
43、G.107.1 Recommendation ITU-T G.107.1 (2015), Wideband E-model. ITU-T G.113 Recommendation ITU-T G.113 (2007), Transmission impairments due to speech processing. ITU-T G.722 Recommendation ITU-T G.722 (2012), 7 kHz audio-coding within 64 kbit/s. ITU-T G.722.1 Recommendation ITU-T G.722.1 (2005), Low-
44、complexity coding at 24 and 32 kbit/s for hands-free operation in systems with low frame loss. ITU-T G.722.2 Recommendation ITU-T G.722.2 (2003), Wideband coding of speech at around 16 kbit/s using Adaptive Multi-Rate Wideband (AMR-WB). ITU-T P.56 Recommendation ITU-T P.56 (2011), Objective measurem
45、ent of active speech level. ITU-T P.341 Recommendation ITU-T P.341 (2011), Transmission characteristics for wideband digital loudspeaking and hands-free telephony terminals. ITU-T P.501 Recommendation ITU-T P.501 (2012), Test signals for use in telephonometry. ITU-T P.800 Recommendation ITU-T P.800
46、(1996), Methods for subjective determination of transmission quality. ITU-T P.830 Recommendation ITU-T P.830 (1996), Subjective performance assessment of telephone-band and wideband digital codecs. ITU-T P.833.1 Recommendation ITU-T P.833.1 (2009), Methodology for the derivation of equipment impairm
47、ent factors from subjective listening-only tests for wideband speech codecs. ITU-T P.834 Recommendation ITU-T P.834 (2015), Methodology for the derivation of equipment impairment factors from instrumental models. ITU-T P.862.2 Recommendation ITU-T P.862.2 (2007), Wideband extension to Recommendation
48、 P.862 for the assessment of wideband telephone networks and speech codecs. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation None. Rec. ITU-T P.834.1 (06/2015) 3 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: AD
49、PCM Adaptive Differential Pulse Code Modulation CELP Codebook-Excited Linear Prediction MLTC Modified Lapped Transform Coding MOS Mean Opinion Score 5 Conventions None. 6 Experimental set-up and data processing The instrumental methodology in this Recommendation is mainly based on the auditory equivalent specified in ITU-T P.833.1, substituting the auditory test by an instrumental model, e.g., that described in ITU-T P.862.2. Apart from this substitution, both methodologies are very simi
