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Cropp a skewed video using corner pins or similar tool

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Marin Aldimirov
Cropp a skewed video using corner pins or similar tool
on Apr 12, 2017 at 2:40:16 pm

Hello all,
I am not really into video editing, I just need to do 1 simple thing to edit a video for my PhD research.
The setup:
On the ground I have drawn 4 white markers marking the endpoints of a coordinate system that is 20x30 meters. A video is shot from a Phantom 3 Pro of a marked car moving inside the coordinate system. I need to crop the video so that my 4 ground markers align with the borders of the video. In the end the video borders must align with the coordinate system's borders. So when I track the movement of the marker placed on top of the car, the tracked coordinates translate to the real world coordinates of the car inside my coordinate system.
I know I can do it by using corner pins and manually dragging them, but my laptop is really slow at this and it will take forever to properly align.
The question:
Is there a simple way to just click the four markers (or any four points) in the video and say, these are the new video borders, deal with it and render my cropped video 😎 Like you can create a mask by clicking with the pen tool.

Here is a link to a sample video so you can better understand what I have to do. You may notice there are a lot of markers on the ground. Don't worry I know which ones are mine 😋 As you can see I cannot simply pan or zoom to produce perfect results. And I need them to be perfect because this is a technical measurement not a video fx.

P.S.: If anyone has any idea of a program that will track the markers on the car and export a list of coordinates to a file, it will be a priceless information for me.


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Dave LaRonde
Re: Crop a skewed video using corner pins or similar tool
on Apr 12, 2017 at 4:06:34 pm
Last Edited By Dave LaRonde on Apr 12, 2017 at 4:53:07 pm

I don't know how closely you will be able to come to exact coordinates. I presume you already have them for this shot. How do you intend to represent them visually, if at all?

I'm sorry, but this WILL take forever to align precisely. Although you took great pains to shoot straight down, once you crop to the corner points, I suspect the resulting shape will be a trapezoid and not a rectangle... which means distortion will occur in the image.

This is more of a task to be done in After Effects than in Premiere Pro.
I would farm it out to someone else if I were you.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Marin Aldimirov
Re: Crop a skewed video using corner pins or similar tool
on Apr 12, 2017 at 8:57:00 pm

First, thanks for the quick reply.
It's a bummer that there is no easier way than manual dragging of the corner pins.

I did start on After Effects, but after a few tutorials, thought it would be easier to do it in Premiere Pro.

I am aware that some loss of information will occur in the transformation, due to interpolation of the visual data, but I think it will not mess up the whole experiment. The end goal is to use the exported coordinates to check the accuracy of a physical tracking system I am developing for my PhD.


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