1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.108.1TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2000) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS International telephone connections and circuits General definitions Guidance for assessing conversational speech trans
2、mission quality effects not covered by the E-model ITU-T Recommendation G.108.1 (Formerly CCITT Recommendation) ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 General definitions G.100G.109 Gener
3、al Recommendations on the transmission quality for an entire international telephone connection G.110G.119 General characteristics of national systems forming part of international connections G.120G.129 General characteristics of the 4-wire chain formed by the international circuits and national ex
4、tension circuits G.130G.139 General characteristics of the 4-wire chain of international circuits; international transit G.140G.149 General characteristics of international telephone circuits and national extension circuits G.150G.159 Apparatus associated with long-distance telephone circuits G.160G
5、.169 Transmission plan aspects of special circuits and connections using the international telephone connection network G.170G.179 Protection and restoration of transmission systems G.180G.189 Software tools for transmission systems G.190G.199 INTERNATIONAL ANALOGUE CARRIER SYSTEM GENERAL CHARACTERI
6、STICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALL
7、IC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 DIGITAL TRANSMISSION SYSTEMS TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 For further details, please refer to the list of ITU-T Recommendations. ITU-T G
8、.108.1 (05/2000) i ITU-T Recommendation G.108.1 Guidance for assessing conversational speech transmission quality effects not covered by the E-model Summary This ITU-T Recommendation provides guidance for transmission planners on how to evaluate those effects impacting end-to-end speech transmission
9、 performance which are not covered by the E-model (ITU-T Recommendation G.107 2 The E-model, a computational model for use in transmission planning) and its associated Planning Guide (ITU-T Recommendation G.108 3 Application of the E-model A planning guide). Procedures for informal subjective and ob
10、jective evaluations that can be used to complement the E-model are provided here. Source ITU-T Recommendation G.108.1 was prepared by ITU-T Study Group 12 (1997-2000) and approved under the WTSC Resolution 1 procedure on 18 May 2000. Keywords Conversational impacts, E-model, speech transmission qual
11、ity, voice quality. ii ITU-T G.108.1 (05/2000) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying
12、 technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T study groups
13、 which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSC 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
14、 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recomm
15、endation 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 or others outside of the Recommendation development process. As of the date of appr
16、oval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB
17、patent database. Ge3 ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T G.108.1 (05/2000) iii CONTENTS Page 1 Scope. 1 2
18、 References. 1 3 Abbreviations and definitions. 2 3.1 Abbreviations 2 3.2 Definitions 2 4 General considerations 2 4.1 Parameters describing speech transmission quality (including terminals) . 6 4.2 Test setup for terminals. 7 4.3 Test setup for echo cancelling devices 8 4.4 Test signals for convers
19、ational evaluation 8 5 Evaluation of the conversational situation 8 5.1 Double talk performance. 9 5.2 Subjective evaluations 9 5.2.1 Conversational evaluation . 9 5.2.2 Specific double talk tests and listening only tests . 11 5.3 Objective evaluations 12 6 Guidance on the improvement of conversatio
20、nal speech quality 12 6.1 Delay and echo 13 6.2 Background noise transmission 13 6.3 Double talk performance. 14 6.4 Quality of speech sound and loudness 14 iv ITU-T G.108.1 (05/2000) Introduction This ITU-T Recommendation provides guidance for transmission planners on supplementary conversational p
21、arameters impacting end-to-end speech transmission performance which are not covered by ITU-T Recommendation G.108, since: these supplementary factors are not covered by the E-model as it stands; the guidelines and principles in ITU-T Recommendation G.108 are based on the use of the E-model, which i
22、s applicable to 3.1 kHz handset telephony, only; the current E-Model cannot completely predict the conversational effects of electric or acoustic echo cancelling devices, which may affect quality during only some time segments of the conversation; conversational impacts on end-to-end speech transmis
23、sion performance will occur in conjunction with conversation over hands-free terminals. ITU-T G.108.1 (05/2000) 1 ITU-T Recommendation G.108.1 Guidance for assessing conversational speech transmission quality effects not covered by the E-model 1 Scope This ITU-T Recommendation is intended to provide
24、 guidance on the conversational impairments which are not covered by the E-model and which are thus not included in ITU-T Recommendation G.108 3. Those impairments have been investigated thoroughly by ITU-T during the study period 1997-2000. 2 References The following ITU-T Recommendations and other
25、 references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encourag
26、ed to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. 1 ITU-T Recommendation G.100 (1993), Definitions used in Recommendations on general characterist
27、ics of international telephone connections and circuits. 2 ITU-T Recommendation G.107 (2000), The E-model, a computational model for use in transmission planning. 3 ITU-T Recommendation G.108 (1999), Application of the E-model: a planning guide. 4 ITU-T Recommendation G.167 (1993), Acoustic echo con
28、trollers. 5 ITU-T Recommendation G.168 (2000), Digital network echo cancellers. 6 ITU-T Recommendation P.50 (1999), Artificial voices. 7 ITU-T Recommendation P.57 (1996), Artificial ears. 8 ITU-T Recommendation P.58 (1996), Head and torso simulator for telephonometry. 9 ITU-T Recommendation P.59 (19
29、93), Artificial conversational speech. 10 ITU-T Recommendation P.64 (1999), Determination of sensitivity/frequency characteristics of local telephone systems. 11 ITU-T Recommendation P.340 (2000), Transmission characteristics and speech quality parameters of hands-free terminals. 12 ITU-T Recommenda
