113 research outputs found
Quality of media traffic over Lossy internet protocol networks: Measurement and improvement.
Voice over Internet Protocol (VoIP) is an active area of research in the world of
communication. The high revenue made by the telecommunication companies is a
motivation to develop solutions that transmit voice over other media rather than
the traditional, circuit switching network.
However, while IP networks can carry data traffic very well due to their besteffort
nature, they are not designed to carry real-time applications such as voice.
As such several degradations can happen to the speech signal before it reaches its
destination. Therefore, it is important for legal, commercial, and technical reasons
to measure the quality of VoIP applications accurately and non-intrusively.
Several methods were proposed to measure the speech quality: some of these
methods are subjective, others are intrusive-based while others are non-intrusive.
One of the non-intrusive methods for measuring the speech quality is the E-model
standardised by the International Telecommunication Union-Telecommunication Standardisation
Sector (ITU-T).
Although the E-model is a non-intrusive method for measuring the speech quality,
but it depends on the time-consuming, expensive and hard to conduct subjective
tests to calibrate its parameters, consequently it is applicable to a limited number
of conditions and speech coders. Also, it is less accurate than the intrusive methods
such as Perceptual Evaluation of Speech Quality (PESQ) because it does not consider
the contents of the received signal.
In this thesis an approach to extend the E-model based on PESQ is proposed.
Using this method the E-model can be extended to new network conditions and
applied to new speech coders without the need for the subjective tests. The modified
E-model calibrated using PESQ is compared with the E-model calibrated using
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subjective tests to prove its effectiveness.
During the above extension the relation between quality estimation using the
E-model and PESQ is investigated and a correction formula is proposed to correct
the deviation in speech quality estimation.
Another extension to the E-model to improve its accuracy in comparison with
the PESQ looks into the content of the degraded signal and classifies packet loss
into either Voiced or Unvoiced based on the received surrounding packets. The accuracy
of the proposed method is evaluated by comparing the estimation of the new
method that takes packet class into consideration with the measurement provided
by PESQ as a more accurate, intrusive method for measuring the speech quality.
The above two extensions for quality estimation of the E-model are combined
to offer a method for estimating the quality of VoIP applications accurately, nonintrusively
without the need for the time-consuming, expensive, and hard to conduct
subjective tests.
Finally, the applicability of the E-model or the modified E-model in measuring
the quality of services in Service Oriented Computing (SOC) is illustrated
A Study of the relationship of Sheffield & IGT methods for determining paper smoothness and their ability to predict gravure printability
A variety of methods have been devised for the measurement of the smoothness of paper. These are reviewed and summarized in this work. Of the available methods, two of the most widely used have been selected for study. The air-leak method exemplified by the Sheffield instrument, and the nip-spreading method of the IGT printability tester are specifically presented and performed. The data obtained in empirical experiments are statistically analyzed and plotted, so as to determine if there is a functional relationship between the responses of these two methods. A linear relationship between the two is shown to be an appropriate model. This paper also indicates the predictability of gravure printing quality on the basis of paper smoothness/roughness. The percentage of missing cells of the gravure prints are shown to be related to both forms of smoothness/roughness measurement. 78% of the gravure cell skipping data variation as printed by the IGT printability tester is attributable to smoothness/roughness measurement. The remaining amount of variation is associated with error or untested factors. Compressibility and oil absorbency of paper should be further studied and incorporated into similar studies. It is expected that the addition of these variables would improve laboratory prediction of gravure printability as defined by cell skipping
Validation study of the autonomy and deference subscales of the Edwards personal preference schedule
Speech quality prediction for voice over Internet protocol networks
Merged with duplicate record 10026.1/878 on 03.01.2017 by CS (TIS). Merged with duplicate record 10026.1/1657 on 15.03.2017 by CS (TIS)This is a digitised version of a thesis that was deposited in the University Library. If you are the author please contact PEARL Admin ([email protected]) to discuss options.IP networks are on a steep slope of innovation that will make them the long-term carrier
of all types of traffic, including voice. However, such networks are not designed to support
real-time voice communication because their variable characteristics (e.g. due to delay, delay
variation and packet loss) lead to a deterioration in voice quality. A major challenge in such networks
is how to measure or predict voice quality accurately and efficiently for QoS monitoring
and/or control purposes to ensure that technical and commercial requirements are met.
Voice quality can be measured using either subjective or objective methods. Subjective
measurement (e.g. MOS) is the benchmark for objective methods, but it is slow, time consuming
and expensive. Objective measurement can be intrusive or non-intrusive. Intrusive methods
(e.g. ITU PESQ) are more accurate, but normally are unsuitable for monitoring live traffic
because of the need for a reference data and to utilise the network. This makes non-intrusive
methods(e.g. ITU E-model) more attractive for monitoring voice quality from IP network impairments.
However, current non-intrusive methods rely on subjective tests to derive model
parameters and as a result are limited and do not meet new and emerging applications.
The main goal of the project is to develop novel and efficient models for non-intrusive
speech quality prediction to overcome the disadvantages of current subjective-based methods
and to demonstrate their usefulness in new and emerging VoIP applications. The main contributions
of the thesis are fourfold:
(1) a detailed understanding of the relationships between voice quality, IP network impairments
(e.g. packet loss, jitter and delay) and relevant parameters associated with speech (e.g.
codec type, gender and language) is provided. An understanding of the perceptual effects of
these key parameters on voice quality is important as it provides a basis for the development
of non-intrusive voice quality prediction models. A fundamental investigation of the impact of
the parameters on perceived voice quality was carried out using the latest ITU algorithm for
perceptual evaluation of speech quality, PESQ, and by exploiting the ITU E-model to obtain an
objective measure of voice quality.
(2) a new methodology to predict voice quality non-intrusively was developed. The method
exploits the intrusive algorithm, PESQ, and a combined PESQ/E-model structure to provide a
perceptually accurate prediction of both listening and conversational voice quality non-intrusively.
This avoids time-consuming subjective tests and so removes one of the major obstacles in the
development of models for voice quality prediction. The method is generic and as such has
wide applicability in multimedia applications. Efficient regression-based models and robust
artificial neural network-based learning models were developed for predicting voice quality
non-intrusively for VoIP applications.
(3) three applications of the new models were investigated: voice quality monitoring/prediction
for real Internet VoIP traces, perceived quality driven playout buffer optimization and
perceived quality driven QoS control. The neural network and regression models were both
used to predict voice quality for real Internet VoIP traces based on international links. A new
adaptive playout buffer and a perceptual optimization playout buffer algorithms are presented.
A QoS control scheme that combines the strengths of rate-adaptive and priority marking control
schemes to provide a superior QoS control in terms of measured perceived voice quality is
also provided.
(4) a new methodology for Internet-based subjective speech quality measurement which
allows rapid assessment of voice quality for VoIP applications is proposed and assessed using
both objective and traditional MOS test methods
The measurement of personality including a description and evaluation of certain tests of personality and character /
Thesis (M.A.)--Boston University, 1930. This item was digitized by the Internet Archive
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