{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,15]],"date-time":"2026-01-15T03:46:42Z","timestamp":1768448802741,"version":"3.49.0"},"reference-count":60,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2021,8,5]],"date-time":"2021-08-05T00:00:00Z","timestamp":1628121600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100010418","name":"IITP","doi-asserted-by":"publisher","award":["2020-0-00347"],"award-info":[{"award-number":["2020-0-00347"]}],"id":[{"id":"10.13039\/501100010418","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Imaging"],"abstract":"<jats:p>Currently available 360\u00b0 cameras normally capture several images covering a scene in all directions around a shooting point. The captured images are spherical in nature and are mapped to a two-dimensional plane using various projection methods. Many projection formats have been proposed for 360\u00b0 videos. However, standards for a quality assessment of 360\u00b0 images are limited. In this paper, various projection formats are compared to explore the problem of distortion caused by a mapping operation, which has been a considerable challenge in recent approaches. The performances of various projection formats, including equi-rectangular, equal-area, cylindrical, cube-map, and their modified versions, are evaluated based on the conversion causing the least amount of distortion when the format is changed. The evaluation is conducted using sample images selected based on several attributes that determine the perceptual image quality. The evaluation results based on the objective quality metrics have proved that the hybrid equi-angular cube-map format is the most appropriate solution as a common format in 360\u00b0 image services for where format conversions are frequently demanded. This study presents findings ranking these formats that are useful for identifying the best image format for a future standard.<\/jats:p>","DOI":"10.3390\/jimaging7080137","type":"journal-article","created":{"date-parts":[[2021,8,5]],"date-time":"2021-08-05T21:43:53Z","timestamp":1628199833000},"page":"137","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Evaluation of 360\u00b0 Image Projection Formats; Comparing Format Conversion Distortion Using Objective Quality Metrics"],"prefix":"10.3390","volume":"7","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9888-6791","authenticated-orcid":false,"given":"Ikram","family":"Hussain","sequence":"first","affiliation":[{"name":"Department of Electrical Engineering, Sejong University, 209 Neungdong-ro, Seoul 05006, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9877-8982","authenticated-orcid":false,"given":"Oh-Jin","family":"Kwon","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, Sejong University, 209 Neungdong-ro, Seoul 05006, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Hosseini, M., and Swaminathan, V. (2016, January 11\u201313). Adaptive 360 VR video streaming: Divide and conquer. Proceedings of the 2016 IEEE International Symposium on Multimedia (ISM), San Jose, CA, USA.","DOI":"10.1109\/ISM.2016.0028"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"TaghaviNasrabadi, A., Mahzari, A., Beshay, J.D., and Prakash, R. (2017, January 18\u201322). Adaptive 360-degree video streaming using layered video coding. Proceedings of the 2017 IEEE Virtual Reality (VR), Los Angeles, CA, USA.","DOI":"10.1109\/VR.2017.7892319"},{"key":"ref_3","unstructured":"Timmerer, C., Graf, M., and Mueller, C. (2017, January 22\u201327). Adaptive streaming of vr\/360-degree immersive media services with high qoe. Proceedings of the 2017 NAB Broadcast Engineering and IT Conference (BEITC), Las Vegas, NV, USA."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Ochi, D., Kunita, Y., Kameda, A., Kojima, A., and Iwaki, S. (2015, January 23\u201327). Live streaming system for omnidirectional video. Proceedings of the 2015 IEEE Virtual Reality (VR), Arles, France.","DOI":"10.1109\/VR.2015.7223439"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"427","DOI":"10.1111\/cgf.13431","article-title":"Maps and globes in virtual reality","volume":"37","author":"Yang","year":"2018","journal-title":"Comput. Graph. Forum"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Yang, S., Zhao, J., Jiang, T., Rahim, J.W.T., Zhang, B., Xu, Z., and Fei, Z. (2017, January 10\u201313). An objective assessment method based on multi-level factors for panoramic videos. Proceedings of the 2017 IEEE Visual Communications and Image Processing (VCIP), Saint Petersburg, FL, USA.","DOI":"10.1109\/VCIP.2017.8305133"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Li, L., Li, Z., Budagavi, M., and Li, H. (2017, January 17\u201320). Projection based advanced motion model for cubic mapping for 360-degree video. Proceedings of the 2017 IEEE International Conference on Image Processing (ICIP), Beijing, China.","DOI":"10.1109\/ICIP.2017.8296517"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1109\/LCOMM.2017.2764021","article-title":"Scalable video coding based on user\u2019s view for real-time virtual reality applications","volume":"22","author":"He","year":"2017","journal-title":"IEEE Commun. Lett."