Presenatation

1
Future work on objective speech quality
measurements in ITU-T
Jens Berger SwissQual AG, Switzerland jens.berger_at_
swissqual.com
Workshop on Wideband Speech Quality in Terminals
and Networks Assessment and Prediction 8th and
9th June 2004 - Mainz, Germany
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Structure

• History in ITU-T / CCITT
• Current Work Listening Quality
• New Aspects in the Coming Study Period of ITU-T

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History in ITU-T / CCITT
1981-1984 Models for predicting transmission quality from objective measurements Q7/XII
Non-linear distortion of telephone apparatus Q13/XII
1985-1988 Models for predicting transmission quality from objective measurements Q7/XII
Non-linear distortion of telephone apparatus Q13/XII
1988-1992 Models for predicting transmission quality from objective measurements Q7/XII
Methods for the evaluation of non-linear distortion Q13/XII
1993-1996 Methods for measuring and modeling the effects of non-linear processes on the speech quality of transmission systems Q13/XII
1996-2000 Objective measurement of speech quality under conditions of non-linear processing Q13/12
1996-2004 Objective measurement of speech quality under conditions of non-linear and time varying processing Q9/12

2005-2008 Perceptual-based objective methods for voice, audio and visual quality measurements in telecommunication services
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History in ITU-T / CCITT

• Before 1990
• classical measurements of transmission /
  terminal characteristics
• early spectral- / cepstral-based measures
• 1996 P.861 PSQM ? 1st psychoacoustic based
  measure for predicting listening Quality
• Only Core-Model (no gain-/time-alignment)
• 2001 P.862 PESQ ? Replaced P.861
• Complete method incl. time-/gain-alignement
• 2004 P.563 ? 1st single ended model for LQ
  assessments
• Still Open ? Listening Quality for Wideband
  speech
• ? Listening Quality at Acoustical Interfaces

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Current Focus Listening Quality

• Main progression within the last few years
• Acceptance of psycho-acoustic based measures
  modelling results of auditory tests on subjective
  scales
• but
• Restriction to Listening Quality
• Only applicable on narrow-band voice telephony
  services
• Serving only electrical interfaces

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Work program starting 2005

• Ongoing activities of former question 9/12
• Wide-band speech (listening) quality
• Listening quality at acoustical interfaces
• and extensions to
• Audio- and noise-signals over telephone channels
• Audio-visual aspects
• Talking quality and relations to conversational
  quality
• but
• Restriction to perceptual based models only

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Work program starting 2005
Principle concept Objective measures model
specific subjective (auditory) test scenarios and
predict their results on a similar
scale. Consequence A subjective test scenario
has to be defined and established before the
corresponding objective model can be
developed. Experience The better the auditory
tests are defined and the stronger their
requirements are the more accurate the predicted
results will be.
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Wide-band speech scenarios

• Current status
• Proposal from BT and KPN to extend
  P.862(COM-12/D180, Feb. 2001)
• Several studies from NTT in 2004 analyze pros
  and cons of this proposal
• Awaiting advanced solutions for initial meeting
  in 2005
• Open points
• Corresponding auditory tests (pure wide-band,
  mixed with narrow band, which ratio?, which
  terminal(s)?)
• What about half-wideband (e.g. 200-5000Hz)?
• Wider influence on terminal characteristics. Is
  wide-band speech analysis useful without
  acoustical interfaces?

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Acoustical interfaces

• Current status
• Work item P.AAM currently stopped because
  disagreement on test scenarios to be served by
  the approach.
• Awaiting precise definitions about the scope and
  the expected applications of the model
• Open points
• Corresponding auditory tests for noise at
  listener side
• Handling of handsfree in auditory tests (pure
  handsfree or mixed with handset)
• Handling of different terminals (mix of monotic
  and diotic, influence of loss of acoustical
  coupling to real environment?)

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Talking Quality

• Current status
• Proposal from KPN for an perceptual based model
  (COM-12/10, Nov. 2000 COM-12/D089, Jan. 2003)
• Open points
• The subjective test procedure is neither defined
  nor established
• Current proposal does not consider real terminals
• Extension to the acoustical interface is needed

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Audio- and noise-signals

• Current status
• New action points
• First steps Music over telephone channels
• Applicability of ITU-R Recommendations?
• Modifications on speech quality approaches
  sufficient?
• First steps Noise handling / Noise reduction
• Starting point P.835 describes the subjective
  test
• Impact on clean speech could be handled by P.862
  / P.AAM
• Improvement / degradation of noisy speech could
  be handled by framing of listening quality models
• Quality of residual noise is an open point, an
  Annoyance model is needed

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Audio-visual quality assessment

• Current status
• New action point
• Audio-visual quality aspects in telecommunication
  scenarios (lower bitrate, small image sizes) are
  interesting for SG12
• Initiating contribution (COM-12/D180, Feb. 2001)
• Cooperation with SG9 and VQEG
• Joint Rapporteurs Group on Multi-Media Quality
  Assessment is already established
• Drafting of testplans

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Structuring of work

• To be discussed in ITU-T
• Is a Recommendation / Appendix for wideband
  speech assessment at electrical interfaces a
  migration step to a more complete solution only?
  
• How should the Recommendation(s) for measurements
  at the acoustical interfaces be structured?
• Inclusion of wide-band?
• Separation of handsfree (separate model or only
  switch)?
• Handling of binaural signals compared to
  classical handset?
• Two / four separate models corresponding to the
  combinations of interfaces ?
• electrical electrical
• acoustical electrical
• electrical acoustical
• acoustical acoustical

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Thank you for your attention!