[Peter Rongsted]

If you are referring to the slight bend of the video layers in 3D space I think you are going to have to use a plug-in. Something like Zaxwerks 3D-Warps should do the trick.
Unfortunately that’s a relatively expensive plug’in…
But I don’t think you can do it with the regular AE tools.
Someone please correct me if I am wrong.

[Peter Rongsted]

If you have enough contrast between the people walking and the background you may be able to crush the whites and blacks together with a levels and a curves effect. Thus trying to create a luma matte.
May not work if the quality is too poor, but worth a try.

[Peter Rongsted]

it just works like any other displacement map. The lighter the map the more that part of the image will extrude from the background.
Just bring your photo into photoshop and start painting on a separate black layer with a very soft white brush. When you’re done just discard the original photo in photoshop so that just the displacement map is left. Bring both the map and the original photo into After Effects. Put the displacement map effect on the original photo and point the source layer to the map you just made in Photoshop.
I think that should do the trick.

It can be bit tricky to get it exactly right though. But you did an excellent job with the King Kong image.