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Duanmu, F., Mao, Y., Liu, S., Srinivasan, S., and Wang, Y. (2018, January 23\u201327). A subjective study of viewer navigation behaviors when watching 360-degree videos on computers. Proceedings of the 2018 IEEE International Conference on Multimedia and Expo (ICME), San Diego, CA, USA.","DOI":"10.1109\/ICME.2018.8486537"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.dsp.2018.09.011","article-title":"Utility-oriented resource allocation for 360-degree video transmission over heterogeneous networks","volume":"84","author":"Huang","year":"2019","journal-title":"Digit. Signal Process."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1649","DOI":"10.1109\/TCSVT.2012.2221191","article-title":"Overview of the high efficiency video coding (HEVC) standard","volume":"22","author":"Sullivan","year":"2012","journal-title":"IEEE Trans. Circuits Syst. Video Technol."},{"key":"ref_12","unstructured":"(2020, November 25). Joint Video Exploration Team (JVET). Available online: http:\/\/wftp3.itu.int\/av-arch\/jvet-site\/jvet-info.htm."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Zelnik-Manor, L., Peters, G., and Perona, P. (2005, January 17\u201321). Squaring the circle in panoramas. Proceedings of the Tenth IEEE International Conference on Computer Vision (ICCV\u201905), Beijing, China.","DOI":"10.1109\/ICCV.2005.231"},{"key":"ref_14","first-page":"259","article-title":"Comparison of spherical cube map projections used in planet-sized terrain rendering","volume":"31","author":"Lambers","year":"2016","journal-title":"Facta Univ. Ser. Math. Inform."},{"key":"ref_15","unstructured":"(2020, November 25). Omnidirectional Media Format. Available online: https:\/\/mpeg.chiariglione.org\/standards\/mpeg-i\/omnidirectional-media-format."},{"key":"ref_16","unstructured":"Snyder, J.P. (1997). Flattening the Earth: Two Thousand Years of Map Projections, University of Chicago Press."},{"key":"ref_17","unstructured":"Ye, Y. (2017). JVET-F1003-v1: Algorithm Descriptions of Projection Format Conversion and Video Quality Metrics in 360Lib, ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11."},{"key":"ref_18","unstructured":"Ye, Y., Alshina, E., and Boyce, J. (2017). JVET-H1004: Algorithm Descriptions of Projection Format Conversion and Video Quality Metrics in 360Lib (Version 5), ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11."},{"key":"ref_19","unstructured":"Zhou, M. (2017). AHG8: A Study on Quality Impact of Line Re-Sampling Rate in EAP, ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11."},{"key":"ref_20","unstructured":"(2020, November 25). Transform360. Available online: https:\/\/github.com\/facebook\/transform360."},{"key":"ref_21","first-page":"21","article-title":"Environment mapping and other applications of world projections","volume":"6","author":"Greene","year":"1986","journal-title":"IEEE Comput. Graph. Appl."},{"key":"ref_22","unstructured":"Ye, Y., Alshina, E., and Boyce, J. (2017). JVET-G1003: Algorithm Description of Projection Format Conversion and Video Quality Metrics in 360lib Version 4, ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11."},{"key":"ref_23","unstructured":"Coban, M., Van der Auwera, G., and Karczewicz, M. (2017). AHG8: Adjusted Cubemap Projection for 360-Degree Video, ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11."},{"key":"ref_24","unstructured":"Brown, C. (2020, November 25). Bringing Pixels Front and Center in VR Video. Available online: https:\/\/blog.google\/products\/google-ar-vr\/bringing-pixels-front-and-center-vr-video\/."},{"key":"ref_25","unstructured":"Zhou, M. (2017). AHG8: A Study on Equi-Angular Cubemap Projection (EAC), ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Duanmu, F., He, Y., Xiu, X., Hanhart, P., Ye, Y., and Wang, Y. (2018, January 27\u201330). Hybrid cubemap projection format for 360-degree video coding. Proceedings of the 2018 Data Compression Conference, Snowbird, UT, USA.","DOI":"10.1109\/DCC.2018.00057"},{"key":"ref_27","unstructured":"Lee, Y., Lin, J., Chang, S., and Ju, C. (2018). CE13: Modified Cubemap Projection in JVET-J0019 (Test 5), ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11, JVET-K0131."