[FFmpeg-user] fftfilt

Michael Koch astroelectronic at t-online.de
Tue Oct 12 11:54:19 EEST 2021

I have a question about the "fftfilt" filter. What's the default value 
of the weight_U and weight_V options? I'm asking because I get an 
unexpected result.

This command line creates my input image for testing:

ffmpeg -f lavfi -i color=black:s=300x50 -lavfi 
-frames 1 -y test.png

This is the fftfilt lowpass example from the official documentation:

ffmpeg -i test.png -vf fftfilt=dc_Y=0:weight_Y='squish((Y+X)/100-1)' -y 

Problem: The output has a greenish tint.

If I set the weight_U and weight_V options to 1, then the greenish tint 

ffmpeg -i test.png -vf 
fftfilt=dc_Y=0:weight_Y='squish((Y+X)/100-1)':weight_U=1:weight_V=1 -y 


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