Virtual reality(VR) environment can provide immersive experience to viewers.Under the VR environment, providing a good quality of experience is extremely important.Therefore, in this paper, we present an image quality...Virtual reality(VR) environment can provide immersive experience to viewers.Under the VR environment, providing a good quality of experience is extremely important.Therefore, in this paper, we present an image quality assessment(IQA) study on omnidirectional images. We first build an omnidirectional IQA(OIQA) database, including 16 source images with their corresponding 320 distorted images. We add four commonly encountered distortions. These distortions are JPEG compression, JPEG2000 compression, Gaussian blur, and Gaussian noise. Then we conduct a subjective quality evaluation study in the VR environment based on the OIQA database. Considering that visual attention is more important in VR environment, head and eye movement data are also tracked and collected during the quality rating experiments. The 16 raw and their corresponding distorted images,subjective quality assessment scores, and the head-orientation data and eye-gaze data together constitute the OIQA database. Based on the OIQA database, we test some state-of-the-art full-reference IQA(FR-IQA) measures on equirectangular format or cubic formatomnidirectional images. The results show that applying FR-IQA metrics on cubic format omnidirectional images could improve their performance. The performance of some FR-IQA metrics combining the saliency weight of three different types are also tested based on our database. Some new phenomena different from traditional IQA are observed.展开更多
A point cloud is considered a promising 3D representation that has achieved wide applications in several fields.However,quality degradation inevitably occurs during its acquisition and generation,communication and tra...A point cloud is considered a promising 3D representation that has achieved wide applications in several fields.However,quality degradation inevitably occurs during its acquisition and generation,communication and transmission,and rendering and display.Therefore,how to accurately perceive the visual quality of point clouds is a meaningful topic.In this survey,we first introduce the point cloud to emphasize the importance of point cloud quality assessment(PCQA).A review of subjective PCQA is followed,including common point cloud distortions,subjective experimental setups and subjective databases.Then we review and compare objective PCQA methods in terms of modelbased and projection-based.Finally,we provide evaluation criteria for objective PCQA methods and compare the performances of various methods across multiple databases.This survey provides an overview of classical methods and recent advances in PCQA.展开更多
Currently the indoor environment quality is described or evaluated mainly by the subjective or objective data.However,research increasingly has demonstrated that objective and subjective data both had some weaknesses ...Currently the indoor environment quality is described or evaluated mainly by the subjective or objective data.However,research increasingly has demonstrated that objective and subjective data both had some weaknesses to characterize the indoor environment quality,and they can compensate for each other's relative weaknesses.Hence,this study aims to develop an integration model to allow indoor subjective and objective data to be combined based on the structural equation modeling approach,using the Northeast China residential indoor environmental survey data.The results indicated that the integration model had a good fit for the survey data,and the model validity was confirmed.Moreover,in contrast to the subjective data(R^(2)=0.363)and objective data(R^(2)=0.239),the integrated data(R^(2)=0.553)improved the explanatory power on the satisfaction with the overall indoor environment.Furthermore,this integration model demonstrated that indoor subjective data assigned more weights to the integrated data than the corresponding objective data.The association strength of thermal environment and indoor air quality(0.43 or 0.47)was the strongest among the interactions of thermal,air quality,acoustic,and lighting environments.Consequently,the main contribution of this paper was that it provided a comprehensive model to accomplish the integration of indoor environmental subjective and objective data,promoting the ability to describe and assess the indoor environment quality.展开更多
文摘Virtual reality(VR) environment can provide immersive experience to viewers.Under the VR environment, providing a good quality of experience is extremely important.Therefore, in this paper, we present an image quality assessment(IQA) study on omnidirectional images. We first build an omnidirectional IQA(OIQA) database, including 16 source images with their corresponding 320 distorted images. We add four commonly encountered distortions. These distortions are JPEG compression, JPEG2000 compression, Gaussian blur, and Gaussian noise. Then we conduct a subjective quality evaluation study in the VR environment based on the OIQA database. Considering that visual attention is more important in VR environment, head and eye movement data are also tracked and collected during the quality rating experiments. The 16 raw and their corresponding distorted images,subjective quality assessment scores, and the head-orientation data and eye-gaze data together constitute the OIQA database. Based on the OIQA database, we test some state-of-the-art full-reference IQA(FR-IQA) measures on equirectangular format or cubic formatomnidirectional images. The results show that applying FR-IQA metrics on cubic format omnidirectional images could improve their performance. The performance of some FR-IQA metrics combining the saliency weight of three different types are also tested based on our database. Some new phenomena different from traditional IQA are observed.
