Changing from white to coloured background on mp4

[PaulineNatalie]

Hi!

I have an mp4-file showing an object in motion with a white background. I would like to change the white background to a different colour (while keeping all the shadows). How do I go about it? 
The video is attached. 

Thank you! 

Best, 
Pauline

[Rick Gerard]

You will need to create a matte to hold out all of the parts of the video you do not want to color correct. You might be able to get part way there by duplicating the layer and applying some severe color correction. There are parts of the shot that are going to require some Rotoscoping. Rotobrush may work on a few frames, but others will require manual animation. Mocha AE can help speed up the process by tracking the surfaces (planes) in the shot. When you have the matte created, you can use that as a track matte for an adjustment layer that changes the color, or you can use the matte to cut out a copy of the rotating furniture and overlay that on a color-corrected copy of the shot.

Here's a start using your footage, Curves, Fill, some masking for the fill, and an adjustment layer with a radial grid.

I have also uploaded a project file for you to look at. It might give you a starting point.

I have done a lot of Roto using Mocha AE and Mocha Pro, and I would estimate that the Roto will take you several hours. The idea is to create a perfect matte for the color change. You'll probably need several copies of the original footage in a Pre-comp.