Erase background

[bigplac]

Hello,
I would like to know how can I erase a background in a 8 seconds video. In the video appears a baby in a cradle, and I want to change the background, leaving the baby as it is now.
Does anybody know how to do it?
It is a kink of delogo filter but invert.

Thanks.

[Zarxrax]

Doing something like that requires rotoscoping (frame by frame editing) of the image. You need a program like Adobe After Effects or Premiere+Photoshop to do this.

[scharfis_brain]

I think, that motionmaksing could help here.

[emdiem]

Motionmasking might be the way to do it, painting over every frame by hand is alot of work

[Zarxrax]

I don't see how motion could help anything... unless the cradle is rolling across the floor, lol.

[esby]

he could do frame by frame editing
with avs...
He needs to calculate the appropriate mask to apply for each frames...

There are three cases:

* the craddle is static on the picture:
In this case he needs to do a mask and apply it to the frames.
(quite easy)

* the craddle is moving on the picture, but moving.
In this case, he needs to adjust the coordinate of the mask for each series of frames where the craddle move.

* the craddle changes form and or move... in this case,
recalculating (redrawing) the mask at each frame will be needed.

In all cases,
have a look on Layer...

first case should look like that :
src = avisource("...")

mask = imagereader(".tga")

mask = mask.resetmask()
mask = mask.ColorKeyMask( XX , YY )
XX should be set according to the color used for alpha, YY is the tolerance eg XX = $00FFFFFF YY = 205 for 'white background'

dest = layer(src,mask,"add")
return dest

the mask should contain here the background you want to add, and white parts for what you want to keep.

If you want to alter the mask position , use x & y parameters of Layer()

Of course using after effects might be easier...
but you might do a somewhat correct job with that.
You just need to capture the picture, edit them correctly
and apply it to a script if you want to go without after effects like solution...

esby