文摘A point cloud is considered a promising 3D representation that has achieved wide applications in several fields.However,quality degradation inevitably occurs during its acquisition and generation,communication and transmission,and rendering and display.Therefore,how to accurately perceive the visual quality of point clouds is a meaningful topic.In this survey,we first introduce the point cloud to emphasize the importance of point cloud quality assessment(PCQA).A review of subjective PCQA is followed,including common point cloud distortions,subjective experimental setups and subjective databases.Then we review and compare objective PCQA methods in terms of modelbased and projection-based.Finally,we provide evaluation criteria for objective PCQA methods and compare the performances of various methods across multiple databases.This survey provides an overview of classical methods and recent advances in PCQA.
文摘目的:主观评价和客观评估不同成像参数下CBCT的图像质量,分析图像质量的主观评价和客观评价间的关系。方法:分别采用6台不同品牌CBCT扫描仪〔3D Accuitomo(Morita)、i-CAT(Kavo)、5G(NewTom)、Smart3D(北京朗视)、DCT Pro(Vatech)、VGi(NewTom)〕,在各个品牌的典型曝光条件下(电压和电流强度不同)扫描空间分辨率模体和高仿真头模,7位医师对拍摄的CBCT图像进行主观评价打分,比较不同CBCT扫描仪的空间分辨率和对常见口腔解剖结构的可见性。客观评价指标采用各仪器所获的图像空间分辩率(LP/mm)。结果:7位医师的组内一致性和组间一致性均无显著性差异。主观评价New Tom 5G为2分,i-CAT为5分,其余4个品牌匀为4分,客观评价i-CAT的LP/mm为1.8,Smart3D为2.0,其余4个品牌为1.0~1.7。在相同管电流条件下,不同管电压的图像主观质量有显著性差异。在相同管电压条件下,不同管电流的图像主观质量有显著性差异。结论:图像质量的主客观评价具有一定的一致性,不同品牌之间的客观评价差异可能与电压、电流强度不同有关。
基金supported by the National Natural Science Foundation of China(No.51978121 and No.51578103)the Key Projects in the National Science&Technology Pillar Program during the 12th Five-year Plan Period of China(No.2012BAJ 02B05)the National Key R&D Program during the 13th Five-year Plan Period of China(No.2018YFD1100701).
文摘Currently the indoor environment quality is described or evaluated mainly by the subjective or objective data.However,research increasingly has demonstrated that objective and subjective data both had some weaknesses to characterize the indoor environment quality,and they can compensate for each other's relative weaknesses.Hence,this study aims to develop an integration model to allow indoor subjective and objective data to be combined based on the structural equation modeling approach,using the Northeast China residential indoor environmental survey data.The results indicated that the integration model had a good fit for the survey data,and the model validity was confirmed.Moreover,in contrast to the subjective data(R^(2)=0.363)and objective data(R^(2)=0.239),the integrated data(R^(2)=0.553)improved the explanatory power on the satisfaction with the overall indoor environment.Furthermore,this integration model demonstrated that indoor subjective data assigned more weights to the integrated data than the corresponding objective data.The association strength of thermal environment and indoor air quality(0.43 or 0.47)was the strongest among the interactions of thermal,air quality,acoustic,and lighting environments.Consequently,the main contribution of this paper was that it provided a comprehensive model to accomplish the integration of indoor environmental subjective and objective data,promoting the ability to describe and assess the indoor environment quality.
