Masking virtual objects with real ones

I’m working on an AR project (Windows, fixed camera, no tracking) and I’m looking for a way to occlude virtual objects with physical ones.
The videocapture is shown in the back of my scene so technically virtual objects are always in front of physical ones.
But I have the 3D models of the physical objects I want to use for occlusion. So I’m looking for a technique (material/masking…) that will hide everything behind those objects except the videocapture. Does it make sense? Any idea?