},{"key":"ref_28","unstructured":"Van der Auwera, G., and Karczewicz, M. (2017). AHG8: Equatorial Cylindrical Projection for 360-Degree Video, ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11."},{"key":"ref_29","unstructured":"Kuzyakov, E., and Pio, D. (2020, November 25). Next-Generation Video Encoding Techniques for 360 Video and VR. Available online: https:\/\/engineering.fb.com\/2016\/01\/21\/virtual-reality\/next-generation-video-encoding-techniques-for-360-video-and-vr\/."},{"key":"ref_30","unstructured":"Alshina, E., Boyce, J., Abbas, A., and Ye, Y. (2017, January 13\u201321). JVET Common Test Conditions and Evaluation Procedures for 360 Degree Video. Proceedings of the JVET Document, JVET-G1030; Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO\/IEC JTC 1\/SC 29\/WG 11 7th Meeting, Torino, Italy."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1016\/j.sigpro.2018.01.004","article-title":"Recent advances in omnidirectional video coding for virtual reality: Projection and evaluation","volume":"146","author":"Chen","year":"2018","journal-title":"Signal Process."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Upenik, E., Rerabek, M., and Ebrahimi, T. (June, January 31). On the performance of objective metrics for omnidirectional visual content. Proceedings of the 2017 Ninth International Conference on Quality of Multimedia Experience (QoMEX), Erfurt, Germany.","DOI":"10.1109\/QoMEX.2017.7965660"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Xiu, X., He, Y., Ye, Y., and Vishwanath, B. (2017, January 10\u201313). An evaluation framework for 360-degree video compression. Proceedings of the 2017 IEEE Visual Communications and Image Processing (VCIP), Saint Petersburg, FL, USA.","DOI":"10.1109\/VCIP.2017.8305084"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"634","DOI":"10.1109\/TMM.2009.2017626","article-title":"The rhombic dodecahedron map: An efficient scheme for encoding panoramic video","volume":"11","author":"Fu","year":"2009","journal-title":"IEEE Trans. Multimed."},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Li, J., Wen, Z., Li, S., Zhao, Y., Guo, B., and Wen, J. (2016, January 25\u201328). Novel tile segmentation scheme for omnidirectional video. Proceedings of the 2016 IEEE International Conference on Image Processing (ICIP), Phoenix, AZ, USA.","DOI":"10.1109\/ICIP.2016.7532381"},{"key":"ref_36","unstructured":"Park, G.-H. (2009). Method and Apparatus for Encoding and Decoding an Icosahedron Panorama Image. (No. 7,483,588), U.S. Patent."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Yu, M., Lakshman, H., and Girod, B. (2015, January 26\u201330). Content adaptive representations of omnidirectional videos for cinematic virtual reality. Proceedings of the 3rd International Workshop on Immersive Media Experiences, Brisbane, Australia.","DOI":"10.1145\/2814347.2814348"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"195","DOI":"10.5573\/IEIESPC.2018.7.3.195","article-title":"An efficient frame packing method for icosahedral projection in 360 video coding","volume":"7","author":"Kim","year":"2018","journal-title":"IEIE Trans. Smart Process. Comput."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"2342","DOI":"10.1109\/TIP.2018.2885482","article-title":"Advanced spherical motion model and local padding for 360\u00b0 video compression","volume":"28","author":"Li","year":"2018","journal-title":"IEEE Trans. Image Process."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1767","DOI":"10.1109\/TCSVT.2018.2846042","article-title":"Spherical domain rate-distortion optimization for omnidirectional video coding","volume":"29","author":"Li","year":"2018","journal-title":"IEEE Trans. Circuits Syst. Video Technol."},{"key":"ref_41","unstructured":"Hanhart, P., Boyce, J., Choi, K., and Lin, J. (2018). JVET Common Test Conditions and Evaluation Procedures for 360 Video, ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11."},{"key":"ref_42","unstructured":"(2021, August 04). 360Lib. Available online: https:\/\/jvet.hhi.fraunhofer.de\/svn\/svn_360Lib\/tags\/360Lib-8.0."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"600","DOI":"10.1109\/TIP.2003.819861","article-title":"Image quality assessment: From error visibility to structural similarity","volume":"13","author":"Wang","year":"2004","journal-title":"IEEE Trans. Image"},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Sheikh, H.R., and Bovik, A.C. (2005, January 23\u201325). A visual information fidelity approach to video quality assessment. Proceedings of the First International Workshop on Video Processing and Quality Metrics for Consumer Electronics, Scottsdale, AZ, USA.","DOI":"10.1016\/B978-012119792-6\/50120-0"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1587\/transinf.2017MUP0011","article-title":"A study on quality metrics for 360 video communications","volume":"101","author":"Tran","year":"2018","journal-title":"IEICE Trans. Inf. Syst."