Slide show grabber

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Slide show grabber

• Anže Cesar

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Introduction

• I made a slide show grabber application
• In essence it is simplified hard cut detection

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Definition The Problem

• Why?
• At the non-profit organization Kiberpipa we
  record every lecture
• We also do live streaming
• The Problem

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The Idea

• Record slides separately
• As a video waste of space
• As images
• How do I get the images?

?
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The solution

• Poor man's choice
• Another camera, specifically for the slides
• VGA frame grabber
• To get normal resolutions 1600

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Now what?

• Detect slide changes and filter out animations
  and other disturbances

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How do I do that?

• Based on Video Cut Detection using Frame
  Windows 1
• Simplified, because slides are mostly static
• Make a window of frames size n (should be odd)?
• (n-1)/2 are in the past and (n-1)/2 are in the
  future
• Middle one frame is the current frame
• Compute the difference between the frames and
  current frame

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New Slide

• All the slides in the past part of the window are
  similar to current frame and to each other
• All the slides in the future part of the window
  are different from current frame

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Tools Used

• Qt 4
• LGPL, acquired by Nokia
• Cross-platform C library
• Not just GUI
• Even embedded
• Signals/Slots framework
• Decoupling of components
• Qwt
• Plotting library for Qt
• OpenCV

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Conclusion

• Usage of additional camera is an overhead
• The quality of gathered pictures may suffer
• It is however cheaper than frame grabbers
• The program satisfies most use cases
• There is room for improvement
• Qt provides enough maneuvering space
• Performance of the algorithm is good
• Also due to low frame rate requirement

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Resources

• VGA Master http//www.pixelsmart.com/vga.html
• Epiphan grabbers http//www.epiphan.com/products/
  frame-grabbers/
• 1 http//portal.acm.org/citation.cfm?id1082161.
  1082183