VCIP C

147 papers

YearTitle / Authors
20202020 IEEE International Conference on Visual Communications and Image Processing, VCIP 2020, Macau, China, December 1-4, 2020
20203D-CNN Autoencoder for Plenoptic Image Compression.
Tingting Zhong, Xin Jin, Kedeng Tong
20204D-DCT Hardware Architecture for JPEG Pleno Light Field Coding.
Matheus Jahnke, Jones Goebel, Daniel Palomino, Guilherme Corrêa, Luciano Agostini, Marcelo Schiavon Porto, Bruno Zatt
2020A Dense-Gated U-Net for Brain Lesion Segmentation.
Zhongyi Ji, Xiao Han, Tong Lin, Wenmin Wang
2020A Discrete Cosine Model of Light Field Sampling for Improving Rendering Quality of Views.
Ying Wei, Changjian Zhu, You Yang, Yan Liu
2020A Hybrid Model for Natural Face De-Identiation with Adjustable Privacy.
Yunqian Wen, Bo Liu, Rong Xie, Yunhui Zhu, Jingyi Cao, Li Song
2020A Marked Point Process Model For Visual Perceptual Groups Extraction.
Amal Mbarki, Mohamed Naouai
2020A Mixed Appearance-based and Coding Distortion-based CNN Fusion Approach for In-loop Filtering in Video Coding.
Jian Yue, Yanbo Gao, Shuai Li, Menghu Jia
2020A Multi-Model Fusion Framework for NIR-to-RGB Translation.
Longbin Yan, Xiuheng Wang, Min Zhao, Shumin Liu, Jie Chen
2020A New Bounding Box based Pseudo Annotation Generation Method for Semantic Segmentation.
Xiaolong Xu, Fanman Meng, Hongliang Li, Qingbo Wu, King Ngi Ngan, Shuai Chen
2020A Novel Quality Enhanced Low Complexity Rate Control Algorithm for HEVC.
Fei Zhao, ChungWen Ku, Guoqing Xiang, Huizhu Jia, Yuehua Cui, Yuan Li, Xiaodong Xie
2020A Novel Visual Analysis Oriented Rate Control Scheme for HEVC.
Qi Zhang, Shanshe Wang, Siwei Ma
2020A Progressive Fast CU Split Decision Scheme for AVS3.
Yuyuan Chen, Songlin Sun, Jiaqi Zhang, Shanshe Wang
2020A Robust Multilinear Mixing Model with l2, 1 norm for Unmixing Hyperspectral Images.
Minglei Li, Fei Zhu, Alan J. X. Guo
2020A Theory of Occlusion for Improving Rendering Quality of Views.
Yijun Zeng, Weiyan Chen, Mengqin Bai, Yangdong Zeng, Changjian Zhu
2020A Unified Single Image De-raining Model via Region Adaptive Coupled Network.
Qingbo Wu, Li Chen, King Ngi Ngan, Hongliang Li, Fanman Meng, Linfeng Xu
2020A Vision Based Fish Processing System.
Zongjian Zhang, Litao Yu, Jian Zhang, Qiang Wu
2020A Weighted Mean Absolute Error Metric for Image Quality Assessment.
Sihan Hao, Sumei Li
2020A night-time outdoor data set for low-light enhancement.
Yudong Zhou, Ronggang Wang, Yang Zhao
2020A point cloud compression framework via spherical projection.
Yingshen He, Ge Li, Yiting Shao, Jing Wang, Yueru Chen, Shan Liu
2020A review of data preprocessing modules in digital image forensics methods using deep learning.
Alexandre Berthet, Jean-Luc Dugelay
2020A semantic labeling framework for ALS point clouds based on discretization and CNN.
Xingtao Wang, Xiaopeng Fan, Debin Zhao
2020APL: Adaptive Preloading of Short Video with Lyapunov Optimization.
Haodan Zhang, Yixuan Ban, Xinggong Zhang, Zongming Guo, Zhimin Xu, Shengbin Meng, Junlin Li, Yue Wang
2020Absolute 3D Human Pose Estimation via Weakly-supervised Learning.
Yiru Guo, Zerui Chen
2020Adaptive Color Transform in VVC Standard.
Hong-Jheng Jhu, Xiaoyu Xiu, Yi-Wen Chen, Tsung-Chuan Ma, Xianglin Wang
2020Adaptive Resolution Change for Versatile Video Coding.
