# Efficient Transcoding and Encryption for Live 360 CCTV System
## 4 Performance Evaluation
### Evaluation
The output 360 DrivingIncCity video was decoded by openHEVC decoder, as shown in Figure (c)c. Additionally, by using hevcbrowser software, as shown in Figure (b)b, we can confirm that VPS, PPS, and SPS NAL units were encrypted successfully, while Figure (a)a shows the output HEVC bitstream of Session 0 without encryption. In Table 6, the WS-PSNR values show unsatisfactory performance compared to other quality metrics when it comes to estimating the quality of images and videos as perceived by humans. We verified the comparison for both 1080p and 4K video. All WS-PSNR values of three channels were higher than 38 (dB), thus the quality of 360 videos at control center was reasonable to feel fully immersed in 360 videos. \begin{table}
\begin{tabular}{l c c} \hline \hline
**Test\_Sequence** & **x265** & **Proposed** \\ \hline Basketball\_1920 \(\times\) 1080\_500 frames\_25 fps\_qp22 & 53.45 s (9.36 fps) & 11.89 s (42.05 fps) \\ Cactus\_1920 \(\times\) 1080\_500 frames\_25 fps\_qp22 & 42.23 s (11.84 fps) & 11.92 s (41.94 fps) \\ Kimono\_1920 \(\times\) 1080\_240 frames\_25 fps\_qp22 & 24.79 s (9.68 fps) & 5.61 s (42.7 fps) \\ ParkScene\_1920 \(\times\) 1080\_240 frames\_25 fps\_qp22 & 21.76 s (11.03 fps) & 5.596 s (42.88 fps) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The 2D transcoding comparison. Figure 16: FFmpeg parsing: (**a**) unencrypted HEVC bitstream; (**b**) encrypted HEVC bitstream; (**c**) decoded output video. \begin{table}
\begin{tabular}{l c c} \hline \hline
**Test\_Sequence** & **x265** & **Proposed** \\ \hline DrivingIncCity\_1920 \(\times\) 1080\_300 frames & 20.78 s (14.48 fps) & 7.03 s (42.8 fps) \\ GasLamp\_1920 \(\times\) 1080\_300 frames & 22.12 s (13.56 fps) & 8.45 s (35.50 fps) \\ Harbor\_1920 \(\times\) 1080\_300 frames & 22.45 s (13.37 fps) & 8.58 s (34.9 fps) \\ KiteFlite\_1920 \(\times\) 1080\_300 frames & 22.37 s (13.41 fps) & 8.65 s (34.68 fps) \\ Trolley\_1920 \(\times\) 1080\_300 frames & 22.2 9s (13.45 fps) & 8.62 s (34.80 fps) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The 360 transcoding comparison. Figure 18 shows the video decryption and video client display. Here, the transcoder box will encrypt the entire video. With correct ARIA keys, as shown in Figure 18a, the video client can show the video after the decryption process. As shown in Figure 18b, video client cannot decrypt the VPS, SPS and PPS NAL units. Thus, it could not find correct video stream info while parsing the RTSP stream. To verify the encryption efficiency, the proposed system was used for experiments with AES and ARIA algorithms. Table 7 shows the comparison between AES and ARIA on the transcoder box with the master key sizes of 128 bits and 256 bits. The results prove that the AES algorithm could provide the encryption speed up to 33.4 times when compared to the ARIA algorithm. Additionally, transcoding and AES encryption process could reduce the total processing time by around 5-10% when compared to the ARIA algorithm, as shown in Table 8. The percentage of AES encryption time over the total processing time decreases when the CCTV video duration time increases. The ARIA encryption gives the result in the same way with higher percentage than AES encryption. Finally, from the security point of view, AES encryption was one of the best choices to secure data.