1、 International Telecommunication Union ITU-T P.502TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1(05/2010) SERIES P: TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Objective measuring apparatus Objective test methods for speech communication systems using complex test signals
2、Amendment 1: New Appendix III Automated double talk analysis procedure Recommendation ITU-T P.502 (2000) Amendment 1 ITU-T P-SERIES RECOMMENDATIONS TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Vocabulary and effects of transmission parameters on customer opinion of transmission quality
3、Series P.10 Voice terminal characteristics Series P.30 P.300 Reference systems Series P.40 Objective measuring apparatus Series P.50P.500Objective electro-acoustical measurements Series P.60 Measurements related to speech loudness Series P.70 Methods for objective and subjective assessment of speech
4、 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 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T P.502 (2000)/A
5、md.1 (05/2010) i Recommendation ITU-T P.502 Objective test methods for speech communication systems using complex test signals Amendment 1 New Appendix III Automated double talk analysis procedure Summary Amendment 1 to Recommendation ITU-T P.502 adds new Appendix III to the Recommendation. The appe
6、ndix describes the methodology for an objective post analysis of measured double talk curves. History Edition Recommendation Approval Study Group 1.0 ITU-T P.502 2000-05-18 12 1.1 ITU-T P.502 (2000) Amend. 1 2010-05-27 12 ii Rec. ITU-T P.502 (2000)/Amd.1 (05/2010) FOREWORD The International Telecomm
7、unication Union (ITU) is the United Nations specialized agency in the field of telecommunications, 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 tarif
8、f questions and issuing Recommendations on them with a view to standardizing telecommunications 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 Recommen
9、dations on these topics. The approval of ITU-T Recommendations is covered by the procedure 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 Recommenda
10、tion, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interoperabilit
11、y or applicability) and compliance with the Recommendation is achieved when all of these 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 complia
12、nce with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws 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 o
13、r applicability of claimed Intellectual Property Rights, whether asserted by ITU members or 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 t
14、o implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 All rights reserved. No part of this publication may be reproduced, by
15、 any means whatsoever, without the prior written permission of ITU. Rec. ITU-T P.502 (2000)/Amd.1 (05/2010) 1 Recommendation ITU-T P.502 Objective test methods for speech communication systems using complex test signals Amendment 1 New Appendix III Automated double talk analysis procedure 1) New App
16、endix III Add the following new Appendix III. Appendix III Automated double talk analysis procedure (This appendix does not form an integral part of this Recommendation) III.1 Introduction ITU-T P.340 describes test methods for double talk analyses of hands-free terminals based on signals and analys
17、is procedures standardized in this Recommendation and in ITU-T P.501. These measurements allow the analysis of the attenuation range in sending and receiving directions based on double talk composite source signals. Basically, the measurements are performed by subtracting the time dependent level of
18、 a transmitted test signal during double-talk by its corresponding time synchronized level during single talk. However, due to slight time misalignments, non-linear, time variant signal processing and other fractures, an objective analysis which can be performed reproducibly and unambiguously in dif
19、ferent labs is not always possible. The result often depends on the interpretation of the operator. This appendix describes a new procedure which allows the automated objective analysis in a clearly defined way. The method has been proven to reduce the ambiguity in interpretation of double talk meas
20、urements. The accuracy of this method in predicting the mean value of the attenuation range derived by a jury of test conductors manually calculating the attenuation range is unknown. Currently, this method is only intended to check consistency in measurements between labs. The method was not valida
