Terms Of Mean Opinion Score Research Articles

A generic quantitative relationship between quality of experience and quality of service

Quality of experience ties together user perception, experience, and expectations to application and network performance, typically expressed by quality of service parameters. Quantitative relationships between QoE and QoS are required in order to be able to build effective QoE control mechanisms onto measurable QoS parameters. Against this background, this article proposes a generic formula in which QoE and QoS parameters are connected through an exponential relationship, called IQX hypothesis. The formula relates changes of QoE with respect to QoS to the current level of QoE, is simple to match, and its limit behaviors are straightforward to interpret. It validates the IQX hypothesis for streaming services, where QoE in terms of Mean Opinion Scores is expressed as functions of loss and reordering ratio, the latter of which is caused by jitter. For web surfing as the second application area, matchings provided by the IQX hypothesis are shown to outperform previously published logarithmic functions. We conclude that the IQX hypothesis is a strong candidate to be taken into account when deriving relationships between QoE and QoS parameters.

VoIP over DVB-RCS satellite systems: Trial results and the impact of adaptive speech coding using cross-layer design

VoIP is one of the most popular applications on the Internet. The DVB-S2 (digital video broadcasting-satellite version 2) and DVB-RCS (digital video broadcasting-return channel satellite) standards provide the potential for reliable and efficient voice and data transfer over satellite networks. This is important, as satellites can play a role in broadband service provision by addressing the cases of limited terrestrial access such as in rural or underserved areas. The first part of this paper presents the results of our VoIP trials with different commercial DVB-S/RCS satellite offers and popular internet telephony and videoconferencing applications (Skype, MSN, etc.). These results reveal that packet delay and jitter are strongly affected by the satellite network component as well as the type of speech codec used. Accordingly, research presented in the second part of this paper is focused on dynamic speech coding rate control adapted to the conditions of the underlying network, in which the satellite domain presents the most challenging portion of the end-to-end path. For this purpose, a novel cross-layer mechanism is proposed to facilitate and increase the accuracy of the speech coding rate adaptation mechanism. Cross-layer design is a relatively new idea aiming to exploit information exchange among layers of the protocol stack. Our simulation analyses show that the proposed cross-layer mechanism can help us in optimally adjusting the speech coding rate to maintain the user-perceived quality in terms of MOS (mean opinion score) in the face of time-varying available satellite channel capacity.

멀티미디어 응용을 위한 주관적 동영상 품질평가 방법의 비교분석

본 논문에서는 멀티미디어 응용을 위한 동영상의 주관적 품질평가방법으로 널리 사용되는 DSCQS(Double Stimulus Continuous Quality Scale method) 및 ACR(Absolute Category Rating)방법을 비교분석하였다. 두 가지 방법을 비교 실험한 결과 MOS (Mean Opinion Score) 값의 경우 DSCQS와 ACR의 평가치가 매우 높은 상관도를 보이는 것을 확인할 수 있었다. 또한 DMOS (Difference Mean Opinion Score)값의 경우에는 DSCQS와 ACR 방법이 MOS 값의 경우보다 약간 낮은 정도의 상관도를 보였다. 이 같은 결과는 ACR 방식이 DSCQS에 필적하는 성능을 제공하며 많은 수의 영상을 평가 할 수 있는 효율적인 주관적 품질평가 방법임을 보여주고 있다. In this paper, we compared two subjective assessment methods DSCQS(Double Stimulus Continuous Quality Scale method) and ACR(Absolute Category Rating). These methods are widely used in order to evaluate video quality for multimedia application. We performed subjective quality tests using DSCQS and ACR methods. The subjective scores obtained by the DSCQS and ACR methods show that these methods are highly correlated in terms of MOS(Mean Opinion Score) and have slightly lower correlation in terms of DMOS(Difference Mean Opinion Score). The results indicate that ACR method is an effective subjective quality assessment method, which shows compatible performance with DSCQS method and can evaluate a larger number of video sequences.

