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- Title
Latitude-Adaptive Integer Bit Allocation for Quantization of Omnidirectional Images.
- Authors
Sima, Qian; Feng, Hui; Hu, Bo
- Abstract
Omnidirectional images have gained significant popularity and drawn great attention nowadays, which poses challenges to omnidirectional image processing in solving the bottleneck of storage and transmission. Projecting onto a two-dimensional image plane is generally used to compress an omnidirectional image. However, the most commonly used projection format, the equirectangular projection (ERP), results in a significant amount of redundant samples in the polar areas, thus incurring extra bitrate and geometric distortion. We derive the optimal latitude-adaptive bit allocation for each image tile. Subsequently, we propose a greedy algorithm for non-negative integer bit allocation (NNIBA) for non-uniform quantization under an omnidirectional image quality metric WMSE. In our experiment, we design quantization tables based on JPEG and compare our approach with other sampling-related methods. Our method achieves an average bit saving of 7.9% compared with JPEG while outperforming other sampling-related methods. Besides, we compare our non-uniform quantization approach with two proposed bit allocation methods, achieving an average improvement of 0.35 dB and 2.66 dB under WS-PSNR, respectively. The visual quality assessment also confirms the superiority of our method.
- Subjects
INTEGERS; GREEDY algorithms; IMAGE processing; JPEG (Image coding standard); IMAGE compression
- Publication
Applied Sciences (2076-3417), 2024, Vol 14, Issue 5, p1861
- ISSN
2076-3417
- Publication type
Article
- DOI
10.3390/app14051861