Optical flow and tracklets

[LillyGal]

Hi,
I am using a traffic video - and obtained the motion vectors by means of optical flow. Now i want to extract tracklets (small tracjectories) by temporally connecting motion vectors e.g. at pixel level.
How may I do this please?
Also, how may I save the tracklets values after? as i am unsure of the best way to do this.
Thanks alot
Lil

 

[IRstuff]

Did you ask your instructor?

TTFN
faq731-376

 

[LillyGal]

Haven't got one as I'm doing this on my own.
I don't want anyone to give me the code I just want advise on how to proceed... then i'll try and figure it out in matlab
Cheers

 

[GregLocock]

well loosely speaking you need to find the tracklet in the next frame that starts where the tracklet in the previous frame ends. Since I don't have much of an idea what form your data takes, that'd be as much as I can guess.

So

for each tracklet at time t, identify the location of the end of the tracklet, and then look in the data for t+1 and find the tracklet that starts near there.




Cheers

Greg Locock


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[IRstuff]

How many "tracklets" are we talking? dozens, hundreds, thousands?

In any case, as Greg as stated, the object is to correlate each tracklet in each frame with its counterpart in each subsequent frame. This is typically based on comparing the various parameters of each tracklet, such as position, speed, size, etc., and assigning a score for each comparison that allows the tracker to automatically determine what the true track is. In many systems, there may be multiple possible correlations, and the tracker tries to maintain each one as long as plausible. Note that in complex scenes, there may be dozens of erroneous cross-correlations that must eventually die or be killed off.

You may want to consult a good textbook, such as:
Multiple-target Tracking with Radar Applications by S. Blackman, Artech House
Multitarget-Multisensor Tracking by Y. Bar-Shalom, Artech House

Artech House is probably a good go-to publisher for this subject. The other large resource is IEEE, which has published tons of articles on trackers.

TTFN
faq731-376

 

[IRstuff]

Oops, also, direction should be in that list.

TTFN
faq731-376