LARGE-SCALE EXPERIMENT
A. ANOVA Tests
In that, μ and σ are the mean and standard deviation of all scores obtained from tracks of the same (hr, lr ) pair. The z-score was then used for ANOVA tests.
Accuracy of prediction
EVALUATION
B. Comparison to PESQ
1) Fixed Rate
Prediction error: SILK versus PESQ for fixed-rate tracks
For the fixed-rate comparison, we included tracks in both the preliminary and large-scale experiment
B. Network Design
A solid understanding of multimedia content is fundamental to better engineering of the network applications.
C. Multimedia Content
Taking Skype as the first research target, this study investigates the influence of different bit rates and rate changes of audio streams produced by the SILK codec.
3) Subroutine of Variable-Rate Formula
EVALUATION
A. Prediction Accuracy
The scatter plot in Fig shows the fitted score (as the χ-axis) and the user score (as the Υ-axis) for each rate pair and time interval test set
Modeling the QoE of Rate Changes in Skype/SILK VoIP Calls
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BACKGROUND
PRELIMINARY EXPERIMENT PROPOSED MODEL
Fixed-Rate Model Variable-Rate Model

user-centric approach rate adaptation mechanisms Weber–Fechner’s Law

Early rate-control mechanisms attempted to improve QoS for the data delivered. An increasing trend in this area is to measure network services using the quality of experience (QoE).
Nonparallel MOS–ΔT relationships indicate interaction
LARGE-SCALE EXPERIMENT
B. Model Specifics
1) Coefficients of Fixed-Rate Formula
2) Subroutine of Variable-Rate Formula

QoS–QoE Synergyrate adaptation mechanisms QoE-Based Adaptation Psychophysics
PRELIMINARY EXPERIMENT
The purpose of the preliminary experiment in this study was to examine, through user tests, whether changes in sending rates decreases the user experience, and at what scale the MOS is influenced by the magnitude and frequency of changes. MOS–bit-rate plot of fixed rate tests
PROPOSED MODEL
B. Variable-Rate Model
where the effect of change frequency is distributed to the logarithm term, and the effect of hr and lr is distributed to the two subroutines, SCALE() and SHIFUTURE WORK
A. QoE Measurement
In this study, we quantify the relationship between user experience and bit rate changes for Skype/SILK calls.
Goodness of fit of training data
EVALUATION
A. Prediction Accuracy
Fig shows the accuracy of the proposed model. In this figure, the predictions of both data sets closely track the measured data, regardless of the difference in audio content and speaker
EVALUATION
B. Comparison to PESQ
2) Variable Rate
Prediction error: SILK versus PESQ for fixed-rate tracks
A similar comparison was also conducted for variable tracks, and the accuracy of prediction of both the proposed model and PESQ are indicated in Fig
PROPOSED MODEL
A. Fixed-Rate Model
where br is the bit rate, and α, β, and γ are coefficients to be determined by SILK characteristics. The bit-rate shift (α) is caused by the limit of human perception. According to the formula, the term br - α, being inside the operator, can only be positive.
Thank You !

LARGE-SCALE EXPERIMENT EVALUATION CONCLUSION AND FUTURE WORK
Background

THE EFFECTIVE end-to-end transport of delay-sensitive voice data has long been a subject of study in multimedia networking.