},{"key":"ref_46","unstructured":"Sun, Y., Lu, A., and Yu, L. (2016, January 15\u201321). JVET-D0040, AHG8: WS-PSNR for 360 video objective quality evaluation. Proceedings of the Document Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO\/IEC JTC 1\/SC 29\/WG 11 4th Meeting, Chengdu, China."},{"key":"ref_47","first-page":"1408","article-title":"Weighted-to-spherically-uniform quality evaluation for omnidirectional video","volume":"24","author":"Sun","year":"2017","journal-title":"IEEE Signal Process. Lett."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Yu, M., Lakshman, H., and Girod, B. (October, January 29). A framework to evaluate omnidirectional video coding schemes. Proceedings of the 2015 IEEE International Symposium on Mixed and Augmented Reality, Fukuoka, Japan.","DOI":"10.1109\/ISMAR.2015.12"},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Zakharchenko, V., Choi, K.P., and Park, J.H. (2016, January 29\u201330). Quality metric for spherical panoramic video. Proceedings of the Optics and Photonics for Information Processing X, San Diego, CA, USA.","DOI":"10.1117\/12.2235885"},{"key":"ref_50","unstructured":"Asbun, E., He, Y., He, Y., and Ye, Y. (2016). AHG8: InterDigital Test Sequences for Virtual Reality Video Coding, ITU. Joint Video Exploration Team of ITU-T SG16 WP3 and ISO\/IEC JTC1\/SC29\/WG11."},{"key":"ref_51","unstructured":"(2020, November 25). Easypano the Virtual Tour Way. Available online: http:\/\/www.easypano.com\/panorama-software.html."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"289","DOI":"10.1007\/s11760-009-0117-4","article-title":"No-reference assessment of blur and noise impacts on image quality","volume":"4","author":"Cohen","year":"2010","journal-title":"Signal Image Video Process."},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Hasler, D., and Suesstrunk, S.E. (2003, January 21\u201324). Measuring colorfulness in natural images. Proceedings of the Human Vision and Electronic Imaging VIII, Santa Clara, CA, USA.","DOI":"10.1117\/12.477378"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"257","DOI":"10.1016\/j.image.2013.09.005","article-title":"Tone mapping based HDR compression: Does it affect visual experience?","volume":"29","author":"Narwaria","year":"2014","journal-title":"Signal Process. Image Commun."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"643","DOI":"10.1109\/TCE.2013.6626251","article-title":"No reference color image contrast and quality measures","volume":"59","author":"Panetta","year":"2013","journal-title":"IEEE Trans. Consum. Electron."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"391","DOI":"10.1007\/s11760-013-0442-5","article-title":"Survey of information theory in visual quality assessment","volume":"7","author":"Soundararajan","year":"2013","journal-title":"Signal Image Video Process."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"657","DOI":"10.1109\/TIP.2012.2221725","article-title":"Objective quality assessment of tone-mapped images","volume":"22","author":"Yeganeh","year":"2012","journal-title":"IEEE Trans. Image Process."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"743","DOI":"10.1109\/TCE.2010.5505996","article-title":"A new no-reference quality metric for JPEG2000 images","volume":"56","author":"Zhang","year":"2010","journal-title":"IEEE Trans. Consum. Electron."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"7371","DOI":"10.1109\/ACCESS.2017.2694038","article-title":"A method for fast multi-exposure image fusion","volume":"5","author":"Choi","year":"2017","journal-title":"IEEE Access"},{"key":"ref_60","doi-asserted-by":"crossref","unstructured":"Hussain, I., Kwon, O.-J., and Choi, S. (2021). Evaluating the coding performance of 360\u00b0 image projection formats using objective quality metrics. Symmetry, 13.","DOI":"10.3390\/sym13010080"}],"container-title":["Journal of Imaging"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2313-433X\/7\/8\/137\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:41:18Z","timestamp":1760164878000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2313-433X\/7\/8\/137"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,8,5]]},"references-count":60,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2021,8]]}},"alternative-id":["jimaging7080137"],"URL":"https:\/\/doi.org\/10.3390\/jimaging7080137","relation":{},"ISSN":["2313-433X"],"issn-type":[{"value":"2313-433X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,8,5]]}}}