Create the video mode first, then import your video.
Do not change any settings in Advanced when Exporting video.
A video clip in 21:9 aspect ratio.
Source video dimension 1920x1080, cropped top & bottom.
To compare the different with a 16:9 aspect ratio with the same underlying video clip.
You’ll have to click here to watch it on YouTube’s page to see it. Forum software will show black bars because it’s player window is set to a 16:9 ratio.