Tsui-Shan Chang, Yu-Chen Sun, Ling Zhu, Jian Lou
2020An Empirical Study of Emotion Recognition from Thermal Video Based on Deep Neural Networks.
Herman Prawiro, Tse-Yu Pan, Min-Chun Hu
2020An Optimized Video Encoder Implementation with Screen Content Coding Tools.
Xiaozhong Xu, Shitao Wang, Yu Chen, Yiming Li, Qing Zhang, Yushan Zheng, Shan Liu
2020Application of Brain-Computer Interface and Virtual Reality in Advancing Cultural Experience.
Hao-Lun Fu, Po-Hsiang Fang, Chan-Yu Chi, Chung-ting Kuo, Meng-Hsuan Liu, Howard Muchen Hsu, Cheng-Hsun Hsieh, Sheng-Fu Liang, Shulan Hsieh, Cheng-Ta Yang
2020Attention-Guided Fusion Network of Point Cloud and Multiple Views for 3D Shape Recognition.
Bo Peng, Zengrui Yu, Jianjun Lei, Jiahui Song
2020Attribute Mix: Semantic Data Augmentation for Fine Grained Recognition.
Hao Li, Xiaopeng Zhang, Qi Tian, Hongkai Xiong
2020Automatic Sheep Counting by Multi-object Tracking.
Jingsong Xu, Litao Yu, Jian Zhang, Qiang Wu
2020Bidirectional Consistency Constrained Template Update Learning for Siamese Trackers.
Kexin Chen, Xue Zhou, Chao Liang, Jianxiao Zou
2020CNN-Based Anomaly Detection For Face Presentation Attack Detection With Multi-Channel Images.
Yuge Zhang, Min Zhao, Longbin Yan, Tiande Gao, Jie Chen
2020CSCNet: A Shallow Single Column Network for Crowd Counting.
Zhida Zhou, Li Su, Guorong Li, Yifang Yang, Qingming Huang
2020Chain Code-Based Occupancy Map Coding for Video-Based Point Cloud Compression.
Runyu Yang, Ning Yan, Li Li, Dong Liu, Feng Wu
2020Cloud-assisted Augmented Reality Streaming Service System: Architecture Design and Implementation.
Hyunmin Noh, Hwangjun Song
2020Compressing Facial Makeup Transfer Networks by Collaborative Distillation and Kernel Decomposition.
Bianjiang Yang, Zi Hui, Haoji Hu, Xinyi Hu, Lu Yu
2020Content-aware Hybrid Equi-angular Cubemap Projection for Omnidirectional Video Coding.
Jinyong Pi, Yun Zhang, Linwei Zhu, Xinju Wu, Xuemei Zhou
2020DEN: Disentanglement and Enhancement Networks for Low Illumination Images.
Nelson Chong Ngee Bow, Vu-Hoang Tran, Punchok Kerdsiri, Yuen Peng Loh, Ching-Chun Huang
2020DENESTO: A Tool for Video Decoding Energy Estimation and Visualization.
Matthias Kränzler, Christian Herglotz, André Kaup
2020DOVE: Decomposition Oriented Video super-rEsolution.
Huairui Wang, Wanjie Sun, Zhenzhong Chen, Daiqin Yang
2020Deep Blind Video Quality Assessment for User Generated Videos.
Jiapeng Tang, Yu Dong, Rong Xie, Xiao Gu, Li Song, Lin Li, Bing Zhou
2020Deep Convolutional Neural Network Based on Multi-Scale Feature Extraction for Image Denoising.
Jing Zhang, Liu Sang, Zekang Wan, Yuchen Wang, Yunsong Li
2020Deep Inter Coding with Interpolated Reference Frame for Hierarchical Coding Structure.
Yu Guo, Zizheng Liu, Zhenzhong Chen, Shan Liu
2020Deep Learning Based EBCOT Source Symbol Prediction Technique for JPEG2000 Image Compression Architecture.
I-Hsiang Wang, Jian-Jiun Ding
2020Deep Learning-Based Nonlinear Transform for HEVC Intra Coding.
Kun Yang, Dong Liu, Feng Wu
2020Deep Local and Global Spatiotemporal Feature Aggregation for Blind Video Quality Assessment.
