3. Extension of Auditory and Visual Quality Estimation Functions for Videotelephony

ITU-T Recommendation G.1070 defines an opinion model for the prediction of the audiovisual conversational quality for videotelephony applications. The model outputs three quality related values: the audio, the video and the audiovisual quality as perceived by the user. In addition, it takes into account the one-way delay and integrates it to provide a multimedia score that reflects the quality of the overall experience. In this chapter, improvements to the video and audio quality estimation functions are proposed. On the video side, the coefficients of the video quality functions are estimated for several video codecs based on the procedure defined in the Annex A of ITU-T Rec. G.1070. Then, the quality impact of two application-related parameters influencing the values of the video coefficients, namely the encoding resolution and the display size, is integrated in the model, hence reducing the coefficients dependency on input parameters. On the audio side, the quality function is extended to wideband applications by adapting the WB-E-model to comply with the assumptions of the G.1070 model. Finally, the performance of both functions is evaluated on four separate datasets including different video and audio codecs and experimental contexts, i.e. passive listening and viewing and interactive.