Image is skewed diagonally. How to un-skew?
by Marc Brown
on
May 19, 2008 at 7:22:03 pm
I've recently been toying around with a video processing plugin which seems to do what it's supposed to, but it also does something frankly inexplicable. I've got a 720x480 (DV) composition in this instance.
From top to bottom, each consecutive horizontal line is skewed to the right one pixel. (Or it may be that every two lines are skewed to the right by two pixels; it's difficult to really tell.) To put it into a formula of sorts, the y position of the video dictates an x+1 offset. Visually, this shows up as a diagonal skew to the right. The portion of the video which is shoved off the right edge of the layer is wrapped back around to the left. And finally, at the bottom of the frame where the skew has reached its maximum, what used to be the video's left edge, x position 0, is now at x position 479 (or 480, near enough).
Not being familiar with the kinds of incompatibilities which may crop up, I am tentatively chalking this phenomenon up to the fact that the plugin was designed for AE6 and I am stuck with AE7.
Anyway, I still definitely want to make use of this plugin, and this weird problem is not actually destructive to the video, so I'm after a post-processing solution. I am not expecting there to be any sort of plugin fix for such a unique "effect" but perhaps somebody could offer an expression formula to try out on the video, and suggest its implementation. So far, while I can be pretty good with the kind of scripting involved, I simply don't have a working understanding of the syntax of AE's expression system, nor, by consequence, any kind of grasp of what's possible.
Hope my description was sufficient, and very grateful for any help. Thank you.
Re: Image is skewed diagonally. How to un-skew? by Jeremy Allen on May 19, 2008 at 8:07:12 pm
I think I understand what's going on, but I don't really have any advice, except that maybe a screenshot of the problem will help others easily understand the problem.
Remember, I'm not really looking for a _solution_ (as I doubt there is one) but rather a _fix_, as in an expression (or whatever) which can correct the very elementary problem this plugin is engendering. Again, thanks in advance!
Re: Image is skewed diagonally. How to un-skew? by Marc Brown on May 19, 2008 at 9:32:02 pm
The plugin was discontinued, so yeah. (Besides which, this isn't my pc I'm using this software on, so updating software on it, even if an update existed, is an option that I effectively don't have.)
Again, it's not a solution I'm after. If I really, truly had to, I could separate the project into 480 horizontal lines and adjust their x position individually, and that would, as far as I can tell, be a fix that works. (It's probably obvious why I don't pursue that option.) That's all I'm after.. something that can correct the problem.
Re: Image is skewed diagonally. How to un-skew? by Dave LaRonde on May 19, 2008 at 10:21:49 pm
[Marc Brown]"If I really, truly had to, I could separate the project into 480 horizontal lines and adjust their x position individually"
Doing that in conjunction with the Offset effect might just do the trick.
But I'd think by the time it would take you to fix the footage, you could have found another machine running AE6, where the plugin would run properly. If the only reason you need AE6 is for that one plugin, you could render out the footage with the plugin applied, then proceed in AE7.
Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
