[FFmpeg-user] Question about videos with alpha channel - Pro res 4444

[vishopper]

Hi

I have a question about video Pro res 4444 with alpha channel.

In original video I have an person on transparent background. While 
converting in to other video formats transparent background is turned to 
black color.

Quicktime player shows video same way - background turned to black.

Is it a possible to use any tags, so that background will appear white 
instead of black, while converted to other formats like MPEG?

Here is a sample clip (64 MB) 
https://www.dropbox.com/scl/fi/p5e8qgicii5tvmpox1wek/carla_mini.mov?rlkey=qo372qz4tswk5yyiojanwud92&dl=0

Thank you!

Martin