Browsing by Author "Ding, Lijing"

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Measurement of the effects of temporal clipping on speech quality
(IEEE, 2006) Ding, Lijing; Radwan, Ayman; Samy El-Hennawey, Mohamed; A Goubran, Rafik
This paper investigates the effects of temporal clipping on perceived speech quality. Temporal clipping usually results from voice activity detection (VAD), or line echo canceller's nonlinear processor, and the clipped speech portions are replaced by comfort noise. A nonintrusive algorithm is proposed to predict speech quality based on the clipping statistics. Mean opinion score (MOS) is used as a metric for speech quality and is measured by perceptual evaluation of speech quality (PESQ). The impacts of speech frame size and noise spectrum on the algorithm are also investigated. The results show that the proposed algorithm can efficiently predict the speech quality. The correlation coefficient between the prediction and the measurement is about 0.975, and the root mean square error for the prediction is 0.20 MOS. The algorithm can be used as an integral part of a general speech quality assessment scheme in voice over Internet protocol (VoIP)
Method and apparatus for non-intrusive single-ended voice quality assessment in VoIP
(RPX Clearinghouse LLC, 2012) El-Hennawey, Mohamed; Goubran, Rafik; M. Radwan, Ayman; Ding, Lijing
An apparatus (1240), method, and computer program to assess VoIP speech quality (130) using access to degraded signals is provided. Different types of impairment (110) have different effect, on speech quality. Preferred embodiments address up to four different types of impairment that affect VoIP signal quality: packet loss (230), speech clipping in time (850), noise (1400) and echo. An overall assessment algorithm factors in degradation due to various impairment factors to generate an overall speech quality assessment score or value.
Non-intrusive single-ended speech quality assessment in VoIP
(Elsevier, 2007) Ding, Lijing; Lin, Zhong; Radwan, Ayman; Samy El-Hennawey, Mohamed; A Goubran, Rafik
Evaluating speech quality in voice over Internet protocol (VoIP) in a non-intrusive manner is challenging, because it relies on a degraded speech signal only. In this paper, a parametric, non-intrusive VoIP speech quality assessment algorithm is proposed, which adopts a three-step strategy, impairment detection, individual effect modeling and an overall model. Mainly based on voice payload analysis, the algorithm also combines Internet protocol analysis approach and the ITU-T E-model. It quantifies the individual contributions to speech quality from several major VoIP impairments, including packet loss, temporal clipping and noise. Also, an overall assessment model is developed. The performance is evaluated through intensive simulations, and the results show that the algorithm is effective and accurate. For the overall model, the correlation between prediction and measurement is 0.90; the root mean square error (RMSE) is 0.27 mean opinion score (MOS). The algorithm aims to be implemented at the receive-end media gateway or IP terminal, for identifying the root causes of speech quality degradation as well as quality assessment in VoIP.
Nonintrusive Measurement of Echo-Path Parameters in VoIP Environments
(IEEE, 2006) Ding, Lijing; Samy El-Hennawey, Mohamed; A Goubran, Rafik
This paper proposes two echo-path delay measurement methods suitable for voice-over-Internet-protocol environments, where the echo suffers from excessive delay and nonlinear distortion. The proposed methods aim at greatly reducing the computational requirements while maintaining good measurement accuracy. The delay measurement is based on the cross correlation; the computation reduction is achieved by using either downsampled speeches or sparse speeches for the two methods, respectively. The echo-path loss is also measured by using the obtained delay information. The performance under codec distortion, packet loss, noise, and double talk conditions is examined through simulations and real field measurements. The results show that the proposed methods are effective and accurate
Performance Study of Objective Voice Quality Measures in VoIP
(IEEE, 2007) Ding, Lijing; Radwan, Ayman; Samy El-Hennawey, Mohamed; A Goubran, Rafik
With the advent of voice over internet protocol (VoIP) service, assessing its voice quality is an area of intense research interest. Due to time-consuming and expensive natures of widely accepted subjective mean opinion score (MOS) test, objective methods are often used as an alternative. This paper presents applicability and accuracy analysis of several leading objective methods in quality testing. Particularly, the paper focuses on packet loss, which is one of major impairments in VoIP. A speech database covering typical packet loss conditions is designed. The subjective MOS test is conducted and the results are evaluated with objective MOS. The database is also used to verify a non-intrusive VoIP speech quality assessor the authors developed (El-Hennawey et al., 2006). The results show that perceptual evaluation of speech quality (PESQ) based algorithms are generally acceptable for quantifying the effects of packet loss. In addition, we also find that their performance is limited for codec G.711 without packet loss concealment (PLC).