tratamiento digital de voz prof. luis a. hernández gómez ftp.gaps.ssr.upm.es/pub/tdv/doc/...
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Tratamiento Digital de Voz
Prof. Luis A. Hernández Gómez
ftp.gaps.ssr.upm.es/pub/TDV/DOC/Tema2c.ppt
Dpto. Señales, Sistemas y Dpto. Señales, Sistemas y RadiocomunicacionesRadiocomunicaciones
Agenda• Perceptual evaluation of Speech Quality• Traditional evaluation of Speech Quality• A new approach to evaluation of Speech Quality• Perceptual Evaluation of Speech Quality within
ITU-T
The idea
• To simulate the sound perception of subjects in real-life situations
• To have a objective technique based on a perceptual model that will reveal the same MOS score as that of Listening Test
What is MOS?
• Methods and procedures for conducting subjective evaluation of transmission quality (ITU -T Rec. 800)
• Quality of speech based on Listening Tests
A new approach to evaluation of Speech Quality
Objective techniques used for predicting subjective test scores
• PSQM (Perceptual Speech Quality Measure)
• PSQM+ (ITU -T Rec. 861)
• PESQ (Perceptual Evaluation of Speech Quality) (ITU -T Rec. 862)
• and others like MNB, PAMS, TOSQA, PACE, VQI and PESQM.
About PSQM, PSQM+, PESQ
• For jugging the listening and talking quality of Telephone band speech signals (300-3400Hz)
• Signals of the input and output of the device under test are mapped onto a psychophysical representation that match as close as possible the internal representation inside our head
A new approach to evaluation of Speech Quality
Agenda• Perceptual evaluation of Speech Quality• Traditional evaluation of Speech Quality• A new approach to evaluation of Speech Quality• Perceptual Evaluation of Speech Quality within
ITU-T
Generic perceptual measurement algorithm
Perceptual Model
Feature-Extractor
Test
Perceptual Model
Reference
Cognitive Model
Quality measure
Impairment Grade
Excellent 5
Good 4
Fair 3
Poor 2
Bad 1
Perceptual Model
Is a model of the Human Ear
Cognitive Model
Is a model of the judgement behaviour
of the test subject
Basic model of PSQM & PSQM+ algorithm
Perceptual Model
Internal representation of the reference signal
Test
Perceptual Model
Reference
Cognitive Model
Quality measureDifference in internal
representation
Internal representation of the test signal
Improvements in PSQM+• Time alignment: variable delay, frame repeats• Weight of distortion: time clipping, time frequency distortion
Improvements in PSQM+
• Time alignment: variable delay, frame repeats• Weight of distortion: time clipping, time frequency distortion
Basic model of PESQ algorithm
Auditory transform
Degraded
Level align
Reference
Cognitive Modelling
Quality measure
Input filter
Auditory transform
Disturbance processing
Identify bad intervals
Time align and
equalise
Level align
Input filter
Next step is PESQM
• Assessment of Handset on a perceptual basis using HATS
• Covering echo and Sidetone
Next step is PESQM
• Assessment of Handset on a perceptual basis using HATS
• Covering echo and Sidetone
Perceptual measurement algorithms - roadmap
PSQM P.861, 1996
Intrusive Narrowband
Speech Quality
PSQM+ 1996
PESQ P.862, 1996
PESQM 2001,2002
Conversational Quality
P3SQM 2001,2002
Echo and Acoustical
measurement
Non-Intrusive Narrowband
Speech Quality
Wideband Audio
Video measurement
PEAQ BS1387, 1996
PEAQ+ 2002
Acoustical PESQ
extension
Single-ended Voice Quality
PEVQ
Wideband Voice Quality
Audiovisual Quality
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