For gif animation are available 2 modes, replace and combine but as far i know for normal video files only the replace mode is available
If that true, if there is no way to chose the combine mode when exporting to avi or other video format i would love a script to do it, because combine mode allow effect not possible with other methods
the concept is simple, but do manually would be a nightmare, basically the script should
1 take a gimp animation as input call it A
2 create a new image (as container for the output) call this B
3) make all layers of A except the BG
INVISIBLE4) copy the visible from A...paste as BG layer of B
5) make visible in A also the layer above the visible
6) as 4: paste the visible of A as new layer of B
7) as 5, make make another layer above visible in A
and so on and on till the top layer
Or as alternative save the output not as layers of a new image but as a series of frames (this may reduce the risk to create a too huge images that may become to heavy to be saved)
This should allow to use the combine effect also for video, not only for gif
![Yes!!! :yes](./images/smilies/yesssmileyf.gif)