Need help with deflickering of video of projector screen

[SCDVD]

I shot a video of a technical symposium in which the speakers used a PC attached projector. I am getting a great deal of flicker on the shots of the projector screen. I have experimented with both the Donald Graft and MSU deflicker filters in VirtualDub without much success.

The video was shot with a Sony EX1R at 1920 x 1080, 60i. I would appreciate any suggestions.

[poisondeathray]

Is the flickering in the source, or due to something in the processing chain (like the projecter, connection, deinterlacing or post processing, etc...)

ie. If you watch the source video on PC, does it flicker?

What was the source? eg. timelapse footage?

[SCDVD]

The flickering is in the source footage. The flicker shows however the footage is viewed. The speakers were using PowerPoint presentations - just slides, no video content.

[poisondeathray]

I'm sorry I should have read your post more clearly

It's just the projector screen portion correct? (ie. It displayed at a different refresh rate, and you get different luminance values?)

This is difficult to fix, because global filters will adversely affect parts of the frame which do not flicker (ruining the "good parts"). Ideally you would apply a filter to only that section with masks

Can you upload a sample ?

[SCDVD]

Here is a short sample on Vimeo. This was converted to 1280 x 720, 30p for Vimeo. The flicker is more apparent at the end when the iris is closed down. The overexposure of the screen at the beginning partially obscures it.

http://vimeo.com/12180562 Password - flicker

[poisondeathray]

This is very difficult to fix, because you have undulating bands of different values within a section of a frame

Most deflickering treatments measure luminance value changes between whole frames, then apply some sort of averaging to get more even results

Hopefully others have better suggestions

[Oddy]

You might like to try Dynamic Noise Reduction filter: http://neuron2.net/dnr.zip
It does not soften or blur the image. It works by blending the current frame with previous frame(s), but only where it detects no motion from one frame to the next. This blending averages out the noise, and in the moving parts of the frame where it doesn't blend, the noise is not noticeable.

By chance I discovered it did quite a good job of reducing the flicker of a PC screen that was in a shot. I tried it on your sample clip and it does improve it. But towards the end of your clip the screen darkens - don't know a way to solve that, I'm afraid.

I use this whenever I capture from VHS, and in fact, I am busy capturing 8mm film that was transfered to VHS with a slight flicker, and even that shows less flicker after DNR.

Hope this helps.

Edit: Most times I use the default value or 12. Going much above 16 can sometimes cause ghost images from previous frames.