Wei Zhou, Zhibo Chen
2020Deep Near Infrared Colorization with Semantic Segmentation and Transfer Learning.
Fengqiao Wang, Lu Liu, Cheolkon Jung
2020Deep Temporal Color Constancy for AC Light Sources.
Jun-Sang Yoo, Chan-Ho Lee, Jong-Ok Kim
2020Disparity compensation of light fields for improved efficiency in 4D transform-based encoders.
João M. Santos, Lucas A. Thomaz, Pedro A. Amado Assunção, Luís Alberto da Silva Cruz, Luis M. N. Tavora, Sérgio M. M. de Faria
2020Drone-Based Car Counting via Density Map Learning.
Jingxian Huang, Guanchen Ding, Yujia Guo, Daiqin Yang, Sihan Wang, Tao Wang, Yunfei Zhang
2020ERP-Based CTU Splitting Early Termination for Intra Prediction of 360 videos.
Bernardo Beling, Iago Storch, Luciano Agostini, Bruno Zatt, Sergio Bampi, Daniel Palomino
2020Efficient Light Deep Network for Street Scene Parsing.
Zhehui Wang, Sanyuan Zhao, Jianbing Shen, Zhengchao Lei
2020Enhanced Saliency Prediction via Orientation Selectivity.
Peng Ye, Yongfang Wang, Yumeng Xia
2020Enriching Optical Flow with Appearance Information for Action Recognition.
Yijun Pan, Xiaoyan Sun, Feng Wu
2020Equirectangular Projection Oriented Intra Prediction for 360-Degree Video Coding.
Yingbin Wang, Zhenzhong Chen, Shan Liu
2020Extending CCSDS 123.0-B-1 for Lossless 4D Image Compression.
Panpan Zhang, Xiuheng Wang, Tiande Gao, Zhenfu Feng, Jie Chen
2020FaME-ML: Fast Multirate Encoding for HTTP Adaptive Streaming Using Machine Learning.
Ekrem Çetinkaya, Hadi Amirpour, Christian Timmerer, Mohammad Ghanbari
2020Fast Geometry Estimation for Phase-coding Structured Light Field.
Li Liu, Sen Xiang, Huiping Deng, Jin Wu
2020Fast Intra Coding Algorithm for Depth Map with End-to-End Edge Detection Network.
Chang Liu, Kebin Jia, Pengyu Liu
2020Fast Recolor Prediction Scheme in Point Cloud Attribute Compression.
Chuang Ma, Ge Li, Qi Zhang, Yiting Shao, Jing Wang, Shan Liu
2020Fast Video Saliency Detection based on Feature Competition.
Hang Yan, Yiling Xu, Jun Sun, Le Yang, Yunfei Zhang, Wei Huang
2020Fast compressed sensing recovery using generative models and sparse deviations modeling.
Lei Cai, Yuli Fu, Youjun Xiang, Tao Zhu, Xianfeng Li, Huanqiang Zeng
2020FastSCCNet: Fast Mode Decision in VVC Screen Content Coding via Fully Convolutional Network.
Sik-Ho Tsang, Ngai-Wing Kwong, Yui-Lam Chan
2020FishUI: Interactive Fisheye Distortion Visualization.
Andy Regensky, Christian Herglotz, André Kaup
2020From Low to Super Resolution and Beyond.
Chi-Wah Kok, Wing-Shan Tam
2020Fully Neural Network Mode Based Intra Prediction of Variable Block Size.
Heming Sun, Lu Yu, Jiro Katto
2020GRNet: Deep Convolutional Neural Networks based on Graph Reasoning for Semantic Segmentation.
Yang Wu, Aimin Jiang, Yibin Tang, Hon Keung Kwan
2020Geodesic Disparity Compensation for Inter-View Prediction in VR180.
Kruthika Koratti Sivakumar, Bharath Vishwanath, Kenneth Rose
2020Geometric-visual descriptor for improved image based localization.
Achref Ouni, Eric Royer, Marc Chevaldonné, Michel Dhome
2020Graph Grouping Loss for Metric Learning of Face Image Representations.
Nakamasa Inoue
2020HDR Deghosting Using Motion-Registration-Free Fusion in the Luminance Gradient Domain.
Cheng-Yeh Liou, Cheng-Yen Chuang, Chia-Han Huang, Yi-Chang Lu
2020HDR Image Compression with Convolutional Autoencoder.
