I've got problem with using 3d compositing. Basically what I want to do is to get a 3d model and another real picture of scene such as the basket ball field.
The objective is to animate a 3d object in a real environment (compositing)

I want to have the shadow so I use a skylight and target photometric to simulate sunlight
firstly, I use shader camera map and apply background image to it
Secondly I use chrome ball shader and apply the chrome ball image to it
Thirdly is about the matte shadow material that I have to use. I applied matte shadow to the plane
Forthly is the background switcher shader. In background switcher,
_for the background slot, apply the camera map
_for the reflection slot, apply the chrome ball map

It looks right when I render single frame. When I render multiple frame , the background image isn't displayed and all is just a white background.
Would you please tell me how to resolve the problem? Thank you

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