[FFmpeg-user] stroboscope effect

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Good day,

I've tried to make a stroboscope effect with ffplay but didn't find an
appropriate way. Do you have some tips?

Here are my efforts:
ffplay -f lavfi -i color=black:s=512x512 -vf
"framestep=3,drawbox=x=0:y=0:w=512:h=512:color=white:t=500"
(only a white picture, think it generate a black picture, drop 2 frames
and overlay the third with a white box)

ffplay -f lavfi -i color=black:s=512x512 -filter_complex "split
[main][tmp]; [tmp]
framestep=3,drawbox=x=0:y=0:w=512:h=512:color=white:t=500 [white];
[main][white] overlay"

This did not work, because ffplay did not understand -filter_complex. So
I used ffmpeg to generate a video out of it:
ffmpeg -f lavfi -i color=black:s=512x512 -filter_complex "split
[main][tmp]; [tmp]
framestep=3,drawbox=x=0:y=0:w=512:h=512:color=white:t=500 [white];
[main][white] overlay" -t 30 -framerate 25 foo.mkv

and replayed it, but the video was completely black. My thoughts were to
draw every frame a black frame but overlay it every third frame with a
white box.


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