The advantages of digital media such as the Internet and CD-ROMs lie in the fact that their contents are easy to duplicate, edit, and distribute. These advantages, however, are double-edged swords, because they also facilitate unauthorized use of such contents. Data embedding, which places information into the contents themselves, is an approach to address this issue. Embedded information can be used, for example, for copyright protection, theft deterrence, and inventory. This paper discusses our work on embedding data into three-dimensional (3D) polygonal models of geometry. Given objects consisting of points, lines, polygons, or curved surfaces, the data embedding algorithms described in this paper produce polygonal models with data embedded. Data are placed into 3D polygonal models by modifying either their vertex coordinates, their vertex topology (connectivity), or both. A brief review of related work and a description of the requirements of data embedding is followed by a discussion of where, and by what fundamental methods, data can be embedded into 3D polygonal models. The paper then presents data-embedding algorithms, with examples, based on these fundamental methods. Additional
{"title":"Watermaking three-dimensional polygonal models","authors":"Ryutarou Ohbuchi, H. Masuda, Masaki Aono","doi":"10.1145/266180.266377","DOIUrl":"https://doi.org/10.1145/266180.266377","url":null,"abstract":"The advantages of digital media such as the Internet and CD-ROMs lie in the fact that their contents are easy to duplicate, edit, and distribute. These advantages, however, are double-edged swords, because they also facilitate unauthorized use of such contents. Data embedding, which places information into the contents themselves, is an approach to address this issue. Embedded information can be used, for example, for copyright protection, theft deterrence, and inventory. This paper discusses our work on embedding data into three-dimensional (3D) polygonal models of geometry. Given objects consisting of points, lines, polygons, or curved surfaces, the data embedding algorithms described in this paper produce polygonal models with data embedded. Data are placed into 3D polygonal models by modifying either their vertex coordinates, their vertex topology (connectivity), or both. A brief review of related work and a description of the requirements of data embedding is followed by a discussion of where, and by what fundamental methods, data can be embedded into 3D polygonal models. The paper then presents data-embedding algorithms, with examples, based on these fundamental methods. Additional","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115414725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents an analytical (in contrast to commonlyused simulations) approach to program scheduling in near video-on-demand (NVoD) systems. NVoD servers batch customers’ requests by sourcing the same mr$erial at certain intervals called phase offsets. The proposed approach to analytical modeling integrates both customers’ and serviceprovider’s views to account for the tradeoff between system throughput and customers’ partial patience. We first determine the optimal scheduling of movies of different popularities for maximum throughput and the lowest average phase offset. Next, we deal with quasi video-on-demand (QVoD) systems, in which programs are scheduled based on a threshold on the number of pending requests. The throughput is found to be usually greater in QVoD than in NVoD, except for the extreme case of nonstationary request arrivals. This observation is then used to improve throughput without compromising customers’ QoS in terms of average phase offset and the corresponding dispersion. Index Terms Near video-on-demand (NVoD), quasi videoon-demand (QVoD), partially patient customers, batching, video server throughput.
{"title":"Scheduling video programs in near video-on-demand systems","authors":"Emmanuel L. Abram-Profeta, K. Shin","doi":"10.1145/266180.266387","DOIUrl":"https://doi.org/10.1145/266180.266387","url":null,"abstract":"This paper presents an analytical (in contrast to commonlyused simulations) approach to program scheduling in near video-on-demand (NVoD) systems. NVoD servers batch customers’ requests by sourcing the same mr$erial at certain intervals called phase offsets. The proposed approach to analytical modeling integrates both customers’ and serviceprovider’s views to account for the tradeoff between system throughput and customers’ partial patience. We first determine the optimal scheduling of movies of different popularities for maximum throughput and the lowest average phase offset. Next, we deal with quasi video-on-demand (QVoD) systems, in which programs are scheduled based on a threshold on the number of pending requests. The throughput is found to be usually greater in QVoD than in NVoD, except for the extreme case of nonstationary request arrivals. This observation is then used to improve throughput without compromising customers’ QoS in terms of average phase offset and the corresponding dispersion. Index Terms Near video-on-demand (NVoD), quasi videoon-demand (QVoD), partially patient customers, batching, video server throughput.","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114540782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
to obtain cost-effective QoS. In this paper, we address the issues in designing metrics that are important in evaluating the Quality of Service(QoS) In this paper, we address the issues in designing metrics that are important in evaluating the QoS of video transmission. There has been little work in det ermining effective metrics of QoS for video transmission that characterize both cost (revenue generated or service demand) and guaranteed service. The metrics of analysis and comparison for video transmission must be determined as an end-to-end measure of QoS from video server to end-user(s). By developing these metrics, we hope to enhance the client, server and networking components of a system with monitoring capabilities to measure and evaluate video characterizations. This paper is organized as follows. In Section 2, we discuss a workload model for developing and understanding QoS metrics. Section 3 presents empirical studies and experimental justification for the metric selection based on the three systems VOSAIC, hierarchical VOD and the remote VCR systems. Section 4 proposes a new integrated metric for measuring video QoS and the analytical framework to express the tradeoffs. We also propose a metric-based QoS architecture along with negotiation and reward protocols. In Section 5 we discuss related work and conclude with future research directions in Section 6. of video transmission. We propose a new metric for video QoS called the weighted cost-satisfaction ratio based on requirements from two perspectives: the user and the service provider. To understand real video workload environments and user behavioral patterns, we obtained and analyzed empirical results from the VOSAIC (video-over-the-Web) system, a hierarchical video-on-demand (VOD) system and a remote VCR system. Based on these results, we define parameters of resource consumption (storage and network bandwidth etc.) and user satisfaction (jitter, syncbronization skew) and derive analytical interrelationships among the metric parameters. We also draw an economic relationship between the user-satisfaction and resource consumption factors to solve metric optimization relations.
