Hi matthias ,
Regarding first question - 3A is by default done on the whole frame. So ROI would be (0,0,1,1), and your approach seems correct to me for your use-case. There's no guarantee as focus process isn't instant, maybe after focus value doesn't move too much for eg. 10 frames in a row I would send still event, as in that time the lens would have moved to correct position. Thoughts?