21、ted in a formal double talk test. The procedure described is based on the double talk composite source signal (CSS) which is currently used for double talk testing. However, the method described is not limited to CSS but may be applied to other double talk signals as well. It is intended that real s
22、peech signals be used for testing instead of speech-like signals, if possible. This work is ongoing. It should be noted that if the method described here is applied to other test signals, the method needs to be adapted especially with respect to the histogram limitations. 2 Rec. ITU-T P.502 (2000)/A
23、md.1 (05/2010) III.2 Proposal for an automated double talk analysis procedure A typical result of the analysis of modern terminals with respect to the attenuation range in the sending direction is given in Figure III.1. HFT: Hands-free (telephone) set Figure III.1 Typical results of a double talk te
24、st based on the attenuation range measurement ITU-T P.340 It can be seen, that the blue (HFT 2) curve is already somewhat difficult to interpret with respect to the amount of attenuation inserted during double talk. An unambiguous interpretation of the red (HFT 1) curve is nearly impossible because
25、at different times different attenuations are inserted; the attenuation versus time is highly time-variant. In such cases, the time history signal, as well as some additional subjective verification of the measured result, is currently used in order to finally determine the attenuation range during
26、double talk. However, this does not always lead to the same interpretation of the results by different operators. In order to achieve a clear, consistent and unambiguous interpretation result, an objective procedure is needed. A proposal for such a procedure, which could also be applied for other ty
27、pes of double talk test signals, is shown in Figure III.2. HFT 1HFT 2Sony Ericsson vs. Lexus L/dB-45-40-35-30-25-20-15-10-50t/s0 0.5 1 2 2.5 3LexusSony Ericsson?Rec. ITU-T P.502 (2000)/Amd.1 (05/2010) 3 Figure III.2 Principle of the proposed automated double talk analysis The double talk signal is t
28、ime aligned to the delay inserted by the telephone and the test equipment, and presented to the terminal as described in ITU-T P.340 (“t“). Instead of using the unfiltered double talk CSS signal as reference, the reference signal used is the transmitted test signal for the individual direction (send
29、ing or receiving) without the double talk signal present. Such reference signal includes possible automatic gain control (AGC) influence as well as the individual transfer function of the device under test. Based on the transmitted signal and the new reference signal, the double talk analysis is per
30、formed through the individual interpretation of each CSS burst from the transmitted double talk signal (see Figure III.2). For each CSS burst a level histogram is created, and from this level histogram the amount of attenuation is determined (ah,DT,SNDand ah,DT,RCVrespectively, according to ITU-T P.
31、340). The ah,DT,SNDthat is finally observed determines the double talk category (for the sending direction in this case). The histogram creation and the calculation of attenuation relevant for the final double talk rating is described in the following more in detail using the analysis example in Fig
32、ure III.3. It shows the level versus time difference representation of the CSS bursts of a modern terminal in the sending direction (level of the transmitted signal referred to the level of filtered reference signal): The level versus time L(k) is calculated according to b-IEC 61672 (i.e., DIN EN 61
33、672) with a time constant of 5 ms for both signals (LDT,SND(k) and LRef(k). The difference between both signals L(k) is calculated as L(k) = LDT,SND(k) LRef(k). Minimum and maximum limits for the histogram are derived from minimum and maximum level difference (Lmin= minL(k) and Lmax= maxL(k). Divisi
34、on of histogram in 100 equally spaced bins between the minimum and the maximum histogram limits, Lminand Lmax. DelayRCV-1.5-1-0.500.51p/Pat/s3.5 4 4.5 5.5 6tDT SND-20-100L/dBV/Paf/Hz100 200 5000Freq. Resp. SND_Levelvs.TimeLevelvs.TimeTime WindowReference signal0100200300400500600700-11,05-10,682-10,
