footage for motion tracking

Now that camera/motion tracking is up and going in Blender, perhaps it would be good to list some resources for free footage.

I played around with it this weekend and learned a few things. Most important is that the iphone is NOT good for taking footage because of the image stabilization. It distorts the video in unpredictable ways such that I could not figure out how to correct for it. As long as you are standing still, it’s fine. But once you start moving, it introducing strange warping. The camera tracking can still solve for it, but the solution is pretty bad and is going to cause sliding when the image stabilization kicks in.

Anyway, the result is that I don’t have a camera to take footage and so I searched around the web for free footage.

http://www.hollywoodcamerawork.us/trackingplates.html is one place, though limited
videocopilot.net releases their source files, but you have to dig a bit to find tutorials with good footage.

Other places? Perhaps people will host their own footage that can be used for fun and testing?

Could be because of the rolling shutter effect when moving, if it’s on vertical lines then that’ll be the problem.

There are a few samples available from the developer mailing list, have a look through the vfx section and you’ll see a guy posted a link to some footage (I believe) that was shot in Amsterdam.

In the footage I took, whenever I walked you could see the image warping. I didn’t notice the rolling shutter issue, though I read about it. The image stabilization effect looks like the sides of the image warp and distorts. Kind of like a weird underwater effect.

I’ll check the vfx section. Thanks for the tip!

Actually, I had a related question. I may be bold (or crazy?), but I have been shooting footage with the iPhone 4, and I can’t even seem to get a basic track working. I’ve searched the internet for the correct camera and lens settings to use, but the solution is not even close, the camera is rendered extremely “long” in the interface, and all the tracking points line up in one thin line. Any ideas?

These are what I’ve been using in blender’s camera settings:
Focal length: 3.85mm
Sensor width: 0.1mm
Pixel Aspect Ratio: 1
Optical Center: 640 x 360

Probably caused by that sensor width, you’ll need the correct value.

pftracks has a free demo use that to calibrate your footage and get the correct setting for the camera. but remember every zoom level is considered a different camera, if you are useing zoom get the setting for each zoom level you use. you will need to click on camera after the solve and write everyting down, you cant save anything in the demo.

Thanks for the replies! yeah, I’m not going to be doing any zooming :slight_smile: It’s definitely quite tricky. So far, I’ve determined that the proper sensor width is (roughly) 10mm. I wonder if the wide angle of the natural lens (3.85mm) is just too wide for blender to figure out. It might be worth trying to undistort the footage before placing in blender’s camera tracker, no?

I’d be interested in what you find. I was able to get a fairly decent track with the exception of the warping caused by the image stabilization. I think if I had a dolly or something that would keep the iphone completely stable that I could get a good track. Now, I was using syntheyes, not blender, so maybe it can deal with more uncertainty in the specs. But it was really the warping from image stabilization that was causing this. I read a LOT on the internet about motion tracking with the iphone and pretty much everyone agreed - rolling shutter + image stabilization = very bad tracking.