Green screen tracking

Is there a way to track a green screen within a video where the camera pans across a room and the green screen portion within that room moves across the frame?

Theres a funny video clip that has a crowded bar of people and they are all staring at a giant screen (which has been green screened). Then they go crazy cheering. The camera pans the crowd so the giant screen in the bar moves out of frame. I want to put my podcast logo on the green screen in the bar to make it look like the crowd cheers when they see it, funny right? I have a basic understanding of chroma keying but how do i get that image on the screen in the bar to stay in that place as the camera pans the room?

I’m thinking I must have to use the “Size-Position-Rotate” filter and its keyframes function to move the image with many keyframe points as the camera pans?

It depends. If the shape of the TV screen changes (because of the perspective) while the camera pans the bar, you’ll probably need to use the Corner Pin filter.



This filter will allow you to control the 4 corners of your logo image and make its perspective match the one of the TV as the camera pans the room.

But it will be a lot of work. You’ll probably need to use a keyframe on each frame of the clip.

Can you share your bar scene clip?

Try this link Fans at Ashton Gate Stadium, Bristol, celebrate England winner against Wales at Euro 2016 - YouTube

To have the greenscreen area move, with perspective will as far as I know require 3D perspective transforms, or ‘Homography’.

Try this for the greenscreened version: Bar Crowd Scene Cheer Green Screen Video Download - YouTube

In Adobe After-Effects and Blender, they have Wall perspective replacement areas like this.

I’d welcome the introduction of OpenCV Homography examples using OpenCV Homography ( Python / C ++ ) | ( filters that would allow this to happen.

Natron also have a multi-point tracking feature.
I experimented with it a couple of years ago. It works quite well.

Learning how to use it is not super easy, but there are some tutorials available.

Thank you for hour help. The bar scene is the one shared by david.lyon in this thread below. It would be so great if this worked.

That is the exact clip, yes! Thank uou for your suggestions.

I also found a ‘How to’ for After-Effects and the very same video with a sample Project File for AE included

Just including the link for inspiration and education rather than anything else. It proves at least that it can be made easy.

Thanks so much. Ill see what i can do. I really do appreciate it.

Thanks for using the term “Multi-point” - that helped quite a lot.

I upgraded my experiment to track with 4-points. I now just draw a greenscreen on the area.

The next step to do is to paste the inserted video on the greenscreen area.

Experimental status only

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Looks promising David :+1:

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