Opticom PESQ DATASHEET

PESQ – Perceptual Evaluation
of Speech Quality

Voice
Quality Testing

OPTICOM’s PESQ (Perceptual Evaluation of

Speech Quality) provides accurate and repeat­able estimates of speech quality degradation
occurring through e.g. a telephony network. It
compares the audio signal input to a network
with the corresponding (degraded) audio signal
output from the network. P.862 is based on the
earlier P.861 (PSQM) technology developed by
KPN Research extended to include a time align­ment model.

Being already widely used in active testing in
both lab environments and in network test

Principle

The degraded signal and the reference signal
are individually level aligned and filtered with
the transfer characteristics of a receiving device
(handset). Basically two different filter functions
– a narrow band (IRS) filter and a wide band fil­ter – are available and may be chosen depend­ing on the preferred application. After that the
two signals are time aligned in order to com­pensate for small time shifts that can occur in
e.g. Voice over IP networks due to delay and jit­ter changes and coding.

In order to account for the distortions that are
actually perceived by a human listener the
model transforms the two aligned and filtered
signals from the time-amplitude domain into a
frequency-loudness domain (auditory transform).

equipment, OPTICOM's PESQ has achieved a
great reputation for its ease of use and its relia­bility of its results while lowering the costs for
the measurements.

OPTICOM's PESQ is fully compliant to ITU-T
P.862.x covering the applicability to narrow
band as well as wide band audio signals.

OPTICOM who is the leading provider of signal
based perceptual measurement technologies
offers algorithms for voice, audio and video
quality measurements.

By subtracting the two signal representations
an estimate of the audible differences is
derived. The audible differences are accumulat­ed over time while they are weighted different­ly depending on whether a distortion was
added to the signal or if parts of the signal
were missing after the transmission (cognitive
model).

Finally after the analysis a single Mean Opinion
Score (MOS) is generated. The MOS is common­ly used to describe the voice quality on a scale
from 1 (bad quality) to 5 (excellent quality).

OPTICOM Product Line:
Voice/Audio Quality

PESQ ITU-T P.862
3SQM ITU-T P.563
PSQM ITU-T P.861
ECHO
PEAQ ITU-T BS.1387

Video Quality

PEVQ

Network Quality

VQmon

Key Features:

• Perceptual analysis of
degradations in voice sig­nals

• Well established, repeat­able results

• Output score correlates
very well with subjective
MOS

• Automatic time alignment
capability

• Available as DLL/Library
and Source

Reference
signal

Level
align

System

under test

Level

Degraded
signal

PEVQ™, 3SQM™ and the OPTICOM logo are registered trademarks of OPTICOM GmbH; the ‘single-sided speech quality measure’ and
‘the perceptual quality experts’ are trademarks of OPTICOM GmbH. This information may be subject to change.
All brand and product names are trademarks and/or registered trademarks of their respective owners.
All rights reserved. Copyright © 2005 OPTICOM GmbH – www.opticom.de

align

Input
filter

Time
align and
equalise

Input
filter

Re-align bad intervals

Auditory
transform

Disturbance
processing

Auditory
transform

Cognitive
modelling

Identify bad
intervals

Prediction
of perceived
speech
quality

One of the major advantages of PESQ over
other measurement approaches is that it does
not need to make any assumptions on the net­work under test or the distortion types that may
occur in a specific telephony test scenario. The
only prerequisite employed within the model is
the scientific knowledge on how human speech
is produced and how humans perceive it.

PESQ already includes the effects of both pack­et level impairments (loss, jitter) and signal
related impairments such as noise, clipping and
distortions caused by coding processes. The
impairment model, based on this knowledge is
as generic as it can be and therefore independ­ent from current and future telephony applica­tions and networks.

Specifications

PESQ – Perceptual Evaluation of Speech Quality

Functionality

• ITU-T P.862.x Perceptual Evaluation of
Speech Quality, with mapping to MOS scale

• Narrowband and Wideband operation

Input

• 16 bit linear audio sampled at 8kHz and
16kHz

• Input voice files 6 to 20 seconds in length

Output

• VAD measurements (front end clipping, hold
over time)

• Drop out measurement

• Delay measurement and statistics (min, max,
average, delay vs. time, histogram)

• MOS vs. time

• MOS for speech and silent parts separately

• Attenuation

• Speech level (total, active speech, silence,
reference, test separately)

• Loudness (reference, test)

• AGC measurement

• R Factor (LQ)

Complexity

• P.862 is processed in about 10-20 times
faster than real-time on a Pentium III
733MHz (44-125MFLOPs)

• Data memory: 5.2MB for file pair with 8s
length

• Code memory: App. 200-400kb (depending
on used features and optimizations)

• Floating point library required

Platforms

• Windows

• Linux

• Solaris

About OPTICOM

With PSQM, PESQ and PEAQ,
OPTICOM GmbH, the pioneer
in perceptual quality testing
has been providing three
international world-class
standards for voice and audio
quality measurement since
its foundation in 1995. With
their new single-sided
speech quality measure

™

3SQM

, a joint development
with partners, the perceptual
experts from Germany now
presented their fourth ITU
standard. At its 10th anniver­sary, the presentation of the
new PEVQ™ video measure
leverages the company’s
huge experience towards the
multimedia testing domain.
Recognized an industry refer­ence, OPTICOM’s OPERA
voice/audio quality test tools
are available to users world
wide. And while specialized
on OEM customers in particu­lar, the directory of OEM
licensees today reads like the
‘Who-is-Who’ of the
Telecoms industry. OPTICOM
is a privately held company
located in Erlangen, Germany.

Sales Contacts:

OPTICOM GmbH

Nägelsbachstraße 38
91052 Erlangen, GERMANY
Phone: [phone]
Fax: [phone]
[e-mail]
www.opticom.de

North America:

Telchemy Inc.

Phone [phone]

JDSU - Acterna U.S.

Phone [phone]

Europe, Latin America,
Middle East & Africa,
Asia Pacific, CIS Countries:

PEVQ™, 3SQM™ and the OPTICOM logo are registered trademarks of OPTICOM GmbH; the ‘single-sided speech quality measure’ and
‘the perceptual quality experts’ are trademarks of OPTICOM GmbH. This information may be subject to change.
All brand and product names are trademarks and/or registered trademarks of their respective owners.
All rights reserved. Copyright © 2005 OPTICOM GmbH – www.opticom.de

JDSU - Acterna
Germany GmbH

Phone: [phone]

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