[PD] GEM : fx to make persons appear only when they move

>---------------<[O:O]>---------------< benjah at free.fr
Thu Mar 1 15:41:49 CET 2007


Thanks Max for this example, in fact it is quite close to my first 
trial, it works fine but if there is 2 persons in the image, one move, 
the 2 persons appears and I would like to see only the person who is moving.
I'll dig deeper...

Benjamin


Max Neupert a écrit :
> hi benjamin,
>
> sebastian trippner did exactly this in i seminar i gave. here is the  
> description and patch to download:
> http://kunstundmedien.burg-halle.de/LEF/index.php?labor=erkenntnis&s=LEF
> he was using a very simple method: a snapshot (still image) from the  
> video feed was placed over the video image as soon as the video  
> showed no more movement.
> it's a very simple patch with not many onbjects.
>
> have fun with it.
>
> Am 01.03.2007 um 06:41 schrieb >------------------------------:
>
>   
>> Hi list,
>>
>> I' trying to make an effect on a live camera feed with GEM for an
>> installation in which only persons who move appear on a kind of video
>> mirror, as chameleonTv of effecTv
>> (http://effectv.sourceforge.net/chameleon.html)
>> I tryed severals ways :
>>     
>>> with pix_background and pix_blob, modulating the alpha value of the
>>>       
>> rectangle on which the video is textured in function of the  
>> quantity of
>> movement but if one person moves, everybody appears.
>>     
>>> with pix_multiblob and combination of pix_image pix_rectangle and
>>>       
>> pix_mask, the [pix_multiblob 2] seems to eat all the processor,  
>> even if
>> I [pix_resize 320 240] the image before the multiblob.
>>     
>>> accumulating many (25) pix_movement and using the result by
>>>       
>> pix_masking it with  the live feed dig a hole in the person that  
>> moves a
>> little. Maybe I did not the "average" of alpha channel of the 25
>> previous frame as I thought, due to the fact that pix_movement  
>> works on
>> the previous frame ?
>> is there a better way with opengl instructions ? I tryed to look in  
>> that
>> direction but I didn't manage yet to find  how to analyze and  
>> affect the
>> pixels of a live feed....
>> thanks for any advice
>> benjamin
>>
>>
>>
>> for the tech note : the video feed is from a PCI capture card
>> (AlchemyTv) connected in s-video to a dv camera with [pix_video 720  
>> 576]
>> on a G5 10.4 Pd ext7,
>> for the first trial, I manage to mix this video feed with another DV
>> camera connected in firewire, putting into a buffer an image  
>> background,
>> filling and playing another buffer with PAL images, and playing a non
>> compressed video of the same size  >>> output on a second screen
>> 800x600, with all that, the motion capture was really fast, only  
>> 40% of
>> the proc used, it was really impressive (and stable), great dev  
>> work, thks
>>
>>
>>
>> -- 
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