# Eye Tracking and Human Influence Factors' Impact on Quality of Experience of Mobile Gaming
## 3 Experimental Setup
### Gaze Settings  
Eye tracking on mobile devices can be achieved through various methods: using the mobile phone's camera with a software toolkit, positioning an external camera at an optimal angle to track gaze movements, or employing a dedicated hardware-based commercial solution mounted on the head with multiple cameras to record the user's fixations based on calibrations and the user's view. Given that this study focuses on evaluating user's experience in mobile gaming, it was important to make sure that the user interaction with a mobile device while playing a normal game should be preserved. Thus, the restrictions on user movement, head position, or even device orientation should not affect gaze tracking. Thus, we utilized the Pupil Core with a world-view camera and a monochrome camera setup to capture gaze fixations. Following the mapping of the world view and gaze camera within the calibrated region using the gaze estimation function discussed in Section 2.1, the fixations plugin was employed to detect fixations. The plugin was configured with the following settings:  
* Maximum Dispersion (degrees): 1.50
* Minimum Duration (milliseconds): 80
* Maximum Duration (milliseconds): 220 \begin{table}
\begin{tabular}{c c c c} \hline
**Name** & **Length, seconds** & \(fps\) & **Resolution** \\ \hline \multirow{2}{*}{Animal Crossing} & 9 & 60 & \(1920\times 1080,1280\times 720\) \\  & 9 & 30 & \(1280\times 720\) \\ \hline \multirow{2}{*}{Counter-Strike 2} & 9, 8 (720p) & 60 & \(1920\times 1080,1280\times 720\) \\  & 9 & 30 & \(1280\times 720\) \\ \hline \multirow{2}{*}{Call of Duty} & 9 & 60 & \(1920\times 1080,1280\times 720\) \\  & 9 & 30 & \(1280\times 720\) \\ \hline \multirow{2}{*}{Code Vein} & 9 & 60 & \(1920\times 1080,1280\times 720\) \\  & 9 & 30 & \(1920\times 1080\) \\ \hline \multirow{2}{*}{Fortnite} & 9 & 60 & \(1920\times 1080,1280\times 720\) \\  & 9 & 30 & \(1280\times 720\) \\ \hline \multirow{2}{*}{Minecraft} & 9, 8 (720p) & 60 & \(1920\times 1080,1280\times 720\) \\  & 9 & 30 & \(1280\times 720\) \\ \hline \multirow{2}{*}{PUBG} & 9 & 60 & \(1920\times 1080,1280\times 720\) \\  & 9 & 30 & \(1280\times 720\) \\ \hline \multirow{2}{*}{Rocket League} & 9 & 60 & \(1920\times 1080,1280\times 720\) \\  & 9 & 30 & \(1280\times 720\) \\ \hline \end{tabular}
\end{table} 
Table 1: Reference videos’ specifications. Figure 3: Frames of video stimuli. (**a**) Animal Crossing; (**b**) Counter-Strike 2; (**c**) Call of Duty; (**d**) Code Vein; (**e**) Fortnite; (**f**) Minecraft; (**g**) PUBG; (**h**) Rocket League. The minimum and maximum durations are confined to our requirements to ensure that fixations are neither missed nor duplicated, as users can quickly shift their gaze multiple times per second. The calibration of the mobile screen was performed using the built-in calibration function in Pupil Capture. Since subjects have varying head and face sizes, we ensured during calibration that the device was worn properly to maintain a confidence value close to 1 before commencing the subjective assessment. Pupil Player was utilized to view the world view and eye recordings and to export the data, as shown in Figure 2b. The exported data from each assessment consisted of CSV files containing information such as gaze and pupil positions, fixations, etc. It is important to note that two independent sets of data were obtained from the experiment: the exported files and recordings from individual sessions via Pupil Player, and the mobile application data, which included user information and quality ratings from the Google Firebase database. The gaze confidence values are continuous. To calculate the mean gaze confidence for a specific time when the user viewed a stimulus and provided ratings, we needed to map the gaze data with timestamps stored in the mobile application database during the rating of each stimulus. Let us assume that the gaze confidence of the \(j\)-th user at any time \(t\) is represented by \(GC^{j}(t)\).