Video Masks are Not Showing up in the Right Spot..

RockoRobotics wrote on 12/7/2009, 8:29 AM
My friend and I decided to film our own lightsabre battle for fun, so I am trying to use the masking tool create the glowing blades, but the mask is not showing up in the right spot. Below is a link to an image of mask window and the final render window:

http://www.tabletopbattlefield.com/special/LightSabreIssue.jpg

The setup is two identical video events layered one on top of the other. The video is 1080(60i) HDV shot with an HV-20. The bottom video track is unmodified. The top track has the mask applied to it and I have colored is blue so that the mask is visible.

As you can see in the masking window to the left, the mask is in the correct place. However, in the final window to the right, it is clearly in the wrong place. By looking at the positions of the prop lightsabres in the live video it is clear that the video frames are the same. By comparing the location of the points of the mask between the mask window and the final window, the the mask in the wrong place.

Any ideas on what would cause this? Is it just a some setting I have wrong, or should I be working with a different video format?

Comments

RockoRobotics wrote on 12/7/2009, 8:31 AM
I would also like to add this detail:

If I change the rendering quality of the preview Window to Preview(Full) the mask appears in the right spot, but rendering the video still causes it to show up in the wrong spot.
rs170a wrote on 12/7/2009, 8:50 AM
You have to set the Preview Window to Best/Full to make these adjustments accurately.

Mike
RockoRobotics wrote on 12/7/2009, 9:11 AM
The preview window is set to Best/Full. Can I set the mask editing window to display the Best/Full setting?

I suppose I could ignore the frame in the mask edit window and just align it by the Preview Window, but this would take a lot longer.
RockoRobotics wrote on 12/7/2009, 12:55 PM
I've got something else to add to this problem. I don't think the issue has to do with the preview or best setting. What appears to be happening is the mask that gets displayed on the preview window is a hybrid of what I have set and the automatically generated position between key frames.

I figured this out because there are several frames where my blade is completely covered by my body. During these frames I would move the mask off the screen. In the frames before this happens, the mask moves further away from where it is supposed to be and closer to its eventual off-screen position.

Since I am adding keyframes every frame, I don't need the auto-generated frames. Is there anyway for me to turn this feature off?
RockoRobotics wrote on 12/7/2009, 1:11 PM
I got it all figured out.

By right clicking on a Keyframe and choosing hold for each of the mask keyframes, this issue goes away for Best Rendering Quality. Just render the output in Best quality and it should work alright.

Though, if you render the video and re-import it into the timeline and play it back in preview mode, it looks screwed up. However, it is not.
JohnnyRoy wrote on 12/8/2009, 2:44 AM
One thing to try is to render the footage using a codec that uses intraframe compression like CineForm, Huffyuv, Lagarith, MJPEG, etc. that compresses based on individual frames. HDV uses interframe compression on a group of pictures (GOP) which means that you only get a "real" frame every 15 frames (I-frame). The rest of the frames (B & P-frames) are "estimated" from the I-frame and they are estimated differently depending on if you are playing backwards or forwards as we sometimes do when editing and moving about the timeline. This causes very precise masks to be incorrect because you are basing them on this estimated position which may change. See if it makes a difference in your case.

You also might want to look into FXhome's EffectsLab Pro for doing light sabers. ;-)

~jr