Fei Han, Jin Wang, Ruiqin Xiong, Qing Zhu, Baocai Yin
2020IBC-Mirror Mode for Screen Content Coding for the Next Generation Video Coding Standards.
Jian Cao, Zhen Qiu, Zhengren Li, Fan Liang, Jun Wang
2020Icon Colorization Based On Triple Conditional Generative Adversarial Networks.
Qinru Han, Wenzhe Zhu, Qing Zhu
2020Improving Compression Artifact Reduction via End-to-End Learning of Side Information.
Haichuan Ma, Dong Liu, Feng Wu
2020Improving Robustness of DNNs against Common Corruptions via Gaussian Adversarial Training.
Chenyu Yi, Haoliang Li, Renjie Wan, Alex C. Kot
2020Interpretable and Effective Learning for 3D Point Cloud Registration, Classification and Segmentation.
C.-C. Jay Kuo
2020Introducing Latent Space Correlation to Conditional Autoencoders for Intra Prediction.
Fabian Brand, Jürgen Seiler, André Kaup
2020Learned image and video compression with deep neural networks.
Dong Xu, Guo Lu, Ren Yang, Radu Timofte
2020Learning Convolution Feature Aggregation via Edge Attention Convolution Network for Person Re-Identification.
Chaoqun Lin, Ruo-Pei Guo, Mingkun Li, Xianbiao Qi, Chun-Guang Li
2020Learning From Paired and Unpaired Data: Alternately Trained CycleGAN for Near Infrared Image Colorization.
Zaifeng Yang, Zhenghua Chen
2020Learning Graph Topology Representation with Attention Networks.
Yuanyuan Qi, Jiayue Zhang, Weiran Xu, Jun Guo, Honggang Zhang
2020Learning Matching Behavior Differences for Compressing Vehicle Re-identification Models.
Yi Xie, Jianqing Zhu, Huanqiang Zeng, Canhui Cai, Lixin Zheng
2020Learning Photometric Stereo via Manifold-based Mapping.
Yakun Ju, Muwei Jian, Junyu Dong, Kin-Man Lam
2020Learning Redundant Sparsifying Transform based on Equi-Angular Frame.
Min Zhang, Yunhui Shi, Xiaoyan Sun, Nam Ling, Na Qi
2020Learning the Connectivity: Situational Graph Convolution Network for Facial Expression Recognition.
Jinzhao Zhou, Xingming Zhang, Yang Liu
2020Learning to encode user-generated short videos with lower bitrate and the same perceptual quality.
Shengbin Meng, Yang Li, Yiting Liao, Junlin Li, Shiqi Wang
2020Lightweight Color Image Demosaicking with Multi-Core Feature Extraction.
Yufei Tan, Kan Chang, Hengxin Li, Zhenhua Tang, Tuanfa Qin
2020Low Resolution Facial Manipulation Detection.
Xiao Han, Zhongyi Ji, Wenmin Wang
2020Machine Learning for Photometric Redshift Estimation of Quasars with Different Samples.
Yanxia Zhang, Xin Jin, Jingyi Zhang, Yongheng Zhao
2020Mining Larger Class Activation Map with Common Attribute Labels.
Runtong Zhang, Fanman Meng, Hongliang Li, Qingbo Wu, King N. Ngan
2020Mono is Enough: Instance Segmentation from Single Annotated Sample.
Longrong Yang, Hongliang Li, Qingbo Wu, Fanman Meng, King Ngi Ngan
2020Motion Estimation for Spike Camera Data Sequence via Spike Interval Analysis.
Jing Zhao, Ruiqin Xiong, Rui Zhao, Jin Wang, Siwei Ma, Tiejun Huang
2020Multi-Scale Video Inverse Tone Mapping with Deformable Alignment.
Jiaqi Zou, Ke Mei, Songlin Sun
2020NIR Image Colorization Using SPADE Generator and Grayscale Approximated Self-Reconstruction.
Tian Sun, Cheolkon Jung
2020NIR image colorization with graph-convolutional neural networks.
Diego Valsesia, Giulia Fracastoro, Enrico Magli
2020Network Update Compression for Federated Learning.
