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 Post subject: Lightdog Films tutorials
PostPosted: Mon Apr 27, 2009 7:53 pm 

Joined: Tue Apr 07, 2009 8:03 am
Posts: 33
I posted a tutorial on 4-camera calibration here:

http://www.lightdogfilms.com/mocap/page0/page0.html

"DMC_calibration_v02.mov.zip"

It's a 9MB Quicktime clip, no audio (explanations are in embedded text elements).

Comments/questions/clarifications are welcome.

[EDIT: this video has been updated as of May 2nd]
[2nd EDIT: tutorial moved to a new download page on May27th]


Last edited by lightdog on Wed May 27, 2009 12:58 pm, edited 2 times in total.

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PostPosted: Tue Apr 28, 2009 9:40 am 

Joined: Tue Apr 07, 2009 8:03 am
Posts: 33
[EDIT: Version 2 posted as of May 2nd. See info in first post.]


Last edited by lightdog on Sat May 02, 2009 11:09 am, edited 1 time in total.

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PostPosted: Thu Apr 30, 2009 8:49 pm 

Joined: Sun Apr 12, 2009 8:38 pm
Posts: 16
thanks for taking the time to do these and share 'em! ;)

it's appreciated. :)


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PostPosted: Fri May 01, 2009 12:40 pm 

Joined: Wed Apr 08, 2009 6:41 pm
Posts: 22
Hi LightDog.

What are your system specs for your 4 camera recording machine?

I have a 1.8gig Toshibia laptop (with 1Gig RAM) and I'm finding that even with 2 cameras the frame rates are dropping down to around 15 FPS. I am now getting setup for 4 cameras and fear my machine may not be able to keep up with the frame rates (causing my high speed motions to fail misserably)

thanks
David

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 Post subject: system specs
PostPosted: Fri May 01, 2009 1:50 pm 

Joined: Tue Apr 07, 2009 8:03 am
Posts: 33
The laptop I use to capture 4-camera video is a Dell M90 with 4GB RAM and a 2.33GHZ Core2 Duo processor. All USB connections are directly into the PC (as opposed to going through a hub. A hub could be a source for slowdowns).

When you use iPi Recorder, does the "Actual Frames per second" value drop to 15 FPS? In low-light situations, the cameras themselves might drop down to 15fps (to let in more light, if they are set to auto-exposure), even though iPi Recorder can still capture at full speed.


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PostPosted: Fri May 01, 2009 3:06 pm 
iPi Soft

Joined: Tue Mar 31, 2009 9:13 pm
Posts: 804
Hi David,

What cameras are you using?

The frame rate is most probably affected by Exposure or Shutter Speed of your cameras. Try playing with Exposure - this should help you get 30 FPS.

iPi Recorder monitors actual frame rate, so if you are getting 15 FPS, that's what your camera is sending. This is not affected by CPU speed. You should have no problems with CPU speed at 320x240 even if you have slow CPU.

Some cameras (like Philips cameras) may require you to set frame rate through their own driver control panel. Some cameras (like Microsoft webcams) do not have frame rate control at all, that's why we do not recommend them.


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PostPosted: Fri May 01, 2009 3:21 pm 
iPi Soft

Joined: Tue Mar 31, 2009 9:13 pm
Posts: 804
By the way, the system is extremely sensitive to frame rate. Low frame rate (like 15 FPS) means throwing away too much information and dramatically affects reconstructed motion.


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PostPosted: Sat May 02, 2009 11:07 am 

Joined: Tue Apr 07, 2009 8:03 am
Posts: 33
I updated the 4-camera calibration tutorial to reflect a clarification from iPiSoft: you don't have to set ground markers before calibrating.


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PostPosted: Sat May 02, 2009 7:25 pm 

Joined: Wed Apr 08, 2009 6:41 pm
Posts: 22
I'm using 4 Logitech 9000's.

I have the focus set to manual for all of the cameras, as well as the automatic light correction function turned off.

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PostPosted: Sat May 02, 2009 8:02 pm 
iPi Soft

Joined: Tue Mar 31, 2009 9:13 pm
Posts: 804
DavidWinter wrote:
I'm using 4 Logitech 9000's.


You should set Exposure to a lower value. Decrease it until iPi Recorder shows Actual Frame Rate of 30 FPS. The picture can become a bit dim, that's normal and should not affect motion capture. Our system uses gradients, not absolute values, so as long as actor is distinctive from background, everything should work.


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