Hi folks:

I had my first test shoot last night, and the majority of problems were operator error ;). However, I ordered the cameras incorrectly when I did the shoot, and it seems to mess up the calibration. I've seen posts about using Virtualdub to reorder the cameras, but nothing on how that is done. Would someone please tell me how to make the changes in Virtualdub? I recorded in Raw Bayer mode. The camera I numbered 1 should be numbered 6, so the video needs the camera columns moved one camera to the left and the camera currently in the first column should be moved to the last column. I'm not sure how to do this in Virtualdub.

Thanks,

Michael

I did that a year or two ago and I used a compositing program to correct the camera layout. I like to use Fusion (it's what we use at my job) but you can do this with AfterEffects as well. Basically, you want to break out and crop each camera monitor into its own node or layer, and place them in proper order on a background node/layer that's the exact size of your original video. When you're done, render out the new video using an appropriate codec for iPi DMC.

Back then I thought I might create a macro tool to do this for me automatically but to be honest I never made this mistake again. (Once was enough!) :)

I'm not sure how you would do this with Virtual Dub but you can probably do this with just a little more effort in a video editing program that has some basic compositing tools (like Vegas Pro or Premiere.)

By the way, before you do this, try manually moving the cameras in iPi DMC to the approximate the 'misplaced' locations and then do a calibration. DMC prefers the cameras to be in order but it might still work if you help it out before running the calibration. Worth a try anyway.

Hope this helps.

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Greenlaw
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How do I move the cameras in DMC (is ipisoft Motion Capture Studio)? I tried clicking and dragging, but they didn't move.

Thanks,

Michael

Select the camera you want to move from the toolbar, then click on the Scene tab. There you'll see the camera controls. It's awkward to use but you only need to approximate the positions.

Normally, Auto Detect Initial Positions will do this for you automatically but I think it gets confused if the camera order isn't what's expected. (Maybe somebody from iPi will confirm if this is true.)

BTW, iPi DMC is short for iPi Desktop Motion Capture which is the mocap tracking and retargeting program, as opposed to iPi Recorder which of course is the mocap video recording program. The motion capture system as a whole (both programs) is called iPi Studio.

G.

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Greenlaw
Artist/Partner - Little Green Dog | My Demo Reels (2013,) (2015,) (2017,) and (2019)

Watch a one minute excerpt on Vimeo now!

Hi Greenlaw:

I tried this, but it still came up with a lousy calibration (perhaps because of too few points). I have two other calibration takes which I will try and let you know if they worked.

When I tried orbiting the cameras the first time (at the start of this post), I couldn't change the orientation of the figure. However, when I turned the skin off, it allowed me to rotate the cameras more (bug?).

Off to try it again & thanks,

Michael

I found that if I hold the maglight as far away from my body and move slowly but evenly and keep the light on the floor for 2 seconds I get a much better calibration. Taking the time for a good calibration and saving it, save time on all the other takes.

OK, I've written a program in Matlab to reorder the cameras in the video - whatta pain. I'll try it to see if that helps.

The other mocap system I use has the same type of calibratiion with a bright light (Svboda's technique), and so I've got both a maglight and a LED flashlight mounted on either end of a long black stick which keeps it far away from my body. I may have to use the techniques I use with the other system to get good tracking points. The other system only requires that points be seen by 3 cameras at a time to get good sub-pixel calibration.

More experiments to follow,

Michael

OK, I thought I had this fixed, and then I hit the AVI 2GB barrier.

So...

I figured out how to split the video automatically in Virtualdub. I will then run the segments through a program that swaps cameras, and then combine them back together in Virtualdub. I have tried using a single segment, and it loads fine in mocap studio. In addition, it looks like the scene camera alignment isn't the ridiculous convoluted process is was before. I'm definitely renumbering the cameras during the shoot next time.

I'll post more details for anybody who's interested.

Michael

I recommend that you do not bother re-ordering the cameras on video. Just use the controls on "Scene" tab to move the cameras into appropriate initial position before calibration (you don't need to be very accurate, just make sure not to mess up left and right). Or you can use "Auto-detect initial camera positions" option (it should be used before calibration). Auto-detect works most of the time but may occasionally fail.

In current version of iPiStudio the exact order of cameras is irrelevant. Having cameras in certain order is just useful for operator/user for visually assessing what is happening on video.

Well, I guess that was a lot of work for nothing.

I have tried calibration with autodetect camera both checked and unchecked with the same weird results.

Michael 2