# Intra Prediction-Based Hologram Phase Component Coding Using Modified Phase Unwrapping
## 4 Experiment and Result
### Coding Result  
In this section, we show the compression and decompression results as graphs expressed in compression ratio and PSNR. We performed experiments for all combinations of conditions shown in Table 2, and selected only the best results among them and plotted them as a graph. According to the unwrapping direction, the PSNR results according to the compression ratio from Figures 13-15 are plotted as a graph. Each figure shows the quality of the phase and the quality of the reconstruction result according to the compression rate. We used the original amplitude in order to accurately observe the compression effect of the phase. Each graph must include the dynamic range of \(4\pi\), \(8\pi\), \(16\pi\), and \(32\pi\), and the segment and the size of the CU were selected under conditions that showed the best results. Figures 13-15 are compression results for the unwrapped phase in the vertical, horizontal, and diagonal directions, respectively. Although there are some differences in quantitative results, it can be seen that the PSNR of the hologram and the reconstruction according to the compression ratio for each dynamic range are almost similar. As can be seen from the experimental results of Figure 4, the same trend (a phenomenon in which the error per bit increases and the compression efficiency decreases as the dynamic range increases) occurred in the results of Figures 13-15. The results for the case of \(32\pi\) show poor quality at most compression rates. However, unlike the results in Figure 4, there is no significant difference in compression efficiency according to each dynamic range. This can be interpreted as proving that unwrapping improves the compression efficiency as a whole. Figure 12: Result of the proposed phase unwrapping for limiting dynamic range to (**a**) \(4\pi\), (**b**) \(16\pi\) and (**c**) \(32\pi\) (In each subfigure, the first row is the vertical unwrapping, the second is the horizontal unwrapping, and the last is the diagonal unwrapping). In the results of Figure 13, it can be seen that compression efficiency is generally high under the condition that the segment size is \(64\times 64\) and the CU is \(32\times 32\). In the results of Figure 14, it can be seen that compression efficiency is generally high under the condition that the segment size is \(64\times 64\) and the CU size is \(64\times 64\). The compression result using the horizontal unwrapping was superior to the vertical unwrapping result in the condition of the larger CU size. In the case of the horizontal unwrapping, unlike other cases, the difference in reconstruction results is very small. In the result of Figure 15, it can be seen that compression efficiency is high in both the segment and the CU size are \(64\times 64\). Overall, the quality according to the compression ratio is almost the same as in other cases. Figure 16 plots the results of the best performance condition among each method. In addition, the result of phase compression using the HEVC Intra and the JPEG2000 without applying unwrapping was plotted together. Figure 16a shows the phase compression results, and Figure 15b shows the restoration results. Figure 16c,d are the conversion of the phase compression results into real and imaginary parts, respectively. In Figure 16a,b, compression efficiency is excellent when the vertical unwrapping method is used in most cases. The degree of improvement of the compression performance varies depending on the compression ratio, but the proposed method shows better characteristics as the compression ratio increases. The JPEG2000 has the lowest overall performance in high compression, but some good performance in low compression. At a compression ratio of 50:1 or higher, all proposed schemes showed better performance than the case of using the HEVC Intra and the JPEG2000. At a compression  
Figure 14: Compression results with the horizontal unwrapping: (a) phase, (b) reconstruction result. Figure 13: Compression results with the vertical unwrapping: (a) phase, (b) reconstruction result.