In multimedia-based e-learning systems, the accessibility and searchability of most lecture video content is still insufficient due to the unscripted and spontaneous speech of the speakers. Moreover, this problem becomes even more challenging when the quality of such lecture videos is not sufficiently high. To extract the structural knowledge of a multi-topic lecture video and thus make it easily accessible it is very desirable to divide each video into shorter clips by performing an automatic topic-wise video segmentation. To this end, this paper presents the TRACE system to automatically perform such a segmentation based on a linguistic approach using Wikipedia texts. TRACE has two main contributions: (i) the extraction of a novel linguistic-based Wikipedia feature to segment lecture videos efficiently, and (ii) the investigation of the late fusion of video segmentation results derived from state-of-the-art algorithms. Specifically for the late fusion, we combine confidence scores produced by the models constructed from visual, transcriptional, and Wikipedia features. According to our experiments on lecture videos from VideoLectures.NET and NPTEL 1 , the proposed algorithm segments knowledge structures more accurately compared to existing state-of-theart algorithms. The evaluation results are very encouraging and thus confirm the effectiveness of TRACE.

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The number of lecture videos available is increasing rapidly, though there is still insufficient accessibility and traceability of lecture video contents. Specifically, it is very desirable to enable people to navigate and access specific slides or topics within lecture videos. To this end, this paper presents the ATLAS system for the VideoLectures.NET challenge (MediaMixer, transLectures) to automatically perform the temporal segmentation and annotation of lecture videos. ATLAS has two main novelties: (i) a SVM hmm model is proposed to learn temporal transition cues and (ii) a fusion scheme is suggested to combine transition cues extracted from heterogeneous information of lecture videos. According to our initial experiments on videos provided by VideoLectures.NET, the proposed algorithm is able to segment and annotate knowledge structures based on fusing temporal transition cues and the evaluation results are very encouraging, which confirms the effectiveness of our ATLAS system.

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