Anže Cesar. Slide show grabber. Introduction. I made a slide show grabber application In essence it is simplified hard cut detection. Definition – The Problem. Why? At the non-profit organization Kiberpipa we record every lecture We also do live streaming The Problem:. The Idea.
Anže Cesar Slide show grabber
Introduction I made a slide show grabber application In essence it is simplified hard cut detection
Definition – The Problem Why? At the non-profit organization Kiberpipa we record every lecture We also do live streaming The Problem:
The Idea Record slides separately As a video: waste of space As images How do I get the images? ?
The solution Poor man's choice Another camera, specifically for the slides VGA frame grabber To get normal resolutions: $1600
Now what? Detect slide changes and filter out animations and other disturbances
How do I do that? Based on “Video Cut Detection using Frame Windows”  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”
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
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
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
Resources VGA Master: http://www.pixelsmart.com/vga.html Epiphan grabbers: http://www.epiphan.com/products/frame-grabbers/  http://portal.acm.org/citation.cfm?id=1082161.1082183