# Perceptual Quality of Audio-Visual Content with Common Video and Audio Degradations
## 2 Previous Work on Perceptual Quality Assessment  
As commented before, perceptual experiments help researchers comprehend how different artifacts affect the perceived quality of media content such as audio, video and audio-visual. The studies listed in this section are presented in Table 1. For visual content, the quality impact of packet-loss, bitrate compression and frame-freezing have been studied throughout a range of perceptual experiments. For example, the effects of frame-freezing and packet-loss over full-length movie clips were reported in a perceptual experiment conducted by [PERSON] et al. [26]. The experiment collected the responses from 56 non-expert viewers for 80 DVD clips in a home viewing environment. The study concluded that participants were more tolerant towards frame-freezing errors, possibly due to the length of the stimuli and the viewing conditions. In another study, [PERSON] et al. [27] included a range of impairments such as video compression, frame-freezing, wireless-channel packet-loss and rate adaptation over a mobile-platform setup. A video-only dataset (with a range of content material) was presented to 30 participants during the experiment. The results concluded that viewers were more tolerant to few longer stalling events than several shorter ones. However, these results varied according to the type of content being displayed. A recent study explored the impact of video quality using several video encoding parameters like bitrate, frame-rate and video resolution in multiparty telemeetings. Perceptual results showed that participants' detection of some visual distortions was influenced by how active they were during the calls. The study indicates that, for this particular scenario, ensuring enough resources to active participants and prioritizing the audio quality are key to the overall audio-visual quality [28]. \begin{table}
\begin{tabular}{l l l l l l} \hline
**Component** & **Scope** & **DiDieterous** & **Material** & **Reference** \\ \hline \multirow{6}{*}{Video} & Video quality assessment in home environment & frame-freeing & full-length movie clips & [24] \\ \cline{2-6}  & & packet-loss & & \\ \cline{2-6}  & Video quality assessment over a mobile pattern & Video compression & & \\ \cline{2-6}  & Video quality assessment over a mobile pattern & frame-freeing & HD video clips & [27] \\  & & wireless-channel packet-loss & & \\ \cline{2-6}  & & Bitrate adaptation & & \\ \cline{2-6}  & Video compression & & \\ \cline{2-6}  & Video quality assessment in multiparty kilometres & Frame-rate & & \\ \cline{2-6}  & Video resolution & & \\ \hline \multirow{6}{*}{Audio} & Speech intelligibility & Background noise & & \\ \cline{2-6}  & & Synstatic complexity & & \\ \cline{2-6}  & & Background noise & & \\ \cline{2-6}  & & Computing speaker & & \\ \cline{2-6}  & Speech quality assessment for NaP & Clipping & & \\ \cline{2-6}  & Echo & & & \\ \cline{2-6}  & & Chepered speech & & \\ \cline{2-6}  & \multicolumn{2}{l}{Music and video-streaming consumption} & Stelling factor & & \\ \cline{2-6}  & \multicolumn{2}{l}{Video compression} & & \\ \hline \multirow{6}{*}{Audio-visual quality assessment in a controlled environment} & Audio compression & HD video clips & [29] \\ \cline{2-6}  & Audio-visual quality assessment over different devices. & Video compression & & \\ \cline{2-6}  & Audio-visual quality assessment in a controlled environment & Audio compression & HD video clips & [19] \\ \cline{2-6}  & Video scaling & & \\ \cline{2-6}  & Audio-visual quality assessment over live music streaming & Video compression & & \\ \cline{2-6}  & \multicolumn{2}{l}{Nonocular errors} & & \\ \cline{2-6}  & \multicolumn{2}{l}{Image adaptation} & & \\ \cline{2-6}  & \multicolumn{2}{l}{Network errors} & & \\ \cline{2-6}  & Audio-visual quality assessment in a real-time scenario & Frame-rate & HD video clips & [29] \\ \cline{2-6}  & \multicolumn{2}{l}{Quantitation parameters} & & \\ \cline{2-6}  & Audio and video packet-loss & & \\ \hline \end{tabular}
\end{table}