Hi,
I am having problems on tracking multiple objects on a video file.
I have a set of logic image ( frames ), where I can separate the various objects( blobs ) and they move theirselves.
My goal is to track each one of these objects separatelly.
But I have no Idea on how to do that.

Best Regards.

On 10-11-09 12:43 PM, Wagner Johnes wrote:

> I am having problems on tracking multiple objects on a video file.
> I have a set of logic image ( frames ), where I can separate the various
> objects( blobs ) and they move theirselves.
> My goal is to track each one of these objects separatelly.
> But I have no Idea on how to do that.

Imagine two objects of the same shape and color, starting at opposite 
diagonals of a screen. The two objects move towards each other along the 
diagonal, overlaying each other completely as they meet, and continuing on to 
the other corner.

Now imagine almost the same scenario, except that at the moment when the two 
objects completely overlay each other, the two reverse course and move back to 
their original corners.

Now, how do you tell the difference between the above two cases?

"Oh!", you say, "they are different colors". Okay then, let the above cases 
play out except with variable coloring of the light, or varying shadows (both 
of which are common real world situations)

So do you add the constraint that the objects will be distinctly different 
shapes, even taking in to account altering over time when perspective or 
clipping due to obstruction is taken in to account? Is there some handy 
radio-beacon information that can be integrated in to track which object is which?

Wagner Johnes:
There are some ambiguities and challenges like Walter says.  However
many times, for many situations, all is not lost - there are things
you can do.  Lots of people have looked at motion analysis and all
their papers are listed here.  I invite you to read them:

http://iris.usc.edu/Vision-Notes/bibliography/contentsmotion-i.html#Motion%20Analysis%20--Low-Level,%20Image%20Level%20Analysis,%20Mosaic%20Generation,%20Super%20Resolution,%20Shape%20from%20Motion

Well, all the objects on my video are different, and there is no overlaying between them. It's simpler then the situation you described.
I just dont really know how to track multiple objects.

On Nov 10, 9:35=A0am, "Wagner Johnes" <conta...@yahoo.com.br> wrote:
> Well, all the objects on my video are different, and there is no overlayi=
ng between them. It's simpler then the situation you described.
> I just dont really know how to track multiple objects.
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How about just thresholding, labeling (call bwlabel), calling
regionprops, and finding the centroids?  Then find the centroid in the
(n+1)st frame that is closest to the centroid in the nth frame to
identify which objects moved where.  This is about the simplest
situation which will work in only the simplest situations (contrasty
particles moving slowly in front of a uniform background).  You can
fancy it up from there for more complicated situations.

That sounds pretty good.
I'll definitely try that. Thanks

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