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3. Implementation

3.1 Data

CVN provides one directory of JPEG images per lecture class. All slides, with the exception of PowerPoint slides and the title slide, are numbered consecutively 1 through n, i.e. [1.jpg, 2.jpg, ...] . The title slide is named title.jpg , and electronic slides are named with some proprietary convention not worth elaborating on here.

The collection of key frames is renamed and organized for the Lecture Browser as follows:

  • Numbered key frames remain the same
  • title.jpg is renamed to 0.jpg
  • Electronic slides are renamed to reflect their position in the ordered sequence of slides, and are given subscripts, i.e. X-Y.jpg , where X refers to a point in the numerical sequence of slides and Y refers to a local sequence of such slides, e.g. [74-1.jpg, 74-2.jpg, 74-3.jpg] are three PowerPoint slides between key frames 74.jpg and 75.jpg .

Figure 1.2: CVN Interface: Index of Key Frames
Click image to enlarge, or click here to open

3.2 Directory structure

The classified and segmented sequence of Slides is stored in a directory tree structure that reflects media types and topics. Media types are enumerated as sub-directories (board, class, computer, podium, sheet) to the lecture's arbitrarily named root directory. Any media type not used needs not be enumerated. Each media type directory contains a numerically ordered list of Topic sub-directories (1, 2, 3 ..), which contain the Slides for each Topic. The Slides in each Topic directory must not be consecutive Slides, especially if a Topic contains several Sections, i.e. there exist breaks in the sequence of Slides for a Topic.

Figure 1.3: Class Data Directory Structure

3.3 Sections: Breaks in the Sequence of a Topic

The Lecture Browser is designed to map those Topics into Sections, which exhibit breaks in the numerical sequence of Slides. For example, if the contents for a topic is the set of Slides {10.jpg 11.jpg 12.jpg 70.jpg 71.jpg} , then the Lecture Browser generates two Sections for this Topic: {10.jpg 11.jpg 12.jpg} and {70.jpg 71.jpg} .