## 4 Experiment
### Threshold Estimation and Scenario-Based Experimental Results
#### 4.2.3 Scenario 2  
Under scenario 2, an investigator secured an original video and detected all edited and manipulated videos to be distributed in the suspect's mobile device. The comparison process under this scenario has the same steps as in Scenario 1. Nevertheless, when a query section is set in step 1, all parts considered to be crimes are included in the query section and are compared with a comparison video. If any of them is determined to be similar to the comparison video, the query video is identified as a manipulated video. Under scenario 2, two parts of the original video were set as a query section. Table 8 presents the original video secured by an investigator and two query videos determined based on the query section selected by the investigator. All video names also show the criteria for the videos, as listed in Table 4. In other words, if a video is original, its name has an 'O' (original) after the underscore (_); if manipulated, it has an 'E' (edit); and if unrelated to an original video, it has a 'D' (different). Table 9 shows the videos of a suspect's mobile device. As presented in Figure 9, these videos were compared with query videos using an optimized comparison search. The suspect's mobile device has five videos: two videos irrelevant to the query videos (DNM_D, Dark+Near+Middle_Different video; and BNH_D, Bright+Near+High_Different video), one original video of the query videos (BNM_O, Bright+Near+Middle_Original video), and two manipulated videos (BNM_E2; Bright+Near+Middle_Edit video1; and BNM_E2, Bright+Near+Middle_Edit video2). Because these five videos have different run times, the total number of frames extracted is also different. A comparison was carried out in order of the videos listed in Table 7. From the middle of the total frames of each video, a frame was compared with the query frame in accord with the pseudocode shown in Figure 3. Subsequently, a similar video was identified based on the BNM threshold in Table 5. If all results from the three algorithms for one frame are within the range of threshold for over 10 separate trials, the comparison process stops, and the video is identified as having been manipulated or identical. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Video Name** & **Running Time** & **File Size** & **Frame (Width \(\times\) Height)** & **Frame Speed** \\ \hline Original video (BNM\_O) & 9 min 14 s & 210 MB & 1920 \(\times\) 1088 & 29.97 frames/s \\ Query video\_1 & 1 min 46 s & 40.4 MB & 1920 \(\times\) 1088 & 29.97 frames/s \\ Query video\_2 & 2 min 5 s & 47.8 MB & 1920 \(\times\) 1088 & 29.97 frames/s \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Video secured by investigators and query videos (scenario 2). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Video Name** & **Running Time** & **File Size** & **Frame (Width \(\times\) Height)** & **Frame Speed** \\ \hline DNM\_D & 31 s & 11.9 MB & 1920 \(\times\) 1088 & 24.00 frames/s \\ BNM\_O & 9 min 14 s & 210 MB & 1920 \(\times\) 1088 & 29.97 frames/s \\ BNM\_E1 & 2 min 10 s & 49.8 MB & 1920 \(\times\) 1088 & 29.98 frames/s \\ BNH\_D & 9 min 14 s & 210 MB & 1920 \(\times\) 1088 & 29.97 frames/s \\ BNM\_E2 & 2 min 58 s & 68.0 MB & 1920 \(\times\) 1088 & 29.97 frames/s \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Videos in suspect’s smart phone (scenario 2). Figure 10a illustrates the result from the correlation similarity comparison between Query Video_1 and the videos in the suspect's mobile device under scenario 2. For two videos irrelevant to the Query video_1 (DNM_D and BNH_D), the optimization search began from the middle of the video in line with the pseudocode shown in Figure 3. As a result, no frame had a similarity of 0.47 or higher, which is the threshold of the correlation algorithm in the BNM environment. Therefore, once all frames were searched, the comparison process moved to the next video.