30、tion P.501 (2000), Test signals for use in telephonometry. 13 ITU-T Recommendation P.502 (2000), Objective test methods for speech communication systems using complex test signals. 14 ITU-T Recommendation P.581 (2000), Use of head and torso simulator (HATS) for hands-free terminal testing. 15 ITU-T
31、Recommendation P.800 (1996), Methods for subjective determination of transmission quality. 16 ITU-T Recommendation P.831 (1998), Subjective performance evaluation of network echo cancellers. 2 ITU-T G.108.1 (05/2000) 17 ITU-T Recommendation P.832 (2000), Subjective performance evaluation of hands-fr
32、ee terminals. 18 ITU-T Recommendation P.861 (1998), Objective quality measurement of telephone-band (300-3400 Hz) speech codecs. 19 ETSI EG 201 377-1 (1999), Speech Processing, Transmission and Quality Aspects (STQ); Specification and measurement of speech transmission quality; Part 1: Introduction
33、to objective comparison measurement methods for one-way speech quality across networks. 3 Abbreviations and definitions 3.1 Abbreviations This ITU-T Recommendation uses the following abbreviations: DCME Digital Circuit Multiplication Equipment ECD Echo Cancelling Device HATS Head and Torso Simulator
34、 HEC Half Echo Canceller ITU International Telecommunication Union ITU-T International Telecommunication Union Telecommunication Standardization Sector (former CCITT) NLP Non-Linear Processor RCV Receive SCT Short Conversational Test SND Send TCLw Terminal Coupling Loss weighted VAD Voice Activity D
35、etection 3.2 Definitions This ITU-T Recommendation defines the following term: The term “Lab Conditions“ is used in this ITU-T Recommendation in order to describe a testing environment which is well controllable and which allows for speech quality testing under defined and reproducible conditions. 4
36、 General considerations When evaluating the end-to-end speech transmission quality, it may be found that networks and terminals impact the speech quality of a telephone connection quite significantly: coding and decoding processes, introduction of additional delay, packetization and signal processin
37、g techniques as implemented, e.g. in echo cancelling devices or DCME are mainly deployed in the network domain but can increasingly be found in terminal devices as well. The frequency response and loudness ratings of a connection are mainly determined by the terminals, the background noise and the b
38、ackground noise transmission are highly influenced by the terminal and the acoustical environment the terminal is exposed to. The conversational properties which are the most important ones in a conversation are determined by the terminal in combination with the network: double talk capability, swit
39、ching characteristics and delay are dominant impairments which are often introduced. ITU-T G.108.1 (05/2000) 3 In order to evaluate the factors which determine end-to-end speech transmission quality a set of subjective test procedures has been developed. These procedures allow to extract the dominan
40、t quality aspects: conversational tests, talking and listening tests, double talk tests and listening only tests as described in ITU-T Recommendations P.800 15, P.831 16 and P.832 17 are the basis for the parameter extraction procedure. An overview of the methodologies is given in Figures 1 through
41、3. T1212320-00Sound qualityTestEnvironmentAuditoryTestsPerformanceParametersRealistic Conditions“Human Factor“Conversational Tests2 subjects involved(one at the near end ofthe telephone connection,the other at the far end)orIncreasing reality of the testing Increasing comparability,moreanalyticEnd-t
42、o-end speechtransmission qualityDifficulty in communicatingDouble TalkTests2 subjects involved(one at the near end ofthe telephone connection,the other at the far end)Talking and ListeningTests1 artificial head used(at the near end of thetelephone connection),1 subject involved(at the far end), acti
43、ng aslistener and talkerAnnoyance caused byechoes and switchingDouble talk performanceMethod of backgroundnoise transmissionSpeech level variationsvs. timeComparison of individual parameters under definedconditionsClassification ofdisturbancesDatabase forfurther testsListening-onlyTests2 artificial
44、heads used(one at the near end ofthe telephone connection,the other at the far end)1 subject as “observer“Measurement Conditions(exactly defined andidentical for each testand reproducible)NOTE The assignment of “near end“ and “far end“ is chosen according to the E-model (ITU-T Recommendation G.107).
45、Figure 1/G.108.1 Overview of test methods used for subjective evaluation direct parameter access 4 ITU-T G.108.1 (05/2000) T1212330-00Sound qualityTestEnvironmentAuditoryTestsPerformanceParametersRealistic Conditions“Human Factor“Conversational Tests2 subjects involved(one at the near end ofthe tele
46、phone connection,the other at the far end)orIncreasing reality of the testing Increasing comparability,moreanalyticEnd-to-end speechtransmission qualityDifficulty in communicatingDouble TalkTests2 subjects involved(one at the near end ofthe telephone connection,the other at the far end)Talking and L
47、isteningTests1 artificial head used(at the near end of thetelephone connection),1 subject involved(at the far end), acting aslistener and talkerAnnoyance caused byechoes and switchingDouble talk performanceMethod of backgroundnoise transmissionSpeech level variationsvs. timeComparison of individual
48、parameters under definedconditionsClassification ofdisturbancesDatabase forfurther testsListening-onlyTests2 artificial heads used(one at the near end ofthe telephone connection,the other at the far end)1 subject as “observer“Measurement Conditions(exactly defined andidentical for each testsand repr
49、oducible)NOTE The assignment of “near end“ and “far end“ is chosen according to the E-model (ITU-T Recommendation G.107).Figure 2/G.108.1 Overview of test methods used for subjective evaluation Parameter access via interviews ITU-T G.108.1 (05/2000) 5 T1212340-00Sound qualityTestEnvironmentAuditoryTestsPerformanceParametersRealistic Conditions“Human Factor“Conversational Tests2 subjects involved(one at the near end ofthe telephone connection,the other at the far end)orIncreasing reality of the testing In
