With "returned something" do you mean that the autofocus has returned with a callback? If so, it does already wait for that before calling the autofocus. The refocus checks a flag which is called "focusing" which is set to false whenever the autofocus returns with a state (failed, success, etc.). The state is what you see in the output when running mbarcode.

I think we should test to see if it helps to wait for the decoders to finish decoding the previous image as well (if that is possible in a smart way, given that there are two decoders).