# Assessment of the Quality of Video Sequences Performed by Viewers at Home and in the Laboratory
## 3 Results and Discussion
### Objective Quality Assessment of Video Encoded Using H.264, H.265, and VP9 Standards  
The results of the objective video quality assessment are presented using three metrics: PSNR, SSIM, and VMAF (see Figures 14-16). It can be noted that, just like in the case of subjective quality assessment, the objective video quality results are directly proportional to the used coding bit rate, which is valid for all presented metrics and video codecs. The most significant changes in quality are observed for low bit rates, while for higher bit rates, the quality changes seem to be very small or imperceptible. The results are also consistent with those presented in the literature, where the H.265 and VP9 codecs are more efficient than the H.264 codec. A very important  
Figure 14: Relationship of the objective assessment of video quality encoded in the H.264 standard vs. bit rate for the resolutions 640 \(\times\) 360, 858 \(\times\) 480, 1280 \(\times\) 720, and 1920 \(\times\) 1080. Figure 13: Difference between the results of the subjective evaluation of the VP9-encoded video (AMOS), conducted in the laboratory and at home, as a function of bit rate for different resolutions. All tests and calculated correlations were conducted for the selected video resolutions and a limited number of coding bit rates (i.e., 18 coding bit rates for each video sample of a specific resolution). To validate these results and check how much of the whole population of different cases is well described by this research, a determination coefficient (R2) was calculated for each previously determined correlation. Taking into account each codec, it can be stated that the determination coefficients fluctuated as follows:  
1. For the H.264 codec: from 0.9 to 0.996;
2. For the H.265 codec: from 0.931 to 0.998;
3. For the VP9 codec: from 0.905 to 0.998. This means that the obtained results of the correlations well describe 90 to 99 percent of the whole population. This leads to the conclusion that the obtained correlations are very strong and that they are representative for a population that can be much wider than the video set that was used during the research. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & & \multicolumn{8}{c}{**QoS vs. QoE Correlations**} \\ \cline{3-10}  & & \multicolumn{4}{c}{**Lab**} & \multicolumn{4}{c}{**Home**} \\ \cline{3-10}  & & **360p** & **480p** & **720p** & **1080p** & **360p** & **480p** & **720p** & **1080p** \\ \hline PSNR & 360p & 0.998 & 0.997 & 0.997 & 0.998 & 0.991 & 0.995 & 0.996 & 0.997 \\  & 480p & 0.999 & 0.991 & 0.990 & 0.993 & 0.993 & 0.994 & 0.995 & 0.996 \\  & 720p & 0.995 & 0.981 & 0.980 & 0.983 & 0.991 & 0.989 & 0.991 & 0.989 \\  & 1080p & 0.991 & 0.975 & 0.973 & 0.977 & 0.989 & 0.986 & 0.987 & 0.985 \\ \hline SSIM & 360p & 0.993 & 0.997 & 0.999 & 0.998 & 0.986 & 0.991 & 0.992 & 0.993 \\  & 480p & 0.995 & 0.998 & 0.999 & 0.999 & 0.988 & 0.993 & 0.994 & 0.995 \\  & 720p & 0.995 & 0.998 & 0.999 & 0.999 & 0.988 & 0.993 & 0.994 & 0.995 \\  & 1080p & 0.994 & 0.996 & 0.998 & 0.998 & 0.987 & 0.991 & 0.993 & 0.993 \\ \hline VMAF & 360p & 0.998 & 0.995 & 0.992 & 0.995 & 0.989 & 0.994 & 0.995 & 0.998 \\  & 480p & 0.997 & 0.995 & 0.992 & 0.995 & 0.988 & 0.993 & 0.995 & 0.997 \\  & 720p & 0.995 & 0.996 & 0.992 & 0.995 & 0.985 & 0.991 & 0.993 & 0.996 \\  & 1080p & 0.976 & 0.989 & 0.991 & 0.989 & 0.965 & 0.976 & 0.977 & 0.981 \\ \hline \end{tabular}
\end{table} 
Table 11: Correlations between QoS and QoE values (in the lab and home) for H.265 encoded video.