Birendra Kathariya, Li Li, Zhu Li, Lingyu Duan, Shan Liu
2020News Image Steganography: A Novel Architecture Facilitates the Fake News Identification.
Jizhe Zhou, Chi-Man Pun, Yu Tong
2020No-Reference Objective Quality Assessment Method of Display Products.
Huiqing Zhang, Donghao Li, Lifang Wu, Zhifang Xia
2020No-Reference Stereoscopic Image Quality Assessment Based On Visual Attention Mechanism.
Sumei Li, Ping Zhao, Yongli Chang
2020No-Reference Stereoscopic Image Quality Assessment Based on Convolutional Neural Network with A Long-Term Feature Fusion.
Sumei Li, Mingyi Wang
2020No-Reference Stereoscopic Image Quality Assessment Considering Multi-loss Constraints.
Yongtian Han, Sumei Li, Guanghui Yue, Yongli Chang
2020Noise-Aware Texture-Preserving Low-Light Enhancement.
Zohreh Azizi, Xuejing Lei, C.-C. Jay Kuo
2020On 2D-3D Image Feature Detections for Image-To-Geometry Registration in Virtual Dental Model.
Hui Tang, Richard Tai Chiu Hsung, Walter Yu Hang Lam, Leo Y. Y. Cheng, Edmond Ho Nang Pow
2020On Segmentation of Maxillary Sinus Membrane using Automatic Vertex Screening.
Kang Rong Li, Tai-Chiu Hsung, Andy Wai Kan Yeung, Michael M. Bornstein
2020Optical Flow Estimation Between Images of Different Resolutions via Variational Method.
Rui Zhao, Ruiqin Xiong, Shuyuan Zhu, Bing Zeng, Tiejun Huang, Wen Gao
2020Optimization of Sliding-DCT Based Gaussian Filtering for Hardware Accelerator.
Tomoki Otsuka, Norishige Fukushima, Yoshihiro Maeda, Kenjiro Sugimoto, Sei-ichiro Kamata
2020Orthogonal Coded Multi-view Structured Light for Inter-view Interference Elimination.
Zaichao Sun, Guochao Qian, Zhaoyu Peng, Weiju Dai, Dongjun Sun, Gongyuan Zhang, Nongtao Zhang, Jun Xu, Ren Wang, Chunlin Li
2020Orthogonal Features Fusion Network for Anomaly Detection.
Teli Ma, Yizhi Wang, Jinxin Shao, Baochang Zhang, David S. Doermann
2020Point Cloud Attribute Compression via Successive Subspace Graph Transform.
Yueru Chen, Yiting Shao, Jing Wang, Ge Li, C.-C. Jay Kuo
2020Point Cloud Geometry Prediction Across Spatial Scale using Deep Learning.
Anique Akhtar, Wen Gao, Xiang Zhang, Li Li, Zhu Li, Shan Liu
2020Power/QoS-Adaptive HEVC FME Hardware using Machine Learning-Based Approximation Control.
Wagner Penny, Daniel Palomino, Marcelo Schiavon Porto, Bruno Zatt
2020Prediction-Aware Quality Enhancement of VVC Using CNN.
Fatemeh Nasiri, Wassim Hamidouche, Luce Morin, Nicolas Dhollande, Gildas Cocherel
2020Quality of Experience Evaluation for Streaming Video Using CGNN.
Zhiming Zhou, Yu Dong, Li Song, Rong Xie, Lin Li, Bing Zhou
2020Random-access-aware Light Field Video Coding using Tree Pruning Method.
Thuc Nguyen Huu, Vinh Van Duong, Byeungwoo Jeon
2020Real-time Detection and Tracking Network with Feature Sharing.
Ente Guo, Zhifeng Chen, Zhenjia Fan, Xiujun Yang
2020Recent Advances in End-to-End Learned Image and Video Compression.
Wen-Hsiao Peng, Hsueh-Ming Hang
2020Robust Visual Tracking Via An Imbalance-Elimination Mechanism.
Jin Feng, Kaili Zhao, Xiaolin Song, Anxin Li, Honggang Zhang
2020Screen Content Coding in Recently Developed Video Coding Standards.
Xiaozhong Xu, Shan Liu
2020Sensitivity-Aware Bit Allocation for Intermediate Deep Feature Compression.
Yuzhang Hu, Sifeng Xia, Wenhan Yang, Jiaying Liu
2020Sparse Representation-Based Intra Prediction for Lossless/Near Lossless Video Coding.
