Image background colouring

I have 9 sit down interwiews where the background image needs to be re-coloured & changed to a plain white background.It's a very simple task & requires someone to recolour all of the interviews.They're all interviews from the camera,no editing required.All footage will be on an FTP & the image quality must be maintained at the same bit rate and same HD image quality throughout.The audio must also stay synced.