Therdpong Daengsi

A study of VoIP quality evaluation: User perception of voice quality from G.729, G.711 and G.722

This paper presents new evidence about user perception of VoIP quality that is inconsistent with the general understanding of three codecs know as G.729, G.711 and G.722. The focus of the study is aimed at VoIP quality evaluation by Thai users that use the Thai language which is tonal. This study was conducted by using conversation-opinion tests. The results, called MOS-CQS, were then analyzed carefully. After the study and analysis, it has been found that the perception of subjects, who were Thai native speakers, to G.729, G.711 and G.722 is not significantly different.

A study of perceptual VoIP quality evaluation with thai users and codec selection using voice quality - Bandwidth tradeoff analysis

Perceptual VoIP quality is an issue for VoIP applications/services because VoIP applications require real-time support. Not only network factors (e.g. packet loss, packet delay and jitter) but also codec selection that affects VoIP quality. Therefore, this study has been conducted, focusing on the perceptual VoIP quality and codec selection. This paper presents a study of the perception of native Thai subjects to the popular codecs, G.711, G.722, G.723.1 and G.729 using ACR listening opinion tests and conversation opinion tests. It has been found that native Thai users ranked VoIP quality from G.723.1 at 5.3 kbps as the worst, and no statistically significant difference from G.729 (8 kbps), G.711 (64 kbps) and G.722 (64 kbps). Then, the paper proposes voice quality - bandwidth tradeoff analysis approach for codec selection, based on perceptual VoIP quality and bandwidth consumption of voice-payload of codecs. It has been found from this approach that G.729 at 8 kbps is the best choice for VoIP codec selection for Thai users in Thailand, compared to the other codecs.

Comparison of VoIP-QoE from Skype, LINE, Tango and Viber over 3G networks in Thailand

This paper presents a study of VoIP - Quality of Experience (VoIP-QoE) of a well-known VoIP application and three modern ones, Skype, LINE, Tango and Viber, using Perceptual Evaluation of Speech Quality (PESQ) with English speech samples. From this study, it has been found that Skype and LINE tend to provide better VoIP quality than Tango and Viber, particularly when used over good stabile 3G networks. Although, with slight differences between Skype and LINE, it has been found that there is no significant difference between VoIP quality from Skype and LINE over four 3G networks(p-values = 0.291-0.840). Therefore, Skype and LINE are good options for free VoIP calls over most 3G networks in Bangkok, the capital city of Thailand. Nevertheless, it has been found that, referring to instability or low speed 3G networks, there is no significant difference among VoIP quality from Skype, LINE, Tango and Viber.

VoIP Quality of Experience: A proposed subjective MOS estimation model based-on Thai users

To aid authenticity, accuracy and reliability of subjective measurement of VoIP quality measurements, this paper proposes a model that has been created from the subjective MOS, instead of using existing objective measurement methods for VoIP quality measurement. The proposed model of VoIP quality measurement method is based-on Thai users. The data has been gathered from conversation-opinion tests with 400 Thai subjects, referring to packet loss and packet delay effects. This model is called the Thai subjective VoIP Quality Evaluation model (ThaiVQE). It has been evaluated by testing with a test set of subjective MOS, then the results have been compared with the E-model results. Based-on Thai subjects, the evaluation result shows that ThaiVQE can provide better accuracy and reliability than the E-model with improvement of over 20%.

QoE modeling: A simplified e-model enhancement using subjective MOS estimation model

This paper presents an enhanced objective method for VoIP quality evaluation. However, instead of improving the original E-model for G.729, the Simplified E-model has been enhanced using subjective MOS estimation model based-on Thai users, who used Thai-tonal language. The different results from Simplified E-model and subjective MOS estimation model have been used to create the equation called Bias equation, before adding to the Simplified E-model. Based-on the assumption that subjective voice quality evaluation for VoIP is the most authentic and reliable, the results from the enhanced simplified E-model for G.729 show better accuracy when compared to the original simplified E-model obviously.

