Opt Express. 2023 Mar 13;31(6):9146-9164. doi: 10.1364/OE.479281.
Compressing digital holograms have growing attention nowadays due to their huge amount of original data sizes. Although many progresses have been reported for full-complex holograms, the coding performance for phase-only holograms (POHs) has been quite limited so far. In this paper, we present a very efficient compression method for POHs. It extends the conventional video coding standard HEVC (High Efficiency Video Coding) in such a way that the standard can be able to compress not only the natural images but also the phase images effectively. First, we suggest a proper way to calculate differences, distances and clipped values for phase signals by considering the inherent periodicity of phases. Then, some of the HEVC encoding and decoding processes are modified accordingly. The experimental results show that the proposed extension significantly outperforms the original HEVC for POH video sequences; specifically, average BD-rate reductions of 63.3% and 65.5% are achieved in phase domain and numerical reconstruction domain, respectively. It is worth mentioning that the modified encoding & decoding processes are very minimal and also applicable to the VVC (Versatile Video Coding), which is a successor of the HEVC.
由于原始数据量巨大，数字全息图的压缩技术如今备受关注。尽管已经有很多针对全复振幅全息图的压缩方法被报道，但到目前为止，针对纯位相全息图（POH）的编码性能还相当有限。在本文中，我们提出了一种针对 POH 的高效压缩方法。该方法通过扩展传统的视频编码标准 HEVC（高效视频编码），使得该标准不仅能够有效地压缩自然图像，还能够有效地压缩相位图像。首先，我们通过考虑相位的固有周期性，提出了一种计算相位信号差值、距离和裁剪值的合适方法。然后，对相应的 HEVC 编码和解码过程进行了修改。实验结果表明，所提出的扩展方法在 POH 视频序列方面明显优于原始的 HEVC；特别是，在相位域和数值重建域中，平均 BD-rate 分别降低了 63.3%和 65.5%。值得一提的是，所修改的编码和解码过程非常简单，也适用于 HEVC 的后继者 VVC（多功能视频编码）。
