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an analysis of a lecture's structure based on the similarity between the slides used at the lecture

In recent years, research of automatic shooting systems is done to get video contents of lectures.By these researches, the burden by the help is lessened and a lecture's situation can be recorded now. Moreover, those video contents can be used now freely . In these researches, the situation understanding based on a motion and condition of a lecturer and a student is performed, and the technique of determining the method of shooting and the technique of recording lecture data are proposed. However, the research which records the information about presumption of the important situation in the lecture is not made. In addition to shooting a lecture situation, or record of the data used in the lecture ,if the presumption of an important situation becomes possible, such video contents can be used more effectively. Then, it aims at the analysis of lecture structure for recording the information about presumption of the important situation under lecture in this paper.

we thinks that the situation of a lecture is related to the structure of an element which constitute the lecture, such as how to use teaching materials for a lecture situation and time. So we notes the teaching materials as an element of a lecture. Although blackbord, distribution data, the PowerPoint slide, etc. are mentioned as teaching materials used in a lecture, such teaching materials summarize some contents explained by the lecturer or the contents. In this techniques,we regard the lecture using the PowerPoint slide as teaching materials as an object. This is because the following features are mentioned at the lecture which uses the PowerPoint slide.

The concrete technique is as follows. In order to perform analysis of lecture's structure from transition of slides, we note the transition of the slide and slide itself. when each slide explains difference contents , all of the changes of showing slide mean the change of contents. However, when the contents which are explained by using more than one slide , we can't easily deciede the change of contents from the change of slide. Then, it aims at detecting a contents-pause of a lecture by grouping the slides based on the relation between the slides. First, in order to obtain the relation between such slides, each slide needs to be characterized by using the feature of the slide itself. Then, the morphological analysis extracted the keyword contained in a slide, and the feature of a slide was given by using the TF*IDF method . Next, by using this feature, the degree of similarity between slides is defined as a relation between slides, and we group the slides explaining the contents which were similar by using it. Since the information about a group that each slide belongs is acquired, a contents-pause is detected by investigating transition of the group of a slide according to the presentation order of the slide in a lecture. In transition of a slide, the analysis of a lecture's structure is performed by using the distribution of a contents-pause, and the important section is presumed. Moreover, the score of each slide based on the keyword was defined, and it considered as the importance of a slide.

In order to show the validity of this technique described above, it experimented to the lecture which actually uses the PowerPoint slide as teaching materials. When the analysis of the lecture' structure based on the distribution of a contents-pause was performed and the score of a slide was investigated to the slide included in the section presumed to be important, it turns out that it is contained in the category of a high score in the lecture. It checked that the analysis of a lecture's structure for presuming the presentation section of a slide which serves as a candidate of an important portion could be performed.

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