{"title":"An integrated metric for video QoS","authors":"N. Venkatasubramanian, K. Nahrstedt","doi":"10.1145/266180.266389","DOIUrl":"https://doi.org/10.1145/266180.266389","url":null,"abstract":"to obtain cost-effective QoS. In this paper, we address the issues in designing metrics that are important in evaluating the Quality of Service(QoS) In this paper, we address the issues in designing metrics that are important in evaluating the QoS of video transmission. There has been little work in det ermining effective metrics of QoS for video transmission that characterize both cost (revenue generated or service demand) and guaranteed service. The metrics of analysis and comparison for video transmission must be determined as an end-to-end measure of QoS from video server to end-user(s). By developing these metrics, we hope to enhance the client, server and networking components of a system with monitoring capabilities to measure and evaluate video characterizations. This paper is organized as follows. In Section 2, we discuss a workload model for developing and understanding QoS metrics. Section 3 presents empirical studies and experimental justification for the metric selection based on the three systems VOSAIC, hierarchical VOD and the remote VCR systems. Section 4 proposes a new integrated metric for measuring video QoS and the analytical framework to express the tradeoffs. We also propose a metric-based QoS architecture along with negotiation and reward protocols. In Section 5 we discuss related work and conclude with future research directions in Section 6. of video transmission. We propose a new metric for video QoS called the weighted cost-satisfaction ratio based on requirements from two perspectives: the user and the service provider. To understand real video workload environments and user behavioral patterns, we obtained and analyzed empirical results from the VOSAIC (video-over-the-Web) system, a hierarchical video-on-demand (VOD) system and a remote VCR system. Based on these results, we define parameters of resource consumption (storage and network bandwidth etc.) and user satisfaction (jitter, syncbronization skew) and derive analytical interrelationships among the metric parameters. We also draw an economic relationship between the user-satisfaction and resource consumption factors to solve metric optimization relations.","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129418836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Large scale video-on-demand systems require that the serv ers offering the video retrieval and playback services are arranged as a distributed system in order to support a lar ge number of concurrent streams. If such a system is hierarchical, an end-node serv er handles the requests from a particular area, the ne xt server in the hierarchy takes the request over for several end-node servers if those can not answer the request and so on. This architecture pro vides for cost efficiency, reliability and scalability of serv ers. The end-node servers store only a limited set of the o verall available information which changes over time due to user interests. If a video is requested which is not available, this server contacts the next server in the hierarchy. To decide the size and location of the video serv ers and the location of videos in the hierarch y, the access behaviour of users must be considered. Various models for the simulation of user behavior (and thus, of the load induced on the video serv ers) have been presented in the literature. Only a fe w of these models are designed to take long-term effects into account because the basis for most of the models are short-term influences on a single video server and the load on this single machine. In this paper we describe a new user behavior model and show that various assumptions made within other models are unrealistic.
