[FFmpeg-user] Question) Any way to change alpha for overlay while time goes by?

[Lee Mitchell]

Hi.

There are RGBA support qtrle video clips that have no problem with alpha
support.

I'd like to overlay a video on top of base one, and want to change the
transparency while playing
like
"[1:v]alpha='if(between(t,0,10),(1-(t/10)) *
alpha(X,Y),0)'[v0];[v0]overlay[out]"
What kind of filter sequence should I use?

Thank you in advance.
Mitchell