Detailed comparative analysis of PESQ and VISQOL behaviour in the context of playout delay adjustments introduced by VOIP jitter buffer algorithms

This paper undertakes a detailed comparative analysis of both PESQ and VISQOL model behaviour, when tested against speech samples modified through playout delay adjustments. The adjustments are typical (in extent and magnitude) to those introduced by VoIP jitter buffer algorithms. Furthermore, the analysis examines the impact of adjustment location as well as speaker factors on MOS scores predicted by both models and seeks to determine if both models are able to correctly predict the impact on quality perceived by the end user from earlier subjective tests. The earlier results showed speaker voice preference and potentially wideband experience dominating subjective tests more than playout delay adjustment duration or location. By design, PESQ and VISQOL do not qualify speaker voice difference reducing their correlation with the subjective tests. In addition, it was found that PESQ scores are impacted by playout delay adjustments and thus the impact of playout delay adjustments on a quality perceived by the end user is not well modelled. On the other hand, VISQOL model is better in predicting an impact of playout delay adjustments on a quality perceived by the user but there are still some discrepancies in the predicted scores. The reasons for those discrepancies are particularly analysed and discussed.