{"title":"Long-term movie popularity models in video-on-demand systems: or the life of an on-demand movie","authors":"C. Griwodz, M. Bär, L. Wolf","doi":"10.1145/266180.266386","DOIUrl":"https://doi.org/10.1145/266180.266386","url":null,"abstract":"Large scale video-on-demand systems require that the serv ers offering the video retrieval and playback services are arranged as a distributed system in order to support a lar ge number of concurrent streams. If such a system is hierarchical, an end-node serv er handles the requests from a particular area, the ne xt server in the hierarchy takes the request over for several end-node servers if those can not answer the request and so on. This architecture pro vides for cost efficiency, reliability and scalability of serv ers. The end-node servers store only a limited set of the o verall available information which changes over time due to user interests. If a video is requested which is not available, this server contacts the next server in the hierarchy. To decide the size and location of the video serv ers and the location of videos in the hierarch y, the access behaviour of users must be considered. Various models for the simulation of user behavior (and thus, of the load induced on the video serv ers) have been presented in the literature. Only a fe w of these models are designed to take long-term effects into account because the basis for most of the models are short-term influences on a single video server and the load on this single machine. In this paper we describe a new user behavior model and show that various assumptions made within other models are unrealistic.","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129503188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Spotting by Association method for video analysis is a novel metliod to detect video segments with typical semantics. Video data contains various kinds of information through continuous images, natural language, and sound. For videos to be stored and retrieved in a Digital Library, it is essential to segment the video data into meaningful pieces. To detect meaningful segments, we need to identify the segment in each modality (video, language, and sound) that corresponds to the same story. For this purpose, we propose a new method for making correspondences between image clues detected by image analysis and Iangriage clries detected by natural language analysis. As a result, relevant video segments with sufficient informat ion froni every modality are obtained. We applied OUT nietliod to closed-captioned C N N Headline News. Video segments with important events, such as a public speech, meeting, or visit. are detc-cted fairly well.
{"title":"Semantic analysis for video contents extraction—spotting by association in news video","authors":"Yuichi Nakamura, T. Kanade","doi":"10.1145/266180.266391","DOIUrl":"https://doi.org/10.1145/266180.266391","url":null,"abstract":"Spotting by Association method for video analysis is a novel metliod to detect video segments with typical semantics. Video data contains various kinds of information through continuous images, natural language, and sound. For videos to be stored and retrieved in a Digital Library, it is essential to segment the video data into meaningful pieces. To detect meaningful segments, we need to identify the segment in each modality (video, language, and sound) that corresponds to the same story. For this purpose, we propose a new method for making correspondences between image clues detected by image analysis and Iangriage clries detected by natural language analysis. As a result, relevant video segments with sufficient informat ion froni every modality are obtained. We applied OUT nietliod to closed-captioned C N N Headline News. Video segments with important events, such as a public speech, meeting, or visit. are detc-cted fairly well.","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129281348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The development of MBone videoconferencing tools has led to a large number of seminars being broadcast over the internet. Most MBone seminars have little remote participation. One reason might be the absence of good floor control mechanisms. This paper describes a tool we developed, called the Questionboard, that implements floor control to facilitate question asking in large-scale MBone seminars. The qb protocol is described including the mechanisms used for reliable transmission of data and the floor control and crash recovery protocols. (June 10, 1997)
{"title":"Floor control for large-scale MBone seminars","authors":"R. Malpani, L. Rowe","doi":"10.1145/266180.266356","DOIUrl":"https://doi.org/10.1145/266180.266356","url":null,"abstract":"The development of MBone videoconferencing tools has led to a large number of seminars being broadcast over the internet. Most MBone seminars have little remote participation. One reason might be the absence of good floor control mechanisms. This paper describes a tool we developed, called the Questionboard, that implements floor control to facilitate question asking in large-scale MBone seminars. The qb protocol is described including the mechanisms used for reliable transmission of data and the floor control and crash recovery protocols. (June 10, 1997)","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122397540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper reviews studies of attention and recall of expository The results of the studies are taken as a basis to justify the MM presentations, and summarises findings into key guidelines importance of moment by moment design. The problems found in for attentional design. An expert system based design advisor tool attentional design are used to inform a set of guidelines for is then described, which uses the guidelines to analyse MM presentation design. These are then extended to form a method for presentations. analysing MM presentations.
{"title":"Multimedia: design for the “moment”","authors":"Peter Faraday, A. Sutcliffe","doi":"10.1145/266180.266363","DOIUrl":"https://doi.org/10.1145/266180.266363","url":null,"abstract":"The paper reviews studies of attention and recall of expository The results of the studies are taken as a basis to justify the MM presentations, and summarises findings into key guidelines importance of moment by moment design. The problems found in for attentional design. An expert system based design advisor tool attentional design are used to inform a set of guidelines for is then described, which uses the guidelines to analyse MM presentation design. These are then extended to form a method for presentations. analysing MM presentations.","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127621362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Multimedia functionality has become an established component of core computer worHoads. MPEG-2 video decoding represents a particularly important and computationally demanding application example. Instruction set extensions like Intel’s MMX significantly reduce the computational challenges of this and other multimedia algorithms. However, memory subsystem deficiencies have now become the major barrier to increased performance, partly as a consequence of this improved CPU performance. Decoding MPEG-2 video data in software makes significant bandwidth demands on memory subsystems, which is seriously aggravated by cache ineficiencies. Conventional data caches generate many times more cache-memory trafic than required, at best double the minimum necessary to support decoding. Improving eficiency requires understanding the behavior of the decoder and composition of its data set. We provide an analysis of the memory and cache behavior of software MPEG-2 video decoding, and lay out a set of cache-oriented architectural enhancements which offer relief for the problem of excess cache-memory bandwidth. Our results show that cache-sensitive handling of different data types can reduce trafic by 50 percent or more.
