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Computationally Efficient Light Field Image Compression Using a Multiview HEVC Framework
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. (Realistic3D)
COMSATS University Islamabad, Pakistan.
COMSATS University Islamabad, Pakistan.
COMSATS University Islamabad, Pakistan.
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2019 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 143002-143014, article id 8853251Article in journal (Refereed) Published
Abstract [en]

The acquisition of the spatial and angular information of a scene using light eld (LF) technologies supplement a wide range of post-processing applications, such as scene reconstruction, refocusing, virtual view synthesis, and so forth. The additional angular information possessed by LF data increases the size of the overall data captured while offering the same spatial resolution. The main contributor to the size of captured data (i.e., angular information) contains a high correlation that is exploited by state-of-the-art video encoders by treating the LF as a pseudo video sequence (PVS). The interpretation of LF as a single PVS restricts the encoding scheme to only utilize a single-dimensional angular correlation present in the LF data. In this paper, we present an LF compression framework that efciently exploits the spatial and angular correlation using a multiview extension of high-efciency video coding (MV-HEVC). The input LF views are converted into multiple PVSs and are organized hierarchically. The rate-allocation scheme takes into account the assigned organization of frames and distributes quality/bits among them accordingly. Subsequently, the reference picture selection scheme prioritizes the reference frames based on the assigned quality. The proposed compression scheme is evaluated by following the common test conditions set by JPEG Pleno. The proposed scheme performs 0.75 dB better compared to state-of-the-art compression schemes and 2.5 dB better compared to the x265-based JPEG Pleno anchor scheme. Moreover, an optimized motionsearch scheme is proposed in the framework that reduces the computational complexity (in terms of the sum of absolute difference [SAD] computations) of motion estimation by up to 87% with a negligible loss in visual quality (approximately 0.05 dB).

Place, publisher, year, edition, pages
2019. Vol. 7, p. 143002-143014, article id 8853251
Keywords [en]
Compression, light field, MV-HEVC, plenoptic
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-37489DOI: 10.1109/ACCESS.2019.2944765ISI: 000497156000230Scopus ID: 2-s2.0-85077687836OAI: oai:DiVA.org:miun-37489DiVA, id: diva2:1358279
Available from: 2019-10-07 Created: 2019-10-07 Last updated: 2021-03-19Bibliographically approved
In thesis
1. High Efficiency Light Field Image Compression: Hierarchical Bit Allocation and Shearlet-based View Interpolation
Open this publication in new window or tab >>High Efficiency Light Field Image Compression: Hierarchical Bit Allocation and Shearlet-based View Interpolation
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Over the years, the pursuit of capturing the precise visual information of a scenehas resulted in various enhancements in digital camera technology, such as highdynamic range, extended depth of field, and high resolution. However, traditionaldigital cameras only capture the spatial information of the scene and cannot pro-vide an immersive presentation of it. Light field (LF) capturing is a new-generationimaging technology that records the spatial and angular information of the scene. Inrecent years, LF imaging has become increasingly popular among the industry andresearch community mainly for two reasons: (1) the advancements made in optical and computational technology have facilitated the process of capturing and processing LF information and (2) LF data have the potential to offer various post-processing applications, such as refocusing at different depth planes, synthetic aperture, 3Dscene reconstruction, and novel view generation. Generally, LF-capturing devicesacquire large amounts of data, which poses a challenge for storage and transmissionresources. Off-the-shelf image and video compression schemes, built on assump-tions drawn from natural images and video, tend to exploit spatial and temporalcorrelations. However, 4D LF data inherit different properties, and hence there is aneed to advance the current compression methods to efficiently address the correla-tion present in LF data.

In this thesis, compression of LF data captured using a plenoptic camera andmulti-camera system (MCS) is considered. Perspective views of a scene capturedfrom different positions are interpreted as a frame of multiple pseudo-video se-quences and given as an input to a multi-view extension of high-efficiency videocoding (MV-HEVC). A 2D prediction and hierarchical coding scheme is proposedin MV-HEVC to improve the compression efficiency of LF data. To further increasethe compression efficiency of views captured using an MCS, an LF reconstructionscheme based on shearlet transform is introduced in LF compression. A sparse set of views is coded using MV-HEVC and later used to predict the remaining views by applying shearlet transform. The prediction error is also coded to further increase the compression efficiency. Publicly available LF datasets are used to benchmark the proposed compression schemes. The anchor scheme specified in the JPEG Plenocommon test conditions is used to evaluate the performance of the proposed scheme. Objective evaluations show that the proposed scheme outperforms state-of-the-art schemes in the compression of LF data captured using a plenoptic camera and an MCS. Moreover, the introduction of shearlet transform in LF compression further improves the compression efficiency at low bitrates, at which the human vision sys-tem is sensitive to the perceived quality.The work presented in this thesis has been published in four peer-reviewed con-ference proceedings and two scientific journals. The proposed compression solu-tions outlined in this thesis significantly improve the rate-distortion efficiency forLF content, which reduces the transmission and storage resources. The MV-HEVC-based LF coding scheme is made publicly available, which can help researchers totest novel compression tools and it can serve as an anchor scheme for future researchstudies. The shearlet-transform-based LF compression scheme presents a compre-hensive framework for testing LF reconstruction methods in the context of LF com-pression.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2021. p. 46
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 341
National Category
Information Systems
Identifiers
urn:nbn:se:miun:diva-41704 (URN)978-91-88947-81-9 (ISBN)
Public defence
2021-04-22, C312, Holmgatan 10, Sundsvall, 09:00 (English)
Opponent
Supervisors
Available from: 2021-03-23 Created: 2021-03-19 Last updated: 2021-03-23Bibliographically approved

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