I need a quick help on this question. When to draw an AOI? Can I draw AOI After the recording?
There is a page where the developers have provided in-depth analysis of AOI. I recommend you read it to see when it's best to apply an AOI, but usually the area is delimited after the content has been already produced and after you have established some parameters.
Support page: http://www.tobiipro.com/learn-and-support/learn/digging-into-areas-of-interest/