INTERNATIONAL TELECOMMUNICATION UNION
ITU-T
P.862
TELECOMMUNICATION
STANDARDIZATION SECTOR
OF ITU
(02/2001)
SERIES P: TELEPHONE TRANSMISSION QUALITY,
TELEPHONE INSTALLATIONS, LOCAL LINE
NETWORKS
Methods for objective and subjective assessment of
quality
Perceptual evaluation of speech quality (PESQ):
An objective method for end-to-end speech
quality assessment of narrow-band telephone
networks and speech codecs
ITU-T Recommendation P.862
(Formerly CCITT Recommendation)
ITU-T P-SERIES RECOMMENDATIONS
TELEPHONE TRANSMISSION QUALITY, TELEPHONE INSTALLATIONS, LOCAL LINE NETWORKS
Vocabulary and effects of transmission parameters on customer opinion of transmission
quality
Series P.10
Subscribers' lines and sets Series P.30
P.300
Transmission standards 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 subjective assessment of quality Series P.80
P.800
Audiovisual quality in multimedia services Series P.900
For further details, please refer to the list of ITU-T Recommendations.
ITU-T P.862 (02/2001) i
ITU-T Recommendation P.862
Perceptual evaluation of speech quality (PESQ): An objective method for end-to-end speech
quality assessment of narrow-band telephone networks and speech codecs
Summary
This Recommendation describes an objective method for predicting the subjective quality of 3.1 kHz
(narrow-band) handset telephony and narrow-band speech codecs. This Recommendation presents a
high-level description of the method, advice on how to use it, and part of the results from a Study
Group 12 benchmark carried out in the period 1999-2000. An ANSI-C reference implementation,
described in Annex A, is provided in separate files and form an integral part of this
Recommendation. A conformance testing procedure is also specified in Annex A to allow a user to
validate that an alternative implementation of the model is correct. This ANSI-C reference
implementation shall take precedence in case of conflicts between the high-level description as given
in this Recommendation and the ANSI-C reference implementaion.
This Recommendation includes an electornic attachment containing an ANSI-C reference
implementation of PESQ and conformance testing data.
Source
ITU-T Recommendation P.862 was prepared by ITU-T Study Group 12 (2001-2004) and approved
under the WTSA Resolution 1 procedure on 23 February 2001.
ii ITU-T P.862 (02/2001)
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 technical, operating and tariff 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 Recommendations 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-T's 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
telecommunication administration and a recognized operating agency.
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 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 approval of this Recommendation, ITU had 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 patent database.
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 ITU.
ITU-T P.862 (02/2001) iii
CONTENTS
Page
1 Introduction ................................................................................................................ 1
2 Normative references.................................................................................................. 1
3 Abbreviations ............................................................................................................. 1
4 Scope .......................................................................................................................... 2
5 Conventions................................................................................................................ 4
6 Overview of PESQ ..................................................................................................... 4
7 Comparison between objective and subjective scores................................................ 6
7.1 Correlation coefficient................................................................................................ 6
7.2 Residual errors............................................................................................................ 6
8 Preparation of processed speech material................................................................... 7
8.1 Source material........................................................................................................... 7
8.1.1 Choice of source material.............................................................................. 7
8.1.2 ITU-T Temporal structure and duration of source material.......................... 7
8.1.3 Filtering and level calibration ....................................................................... 8
8.2 Addition of background noise .................................................................................... 8
8.3 Processing through system under test......................................................................... 8
9 Selection of experimental parameters ........................................................................ 8
10 Description of PESQ algorithm.................................................................................. 9
10.1 Level and time alignment pre-processing (Figure 3) ................................................. 13
10.1.1 Computation of the overall system gain........................................................ 13
10.1.2 IRS filtering................................................................................................... 13
10.1.3 Time alignment ............................................................................................. 13
10.2 Perceptual model (Figures 4a and 4b) ........................................................................ 15
10.2.1 Precomputation of constant settings.............................................................. 15
10.2.2 IRS-receive filtering...................................................................................... 15
10.2.3 Computation of the active speech time interval............................................ 15
10.2.4 Short-term Fast Fourier Transform ............................................................... 16
10.2.5 Calculation of the pitch power densities ....................................................... 16
10.2.6 Partial compensation of the original pitch power density for transfer
function equalization ..................................................................................... 16
10.2.7 Partial compensation of the distorted pitch power density for time-varying
gain variations between distorted and original signal ................................... 16
10.2.8 Calculation of the loudness densities ............................................................ 16
10.2.9 Calculation of the disturbance density .......................................................... 17
10.2.10 Cell-wise multiplication with an asymmetry factor ...................................... 17