1 Topic by ALes

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Hiya, I’m evaluating Kinovea to see if it will do a specific job for my research. I’m using a GoPro and want to do the lens calibraton. I see from an earlier post on this forum that the way to do this now is via Lens Calibration Mode.

When I reach this point, with my filmed checkerboard visible, I find…
- on the Video menu Lens Calibration is greyed out
- on the tools menu I can get to lens calibration mode but what do I do next??! There’s nothing evident, no pop-ups or prompts and nothing useful when I right click.

Some really basic next steps would be super-helpful. Thanks in advance

Andy

2 Reply by joan

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Hi, the video needs to be short enough that it triggers the "cached" mode. You can increase the memory allocated for this in Preferences > Playback > Memory. And make the video a few seconds long.

The documentation is currently here until it's merged into the main documentation: https://www.kinovea.org/en/forum/viewtopic.php?id=1977

3 Reply by ALes

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Thanks Joan, that works & under Calibration Validation it now says Lens Calibration found, so that all looks good.

I have a feeling I'll be back with more questions in due course, but for now, thanks!

4 Reply by ALes

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My next problem is plane calibration.

I want to calibrate a plane the size of a sheet of A4 paper. It is all well within the video frame. When I click plane calibration and place the perspective grid onto a still from my video I can move the perspective grid fine in the top right and top left corners but neither the bottom left nor bottom right corner moves when I try to pick up. What am I doing wrong?

5 Reply by joan

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That's strange. Must be a UI bug.

There is an area around the corner points that should detect the grab. Can you zoom in more and see if you can grab while zoomed?
What is the resolution of the image/video? Is it particularly big or small? Are you doing this while still in the Lens calibration mode or back in the general Analysis mode?

6 Reply by ALes

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Hi Joan

What I've found today is the problem with plane calibration only occurs if I attempt it after lens calibration (as I guess I should?).

- If I go for plane calibration first I can move all four corners of the grid just fine & drag them to the corners of my object & complete the calibration. (But the plane calibration is not accounting for lens distortion?)
- If I do a lens calibration first and then try to do the plane calibration I have the same problem described above - I can't move the bottom left or bottom right grid corners. Zooming in doesn't help - I get the little grab hand symbol which closes when I click but the grid doesn't move.

Video is full high definition (1080p), 2.07MP per frame.

Any ideas?

Thanks for helping.

7 Reply by joan

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You should be able to do these in either order I think.

I tried to reproduce the problem but for the moment I can't, even if I put the corners in a part of the image that's very distorted by the lens.

I'm thinking that maybe there is an invisible object that is picking up the grab, and has priority over the grid. What if just before trying to grab the grid corner you do a right-click instead, what menu do you get?
Do you get the video background menu (long menu starting with "Mark current time as origin"), the grid menu (it has an "Options" menu with an entry "Show grid"), or another drawing's menu? If it looks like another drawing you can go in its "Configuration" and see which one it is. For the next version I added the name of the drawing at the top but for now you have to infer it.

If it looks like another drawing please make a copy of the KVA before trying to move it around and send it to me so I can more easily debug this.