Stock animation
We are attaching BW's as alpha in the second half.
In the case of AE, it is cut by 15 seconds 01 frame, the second half is overlaid on the first half
Pull out the white part of the second half with a linear color key etc.
After that, if you make the first half layer matte alpha, you will escape confetti.
If you have a free plug-in "unmult", I think that you can withdraw black BG directly.