Making a color transparent in a video clip

I’ve been looking for this but all the videos I’ve seen attack this with already having a video with a proper green background. I have a mp4 video that has a kinda green background as it was shot in front of a wall painted on a greenish color. What I want to do is use that as a Chroma thingie…I added a Chroma and picked the color I get some “transparency” but there are nasty black spots.

Is there a feature where I pick a color and it is treated as the chroma color(or the transparency)?? I see people talking about alpha stuff but not clearly explained to make sense out of it& that is why I’m asking here.

Thanks in advance

Hi @becker666
I’m not an expert on Chroma thingies, but I know that to get the best results, the color you select has to be uniform AND it also needs to have a big contrast with the parts you don’t want to become transparent.
In your case, you use a wall painted in a greenish color.
Even if, to your eyes, the wall color seams uniform, if fact, there will be imperfections, shadows, highlights etc… All things that make your greenish background color not uniform.

There are settings in the Chroma Key filters, but they usually work best when the background color is as uniform as it can be.

That’s true. Probably because Chroma Key preparation usually begins before you shoot a video.

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There is a way of doing this using OBS and ZOOM - both free software. If you forgot to use a green-screen when you recorded your video overlay, or your green -screen is not perfect like yours, this method should solve the problem. See here:

Musical box has given a nice explanation, getting a background that is nice, well lit and uniform is good, and if you do not have that much good background than you could use color correction wheels, brightness & contrast, Lightness and saturation that are already available in shotcut to get that type of result “*(Remember, No one can guaranty that this would always help you, This might not work in some cases)” and then you could use advanced chroma key to get more controls over what you want to do.