Extending AV1 Codec to Enhance Quality in Phase Compression of Digital Holograms in Object and Hologram Planes Abstract—Holography is a 3D capturing and displaying system. Many formats have been suggested to store holographic images with the highest quality and minimum file size. Here, we suggest combining two AV1 codecs to make a secondary error image and use it in a linear regression block to compensate for the main AV1 compression error. Since the phase part is the most challenging part of holograms, the proposed method addresses the compression problem in phase. The obtained results reveal that the proposed method can outperform the state-of-the-art codecs in terms of PSNR and SSIM criteria. Besides, comparing BD-PSNR and BD-Rate results with usual AV1, confirms the proposed method has an average about 5.04dB, which is -22.1% better Object plane performance, and 4.57dB, which is -20.66% better in Holo plane performance, in terms of BDPSNR and BD-Rate, respectively. Keywords—Compression; digital holography; object plane; holo plane; phase compression I. INTRODUCTION Holography is a technique for capturing three- dimensional (3D) images and videos. Holography is first proposed to enhance the quality of electron microscopes that were expanding at that time. In the 1960s, optical holography was advanced considerably by the development of laser [1]. In the early 1990s, decent quality digital holograms were recorded, processed, and stored using a space light modulator (SLM), CCD camera, mathematical algorithms, and fast computers. Nowadays, digital holography is applied to a wide variety of purposes such as electron microscopes [2], interferometry [3, 4, 5], surface sensing [6], data storage, holographic projectors, virtual reality, optical tweezers [7], optical information security [7, 8], and 3D movies [9]. Holograms are computationally intensive, being more evident in video or live scenes. Thus, research about hologram codecs and compression algorithms is currently highly demanded [10]. With the growth of 3D display media on the Internet, 3D imaging technologies are expected to be one of the most exciting imaging areas soon. One of the main hurdles in this new industry is to devise hologram codecs that can use the available bandwidth and transfer 3D images optimally. The existing 3D technologies based on the light field have limitations [11, 12]. In contrast, holography, considered an infinite light field, nominates as an alternative technology to the existing techniques [13]. However, there are numerous challenges to developing all aspects of the 3D holographic industry, including 3D display technology, recording equipment and cameras, noise removal from hologram images [14] and hologram broadcasting. Given the existing challenges, this study proposes a holographic compression based on AOMedia Video 1 (AV1) image compression. It significantly reduces the required bandwidth for holographic image broadcast without lowering the quality of holograms. Due to the high storage and bandwidth required for holographic images (about 10 Gbps), the proposed 3D compression method is highly desirable. It resolves one of the most significant limitations to the future of 3D imaging technology and helps broaden the 3D media field significantly. There are three traditional standards for displaying and recording holographic images [15, 16, 17]: João Manuel R. S. Tavares Departamento de Engenharia Mecânica, Faculdade de Engenharia, Universidade do Porto, Porto, Portugal, tavares@fe.up.pt Azam Bastanfard Islamic Azad University, Karaj Branch Karaj, Iran, azambastanfard1396@gmail.com Abdorreza Alavigharahbagh Faculdade de Engenharia, Universidade do Porto, Porto, Portugal, abalavi.gh@ieee.com Vahid Hajihashemi Faculdade de Engenharia, Universidade do Porto, Porto, Portugal, Hajihashemi.vahid@ieee.com Hamid Esmaeili Najafabadi University of Calgary, 2500 University Dr NW, Calgary, AB T2N 1N4, Canada, hamid.esmaeili@gmail.com