35、313-9,9438-9,5749-9,2061-8,8372-8,4684-8,0995-7,7307-7,3618 -6,993-6,6242-6,2553-5,8865-5,5176-5,1488-4,7799-4,4111-4,0422-3,6734-3,3045-2,9357-2,5668 -2,1980100200300400500600700-11,05-10,682-10,313-9,9438-9,5749-9,2061-8,8372-8,4684-8,0995-7,7307-7,3618 -6,993-6,6242-6,2553-5,8865-5,5176-5,1488-4,
36、7799-4,4111-4,0422-3,6734-3,3045-2,9357-2,5668 -2,1980100200300400500600700-11,05-10,682-10,313-9,9438-9,5749-9,2061-8,8372-8,4684-8,0995-7,7307-7,3618 -6,993-6,6242-6,2553-5,8865-5,5176-5,1488-4,7799-4,4111-4,0422-3,6734-3,3045-2,9357-2,5668 -2,1980100200300400500600700-11,05-10,682-10,313-9,9438-9
37、,5749-9,2061-8,8372-8,4684-8,0995-7,7307-7,3618 -6,993-6,6242-6,2553-5,8865-5,5176-5,1488-4,7799-4,4111-4,0422-3,6734-3,3045-2,9357-2,5668 -2,1980100200300400500600700-11,05-10,682-10,313-9,9438-9,5749-9,2061-8,8372-8,4684-8,0995-7,7307-7,3618-6,993-6,6242-6,2553-5,8865-5,5176-5,1488-4,7799-4,4111-4
38、,0422-3,6734-3,3045-2,9357-2,5668 -2,198HistogramLminLmaxDTCategoryMax.L1L2L3L4L5LmaxTest SystemDT- Signals4 Rec. ITU-T P.502 (2000)/Amd.1 (05/2010) Deletion of the lower 20% and the upper 15% histogram values. New, “effective“ histogram limits are given by Lmin20%and Lmax15%. This can be interprete
39、d as a smoothing of the curve, which allows the suppression of slight level variations not important for the subjective perception, as well as of some strong peaks which last only for a short period of time and are also not important for the subjective double talk quality perception. Calculation of
40、attenuation range ah,DT,SNDaccording to ITU-T P.340 as the difference between Lmin20%and Lmax15%, i.e., ah,DT,SND= Lmax15% Lmin20%. Figure III.3 Result of a double talk analysis of a modern terminal displayed as level difference versus time The result of this level bin is a histogram representation
41、as shown in Figure III.4, which is different for each CSS burst. P.502(00)Amd.1(10)_FIII.4700500400300200100060011,0510,68210,3139,94389,57498,83729,20618,46848,09957,73077,36186,9936,62426,25535,88655,51765,14884,77994,41114,04223,67343,30452,93572,56682,198Number oflevels per binLmax15%Lmin20%Figu
42、re III.4 Histogram representation of the first level versus time representation from Figure III.3 The values 15% and 20% were developed empirically based on subjective experts evaluation of 58 different types of mobile phones. With this subjective experts evaluation, a double talk type class mean er
43、ror between the subjective experts evaluation and the described objective procedures of a mean = 0.0172 and an RMSI = 0.82 could be achieved. J:DTTESTINPUT04-09-02 Sagem H20_DOUBLE_TALK.hdf L/dB-40-35-30-25-20-15-10-505t/s0.5 0.75 1 1.25 1.75 2 2.25 2.5For each “Burst”:divide in 100 level binsRec. I
44、TU-T P.502 (2000)/Amd.1 (05/2010) 5 Although this objective post analysis for ITU-T P.340 signals has not yet been evaluated in a formal subjective listening test, it can be stated that such defined analysis of double talk would greatly improve the comparability of measurement results in different l
45、abs, while at the same time showing some reasonable correlation with subjective experts evaluations. The described post analysis is not limited to the CSS bursts currently defined in ITU-T P.501, the main body of this Recommendation and ITU-T P.340, but can be performed in the same way with differen
46、t types of double talk signals. The analysis could be also applied for double talk signals based on real speech. However, if applied, the parameters of the histogram treatment need to be adapted. This work is under study. 2) Bibliography Add the following new reference: b-IEC 61672 IEC 61672, Electr
47、oacoustics Sound level meters. Part 1 (2002): Specifications. Part 2 (2003): Pattern evaluation tests. Part 3 (2006): Periodic tests. Printed in Switzerland Geneva, 2010 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series D General tariff principles Series E Overall net
48、work operation, telephone service, service operation and human factors Series F Non-telephone telecommunication services Series G Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I Integrated services digital network Series J Cable netwo
49、rks and transmission of television, sound programme and other multimedia signals Series K Protection against interference Series L Construction, installation and protection of cables and other elements of outside plant Series M Telecommunication management, including TMN and network maintenance Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipment Series P Terminals and subjective and obj
