# Analysis of Video Transmission Capabilities in a Simulated OFDM-Based Supplementary BPL-PLC System
## 4 Results  
Since the MPEG-4 is one of the most popular coding formats for content processing and distribution, regardless of whether talking about terrestrial or online services [39; 40; 41], we have decided to source the video material from Netflix [42]. This repository offers \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Description** \\ \hline Code rate & 3/4 \\ \(n_{ldpc}\) & 64,800 bits (normal frame) \\ \(k_{bch}\) & 48,408 bits \\ \(k_{ldpc}\) & 48,600 bits \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Basic parameters of the coding procedure. numerous files in varying formats, as well as different pixel (from standard definition up to high definition) and color (8-bit or 10-bit) resolutions. Each video file consists of five sequences, where the fourth and fifth resemble the same scene, as shown in Figure 9. However, sequence no. 5 was recorded in slow-motion (with a much higher framerate per second). The sequences were ordered as follows:  
1. Walking man--static background with a single man walking along the street;
2. Windmill--static angle with numerous fast moving (rotating) windmills;
3. Traffic--static angle with cars passing along the road, at various speeds. 4. Toddler fountain--playful child walking around a fountain, with lots of movement in the background;
5. Toddler montage--similar material with a playful child recorded in slow-motion (much higher framerate). These were available in a number of bitrates (qualities), from standard definition (SD) up to Full-HD (1920 \(\times\) 1080). After a careful examination, we have selected one video file, available in the 480 \(\times\) 270 resolution, 8-bit color variant. This resolution, being exactly one fourth of 1920 \(\times\) 1080 is easily scalable and popular among many portable devices and user terminals, including media players, consoles, etc. [43]. Next, the video transmission performance was tested in a quality evaluation study. According to the 3 rd Generation Partnership Project (3 GPP) [44], video services can be divided into two main categories, depending on delay and bit error rate, as described in Table 3.  
In our scenario delay may be neglected; therefore, in this particular study, we focused on BERs ranging from \(10^{-3}\) to \(10^{-6}\). During the experiment, the MPEG-4 video file with a resolution of 480 \(\times\) 270 pixels was fed into the simulator. The input (original) as well as \begin{table}
\begin{tabular}{c c c} \hline \hline
**Service** & **Acceptable Delay [ms]** & **Acceptable BER** \\ \hline Live streaming & & \\ (real-time video) & 150 & \(10^{-3}\) \\ Buffered streaming & & \\ (non-real-time video) & 300 & \(10^{-6}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Basic video transmission services with their technical requirements. Figure 9: Transmitted sequence of video content. output (processed) format remained unchanged. Overall, the test involved six different SNR levels, ranging from 24 to 29 dB, that is: 24, 24.4, 27, 28.3, 28.7 and 29 dB, as well as monitored BER before and after forward error correction (FEC). As observed, FEC had a significant impact on the final error rate only for SNR equal to 27.5 dB and above. The initial range of approx. \(10^{-4}\) and \(10^{-3}\) was reduced by tens or even hundreds of times. However, the efficiency of transmission should be evaluated in a subjective manner on the end-user side. The subjective part of this study was performed according to [45] on a 27-inch Full-HD (1920 \(\times\) 1080) screen. The group of viewers consisted of 10 individuals without visual impairments. All of them could adjust the stand and viewing angle of the display according to their own preferences. The processed video content was presented in a randomized way. The results of this experiment are shown in Figure 10.  
According to obtained results, the lowest SNR proved to be unacceptable (MOS score close to 1.0), whereas, in case of the highest value, the quality was ranked between 2 and 3, resembling a poor or fair quality (annoying or slightly annoying).