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Previously it was asked how to prevent flicker when recording a presenter and a slide show simultaneously. I'm interested in how to correct pre-existing video where there are flickering slides.

Here is an example video that demonstrates the flicker.

I appreciate that the flicker is caused by some problem to do with the video and projector refresh rate being out of sync. However, assuming that such film has been taken, I'm interested in ways to remove the flicker. In particular, when filming slides, the rate of movement in slide content is low. So on some level I assume that there is enough information in the video file to restore an image without flicker. Perhaps there is some smoothing effect that can be applied post processing.

So my question is:

How can flicker from a slide projector be removed from existing video footage?

In particular, I'd be interested in simple and efficient solutions available in standard consumer video editing software.

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2 Answers 2

I didn't view the entire video, but from what I saw it looks like a series of static slides. You could grab a still frame from each slide and create a (say) five second repeat of that frame, and use it to cover the section in the video where that slide appears. Every editing package I'm aware of can do this.

Better yet, get the original slide stack and scan them, then do the same as above. You can correct for parallax etc and have more readable content.

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Your best bet is to composite in the screen. That's the typical solution for this kind of problem. You can use a program like After Effects and Mocha to image track if you have any shots that have motion and feed either the original or stills of the presentation in as the image to be mapped on to the area that the screen appears on. Since screens are square with strong edges, they are very easy and reliable to track, so results are generally very good, though it can take a bit of time to do depending on how often the shot changes.

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