# A Framework for Symmetric-Quality S3D Video Streaming Services
## 4 Results
### Test Results and Discussions  
We have identified that, on average, the _PSNR_ of the right-view video should not differ from that of the left-view video by more than 1.9 dB to prevent subjective quality degradation [20]. With this in mind, it is necessary to analyze the experimental results. Figure 12 shows the RD (rate-distortion) curve for each sequence. The RD curve visually represents the relationship between compression efficiency and compression quality in data compression. Here, rate refers to the data transmission speed, expressed in the number of bits transferred per second, and distortion indicates the quality degradation caused by compression. In this experiment, _PSNR_ is used as the indicator of distortion. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sequences** &
\begin{tabular}{c} **Spatial** \\ **Resolution** \\ \end{tabular} & **Frame Rate** & **SI** & **Encoded Frames** \\ \hline Nutjob & & & & \\ Part 1–Part 4 & & & 50, & \\ Sweet Rollercoaster & 3840 \(\times\) 2160 & 24 fps & 100, & 65 \\ Part 1–Part 4 & & & 200 & \\ Secret of the Universe & & & \\ Part 1–Part 4 & & & \\ \hline Quantization & & Left view: 32 & \\ parameters & Right view: base layer = 30, enhancement layer = 30, 32, 34, 36 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Test sequence. Figure 11: Sequence snapshots used in the experiment. Figure 12 shows the bitrate and _PSNR_ values obtained using the proposed method, HEVC, and SHVC at QP levels of 30, 32, 34, and 36. Figure 12: RD curve. In Figure 12, the _PSNR_ values of the left-view video for the NJ sequence's Part 1 to Part 4 are 42.99 dB, 43.84 dB, 40.87 dB, and 42.15 dB, respectively. Therefore, for the right-view video to maintain subjective quality without degradation, its _PSNR_ must reach at least 41.09 dB, 41.94 dB, 38.97 dB, and 40.25 dB for Part 1 to Part 4, respectively. These target _PSNR_ values are indicated by red lines in Figure 12.  
As shown in Figure 12, the RD curve, the proposed algorithm reaches the target _PSNR_ at QP 30 for all parts except the NJ sequence's Part 3, where it reaches the target _PSNR_ at QP 32. However, with conventional HEVC and Cross-View SHVC, QP 34 is required to reach the target _PSNR_. This indicates that the proposed method can achieve the target _PSNR_ with a lower bitrate compared with the existing methods. Thus, the proposed framework demonstrates superior performance in terms of compression efficiency and video quality, as it achieves the target _PSNR_ for the right-view video with a lower bitrate while avoiding subjective quality degradation. The performance of all experimental videos was evaluated using BDBR (Bjontegaard Delta Bit Rate) and BDSNR (Bjontegaard Delta Peak Signal-to-Noise Ratio) to assess the symmetric quality performance. To briefly explain the metrics, BDBR indicates the reduction in bitrate at the same quality level and plays an important role in evaluating compression efficiency. On the other hand, BDSNR measures the quality gain (in terms of _PSNR_) at the same bitrate and is used to compare video quality after compression. Table 2 presents the overall results comparing the proposed method against encoding the right-view video using HEVC and Cross-View SHVC. It shows how much bitrate reduction was achieved and the quality gains provided by the proposed framework. The proposed method demonstrates a significant performance improvement compared with HEVC and Cross-View SHVC. First, according to the BDBR evaluation results, the proposed method achieved an average bitrate reduction of 57.78% compared with HEVC and a 45.10% reduction compared with Cross-View SHVC. This means that it can reduce bandwidth usage by more than half while maintaining the same quality. Such bitrate reduction can play a crucial role in environments with limited bandwidth, such as real-time 3D streaming, low-bandwidth networks, or mobile devices. The BDSNR evaluation results also show that the proposed method provides higher video quality at the same bitrate.