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

Max Neupert abonnements at revolwear.com
Thu Mar 1 12:37:28 CET 2007

hi benjamin,

sebastian trippner did exactly this in i seminar i gave. here is the  
description and patch to download:
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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