{"title":"Optimizing the data cache performance of a software MPEG-2 video decoder","authors":"Peter Soderquist, M. Leeser","doi":"10.1145/266180.266380","DOIUrl":"https://doi.org/10.1145/266180.266380","url":null,"abstract":"Multimedia functionality has become an established component of core computer worHoads. MPEG-2 video decoding represents a particularly important and computationally demanding application example. Instruction set extensions like Intel’s MMX significantly reduce the computational challenges of this and other multimedia algorithms. However, memory subsystem deficiencies have now become the major barrier to increased performance, partly as a consequence of this improved CPU performance. Decoding MPEG-2 video data in software makes significant bandwidth demands on memory subsystems, which is seriously aggravated by cache ineficiencies. Conventional data caches generate many times more cache-memory trafic than required, at best double the minimum necessary to support decoding. Improving eficiency requires understanding the behavior of the decoder and composition of its data set. We provide an analysis of the memory and cache behavior of software MPEG-2 video decoding, and lay out a set of cache-oriented architectural enhancements which offer relief for the problem of excess cache-memory bandwidth. Our results show that cache-sensitive handling of different data types can reduce trafic by 50 percent or more.","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114671682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a new technique for morphing two video sequences. Our approach extends still image metamorphosis techniques to video by performing motion tracking on the objects. Besides reducing the amount of user input required to morph two sequences by an order of magnitude, the additional motion information helps us to segment the image into foreground and background parts. By morphing these parts independently and overlaying the results, output quality is improved. We compare our approach to conventional motion image morphing techniques in terms of the quality of the output image and the human input required.
{"title":"Motion and feature-based video metamorphosis","authors":"R. Szewczyk, A. Ferencz, Henry Andrews, B. Smith","doi":"10.1145/266180.266378","DOIUrl":"https://doi.org/10.1145/266180.266378","url":null,"abstract":"We present a new technique for morphing two video sequences. Our approach extends still image metamorphosis techniques to video by performing motion tracking on the objects. Besides reducing the amount of user input required to morph two sequences by an order of magnitude, the additional motion information helps us to segment the image into foreground and background parts. By morphing these parts independently and overlaying the results, output quality is improved. We compare our approach to conventional motion image morphing techniques in terms of the quality of the output image and the human input required.","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"47 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120907748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose a novel delivery mechanism called 2-Phase Service Model to deliver video data to home users connected to the Internet through a low-bandwidth device such as a modem. In our scheme, non-adjacent fragments of the requested video file are first downloaded to the client during Initialization Phase. The missing fragments are transmitted to the client as the video is being played out, using a novel pipelining technique. This scheme offers several benefits as follows. First, it allows the user to perform a quick preview through the video with minimal delay. Second, it naturally supports VCR functionality with almost no delay as demonstrated by the simulation results shown in the paper. Finally, our mathematical analysis shows that despite the desirable features it offers, 2-Phase Service Model does not incur any more initialization delay than-that of the conventional pipelining technique.
{"title":"A framework for supporting previewing and VCR operations in a low bandwidth environment","authors":"Wallapak Tavanapong, K. Hua, J. Wang","doi":"10.1145/266180.266381","DOIUrl":"https://doi.org/10.1145/266180.266381","url":null,"abstract":"We propose a novel delivery mechanism called 2-Phase Service Model to deliver video data to home users connected to the Internet through a low-bandwidth device such as a modem. In our scheme, non-adjacent fragments of the requested video file are first downloaded to the client during Initialization Phase. The missing fragments are transmitted to the client as the video is being played out, using a novel pipelining technique. This scheme offers several benefits as follows. First, it allows the user to perform a quick preview through the video with minimal delay. Second, it naturally supports VCR functionality with almost no delay as demonstrated by the simulation results shown in the paper. Finally, our mathematical analysis shows that despite the desirable features it offers, 2-Phase Service Model does not incur any more initialization delay than-that of the conventional pipelining technique.","PeriodicalId":250198,"journal":{"name":"MULTIMEDIA '97","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124937305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：