Export QT with alpha channel

[Geraint Pari huws]

facing the lack of a better answer – no I don’t think so, I’ve faced this prolem myself-

workaround (if the sequence isn’t huge, and depending on type of seq/effects)

dupe seq
add a color effect to all you fills to white them out
mix down and export, this will crate a matching matte pass.

you can then add them in ae or similar (track matte) and export from there as video and alpha.

reply for more info

[Geraint Pari huws]

or, depending on where you’re taking the seq, automatic duck will probably solve the issue, but not for free!