Robust processing techniques for voice conversion

Differences in speaker characteristics, recording conditions, and signal processing algorithms affect output quality in voice conversion systems. This study focuses on formulating robust techniques for a codebook mapping based voice conversion algorithm. Three different methods are used to improve voice conversion performance: confidence measures, pre-emphasis, and spectral equalization. Analysis is performed for each method and the implementation details are discussed. The first method employs confidence measures in the training stage to eliminate problematic pairs of source and target speech units that might result from possible misalignments, speaking style differences or pronunciation variations. Four confidence measures are developed based on the spectral distance, fundamental frequency ( f 0) distance, energy distance, and duration distance between the source and target speech units. The second method focuses on the importance of pre-emphasis in line-spectral frequency (LSF) based vocal tract modeling and transformation. The last method, spectral equalization, is aimed at reducing the differences in the source and target long-term spectra when the source and target recording conditions are significantly different. The voice conversion algorithm that employs the proposed techniques is compared with the baseline voice conversion algorithm with objective tests as well as three subjective listening tests. First, similarity to the target voice is evaluated in a subjective listening test and it is shown that the proposed algorithm improves similarity to the target voice by 23.0%. An ABX test is performed and the proposed algorithm is preferred over the baseline algorithm by 76.4%. In the third test, the two algorithms are compared in terms of the subjective quality of the voice conversion output. The proposed algorithm improves the subjective output quality by 46.8% in terms of mean opinion score (MOS).

잡음 패턴의 지능적 추정을 통한 음질 개선 알고리즘

In this paper, we propose an algorithm that improves a tone quality of a noisy audio signal in order to enhance a performance of perceptual filter using intelligent estimation of noise pattern from a band degraded by additive noise. The proposed method doesn`t use the estimated noise which is obtained from silent range. Instead new estimated noise according to the power of signal and effect of noise variation is considered for each frame. So the noisy audio signal is enhanced by the method which controls a estimation of noise Pattern effectively in a noise corruption band. To show the performance of the proposed algorithm, various input signals which had a different signal-to-noise ratio(SNR) such as were used to test the proposed algorithm. we carry out SSNR and NMR of objective measurement and MOS test of subjective measurement. An approximate improvement of in SSNR and in NMR is achieved with the input signals, respectively. And we confirm the enhancement of tone quality in terms of mean opinion score(MOS) test which is result of subjective measurement.

Psychoacoustically motivated objective speech quality evaluation procedures, PSQM, and improvements

PSQM (Perceptual Speech Quality Measure), measuring speech quality objectively, has been standardized by ITU-T as recommendation P.861. PSQM characterizes the perception of the (degraded) output speech signal of the system in comparison to the (ideal) input speech. A perceptual model is used that maps input and output signals onto psychophysical representations using psychophysical equivalents of frequency (Bark) and intensity (compressed Sone). The quality of the device under test is determined with a simple cognitive mapping from the differences in the psychophysical representation to the perceived speech quality in terms of Mean Opinion Scores (MOS). Within an ITU benchmark testing a limited set of unknown codec distortions the PSQM showed high correlations (around 0.97) between subjectively perceived and objectively measured speech quality. When applying PSQM to a wide variety of real world distortions two major limitations show up: First, dynamic time warping effects, as they will be found, e.g., in Internet telephony, cause a degradation in correlation. Second, the perceptual model that is used within the PSQM method is too simple to account for a wide variety of distortions. This presentation discusses extensions to the PSQM method that allows application to real world distortions.

Comparisons of category scales employed for opinion rating

Comparisons have been made between three category scales that have been used for the laboratory assessment of impaired television pictures. Two of the scales, comprising 5 and 6 grades, respectively, are concerned with assessment of the quality of the picture; the third is a 6-grade scale concerned with assessment of the amount of impairment in the picture. In one group of tests, observers assessed television pictures impaired by an undistorted echo of delay 2 μs, and, in another, photographic prints affected by varied amounts of blurring. Various combinations of the scales were used in each group. The 5-grade and 6-grade quality scales gave closely similar results in terms of mean opinion scores, but these results differed from those obtained with the 6-grade impairment scale, which were less critical. Observers preferred the 5-grade quality scale to both of the 6-grade scales.