sep.Bakcground masked sources

[ferromatteo]

Hello, It's more a question than an issue: I would like to understand how actually sep.Background handle background estimation on masked pixel, especially if I set the fw, fh (Filter width and height in number of boxes for the smoothing, I guess) to 0, in order to properly capture a small-scale varying background.

In this case I end up with background estimated in all my 2D array except for the masked pixels, How is it then computed there? Is it just some sort of interpolation of first neighbors pixel values when fw and fh are set to 0, is something similar?

Thank you very much in advance