I need help with borders and composting problem.

So, I have a video that was filmed vertically and contains a person with a background that is all green for chroma keying. The green screen chroma keying is all fine but i want to make my rendered final video fill horizontal, the only thing blocking me from that is black borders on the sides of my video. I’ve noticed that the black boxes are only from the video not from the background video im inserting into the chroma key. I’ve found this out by chroma keying black and the boxes were gone/transparent. So Now, if you can help please let me know how i can remove those black boxes so that I can have my background video on the chroma key fill all parts of the video but the video of the person.

Add a green colour strip and place the video on top of it with an Alpha Over effect strip
You could use a masks

Please use the appropriate support forum for support questions. You may think this is important but it’s hardly worth discussing your problems by posting in the Blender Discussion forum ! As you should be able to see the main page has a scroll bar

Moved to Support / Compositing and Post Processing forum