need a lot more info than what you’ve given (it’s like leaving a mechanic voice mail, telling him your car doesn’t run well and asking if he can repair it).
from what I can tell, this green screen shot isn’t anywhere near properly lit (talent is about as flat as can be). No matter what camera a green screen scene is shot with, poor lighting will make it nasty & unusable.
Btw, I prefer QT over AVI any day. Must also be your render settings also in conjunction with what’s mentioned above.