VoIP quality measurement: Enhanced E-model using bias factor

To enhance the standard E-model, this paper proposes the new factor called Bias factor. Based-on the Thai environment, this factor can be computed by subtracting the subjective test results using conversation tests with native Thai users from the objective test results using an E-model tool. Both E-mode tests and conversation tests were conducted with the same VoIP system and test conditions. Then, the enhanced E-model using the Thai bias factor was evaluated with the test set from other groups of native Thai users. After evaluation, it has been found that the enhanced E-model can gain higher confidence. It delivers improved accuracy and reliability at approximately more than 20% when compared to the standard E-model.

A Comparative Study of VoIP Quality Measurement from G.711 and G.729 Using PESQ and Thai Speech

This paper presents the study of VoIP quality measurements from two popular codecs, G.711 and G.729, using the methods of Perceptual Evaluation of Speech Quality (PESQ) and Thai speech. In this study, from four lists of Thai speech, it has been found that G.711 provides better voice quality than G.729 in every condition of packet loss. Also, it has been found that Objective Listening Quality - Mean Opinion Score (MOS-LQO) of male speech is slightly higher than MOS-LQO of female speech, whereas MOS of child speech is the lowest. Then, MOS-LQO values from four Thai speech lists have been compared. Next, MOS-LQO from PESQ of male and female speech at the best condition have been compared with the Subjective Listening Quality Mean Opinion Score (MOS-LQS) from ACR listening tests in another laboratory. Lastly, referring to packet loss effects, objective MOS from PESQ have been compared with subjective MOS from conversation tests. It has been found that there is no significant difference among MOS-LQO from the four Thai speech lists, but it has been found that there is a significant difference between subjective MOS and objective MOS from each codec in each condition. Therefore, one can say that this is evidence that PESQ requires intensive study with Thai speech to modify PESQ for VoIP quality measurement in Thai environments confidently.

QoE of social network applications: A study of VoIP quality from Skype vs LINE over 3G and 4G

This paper briefly presents the study of VoIP quality from two popular social network applications over 3G and 4G in Bangkok, covering both stationary and mobility. It has been found that, based-on stationary tests, 4G does not provide better VoIP quality than 3G, although the downlink speed of 4G is faster that 3G by about 5-7 times. However, based on mobility tests called semi-dynamic tests, it can be seen that 4G provides better VoIP quality than 3G obviously.

VoIP quality of experience: A study of perceptual voice quality from G.729, G.711 and G.722 with Thai users referring to delay effects

This paper presents the conduction of conversational tests with three codecs; G.729, G.711 and G.722 referring to different one-way delays of <;10 ms, 400 ms and 800 ms, to help investigate delay effects to perceived voice quality by Thai users. The result from this study is found that with the best condition of delay (<;10 ms delay), the delay of 400 ms and 800 ms, the observed difference among three codecs was not statistically significant. Also, it has been found that Thai users did not detect a statistically significant difference of perceived voice quality from the same codec (G.729, G.711 or G.722) among three delay conditions of <;10 ms, 400 ms and 800 ms. This result is not consistent with the ITU-T standard because ITU-T recommended that the delay of 400 ms and above is unacceptable. The possible reasons could be language and cultural effects, which should be investigated in future.

VoIP quality of experience: Comparison of VoIP quality from social networking applications based on the best efforts

This paper presents comparison of VoIP quality from four VoIP applications, Kakao, Line, Skype and Viber. This study was conducted with Thai and English speech files over a broadband network in one province near Bangkok based on the best efforts before gathering the degraded speech files. Then, those files have been processed using Perceptual Evaluation Speech Quality Technique (PESQ) in order to obtain the VoIP quality values called MOS, which stands for mean opinion score. It has been found that there is no significant difference between three of the VoIP applications with a slight difference for Kakao over LINE over Skype. While Viber provides the lowest VoIP quality when compared to the other VoIP application obviously. The major contribution of this work is the first evidence that surprisingly reports VoIP quality with slight difference from Kakao over Skype and LINE, two major players in this arena.