The detection of events is essential to high-level semantic querying of video databases. It is also a very challenging problem requiring the detection and integration of evidence for an event available in multiple information modalities, such as audio, video and language. This paper focuses on the detection of specific types of events, namely, topic of discussion events that occur in classroom/lecture environments. Specifically, we present a query-driven approach to the detection of topic of discussion events with foils used in a lecture as a way to convey a topic. In particular, we use the image content of foils to detect visual events in which the foil is displayed and captured in the video stream. The recognition of a foil in video frames exploits the color and spatial layout of regions on foils using a technique called region hashing. Next, we use the textual phrases listed on a foil as an indication of a topic, and detect topical audio events as places in the audio track where the best evidence for the topical phrases was heard. Finally, we use a probabilistic model of event likelihood to combine the results of visual and audio avent detection that exploits their time cooccurrence. The resulting identification of topical events is evaluated in the domain of classroom lectures and talks.
事件的检测对于视频数据库的高级语义查询至关重要。这也是一个非常具有挑战性的问题,需要针对多种信息形式(例如音频,视频和语言)中的事件进行检测和证据整合。本文着重于检测特定类型的事件,即在教室/演讲环境中发生的讨论事件的主题。具体来说,我们提出了一种查询驱动的方法来检测讨论事件的主题,并使用演讲中使用的铝箔作为传达主题的方法。特别是,我们使用箔纸的图像内容来检测视觉事件,在这些视觉事件中,箔纸在视频流中显示和捕获。视频帧中箔片的识别使用称为区域哈希的技术来利用箔片上区域的颜色和空间布局。接下来,我们使用箔纸上列出的文本短语作为主题的指示,并检测主题音频事件,作为音频轨道中听到主题短语最佳证据的位置。最后,我们使用事件可能性的概率模型来组合利用时间同现的视听音频检测结果。由此产生的主题事件识别将在课堂讲课和演讲中进行评估。 P>
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