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PESQ and Recording Devices Kevin J Cross Malden Electronics Ltd

PESQ – ITU-T Rec. P.862 Speech Quality Metric Compares a clean reference speech file with a degraded speech file Predicts a Mean Opinion Score for Listening Quality

Associated Standards P PESQ-LQO P PESQ-WB P Use of PESQ

How PESQ Works Summary of PESQ Process

Benefits of PESQ A Standard Calibrated against test votes Five years use around the world Works across a wide range of codecs and networks

Limitations of PESQ Noise floor and file length Signal timing Voiced signal compression – low bit rate codecs

Assessment of Recording Devices Functionality – Answer, Replay Start & Stop, Interactive DTMF or Voice Activation Performance under Load Speech Quality of Recorded Messages

Speech Quality Modifiers Recording media FA1000f.rst FA1000f.rst Codec Line interface Network Line interface Phone Amplifier and Equaliser Speaker’s transducer Speaker’s environment

Test Interfaces POTS Handset port Digital source – TDM or VoIP

Test Stimuli Language Phonemic Content Duration Quality vvn from 7905 China2f12dbpoor.rst vvn from 7905 China2f12dbpoor.rst Gender Spectral Content –Narrowband and Wideband material –Intermediate Reference System Send Characteristic

Acoustic Connection - Playback Narrowband speech played back to loudspeaker –Narrowband measurement Wideband speech played back to loudspeaker –Wideband measurement

Acoustic Connection - Record Wideband, flat, speech to Artificial Mouth –Use narrowband IRS or mIRS reference for PESQ on playback through narrowband network –Use wideband, flat, reference for PESQ on playback through wideband network

Test Sequence Laboratory –Measure speech levels –Measure speech quality vs speech levels –Measure speech quality vs background noise type and level – Measure speech quality vs jitter and packet loss vvn from 7905 China2f12db 0ms 0pct.rst vvn from 7905 China2f12db 0ms 0pct.rst vvn from 7905 China2f12db 30ms 0pct.rst vvn from 7905 China2f12db 30ms 1pct.rst

Test Sequence Field –Measure speech levels –Measure speech quality – two male and two female –Assess jitter and packet loss

Results Speech quality Speech levels Noise Jitter Packet loss Time offsets after jitter buffer

Result Accuracy Test Equipment vvn from 7905 Thai.rst vvn from 7905 China2.rst vvn from 7905 Thai.rstvvn from 7905 China2.rst Test Network Eric750if.rst Eric750if.rst Speech Levels vvn from 7905 China2.rst vvn from 7905 China2f12db.rst vvn from 7905 China2.rstvvn from 7905 China2f12db.rst Codecs vvn from vn f alaw.rst vvn from vn f ulaw.rst vvn from vn f alaw.rstvvn from vn f ulaw.rst Volume Controls Automatic Gain Controls

Summary Optimise Test Equipment and Test Network Optimise Speech Levels Choose most favourable Codecs Keep Volume Controls under lock and key

The Perfect Score