[PD] pix_multiblob and tracking multiple objects

John Harrison john.harrison at alum.mit.edu
Thu Apr 18 16:12:03 CEST 2013

FWIW I had just the opposite experience with CCV. CCV has built-in
background adaptive subtraction, smoothing, highpass filter, gain,
contrast, etc. all tweakable. It also tracks blobs uniquely as the original
poster is wanting, which is why I thought of it for their needs. I used
[pix_blobtracker] before and it works OK but I found CCV to be overall a
more robust solution than anything I could efficiently come up with.

I use CCV at 60fps 640x480 w/ a ps3eye on ubuntu 10.04 64 bit and the CPU
load is not significant and reduced from my original Pd-only solution. My
CCV/Pd patch has been on exhibit 24/7 for 5 months now without issue so it
also seems stable. I use CCV version 1.4. I also used CCV on another
exhibit with a Win7 64 bit system and that ran for months as well without
issue. That might have been version 1.5 but I don't remember for sure. I
also know there's a newer version of CCV supporting multiple cameras now,
and I have not had experience with this.

Maybe I'm not understanding the flexibility you are looking for that CCV is
not offering you. All I can imagine is that you can't find a way to change
the order of the filtering. I'm not sure that's something you'll find you
actually need though to improve the result of the blob tracking.

Just my $.02.


On Thu, Apr 18, 2013 at 8:42 AM, Antoine Villeret <
antoine.villeret at gmail.com> wrote:

> i tried CCV one time but i had some driver and performance issues
> moreover, i can't find an easy way to tune the processing chain
> pd is more flexible but, i agree, could be harder
> --
> do it yourself
> http://antoine.villeret.free.fr
> 2013/4/18 John Harrison <john.harrison at alum.mit.edu>
>> I'm not totally clear on the big picture here but it could be you might
>> save yourself a lot of time and effort doing your blob tracking with
>> Community Core Vision (CCV) then sending the blob data to Pd through OSC.
>> After initially doing my blob tracking in Pd only (which did work), I
>> switched to this CCV --> Pd approach and got better results because of all
>> of the built-in filtering etc. that is provided with that open-source
>> cross-platform software.
>> -John
>> On Thu, Apr 18, 2013 at 5:22 AM, Ska Frenz <skafrenz at gmail.com> wrote:
>>> Hi, thank you for the suggestions, I'll check openCv. Can you explain
>>> how to use "morphological filters" to clear up the noise in the image? Are
>>> there examples around? Also, could you please explain me better what do you
>>> mean with "adaptive background subtraction method"?
>>> Thank you for your time :)
>>> francesco
>>> 2013/4/17 Antoine Villeret <antoine.villeret at gmail.com>
>>>> hi,
>>>> the segmentation method (how you extract what is your interest from the
>>>> rest of the image) is very critical in video tracking
>>>> background subtraction is a basic way to extract blob and it works only
>>>> in certain conditions of light (if you want to track something outdoor, you
>>>> should use an adaptive background subtraction method)
>>>> moreover, there is no general method to do video tracking, it depends
>>>> on what you want to track and how it is filmed
>>>> so, the first thing is to have a good image, with not too much lighting
>>>> changes, good contrast between background and features to track
>>>> then you can start thinking about segmentation, and the
>>>> segmentation accuracy depends on the quality of the video
>>>> you may need to do something more than just background subtraction, for
>>>> example, you could apply some morphological filter to remove noise
>>>> after that, you can start tracking
>>>> you could also apply a threshold on the blob size to not track very
>>>> small blob
>>>> blob of interest are often surrounded by very small blobs due to
>>>> segmentation noise
>>>> but you can have a look at pix_opencv objects,
>>>> there is [pix_opencv_blobtrack] which implements a whole processing
>>>> chain, including foreground extractor, blob detector, blob tracker and
>>>> follower
>>>> I'm not sure it's included in pd-extended, but you can find some
>>>> binaries on build server
>>>> hope this help
>>>> antoine
>>>> --
>>>> do it yourself
>>>> http://antoine.villeret.free.fr
>>>> 2013/4/17 Ska Frenz <skafrenz at gmail.com>
>>>>>  Hi everyone, this is my first time on the pd-list so I hope I won't
>>>>> do anything wrong.
>>>>> I'm writing here to get some help about pd tracking objects
>>>>> (pix_blob..). I'm using the background subtraction method, to track objects
>>>>> and I need help to understand how I can track multiple objects with
>>>>> multiples different blobs. I'm trying the pix_multiblob and yes, it show 2
>>>>> blobs..but they track the same object. Then basically I do not understand
>>>>> how can I make the first blob to follow just one object for all the time
>>>>> that specific object is inside the webcam rectangle, and the second blob to
>>>>> track another separate object. I cannot find any material that clearly
>>>>> talks about this.I attached the patch I'm working on. I'd love to see some
>>>>> well-explained examples if you know where to get them.
>>>>> Thank you very much for your help :)
>>>>> Francesco
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