OverlayVideo

OverlayVideo[background,o] gives the result of overlaying o onto a background video or image background. 

OverlayVideo[background,{o1,o2,…}] gives the result of overlaying o1, o2, …. 

OverlayVideo[background,{interval1->o1,…}] overlays each oi during the time interval intervali.

Please visit the official Wolfram Language Reference for more details and examples on core symbols.