[FFmpeg-user] How can chromakey ignore shadows ?

[smoothgroove]

Using chromakey=0x00ff00:0.24:0.14

Is there any way to completely knock out the chromakey background, i.e.
ignorning the lighting level, shadows and structure of the chroma
background?

In the examples:

- The arm is casting a shadow on the greenscreen which is reflected in the
result.
- the face being near to the light automatically causes the chroma
background to darken, which causes the replaced image to unnaturally darken.
- a fold in the greenscreen fabric shows up in the replaced background

What is required is chromakey being insenstitive to the chroma brightness,
that is to totally punch out the background. How could this be accomplished?