Make a tracked point move at constant speed

[blockrocker]

Hi!

This might be a tough one, so I apologize already!

Here it goes:

If I have motion tracked (let's say a red x-mark) an object in a panning shot, is there a way to make that tracked feature move at constant speed at all times, even if the camera motion almost stops in the middle of the shot? I'm thinking if time-remapping (or better yet, time warp) and expressions could somehow help out in this situation -in other words if I could tell AE to increase the time remapping speed to compensate for the slower speed of the tracked object?

This would be handy in situations in which the original panning shot is very jerky -I do realize though it can't be used if there is moving people in the shot (or something else that you would notice the speed change in).

Any help would be great!

[bennn]

Not sure if I understand your problem right, but I sometime do handheld pannings, and then stabilize it with AE.

I just track something, then scale up the layer and keyframe its position, to make it move in a panning motion....

I've thought of adding some expressions, something that optimize the ratio between rescaling and motion, but I've never had the courage.

[blockrocker]

Thanks for the reply!

The problem with reqular stabilizing is the lost resolution/black borders. The way I see it, if the stabilization was done by using time remapping to make the movement constant, there would be no need for upscaling the image.

Maybe I got it wrong though, since nobody seems to confirm that this is doable

[bennn]

One thing is sure, if you want steady panning, which means no up/down motion at all, with something shot handheld, then you have to scale up your picture. With HD video if you don't go beyond 110% it's not really noticable, even on a 23" screen.

Then if your footage is perfectly steady in up/down, there's a ".speed" or ".velocity" that you can use in an expression to get the velocity of a parameter (check out Kramer's "speed particles"). When used on the keyframes of the tracking, you might be able to get something to work. the hard part is that you cannot drive a position with a velocity, but basic physics tells us that at constant speed, position = speed*time, hence time = position/speed...

I'm not on AE right now, so i can't try it.

[blockrocker]

I'm still interested in the possibility to do this. Even after buying a quite expensive tripod my pans are sometimes less smooth than they should be. I find it especially hard to to keep the motion smooth during long (sometimes almost 360') pans.

I still think it should be doable: first track a point in the panned shot, and then use the velocity information of this track point to drive time-remapping and smooth out the velocity curve.

There was an interesting take on this at the cow forum (the last post):
http://forums.creativecow.net/thread/2/956780#970567

However, that experiment ended in frustration. Is there any one here who might give it a go?