1 Topic by skyer

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Hey,

is it possible to align two superpositioned videos manually? I found that I can drag a video in one screen and it's overlay would move in the other as well. But it's hard to get it accurate that way. I would also need to zoom and transform.

In my case, the static background is a plane surface of known size. So, ideally, I would draw two perspective grids (one per video) and use that information to compute the (affine) transformation from one video "plane" to the other. Applying the transformation would give us a nice aligned superposition.

Is that perhaps already possible and I haven't seen it?

Cheers,
Malte

2 Reply by joan

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This operation is not currently possible but that's a very good idea!

A slight generalization of this would be "alignment by coordinate systems" or "by calibration", as the approach could also work with the line-based calibration / coordinate system (just origin + scale, axes stay aligned with image axes). Even if less accurate it's often the only calibration available.

Lens distortion correction might also comes into play.

The original goal with superposition was actually to compute this transform matrix automatically, refining it using the video sequence to ignore the foreground layer. I very much like the idea of being able to do something manually before implementing an automation of it.

We need the full homography matrix by the way, not just affine, as it will map arbitrary quad to arbitrary quad. I've been thinking about how to finally build a platform to experiment with these ideas more easily. I also need to revisit and homogenize the matrix maths in some places. No ETA.

3 Reply by skyer

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Hi Joan,

thanks for the reply. Sound like a great plan. Hope to see that feature integrated at some point in the future!

Cheers,
Malte

4 Reply by Thrice (edited by Thrice 2023-12-01 22:54:31)

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Me too, I hope it's soon.