Linwei Zhu, Yun Zhang, Na Li, Jinyong Pi, Xinju Wu
2020Sparse Spectral Unmixing of Hyperspectral Images using Expectation-Propagation.
Zeng Li, Yoann Altmann, Jie Chen, Steve McLaughlin, Susanto Rahardja
2020Spatial-Channel Context-Based Entropy Modeling for End-to-end Optimized Image Compression.
Chongxin Li, Jixiang Luo, Wenrui Dai, Chenglin Li, Junni Zou, Hongkai Xiong
2020Spatiotemporal Guided Self-Supervised Depth Completion from LiDAR and Monocular Camera.
Zhifeng Chen, Hantao Wang, Lijun Wu, Yanlin Zhou, Dapeng Oliver Wu
2020Special Cane with Visual Odometry for Real-time Indoor Navigation of Blind People.
Tang Tang, Menghan Hu, Guodong Li, Qingli Li, Jian Zhang, Xiaofeng Zhou, Guangtao Zhai
2020Stereo Image Quality Assessment Considering the Asymmetry of Statistical Information in Early Visual Pathway.
Yongli Chang, Sumei Li, Li Ma, Jie Jin
2020Stereoscopic image reflection removal based on Wasserstein Generative Adversarial Network.
Xiuyuan Wang, Yikun Pan, Daniel Pak-Kong Lun
2020Subjective and Objective Quality Assessment of the SoftCast Video Transmission Scheme.
Anthony Trioux, Giuseppe Valenzise, Marco Cagnazzo, Michel Kieffer, François-Xavier Coudoux, Patrick Corlay, Mohamed Gharbi
2020Temporal Action Proposal Generation via Multi-Task Feature Learning.
Handong Ma, Lixin Duan
2020Text-to-Image Generation via Semi-Supervised Training.
Zhongyi Ji, Wenmin Wang, Baoyang Chen, Xiao Han
2020The Enhancement of Underexposed Images with Blurred Reflectance.
Jinchao Zhou, Renjie Wan, Haoliang Li, Alex C. Kot
2020The Hough-Based Multibeamlet Transform.
Agnieszka Lisowska
2020Towards Audio-Visual Saliency Prediction for Omnidirectional Video with Spatial Audio.
Fang-Yi Chao, Cagri Ozcinar, Lu Zhang, Wassim Hamidouche, Olivier Déforges, Aljosa Smolic
2020Towards Quantized DCT Coefficients Restoration for Compressed Images.
Tong Ouyang, Zhenzhong Chen, Shan Liu
2020Two recent advances on normalization methods for deep neural network optimization.
Lei Zhang
2020UGNet: Underexposed Images Enhancement Network based on Global Illumination Estimation.
Yuan Fang, Wenzhe Zhu, Qing Zhu
2020Unsupervised Embedding Learning by Noisy Similarity Label Optimization.
Koki Tsubota, Kiyoharu Aizawa
2020Unsupervised Feedforward Feature (UFF) Learning for Point Cloud Classification and Segmentation.
Min Zhang, Pranav Kadam, Shan Liu, C.-C. Jay Kuo
2020Unsupervised Point Cloud Registration via Salient Points Analysis (SPA).
Pranav Kadam, Min Zhang, Shan Liu, C.-C. Jay Kuo
2020Versatile Video Coding (VVC) Arrives.
Gary J. Sullivan
2020Versatile Video Coding - Algorithms and Specification.
Mathias Wien, Benjamin Bross
2020Video Anomaly Detection Using Open Data Filter and Domain Adaptation.
Chen Zhang, Guorong Li, Li Su, Weigang Zhang, Qingming Huang
2020Video Super Resolution Using Temporal Encoding ConvLSTM and Multi-Stage Fusion.
Yuhang Zhang, Zhenzhong Chen, Shan Liu
2020Volumetric End-to-End Optimized Compression for Brain Images.
Shuo Gao, Yueyi Zhang, Dong Liu, Zhiwei Xiong
2020Wearable Visually Assistive Device for Blind People to Appreciate Real-world Scene and Screen Image.
Jin AI, Menghan Hu, Guodong Li, Guangtao Zhai, Jian Zhang, Qingli Li, Wendell Q. Sun